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Home My WebLink AboutEnviornmental Atlas of AK 1984ta OE ‘gy i} ie A eb Ne at Pre m li veh ai " re : DA N an ! ri WO ih \ vr ‘ ENVIRON MEN TAL ATLAS OF ALASKA CHARLES W. HARTMAN UNIVERSITY OF ALASKA Selendis A ae Charles W. Hartman Research Engineer Institute of Water Resources Philip R. Johnson Research Civil Engineer U.S. Army Cold Regions Research Engineering Laboratory ENVIRONMENTAL ATLAS OF ALASKA Institute of Water Resources/ Engineering Experiment Station University of Alaska Fairbanks, Alaska 99701 All rights reserved. No part may be reproduced in any manner without permission in writing from the University of Alaska. Copyright © 1984 by the University of Alaska Fairbanks, Alaska 2nd Edition, April 1978 Revised, May 1984 Printed in the United States of America PREFACE This atlas gives an overall picture of many aspects of physical Alaska. A great deal of general information about the state has been available but it has been widely scattered and there has been a need to collect and present it as a unit. Maps are the primary means of presenting information but a text and some tables are used to highlight and amplify them. Much of the material in this atlas was obtained directly from published sources. In other cases, published information has been further developed to provide the necessary information and detail. Although the sources have been given, this is not a bibliography and the list of references is not intended to be complete. The principal studies of physical Alaska, including its weather, have been carried out by federal agencies. This atlas has drawn heavily on published material and data of the U. S. Geological Survey, the U. S. Weather Bureau, and the U. S. Coast and Geodetic Survey. In addition it has drawn on the Alaska Rail and Highway Commission, the U. S. Navy, the Alaska Power Ad- ministration, the U. S. Army Cold Regions Research and Engi- neering Laboratory, and the U. S. Army Corps of Engineers. To these agencies which have labored so long and diligently in Alaska, we are all indebted. Much updated information in this edition was obtained from the Arctic Environmental Information and Data Center, University of Alaska, through the kind offices of Mr. David Hickock, the director. Incidentally, for those who are interested in more detailed information than is contained in this atlas, the Regional Profile Series put out by AEIDC is an excellent source. Work on this second edition was supported by the Institute of Water Resources, University of Alaska. Judith Henshaw must be credited for the great improvement in layout and drafting over the first edition; her skill and hard work were indispensable. In addition we are grateful for John Beckler's excellent cover design. University of Alaska Charles W. Hartman April 1978 Philip R. Johnson CONTENTS Page Preface. . 2. 6 2 ee ww we ew ew ewe re . Vv List of Plates... 1... 6... ee eee ee ee es Wil Introduction... 6. ee eee ee ee ee ee we we VA PART I, Physical Description of Alaska ........ 1 PART II, Alaskan Waters. . . 1... 2 ee ew eevee 27 PART III, Light... 2... 1. eee ee ee wee eee 45 PART IV, Climate... .. 2... 2 eee eee een 57 PART V, Engineering Information. ........+.ee-. 83 Selected Bibliography. ... 1... 6. 2 ee eee eee 94 I. PHYSICAL DESCRIPTION OF ALASKA 1. 2. 9. 10. ll. Alaska and its Neighbors. ...--+ - Alaska and the Lower 48. . Scandinavia and Alaska. ...-+ > Strategic Location of Alaska. : Distances within Alaska... +++ Physiographic Provinces of Alaska . Geological Map of Alaska... - += Earthquakes in Alaska. . + +s > Permafrost in Alaska... + +++ Glaciation in Alaska... + +++ Forest Types in Alaska. .. +++ II. ALASKAN WATERS 12. Depths of Alaskan Coastal Waters. 13. Currents of Alaskan Coastal Waters. 14. Sea Temperatures off Alaska, RSS 15. Sea Ice Distribution. ..-+ +++ > 16; River and Coastal Ice Seasons . . 17. Extreme Tides at Alaskan Harbors. . 18. Alaskan Water Crop. »- +++ ++: * III. LIGHT 19. Sun Path Diagrams ...+-+-s + 20. Sunlight in Northern Latitudes. 21. Twilight in Northern Latitudes. . 22. Sunlight Plus Twilight in Northern Latitudes. ...- LIST OF PLATES Page ll 13 15 17 19 21 23 25 31 33 35 37 39 41 43 49 51 53 55 IV. CLIMATE 23. Climatic Zones of Alaska. .- ++ ++ > 24. Mean Annual Precipitation in Alaska. . 25. Wet Days per Year in Alaska... - 26. Probability of a Wet Day at Selected Stations... «+ 06 6 46. 27. Mean Annual Snowfall in Alaska. 28. Mean Minimum and Maximum January Temperatures, °F... ++ +++ 29. Mean Minimum and Maximum July Temperatures, °F. . +--+ eerie 30. Mean Annual Temperature of Alaska, °F . 31. Alaskan Seasonal Temperature Variation, ° suis Mena el tee si isl is) |p| ie |e Seasonal Index. - + +++ + Seasonal Lag in Alaska. . - - 32. Mean Annual Diurnal Temperature Variation in Alaska, °F . eee ta 33. Wind Chill Equivalent Temperature . - - Wind Chill Index Nomogram. . - ENGINEERING INFORMATION 34A. 34B. 35A. 35B. 36A. 36B. 37. Freezing Index, Alaska . - . Design Freezing Index, Alaska... + = Thawing Index, Alaska... + +++: Design Thawing Index, Alaska. Heating Degree Days in Alaska . Degree Days below 0°F in Alaska . Building Design Criteria in Alaska. Page 61 63 65 67 69 71 73 75 77 77 77 79 81 81 87 87 89 91 91 91 93 INTRODUCTION Alaska, whose name is derived from the Aleut root meaning "a great country," extends farther north, farther west, and farther east than any other part of the United States, and is the largest state with the smallest population. It extends through 20 degrees of latitude from the Aleutian Islands to Point Barrow and through 58 degrees of longitude from Hyder in southeastern Alaska to Attu Island at the western end of the Aleutian Islands. As the northwestern peninsula of North America, it approaches Asia only 55 miles across the Bering Strait. Mt. McKinley, in the center of the State, is the highest mountain in North America at 20,320 feet. It is particularly impressive as it rises from a base plain only 2,000-3,000 feet above sea level. Peaks from the Alaska Range, Wrangell Mountains, and St. Elias Range comprise the 14 highest in the United States. The population in Alaska, however, lives almost entirely below 1,000 feet of altitude. Bordered on the west and north by shallow seas, Alaska has much of the continental shelf belonging to the United States. Its southern coastal area lies on the Circumpacific Earthquake Belt and is noted for its magnificent scenery, earthquakes, and, in the west, volcanic activity. The state is spectacular and varied. In its description, superlatives come easy. Furthermore, it is a land of semi-exotics such as snowfields and glaciers, Indians and Eskimos, tundra and muskeg, moose and caribou, oil and gold, salmon and salmon-eating bears, midnight sun and midday darkness in the Arctic, and other strange, unusual and often spectacular phenomena. This atlas describes five general aspects of the environment. These are: Part I. Physical Description Part II. Waters Part III. Light Part IV. Climate Part V. Engineering Information The atlas is admittedly incomplete. For a few subjects, such as tides, relatively adequate information is available. However, for most subjects, comprehensive data has not been collected and detailed description is not possible at this time. Particular limitations of this atlas include the following: 1. Southeastern Alaska with its spectacular but complex topography is not adequately described at the scale used. 2. Data for arctic and southwestern Alaska are so sketchy that we have only samples for the areas. 3. Much data, such as that for weather, are collected along the rivers and seacoasts. Information for the hills and mountains is not available. 4. Only mean values are given in most cases, Real phenomena, such as tem- perature, vary around the mean. No measure of the variation or scatter is given in most cases. With these limitations kept in mind, it is hoped that users will find this atlas of value. PART I PHYSICAL DESCRIPTION OF ALASKA Alaska and its environment can only be understood if one under- stands its location, size and range, and physical features. Plates 1-5 show Alaska's relative size and location. Plate 1 shows Alaska and its environs, which include Canada, Eastern Asia, the Arctic Ocean, and the North Pacific Ocean. Plate 2 gives an idea of the size and extent by showing Alaska super- imposed on the contiguous United States. Plate 3 compares Alaska and the Scandinavian Peninsula, two areas very similar geographically. Plates 4 and 5 show the strategic location of Alaska and distances within the state. Physical features of Alaska are shown in Plates 6-8. These include the physiography, geology, and earthquake distribution in the state. Because the distinction between these three sub- jects is somewhat obscure, a definition of each is included in the discussion accompanying the individual plate and it is suggested the reader examine these definitiona to differentiate among the topics. Permafrost and glaciation, two items of great importance in the state, are shown in Plates 9 and 10. Forest types are shown in Plate 11. Forest types (which show ecological systems) are particularly good indicators of the general environment. Alaska is primarily a subarctic peninsula on the northwest shoulder of North America. It has an arctic fringe on the north and west and a temperate panhandle on the southeast. By its acquisition the United States gained a dominant position in the North Pacific--of military and commerical importance begin- ning during the first half of the twentieth century. It also acquired a strong position in the Arctic Ocean basin--of crucial strategic importance during the second half of the century. Separated from Asia by only 55 miles at the Bering Strait, it has pro- vided backdoor communication between the Old and New Worlds during the recent past. At the present time, it is a potential, but unexploited, communications link between two major powers of the world. Asa keystone in the world jet system, it currently serves polar flights between Europe, the United States, and the Orient. Alaska is bounded on the south by the North Pacific Ocean, on the west by the Bering Sea, and on the north by the Arctic Ocean. The eastern border is an unde- fended land boundary with Canada. The southern part of the Canadian boundary is roughly the height of land of the rugged coastal mountains but north of 61°N the boundary is political, not physical, and easy communication lines cross it at many points. Sea ice in the Arctic Ocean during most of the year and in the Bering Sea during the winter modifies the peninsular character. Climatologically the frozen sea is almost indistinguishable from land, and the winter climate in northern and western Alaska, even on the coast, becomes more continental during the ice season. Relations between Alaska and Canada are good. A community of interests has led to a great deal of scientific and governmental cooperation across the 1538-mile border. Trade is limited, since the economies and products are similar on the two sides, but U. S. products to Alaska cross Canada on land and air routes from the 48 contiguous states, and Canadian mineral products cross southeastern Alaska enroute from the mines to tidewater. On the west, communi- cations with Siberia are almost nil because of USSR policy. Competition for the rich sea resources of the western Bering Sea and North Pacific has existed for more than acentury. Major nationalities involved have included the Americans, Russians, Japanese, and Canadians. Other groups, such as the South Koreans, have moved into the area and have further increased the compe- tition. With the advent of the 200-mile limit, some competition for these resources has been alleviated, but many agreements have been made to allow foreign participation in resource harvest. Alaska contains three climatic zones: temperate, subarctic, and arctic. These zones are continuous across both North America and Eastern Asia. Forest types are the historic and basic means of differentiating climates but defining the boundaries has proven dif- ficult. Plate 11 and the introduction to Part IV discuss this matter further. BEAUFOR SEA GULF OF ALASKA Ne meltian—— — ISLANDS . Environmentol Atign of Alaska 4/78 180" PLATE |. ALASKA AND ITS NEIGHBORS The great area and extent of Alaska can perhaps best be under- stood by comparing it with the 48 contiguous states of the United States. Alaska, with 586,400 square miles, is about one-fifth as large as the 3,022,387 square miles of the 48 states. It is far and away the largest state in land area, which is the basis for the humorous threat to "divide into two states and make Texas the third largest state." When the states are listed in ascending order of size, Alaska exceeds the total of the smaller 21 states. In reality, Alaska is a region with widely varying environmental features and is comparable to the western states or the Mississippi Valley. Despite its large area, Alaska is even more impressive in linear extent. When superimposed on the 48 continguous states it reaches from the Atlantic coast in Georgia to the Pacific coast in California, and from the Canadian border in Minnesota to the Mexican border in Arizona. Alaska is a peninsula on the northwest shoulder of North America. Scandinavia is a similar peninsula on the northwest shoulder of Eastern Asia and the two have much in common. The two peninsulas have surprisingly close latitudes. Malmo, in southern Sweden, is about the latitude of Ketchikan, and in the north, North Cape and Point Barrow have almost identical latitudes. Consequently, both areas enjoy such phenomena as midnight sun during the summer in their northern regions. Regions with similar climates can be found in both peninsulas but there is no point-for-point correlation. A major branch of the Gulf Stream flows northeast along the Norwegian coast into the Arctic Ocean and tempers the climate of Norway. More severe weather is found east of the mountain range which divides Norway from Sweden but arctic conditions are found only in the extreme northeast. Alaska is colder than Scandinavia. Part of the North Pacific Drift (Kuroshio or Japanese Current) which flows eastward from the Japanese Islands to the west coast of North America swings north and warms southern Alaska as the Alaska Current (see Plate 13). However, it does not enter the Bering Sea in quantity and the western Alaskan coast, unlike the Norwegian coast, has a cold sea which freezes during the winter. For this reason, warm seas have relatively little effect on Alaska north of the coastal mountains and the climate is more continental and arctic than that of Scandinavia. Both areas have been glaciated. However, Scandinavia supported a tremendous ice sheet during the Pleistocene and was essentially covered with ice due to the plentiful supply of moisture available from the North Atlantic. Parts of Alaska were also glaciated but lack of moisture inhibited the development of large ice fields in central and northern Alaska and much of Alaska was not glaciated. Most Scandinavian glaciers have now disappeared, but Alaskan glaciers and snowfields still exist in the southern mountains. Plate 10 shows past and present glaciation in Alaska. UAT ello) With the development of long-range jet aircraft, the effective geography of the world has become global and Alaska has become a crossroads rather than an outlying province. Three facts of world economic and political geography contribute to Alaskan importance: 1. Seventy-seven per cent of the world land mass is north of the equator, excluding Antarctica. 2. In this land area, the north temperate zone is the birthplace and home of modern civilization and industry. This zone is a circumpolar belt between 25°N and 65°N. Within this zone three concentrations of industry, population, and political power and leadership are found in Europe, North America, and Eastern Asia. 3. As mariners have known for centuries, great circle (shortest distance) routes in the Northern Hemisphere are deflected to the north. Consequently, communications between these three foci, such as that by commercial jet aircraft, cross the Subarctic and Arctic. Jet aircraft cross both land and water and fly equally well over the tropics and the Arctic. For the first time man has a means of mass transpor- tation free of most physical restrictions and governed primarily by economics and international politics. Economics limit the length of flights by requiring a proper balance between fuel and pay- load, and for subsonic jet aircraft, the economic flight will probably remain under 5,000 miles. International politics govern the routes that air- craft may fly over land areas. Distances between Europe and North America are short and jet transports fly between major cities in the two areas. In the larger Pacific world, distances are greater and flights between North America and the Orient make an intermediate stop in Hawaii if taking the central Pacific route or in Alaska if taking the shorter northern route. Flights between Europe and Japan avoid the Soviet Union. The route to the south, which must also avoid China, is long and the polar flight to Alaska and thence to Japan is a shorter alternative. Surface shipping using vessels competent in the arctic ice may also develop a shorter route between the North Atlantic and Pacific Oceans. In this case Alaska can also serve as a marine way station between the Atlantic and the Orient. STRATEGIC LOCATION OF ALASKA PLATE 4 saDliue vist 8 bUsc2N poands 1. .ask.__.2 Mai. ‘tk rge mmu es anti ind ’ particularly important since much travel in the southcentral Alaska are connected by roads. state is by air. Generally, airlines radiate The table below-right shows road distances in from the two important centers, Anchorage and miles between many of these towns. Fairbanks, to most points in the state. Smaller systems operate in southeastern Alaska and bush A third important transportation method, ocean operations are found throughout the state. shipping, is used to supply freight services. The table below-left gives distances in nautical miles, between selected ports. (Swiftsure Bank lies in the entrance to Puget Sound.) ROAD DISTANCES BETWEEN TOWNS IN ALASKA DISTANCES BELOW ARE IN STATUTE MILES <@— DISTANCES IN NAUTICAL MILES DISTANCES BETWEEN SELECTED PORTS 170° 7 ARCTIC Fairbanks 194 : 458 DISTANCES “| ~ WITHIN ALASKA sy" Given in statute miles CANADA Physiography is the large-scale topography or landforms of an area. Alaska is divided into four major divisions from south to north: the Pacific Mountain System, the Intermontane Pla- teaus, the Rocky Mountain System, and the Interior Plains (Arctic Coastal Plain). All of these divisions are continuations of features of the western United States and Canada which extend | into Alaska and bend to the west and even south- west. The Pacific Mountain System is a continuation of the Coastal Mountain System of the western United States and Canada. It consists of two arcs; the more northernly and larger comprising the Coast Mountains between southeastern Alaska and Canada, the Alaska Range, the Aleutian Range, and the Aleutian Islands. The southern arc consists of the island range of southeastern Alaska, the Fairweather Range, the St. Elias Mountains, the Kenai-Chugach Mountains and Kodiak Island. Between the two arcs is a trough composed of the Inland Passage, the Copper River Lowlands, the Cook Inlet-Susitna Lowlands and Shelikof Strait. This trough is broken by the Wrangell and Tal- keetna Mountains. The Intermontane Plateaus are comparable to the area between the Rocky Mountains and the Coast Mountains in the 48 states and lie north and west of the Alaska Range. They consist of dissected uplands, broad valleys, and lowland basins floored with alluvial deposits. The great river systems of the Yukon, Koyukuk, Porcupine, Tanana, and Kuskokwim Rivers flow through this area. The Brooks Range is the northern extension of the Rocky Mountain System which turns west as it reaches the Arctic Ocean near the Alaska-Canada border. These extremely rugged mountains reach to over 9,000 feet in the east but are lower to the west. Glaciation during the Pleistocene carved the rugged landform which persists at present with little change. The arctic foothills to the north consist of rolling plateaus and low mountains. The Arctic Coastal Plain, an extension of the Great Plains, is a truly arctic region and consists of a broad level plain underlain with permafrost and pockmarked by thousands of shallow lakes and swamps. Source: U.S.G.S. after Clyd ANTERIOR PLAINS ROCKY MOUNTAIN POINT HOPE, MAJOR NORTH AMERICAN PHYS! OGRAPHIC DIVISIONS IN ALASKA v MATTHEW 1 BERING SEA GULF OF ALASKA UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY ALASKA 1964 ° 200 ——— Miles EXPLANATION High rugg untains (Summits more than 5,000 feet) La Low mountains, plateaus, and highlands of generally rolling topography (Summits 1,000-5,000 feet) Plains an wiands (Generally less than 1,000 feet) _ — Boundary between major physiographic divisions pe Environmental Atlas of Alaska 4/78 PLATE 6. PHYSIOGRAPHIC PROVINCES OF ALASKA Geology is the study of the earth, its rocks, and their record of past events. Most of the state has been subject to geologic reconnaissance but only small areas have had detailed study. About 25 per cent is covered with alluvial deposits, which restrict study of the rocks below. The geologic time scale by which events are dated has been evolving during the last century. One system in current use is shown below. All dates are before the present and are time boundaries. THE GEOLOGIC TIME TABLE Eras Periods Dates Quaternary 10,000 Cenozoi zoic 1-2M* 7OM Mesozoic 225M 600M Precambrian *M indicates millions of years Most Precambrian rocks are not definitely dated and are grouped with Paleozoic rocks. In Pale- ozoic and early Mesozoic times, many parts of what is now continental Alaska were ocean basins. These ocean basins were subsequently squeezed and uplifted in response to the relative motion between the moving plates making up the surface of the Earth. Mid-late Mesozoic seems to have been the time of the most dramatic changes in the geography of Alaska, and many of the motions initiated then persist today. Widespread intrusion of granitic bodies into the existing rocks also occurred during the Mesozoic, presumably also a result of the dynamics of lithospheric plate collision. It is not clear what the geography of Alaska looked like prior to the Mesozoic reorganization, but it must have been very different from that which we see today, with some of the southern parts considerably further south, and northern Alaska possibly adjacent to the Arctic-Canadian islands. During the early Tertiary period (60 to 30 million years ago) extensive volcanic activity occurred, particularly in the Wrangell Mountains, the Alaska Peninsula, and the Aleutian Islands. During this warm period, great peat swamps formed which subse- quently produced the coal deposits in the Cook Inlet region and on the northern side of the Alaska Range. Throughout the late Tertiary (30 to 2 million years ago) volcanic activity remained widespread. Periods of uplift were common, reaching a maximum at about the close of the Tertiary. During the Pleistocene ice age great snowfields formed in the Brooks, Alaska, and Coast Ranges and filled the trough between the Alaska Range and the coast ranges. Great glaciers from the snowfields carved the mountains and valleys of Alaska into their present shape and provided the sediments which now floor the valleys and basins. Plate 10 shows both past and present glaciation. Source: Joint Federal -State Land Use Planning Commission for Alaska, |973 ARCTIC GEOLOGICAL MAP OF ALASKA Sedimentary and Metamorphic Rocks QUARTERNARY TERTIARY MESOZOIC PALEOZOIC AND PRECAMBRIAN Igneous Rocks QUATERNARY AND TERTIARY VOLCANIC ROCKS TERTIARY AND MESOZOIC INTRUSIVE ROCKS BERING SEA GULF OF ALASKA aber bp Ber 5 Environmental Atlas of Alaska 4/78 Ninety per cent of the world's earthquakes occur in the Pacific Earthquake Zone, which borders the Pacific Ocean on the east, north, and west. This active zone follows the Pacific coasts of South and North America north to Alaska. In southcentral Alaska it turns west and then southwest and proceeds along the Alaska Peninsula and the Aleutian Islands. It then continues through Japan and southward to disappear in the South Pacific Ocean. Two earthquake zones are recognized in Alaska. One follows the Coast Range from Vancouver Island northwest through south- eastern Alaska. It is characterized by many small earthquakes with larger shocks occurring at widely spaced intervals. The second major Alaskan earthquake zone runs from the Copper River valley west along the Alaska Peninsula and Aleutian Islands to Kamchatka. Most Alaskan earthquakes occur in this zone. Six per cent of the large shallow earthquakes of the world occur in Alaska. North of the Alaska Range earthquakes occasionally occur but large and destructive earthquakes are rare, particularly in northern Alaska. Very large ocean waves (tsunamis) often accompany earthquakes in the coastal areas of Alaska and tsunamis generated by Alaskan earthquakes often affect coastal communities in Japan, Hawaii, California, and Oregon, and even as far distant as Chile. A warning system operated by the U. S. Coast and Geodetic Survey monitors Alaskan earthquakes and alerts Pacific coastal areas of the danger of tsunamis. Plate 37 shows seismic probability zones for building design in Alaska. Source: Arctic Environmental information & Data Center (1974) to structures NONE less than 3.0 MINOR 3.0-45 MODERATE 45-60 MAJOR greater than 6.0 Potential damage is greater than zone 3 due to Peajovic and tectonic factors (prelimis SEISMIC ZONE BOUNDAR' MAJOR FAULT ry) EA RTHQUAKES IN ALASKA Magnitude : T 5.3 -5.9 ° 60-69 : ° 7.0-77 Oo 7.75-85 Filled circles = hypocenter greater than SOKM © Eowener 0 1964 Eorinquate . Seismic zone data is preliminary, Note: subject to change. # Although no earthquake epicenters are shown in the northern part of Alaska, it is thought shocks do occur but are unrecorded due to lack of appropriate equipment in that area. Permafrost, or permanently frozen ground, is found in most of Alaska. It is continuous in the Arctic and becomes discontinuous and then sporadic or isolated as one proceeds south. Only the southern coasts are free of permafrost. Permafrost is defined as: That part of the lithosphere in which a naturally occurring temperature below 0°C (32°F) has existed for two or more years. This definition does not include moisture as a nec- essary ingredient, so an area of solid rock or well-drained gravel free of moisture is classified as permafrost if it meets the definition above. However, most permafrost contains ice in quantities ranging from partial filling of the soil pore space to massive formations of segregated ground ice. Formation and maintenance of permafrost requires a mean annual temperature below freezing. Ground shading and insulation by ground cover such as mosses is favorable to permafrost. Once permafrost is established, it stops the infiltration of ground water and forces melt and rain water to escape by surface drainage. The mosses that form impede surface drainage and permafrost areas develop marsh and tundra characteristics. The ground at and near the surface that goes through an annual freeze-thaw cycle is called the "active layer" and is from a few inches to several feet thick. Permafrost lies below the active layer, or depth of summer thaw, and extends from a few feet thick in the south to over 1,000 feet in the Arctic. Depths of permafrost are variable even within short distances in the discontinuous and sporadic perma- frost zones and depend upon exposure, ground cover, soil characteristics, and other factors. Measured depths in Alaska (where two or more values are known, the maximum depth is given) include 175 feet near Dillingham, 600 feet at Bethel, 100 feet near Tok, 265 feet near Fairbanks, 350 feet near Nome, 1200 feet at Cape Thompson, and 1330 feet near Point Barrow. Permafrost is of great importance in the engi- neering and design of structures and engineering works such as pipelines, roads, and railroads. Particularly in fine-grained soils, the frozen ground forms an extremely strong and stable foun- dation material if it is kept in the frozen state. However, if the permafrost is allowed to thaw, the soil becomes extremely weak and foundation failures are very common. Engineering practice in perma- frost areas uses three approaches: 1. Avoid it. Particularly in the subarctic zones of discontinuous and sporadic perma- frost, areas free of permafrost can be found. 2. Destroy it. By stripping the surface vegetative cover, the depth of thaw can be greatly increased and the upper levels of permafrost destroyed over a period of years. In other cases, permafrost soils are excavated and the area refilled with coarse materials. 3. Preserve it. Buildings are built on piles so there is no thermal path for heat to travel from the building to the ground. Roads and airports can be built up with gravel fill so that the permafrost below is protected from summer thaw even though the surface vegetation has been destroyed. Refrigeration can be used to maintain low ground temperatures. Source: Ferrians (1965) 150° a BERING SEA Cn b owes Environmental Atlos of Alosko 4/78 / ARCTIC OCEAN Prudhoe Bay PERMAFROST IN ALASKA g Generally underlain by continuous permafrost Underlain by discontinuous permafrost Underlain by isolated masses of permafrost Generally free from permafrost A ‘ew °9, Alaska, with over 51,000 square miles of snowfields and glaciers, contains about two-thirds of the glacial ice on the continent of North America. Most of these glaciers are in southern and southeastern Alaska where precipitation is high. Malaspina Glacier, the largest in Alaska, has an area larger than Rhode Island. Smaller glaciers are found in the Alaska Range but only a few are found in the Brooks Range where precipitation is low. Alaskan glaciers include continental glaciers or snowfields, mountain or alpine glaciers, and the rare piedmont glaciers such as the Bering and Malaspina Glaciers. A respectable number of glaciers reach tidewater and calve in the ocean. However, the Pacific water into which they drop is warm and few icebergs enter shipping lanes. As Plate 10 shows, during the Pleistocene all the mountain ranges and the basin between the coastal mountains and the Alaska Range were covered with ice. However, most of the Intermontane Plateaus and the Arctic Coastal Plain were never glaciated, even during the Pleistocene, because of low precipitation. Source: Coulter et al (1965) ARETIO Vi) 4 Lecag ah eg ake Colville R _ 7 “7\ GLACIATION RITZ ‘7 AZ Yr / y HH goa | IN ALASKA Areas covered by existing glaciers | eee eistocene time Y f , 1 My Ap | J Mh —~_ Outer limit of significant 7, ~. as LO LOE eh yy; Ey Dd ¥, my ane The dense forest shown on Plate 11 is the coastal rain forest found in southeastern Alaska and west along the coast to the Cook Inlet area. This forest is composed of Sitka spruce and western hemlock with occasional mountain hemlock, Alaska cedar, and Douglas fir. The trees are large and extend from tidewater to about 2500 feet. This great forest area is primarily in the National Forests and is one of the great forest resources of the world. The moderate and sparse forests are composed of white spruce, birch, aspen, and willow. In good locations in the Subarctic, trees are moderate in size and used locally. In areas which are marginal due to permafrost or altitude, the forests are stunted and of little economic value. In the mountains above treeline and in the arctic regions, forests do not exist. Plant life is com- posed of creeping shrubs, tufted grass-like plants, lichens, and mosses. Southwestern Alaska (the Alaska Peninsula and Aleutian Islands), which is treeless, represents a special situation different from the alpine and arctic areas. Several specialized terms describing vegetation are used in the north. Tundra, a Finnish word meaning "barren land," is applied to the treeless areas in northern and western Alaska (arctic tundra) and the mountains above timberline (alpine tundra). The plant associations in tundra vary but lack erect trees. Permafrost and patterned ground are characteristic. Taiga, a Russian word, is used in two different ways. It may refer to the sub- arctic forests in general, or it may be restricted to the sparse lichen forests. Muskeg, an Algonkian Indian term, refers to a bog found in poorly drained soils throughout the Subarctic. The mat of tangled vegetation around the border of shallow ponds and lakes continuously en- croaches on the open water and slowly reduces the pond to muskeg and ultimately to a peat deposit. Hopkins has shown a general pattern for Alaskan forests based on a combination of summer warmth measured as degree days above 50°F and the mean temperature of the coldest month. The degree-day concept is discussed in the introduction to Part IV. Using 78 Alaskan stations, all forested stations have more than 130 degree days above 50°F and most nonforested stations have less. This then represents a dividing line, based on summer warmth, between tundra and forest. Of the forested stations, those with a mean temperature for the coldest month above 15°F have dense forest while those below have moderate or sparse subarctic forest. On the basis of Hopkins' work, Kodiak Island, Middleton Island, and Dutch Harbor should be forested. On Kodiak Island the forest is advancing following the last ice age. Middleton Island and Dutch Harbor have no sources of seed. Source: U.S. Dept. of Agriculture, Forest Service (1976) ~ | FOREST TYPES IN ALASKA |_| DENSE FOREST | MODERATE FOREST [| SPARSE FOREST NON - FOREST PART IT ALASKAN WATERS Alaska has tremendous water resources. With an annual runoff of 650 million acre-feet (plus 150 million acre-feet inflow from Canada) it has about one-third the total 2,000 million acre-feet of the entire United States, including Alaska. Ninety-four fresh water lakes have an area of 10 square miles or more. Lake Iliamna (1,000 square miles) and Lake Becharof (458 square miles) rank second and fifth in size for lakes wholly within the United States. The Yukon, with its tributaries, is one of the great river systems of the world. Although it rises in British Columbia, a few miles from the tidewater, it flows 1,800 miles through British Columbia, Yukon Territory, and Alaska to empty into the Bering Sea. Other major rivers include the Copper, Susitna, Kuskokwim, Kobuk, Noatak, and Colville besides the many smaller rivers flowing from the Coast Mountains into the sea in southeastern Alaska. Part II covers coastal and ocean waters, their depths, currents, temperatures, ice and tides in Plates 12 through 18. Plate 16 shows the river ice seasons and Plate 18 shows the water crop: the fresh water runoff. Due to its great size, peninsular character, and complexity, Alaska has much of the total United States shoreline. General * Tidal Shoreline Shoreline U.S. Total 12,383 mi. 88,633 mi. Alaska 6,640 33,904 Alaska Percentage 53.7% 38.4% General shoreline represents the general outline of the sea coast while tidal shoreline is a measure of the actual shoreline. Both were taken from maps of the coastal areas. In addition to its extensive coastline, Alaska is bounded on the west and northwest by tremendous continental shelf areas (see Plate 12). No real survey of Alaskan fresh water resources has been made. Plate 18 and its discussion point out some general features of the fresh water situation. * U. S$. Coast and Geodetic Survey, 1961 The Pacific coasts of Alaska from southeastern Alaska to the Alaska Peninsula shelve fairly rapidly and have a continental shelf (from the shore to the 100 fathom line) from a few miles to a few tens of miles wide. Beyond the continental shelf, the water depths soon reach 1,000 fathoms. Farther west in the North Pacific Ocean the Aleutian Trench lies immediately south of the Alaska Peninsula and the Aleutian Islands and little continental shelf exists. This great trench, with depths over 25,000 feet, is comparable to the other great trenches in the Pacific Ocean. The Aleutian Trench and its parallel island arc are the source of many Alaskan earthquakes which occur on the north side of the trench. North of the Aleutian Islands, Alaska is bordered by the shallow Bering and Chukchi Seas. The continental shelf in the Bering Sea is up to 400 miles wide and, to the north, the Chukchi Sea remains less than 100 fathoms deep for about 9 degrees of latitude north of the Bering Strait. To the east of Point Barrow, the continental shelf again narrows to a few tens of miles. The table below shows that the Alaskan continental shelf area is two-thirds of the total United States continental shelf area. Continental Shelf Area Region Sq. Mi. = Alaska 550,000 65 Pacific (Wash., Ore., Calif.) 25,000 3 Gulf of Mexico 135,000 16 Atlantic states 140,000 _16 850,000 100 Source: U.S.C.&G.S. Charts 9000,9302,9400 Fairbanks BERING SEA Ae Environmental Atlos of Aloska 4/78 / DEPTHS OF ALASKAN , COASTAL WATERS Given in fathoms 160° PLATE 12 Summer and winter ocean currents off Alaska are similar, as Plate 13 shows. However, the data shown are very general and must be used with care. The Japanese Current (Kuroshio or North Pacific Drift) rises in the area of the Philippine Islands and Formosa, flows northeast along the main Japanese Islands, and then flows northeast and then east to strike the west coast of North America in the region of Oregon and Washington. A tremen- dous eddy, the Alaska Current, swings north and follows the southern Alaska coastline in a return flow pattern and moderates the Alaskan coastal climate. Limited quantities of Pacific water enter the Bering Sea, producing a net flow through the Bering Strait into the Arctic Ocean. Along the Alaskan arctic coast, a weak current flows westward to the Point Barrow region where it swings north. In addition to the general circulation patterns, coastal currents include wind currents and tidal currents. Tidal currents may be very strong in southeastern Alaska, the Cook Inlet-Kodiak area, and Bristol Bay because of the high tides in these regions. Source: U.S.W.B. & US. Navy H.0. (1958 & 196!) CURRENTS OF ALASKAN COASTAL WATERS in knots Environmental Atlas of Alaska 4/78 PLATE |3 160° 150° T eg or 100 2 P9510! go 03 1 s CSS Foon } <M The warm Alaska Current which flows north from southeastern Alaska into the Gulf of Alaska is shown in the summer sea temperatures by the lobate temperature pattern. In addi- tion, the flow of relatively warm Bering Sea water through the Bering Strait into the Arctic Ocean is shown by a similar lobate pattern. Summer warming occurs and is par- ticularly pronounced in protected shallow areas such as Norton and Kotzebue Sounds where summer sea temperatures rise above 50°F. Ice may be found in the Arctic Ocean off Point Barrow and to the eastward during the summer-fall depending upon summer melting and the effect of winds blowing pack ice on shore. This ice keeps the summer temperature of these waters near 32°F. Summer sea temperatures off Alaska are low compared to those near Scandinavia where the relatively warm ocean water, lack of tidal mixing, and clear spring and early summer weather create bathing areas claimed to be warmest along the European coast north of the Mediterranean Sea. During the winter the Alaska Current keeps the southern Alaska coast free of ice except in protected waters. When sea ice forms off the northern and western Alaska coasts it greatly reduces the moderating effect of the seas and winter air temperatures off-shore will be as cold as those on land. The lower surface of the sea ice and the water below will be at the freezing point of the sea water (29°F) but the upper surface of the ice and snow will be at the cold, ambient temperature. Source: U.SW.B. & U.S.Novy HO. (1958 & 1961) SEA TEMPERATURES OFF ALASKA, °F Temperatures in vicinity of ice approach 30°F Environmental Atias of Alaska 4/78 PLATE |4 Sea ice forms when the sea temperature reaches about 29°F, since the salts in the water depress the freezing point below that of fresh water. However, the freezing process excludes most of the salts and sea ice is much less salty than the water from which it is formed. During the early thaw period in the spring or summer, the salts in the ice tend to drain; and it is widely known that much sea ice during the summer is fresh enough to be used for melting and drinking. As a result, while sea ice freezes at 29°F, it melts at about 32°F. Average sea ice coverage during the summer (August) is shown in the top left of Plate 15 and the average coverage during the winter is shown in the lower right portion of the plate. The actual coverage during the summer is controlled primarily by winds in the Arctic Ocean, which may blow the pack ice in the Arctic Ocean either on or off shore. Sea ice production in the Bering Sea is controlled by winter temperatures, which are quite variable. The actual location of the ice that is formed is affected by the winds which often blow sea ice south against the Alaska Peninsula. No sea ice forms in the open North Pacific Ocean or along the Aleutian Islands. All harbors on the south side of the Alaska Peninsula are free of ice. Ice may occasionally form during an extremely cold spell in the inland waterways of southeastern Alaska and the arms of Prince William Sound. Ice forms each winter in upper Cook Inlet above Anchor Point and often makes navigation into Anchorage difficult or impossible without ice-breaking or strengthened ships. Source: Swift et al (1974) SEA ICE DISTRIBUTION Consolidated or Fast, !.0 Coverage Close, 0.8 -0.9 Coverage Broken, 0.5 -0.7 Coverage Scattered, 0.1 -0.4 Coverage Open < 0.1 Coverage Approx. max. extent of O.! or greater coverage 150° “WINTER Note: } c SCATTERED PIECES OF ICE MAY BE y~ ebruary, ENCOUNTERED BEYOND THE EXTREME LIMIT. Set e forms each inter in upper Agok Inlet eur Kade OF ALASKA ¢ i Environmental Atlas of Alaska 4/78 ae PLATE 15 Average dates of ice freezeup and breakup at selected stations are shown in Plate 16. River stations are shown as circles while coastal stations with sea ice are shown as squares. Three types of ice govern water transportation in Alaska: river ice, coastal sea ice, and ice in the open ocean. Each type has its own seasons and its own importance. River ice forms and breaks up earlier than sea ice. In addition, as shown by the Yukon on Plate 16, rivers break up earlier at the head than at the mouth, a fact that is responsible for the ice jams in the rivers during spring breakup. Variability in breakup date is the basis of the Nenana Ice Classic, the major spring sport in Alaska. The ice on the Tanana River at Nenana has gone out on the following days from 1968-1977: 1968 May 8 1973 May 4 1969 April 28 1974 May 6 1970 May 4 1975 May 10 1971 May 8 1976 May 2 1972 May 10 1977 May 6 Coastal sea ice forms and melts earlier than the ice in the open ocean. Plate 16 shows that coastal sea ice in the Bering Sea and Arctic Ocean breaks up during May and June. However, the ice in Norton Sound is not generally navigable before the middle of June. The ice in Bering Strait and Kotzebue Sound begins to break up by early June and is passable during the latter part of the month. Ice in the Chukchi persists later. At Point Barrow the pack ice breaks off from the shore ice in June. The shore ice leaves the beach in late July but remains in sight until the middle of August or later. Pack ice may remain on or near Point Barrow until late summer and occa- sionally remains throughout the sumner. Eastward of Point Barrow, the pack ice seldom goes far offshore, and ice movement and coastal navigation along the arctic coast is controlled primarily by winds. Source: U.S.C.&6.S (1964) A RIVER AND COASTAL ami)_| ICE SEASONS COASTAL ICE, Average 5/l Date, breakup UI/'9) Date, freezeup RIVER ICE, Average Date, breakup \ors/ Date, freezeup Lb ae . Bo Vans Environmental Atlos of Alosko 4/78 Tides in Alaska vary from very high in parts of southeastern Alaska, Cook Inlet, and Bristol Bay to essentially zero in the Arctic Ocean. Plate 17 shows the extreme high and low tides forecast for 1966. Average tides, of course, are substantially smaller than those shown. In addition, Plate 17 shows tidal co-range lines for Alaskan waters. These are lines of equal average tidal ranges, given in feet. As can be seen from the plate, average tidal ranges are much lower than the tidal ranges that can be computed from the extreme high and low tides. Most of Alaska has two tides per day. However, in the Bering Sea from Dutch Harbor north, diurnal tides (single high and low tides during the day) are normal during parts or all of the month. At Dutch Harbor, this occurs when the moon reaches its maximum north and south declination. Bristol Bay with its very high tidal range is an exception and has two tides per day. In addition to normal tides, the western Alaska coast is subject to wind tides. Strong westerly winds may cause a rise in the seas of several feet on these shallow shelving coasts. The strong tides in southeastern Alaska, Cook Inlet, and Bristol Bay cause strong tidal currents during ebb and flood tides. In addition, strong tidal currents are found in passes through the eastern Aleutian Islands. 1966 Tide Tables and Swift,|974 170° 7 Source: U.S.C.&G.S. ARCTIC IEXTREME TIDES AT | ALASKAN HARBORS __| PRIMARY STATIONS |e Maximum High Tide 1966 Maximum Low |oTHER STATIONS = St. Michael “13.2 Maximum High . : ree ai Maximum Low Tide 1966 22 85. a . . Cape Romanzof res corange lines = mean maximum semi-monthly tide ranges, in feet. 3.9 == Bethel Anchorage -0.5 -6.0 s 14.8 Valdez | 20. = (15.4) 15.1 14.3 : 7 Eek Kenai R. 2&9 -3) C37 Cordon — Nn 20.8 Entrance ~ 16 23-1 clarks Pt. wi -3.0 we 4.6 BERING : : -3.7 rss ? ES tey Boy Bowel § ? 3e Middleton Is. nay -3.0 SEA Hn Seldovig /O 2 Petersburg —™ tethkan 160° PLATE I7 The annual Alaskan water crop or runoff is 800 million acre-feet (MAF), of which 150 MAF is inflow from Canada. Of the 48 contiguous states, those east of the Mississippi have an annual water crop of 660 MAF and those west of the Mississippi have 680 MAF. Consequently, Alaska, with one-third of the total water crop of the nation, is rich in water resources which are almost completely unused. This has led to suggestions that Alaskan water be carried south in continental water management and supply systems, The statement is made that Alaska has no water supply problems foreseeable in the next decade or two. However, while the water crop is large, it is not evenly distributed in space or time; and an investigation by regions shows that this general- ization is not entirely true. The southern coasts of Alaska are rich in water. Precipitation is as high as 200 inches per year and occurs throughout the year. Even here, water short- ages occasionally happen, usually in the winter when precipitation falls as snow. However, the rest of the state is in a much less favorable situation. Central and western Alaska, with 12 to 20 inches of precipitation per year, have generally adequate water supplies for the present and near future. A mature drainage pattern channels available runoff into a well-developed stream system thus concen- trating the waters. However, winter lasts for 5-6 months and all precipitation during that season falls as snow. Total precipitation varies greatly from year to year. Streams have a characteristic flow pattern with high flow during spring breakup, moderate but variable flow during the summer, and low flow during the winter. Because of the vari- ability, water development and conservation may be required locally with population increase and indus- trial development. Northern and northwest Alaska are water poor. Precipitation is low--as low as 4 inches per year-- the winters long, and most villages are located at sites without favorable water supplies. All but the largest rivers freeze to the bottom and flow declines greatly during the winter. As the villages grow into towns, with increased population and per capita consumption, the situation becomes serious. Distillation desalination equipment has been used at Kotzebue and Barrow by the federal government for years. Nonetheless, as Plate 18 shows, Alaska has a tremen- dous water crop. Essentially none is used at present and the only current proposals with economic merit are based on developing the hydroelectric potential of the Susitna River in Devil Canyon. Source: Norwood and Cross (1968) Islands 15, \ t Fairbanks ALASKAN WATER CROP Millions of acre - feet Note: ALASKA WATER CROP TOTALS 800 MAF PER YEAR, INCLUDING 150 MAF INFLOW FROM CANADA. PART III LIGHT Alaskan latitudes receive, on an annual basis, a small bonus in extra sunlight and a large bonus in extra twilight over lower latitudes. The sun, in rising or setting, crosses the horizon at a shallow angle at the northern latitudes and consequently takes longer to rise or set. This lengthens the day slightly and the twilight a great deal. In addition, refraction, or the bending of the sun's rays by the atmosphere, lengthens the day by making the sun visible even when it is below the horizon. Refraction is small in the tropics but fairly large in Alaska, particularly during the winter. The table below shows the percentage of the year that is twilight, sunlight, and both at various latitudes. Sunlight and Latitude Twilight Sunlight Twilight °N % & a 0 3.10 50.30 53.40 25 3.49 50.50 53.99 35 3.92 50.60 54.52 45 4.68 50.75 55.43 55 6.24 51.03 57.27 60 8.11 51.28 59.39 65 10.39 51.87 62.26 70 10.94 51.97 62.91 75 8.93 51.89 60.82 Alaska receives most of its sunlight during the summer. Sunlight distribution patterns vary from that at the equator, where day and night are each 12 hours throughout the year, to the opposite extreme at the poles, where continuous sunlight occurs during the spring-summer and the sun is continuously below the horizon during the fall-winter (see Plate 19). The Arctic Circle (6645°N) separates the area to the north which receives continuous sunlight during part or all of the summer and no sunlight during part or all of the winter, from the area to the south, which has long summer days and long winter nights but in which neither reaches 24 hours. However, in all parts of Alaska, most of the annual sunlight is received during the summer. The sun is never overhead in Alaska. During the longest day of the year the sun only reaches 234°N latitude. North of that point it can only shine obliquely at the earth. The maximum height it can reach above the horizon for any place can be calculated by subtracting the latitude from 113%°. Thus at 65°N at Fairbanks, the highest the sun reaches is 113's°-65°=48%° (see Plate 19). Since the sun's rays strike the ground at an angle in higher latitudes, the energy received on the ground surface is less that it would be if they struck from directly overhead. Thus, radia- tion intensity is lower than at lower latitudes. However, the days are longer and total daily radiation received during the summer is approxi- mately equal to that at lower latitudes. Plates 20, 21, and 22 show the duration of sun- light, twilight, and both at Alaskan latitudes throughout the year. The sun path diagrams in Plate 19 show the overhead position of the sun for latitudes 55°N (Ketchikan), 60°N (Seward), 65°N (Fairbanks), and 70°N (Prudhoe Bay). From these diagrams, the altitude and azimuth of the sun can be determined for any date and time. The altitude, or elevation in degrees of the sun above the horizon, is determined from the concentric circles on the diagrams, while the azimuth is deter- mined from the radial lines. The outer circle (0°) respresents sunrise and sunset. Apparent solar time is given by the heavy lines perpendicular to the sun paths. In these diagrams the effects of the diameter of the sun and refraction are not taken into considera- tion. The curved lines labelled "a" through "k" on the diagrams depict the path of the sun on various dates of the year. Paths "j" and "k" do not show on the 70°N diagram since the sun is below the horizon between the dates of November 22 and January 21. As an example of how to use the diagrams, one can follow the sun path for a given location on a given date. For instance, in Nome (approximately 65°N) on May 1 (line "c"), the sun rises at about N53°E at approximately 3:45 a.m. apparent solar time. At noon the altitude of the sun is about 40° above the horizon in the south. Sunset is at approximately 8:15 p.m. apparent solar time at about 307 degrees azimuth. (To obtain true local time it is necessary to add algebraically a correction for the equation of time to the apparent solar time. Details may be found in any basic surveying text). Since the altitude of the sun varies greatly with latitude and date, so does the energy received at the earth's surface. The following table shows radiation patterns throughout the year at various latitudes for surfaces with various orientations. Total Daily Direct Solar Radiation in Btu/ft- Received on Surfaces with Various Orientations Transmission Coeffictent = 0.9 and Solar Constant Taken as 2.0 cal/” min Feb Mar May June Aug Sept Nov Dec Latitude,° 4 21 6 22 8 23 8 22 (a) Horizontal Surface 90N 0 0 2020 3135 2000 0 0 0 70 20 755 2170 2940 2150 745 20 0 60 310 1265 2470 3035 2445 1245 300 60 50 765 1730 2730 3145 2700 1705 760 405 40 1260 2135 2910 3195 2885 2105 1245 870 (b) Vertical Surface Facing North 70 0 0 390 1590 385 0 0 0 60 0 0 215 650 215 0 0 0 50 0 0 140 450 135 0 0 0 40 0 0 140 385 135 0 0 0 (c) Vertical Surface Facing South 70 480 2210 2045 1805 2025 2175 475 0 60 1520 2175 1770 1450 1750 2145 1505 690 50 2035 2070 1400 1015 1385 2040 2015 1645 40 2190 1810 965 560 960 1785 2170 2085 (d) Vertical Surface Facing East or West 70 60 820 1730 2100 1710 805 55 0 60 320 975 1585 1830 1570 960 315 90 50 575 1065 1445 1640 1430 1050 565 325 40 755 1150 1395 1465 1385 1135 750 555 (e) Vertical Surface Facing Any Direction 90N 0 QO 2210 2315 2190 0 0 0 Note: All figures rounded to nearest 5 units. From: Scott, 1964 Source: Smithsonian Meteorological Tables, 1966 DECLINATION DATES PATH NK MNONANN Sescassvose 2EEK< EEUU TS eco NNR KH NOMKK NN vee env e+ Ofer Environmental Atlas of Alaska 4/78 PLATE 19. SUN PATH DIAGRAMS The length of daily sunlight changes rapidly throughout the year in all of Alaska except when days are longest and shortest. The change is, of course, greatest above the Arctic Circle, where the period goes from zero sunlight to 24 hours of sunlight over a span of a few months. Twenty-four-hour sunlight in the summer extends somewhat farther south than zero sunlight in the winter due to the effects of the semidiameter of the sun and refraction (20' and 16' of arc respectively are average values used). The proportion of the annual sunlight budget that is received during the spring-summer (March 21 - September 21) varies with latitude. The table below shows the distribution of sunlight between the spring-summer and fall-winter seasons for different latitudes. Annual Sunlight Latitude Summer Winter 55° 63% 37% 60 66 34 65 71 29 70 79 21 PLATE 20. SUNLIGHT IN NORTHERN LATITUDES Twilight (civil twilight) is the period when the sun is below the horizon but not more than 6° below. During this period many outdoor activities can be carried out without artificial lighting. This is particularly true in a snow- covered landscape, which makes maximum use of available light. Twilight increases as latitude increases with two important exceptions: 1. North of 604°N during the summer, evening twilight overlaps morning twilight and the net period shortens. North of the Arctic Circle it goes to zero as the mid- night sun appears. 2. North of the Arctic Circle during the winter, twilight again decreases as the sun remains below the horizon. It goes to zero north of 72%° where the sun remains more than 6° below the horizon. However, even Point Barrow, the northernmost point in Alaska, receives some twilight throughout the winter. nywonmentgl Atigs of Alaska 4/78 PLATE 21. TWILIGHT IN NORTHERN LATITUDES Sunlight plus twilight forms the period during which outdoor activities can be carried on without artificial lighting. Plate 22 shows that all of Alaska except the southern part has a 24-hour summer light period centered on June 21. This 24-hour light period is longer at higher latitudes and, at Point Barrow, it runs from late April past mid- August. Environmental Atlas of Alaska 4/78 PLATE 22. SUNLIGHT PLUS TWILIGHT IN NORTHERN LATITUDES PART IV CLIMATE A good definitive description of the Alaska climate is not possible at this time. Weather stations are generally widely scattered, particularly in south- western Alaska and the Arctic where the few stations provide data that is only a sampling of the areas. In addition, most data is collected from coastal and river valley stations and very little is known regarding weather in the hills and mountains. Two primary systems have been used to classify the Alaska climates: 1. Searby used the presence or absence of marine influences to divide Alaska into Maritime, Transitional, Continental, and Arctic Zones. 2. A conventional system based primarily on forests divides Alaska into temperate, sub- arctic, and arctic zones. Searby's zones are shown on Plate 23. Precipitation and temperature information, which is in part the basis for this classification, is shown in succeeding plates. The zones of the conventional system are shown on Plate 1. The problem of defining the boundaries of the temperate, subarctic, and arctic zones is one that has exercised many individuals for more than half a century. One definition in general use for the Northern Hemisphere and used in Plate 1 is as follows: Arctic lands have no months with mean monthly temperatures greater than 50°F and have at least one month with a mean temperature 32°F or colder. Subarctic lands have from one to four months with monthly mean temperatures greater than 50°F and at least one month with a mean tem- perature 32°F or colder. These definitions, like many others, are efforts to define the boundaries between the different types of forests shown on Plate 11. These forests are three main types: temperate climate dense forest, subarctic climate moderate and sparse forest, and nonforest or tundra. The nonforest is composed of the arctic tundra on the north and west margins of the state, the alpine tundra in the mountains above timberline and the nonforested Alaska Peninsula and Aleutian Islands, which lie in the Subarctic. It is apparent from comparison of Plates 1 and 11 that the boundaries given by the above definitions do not fit perfectly in Alaska. Searby divided Alaska into four major climatic zones as shown on Plate 23. Brief descriptions of the climates are: Maritime: Transitional: Continental: Arctic: Dominated by maritime influences. Small tem- perature variations, high humidity, heavy precipitation, and high cloud and fog frequen- cies. Little or no freezing weather. Cool summers and warm winters. Surface winds strong and persistent. More pronounced temperature variations through- out the day and year, less cloudiness, lower precipitation and humidity. Surface winds generally light. Mean annual temperature generally 25-35°F. Dominated by continental climatic conditions. Great diurnal and annual temperature variations, low precipitation, low cloudiness, and low humidity. Surface winds generally light. Mean annual temperature 15-25°F. Temperature variations lower than the conti- nental, precipitation is extremely light and strong winds are not uncommon. Mean annual temperature 10-20°F. The arctic climate may be affected by marine influence in the summer but not to any great extent in the winter. Surface winds strong along coast, but decrease inland. The range of seasonal temperature variation for each zone is given in the discussion of Plate 31. The seasonal lag of the temperature pattern is also given in the discussion of Plate 31. Source: Arctic Environmental Information & Data Center (1974) - - | CLIMATIC ZONES | OF ALASKA M MARITIME TRANSITIONAL CONTINENTAL ARCTIC oy ie 4 SIA AR TY SR 6 QU Environmental” Atlos ot Alosk PLATE 23 Mean annual precipitation varies from over 300 inches in parts of southeastern Alaska to 4 inches along the Arctic coast. The Pacific Mountain System, and particularly its southern arc, intercepts much of the moisture in the air leaving the North Pacific Ocean. To the north, additional mountain ranges dry the air further and mean annual pre- cipitation decreases. North of the Brooks Range, it drops as low as 4 inches per year. The cool Bering Sea is a relatively poor source of moisture and the Arctic Ocean supplies little moisture for precipitation. The Interior and Arctic regions are often incorrectly classed as semiarid and arid because of their low rainfall. However, due to permafrost, which prevents subterranean drainage, and low evaporation and transpiration rates (particularly during the winters) water needs are less than in lower latitudes. The Interior is generally adequately supplied with water and contains large areas of wet muskeg and lakes and has significant river runoff. In the Arctic, the myriad shallow lakes disguise the fact that water supplies are limited though the area never exhibits the standard desert environmental characteristics. Source: National Weather Service (1972) ARCTIC : OCEAN fudhoe Bay DATA IS—-GRNERALLY FROM _ LOW--YING COASTAL AND co? RIVER VALLEY AREAS. IT 71 — IS PROBABLY NOT VALID 7 a hs, FOR HIGHER ELEVATIONS. Ft. Yukon C) a | 16 Ce [ona Atlos of Aloska 4/78 / 60° 150 140° PLATE 24. MEAN ANNUAL PRECIPITATION IN ALASKA Wet days per year (a wet day is defined as one with 0.1 inch or more of water precipitation) are a means of measuring the effect of precipitation on human activities. Plate 25 shows that the number of wet days decreases from south to north and from west to east in Alaska with a minimum of 20 to 30 in the north and northeast parts of the state. Up to 200 wet days per year are found on the outer islands of southeastern Alaska. Most of the state has about 40 wet days per year. Plate 26 shows the seasonal distribution of wet days for 10 stations. US.W.B. (1965) | WET DAYS PER ~wn _|YEAR IN ALASKA , A wet day has 0.1 inch or Xt | more of water precipitation Note: DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS. IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS. PLATE 25 See comments opposite Plate 25. The seasonal pattern of wet days (and thus precipitation) can be shown by the probability of a wet day. Plate 26 shows this probability, by weeks, throughout the year for 10 stations. Of the stations shown, Kodiak, and to a lesser extent Homer and Kasilof, are affected by the North Pacific Ocean. The other stations are more continental and show a well-defined precipitation pattern with maximum probability of a wet day during the late summer. A secondary maximum occurs about February. Late spring and midwinter have very low values. Homer and Kasilof follow this pattern except that the probability of a wet day remains fairly high during the winter. Kodiak has its own pattern. The data used was obtained from Feyerherm, Bark, and Burrows. A smoothing technique was used to remove large irregularities in the data. The study contains additional information of interest in this general field. Source: Feyerherm, Bark and Burrows Fort Yukon — MAY JUNE JULY AUG SEPT OcT NOV DEC Environmental Atlas of Alaska 4/78 PLATE 26. PROBABILITY OF A WET DAY AT SELECTED STATIONS Snowfall is extremely low in Arctic Alaska, among the high- est in the world in the southern coastal mountains, and moderate in the regions between. Snowfall in the coastal mountain ranges provides the source of supply for the snow- fields and glaciers that cover about 20,000 square miles of the state. An impression of the rate of snowfall in this area can be obtained from Thompson Pass (near Valdez), which has recorded up to 225 inches in a single month. On the north and west coasts, snowfall is light to moderate, but the winds continuously rework the snow into drifts. In the Interior, winter winds are low and this combined with the forest cover in the area leaves the snow relatively undisturbed after it falls. In both areas winter thawing is rare and snow, once fallen, tends to persist until spring. South of the Alaska Range, winter thaws often melt the snow on the ground, and snow that falls along the coast seldom remains more than a few weeks. The average density of freshly fallen snow is about 0.10 but is probably lower in the Interior and higher in the southern coastal areas. The density increases from mechanical breakage of the snowflakes during drifting, packing due to snow load above, and recrystallization. Bilello showed that average winter snow densities for snow on the ground vary from 20 to 35 per cent water by volume, and he associated high densities with low average winter temperatures and high average winter wind velocities. His values for average winter snow densities are approximately: Interior Alaska 0.20 to 0.24 gm/cc South of the Alaska Range 0.25 Western Alaska coast 0.28 to 0.30 Arctic coast 0.32 to 0.33 Source: National Weather Service (1972) SNERALLY FROM [NG COASTAL AND RIVER VALLEY AREAS. IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS. -7| Plate 28 shows the mean minimum and maximum temperatures for January in Alaska. It can be seen that the coldest tempera- tures are in the most continental portion of the state near the Canadian border. Since January is, in general, the coldest month in the state, the plate provides a picture of the extreme temperatures that can be expected during a typical winter. The absolute minimum temperatures recorded at a number of Alaskan stations are shown on Plate 37. Source: Watson (1959) MEAN MINIMUM AND MAXIMUM JANUARY TEMPERATURES, °F DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS, IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS, Environmental Atias of Alaska 4/78 PLATE 28 Plate 29 shows the mean minimum and maximum temperatures for July in Alaska. It can be seen that the highest temperatures are in the most continental portion of the state near the Canadian border. Since July is, in general, the warmest month in the state, this plate provides a picture of the highest temperatures that can be expected during a typical summer. Source: Watson (1959) MEAN MINIMUM AND MAXIMUM JULY TEMPERATURES, °F <a ae Wen | a 1B. wD MAXIMUM | DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS. IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS. Environmental Atias of Alaska 4/78 PLATE 29 Mean annual temperatures for Alaska are seen to decrease from south to north in a fairly regular pattern. Mean annual temperature ranges for the different climatic zones are discussed opposite Plate 23. All of Alaska except the southern coastal areas has a mean temperature below freezing (32°F). Mean annual temperatures are primarily of value ag reference temperatures and do not describe the temperature regime of the state. However, when used in conjunction with the sea- sonal temperature variation, a fairly good description of the temperature regime is possible. This technique is described opposite Plate 31. : Searby (1976) 3 ann MEAN ANNUAL-7 | TEMPERATURE 20.gee\ | OF ALASKA, °F Note: 22.5 DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS. IT | IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS. Environmental Atlos of Alosko 4/78 Daily mean temperatures for any place north of the tropics can vary in a seasonal pattern controlled primarily by the declination of the sun. The annual pattern of mean temperatures is sinusoidal because of solar control but the amplitude and phase of the curve depends upon the setting and characteristics of the individual place. For published Alaska stations (U. S. Weather Bureau, 1965) the amplitude and phase for each station were determined by fitting a least-squares sine curve to monthly mean temperatures and were used to develop Plate 31. This amplitude is called seasonal temperature variation in this atlas. During the summer the mean temperature rises above the mean annual temperature by the amount of the seasonal temperature variation and during the winter it falls below the mean annual temperature by the same amount. For example, if a station has a mean annual temperature of 25°F and seasonal temperature variation of 30°F, the mean temperature in the summer will reach 55°F (25+30) and fall to -5°F (25-30) during the winter. Seasonal temperature variations for different climatic zones (see Plate 23) are approximately as follows: Maritime 12-14°F Transitional 20-30°F Continental 32-42°F Arctic 28-32°F The extreme value of 42°F around Fort Yukon shows that mean temperatures vary 84° throughout the year. Real temperatures vary a great deal more and Plate 37 shows that Fort Yukon has an absolute minimum temperature of -75°F, an absolute maximum of 100°F, and thus an absolute temperature range of 175°F. Seasonal temperature variations drop to around 12°F in some locations but the absolute temperature range for all places in Alaska probably exceeds 75°F. The sun's declination follows approximately a sine curve with maximum north declination about June 21 and maximum south declination about December 22 each year (see Plate 19). The temperature patterns for Alaskan stations also follow a sine curve but, because of heat storage, the maximum and minimum mean temperatures lag behind these dates. The amount of lag is variable, being smallest in the Continental Zone (18-21 days), intermediate in the Transitional Zone (to about 26 days), and maximum in the Arctic and Maritime Zones (around 32 days but up to 45 days in the Pribilof and Aleutian Islands). This lag means maximum summer temperatures would be reached in the Interior about July 10 but would be delayed until about August 5 in the Pribilofs. Since mean temperatures over a period of a year follow a sine curve quite closely, the mean temperature for any point in Alaska for any day can be calculated using the information shown on Plates 30 and 31. The general equation is an MAT + (TVAR x Sine (X-@)) MAT is the mean annual temperature, TVAR is the seasonal temperature variation, X is the day of the year expressed in radians, and $ is seasonal lag. To simplify calcu- lations, the quantity "Sine (X-9)"" can be determined graphically on Plate 31 where it is called "Seasonal Index," SI. The above equation then reduces to T = MAT + (TVAR x SI) mean To demonstrate the technique, the mean temperature for Nome on September 15 can be calculated. From Plate 30, MAT is 25°F From Plate 31, TVAR is 26°F From Plate 31, Seasonal lag is 32 days Enter the seasonal index portion of Plate 31 with seasonal lag in days and move to the right to the appropriate date. Moving vertically up the diagram a seasonal index of 0.63 is obtained. The solution is obtained by substituting these values in the above equation T = 25 + (26 x 0.63) = 41.4°F mean The mean temperature for Nome in September, which is also very close to the mean temperature for the 15th of the month, is 41.9°F. Mean temperatures obtained for weather stations using this solution are normally within 1-2°F. However, this technique makes it possible to determine a daily mean temperature for any point in the state and is not restricted to weather stations with adequate records. The accuracy for stations in hills and mountains is probably poor because of the unknown effect of relief on the mean annual temperature and the seasonal temperature amplitude. DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS, IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS, Environmental Atlas of Alaska 4/78 PLATE 3| 2 ALASKAN SEASONAL TEMPERATURE -06-. Days” 08 06 04 02 fe) -02 04 I | + Lt | Lag o4 16 4S se pe ELT EET A PLE EEE + _ _ _ 7 Z — Z| ZL. SEASONAL INDEX The diurnal temperature variation--difference between daily high and low temperatures--varies with the type of climate and time of year. However, the change with time of year is not large--usually less than 25 per cent of the mean annual value--so that the mean annual diurnal temperature variation is a fair measure of daily temperature variation throughout the year. Plate 32 shows a decided similarity to the seasonal tempera- ture variation shown on Plate 31. Areas of high seasonal temperature variation have high daily temperature variation, and areas of low seasonal temperature variation also have low daily temperature variation. In general, minimum daily temperatures are found at or before sunrise and maximum temperatures are found during the afternoon. However, the precise pattern varies with the station, time of year and weather at the station. Source: M.A. Arkin, U.S. Dept. of Commerce WIND VELOCITY (MPH) 4 5 10 15 20 25 30 35 40 45 ORY BULB TEMPERATURE (°F) 4 5 10 15 20 25 30 35 40 45 WIND CHILL EQUIVALENT TEMPERATURE Environmental Atlas of Alaska 4/78 PLATE 33 WIND CHILL COOLING RATE (KG CAL/M?/HR ) 3000 2500 2000 1000 500 TEMPERATURE (°F) -60 -50 -40 -30 -20 -10 oO —- 10 20 30 40 50 CAL M aL -60 -50 -40 -30 -20 -10 ae ae WIND CHILL INDEX —— 10 20 = =030 NOMOGRAM 40 50 60 PART V ENGINEERING INFORMATION Knowledge of the temperature pattern of a place makes it possible to measure various thermal loads over a period of time, usually one year. Of particular interest and in standard use are heating, freezing, and thawing loads measured in degree days per year. Heating loads, measured below 65°F, provide information on which the annual fuel requirement for a heated building can be calculated. The freezing index (degree days below 32°F) provides a basis on which to calculate the depth of annual ground freezing or ice thickness, and the thawing index (degree days above 32°F) provides a measure of ground thaw during the summer. Degree days are a cumulative measure of the duration and magnitude of a thermal load. For example, consider heating load. House heating begins when the air temperature is near 65°F, the index temperature. If a particular day has a mean temperature of 50°F, the heating load for the day is 15 degree days (65-50). For the entire year the heating load is the sum of the daily degree days. If the mean temperature for.a particular day is higher than 65°F, there is assumed to be no heating and thus no heating degree days--if air conditioning were used, this might contribute to a cooling load which would be considered separately. The drawing below shows heating degree days. HEATING DEGREE DAYS (FOR ONE YEAR) Aa 5525505555 QQ OOO OQOOOOO ESS QEXRK KKK KKK H4 / Whey EIR K RK TEMPERATURE OOOO SO 7 2 NRK I HHCY <k nesestatetetatetetgtetetetetet 4 « GRY t ME AN RRR KRY RRR TEMPERATURE RQ w e Plate 37 presents design information, such as windload and snowload, useful for building design. The freezing index, or degree days below freezing, can be used to calculate the depth of ground freezing during the winter, the depth of ice that will be formed on a lake, or the amount of heat which must be added to an exposed water tank to keep it unfrozen. The Alaskan freezing index varies from zero in the extreme south to about 8,500 degree days along the arctic coast. North of the Bering Strait, the lines of equal freezing index at the coast are linear with values farther inland, reflecting the frozen condition of the northern Bering Sea and Chukchi Sea during the winter. In the central and southern Bering Sea a curved pattern shows the influence of the unfrozen sea in that area. The southern limit of isolated permafrost (Plate 9) falls about on the 2,000 degree day freezing index on the Alaska Peninsula. No general relationship between freezing index and other permafrost lines is obvious; the presence or absence of permafrost depends upon thawing as well as freezing at a place. The design freezing index is the average freezing index for the three coldest winters of the last 30 years of record, or, if 30 years of record are not available, the most severe freezing index in the most recent 10-year period. Weather records current through 1967 were used to generate Plate 34B. The thawing index, or degree days above freezing, is a measure of thawing that occurs during a year. It is also a measure of summer duration and temperatures. Areas with thawing indexes much less than their freezing indexes are candidates for at least some permafrost. Areas with small thawing indexes and large freezing indexes tend to have continuous permafrost. The Alaskan thawing index varies from 500 degree days along the arctic coast to 5,000 degree days in extreme southeastern Alaska, However, much of the state has a thawing index of 2,500-3,000 degree days. This uniformity is caused by the higher summer temperatures in the Interior, which compensate for the longer thawing seasons farther south. It results in a fairly uniform type of forest cover except where altitude interferes. The design thawing index is the average thawing index for the three warmest summers of the last 30 years of record, or, if 30 years of record are not available, the highest thawing index in the most recent 10-year period. Weather records current through 1967 were used to generate plate 35B. A. THAWING INDEX, ALASKA B. DESIGN THAWING INDEX, Note: DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS. IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS. Environmental Atlas of Alaska 4/78 PLATE 35 PLATE 36A - HEATING DEGREE DAYS IN ALASKA See the discussion opening Part V. All parts of Alaska require winter heating. Heating degree days vary from 8,000 in southeastern Alaska to 20,000 along the arctic coast. For design and estimating purposes, it should be realized that the heating degree days vary from year to year. A design value based on a one-year-in-ten frequency is closely approximated by adding 1,000 degree days to the plate values for all of the state except for the Aleutians and southeastern Alaska. In these two areas, 500 degree days added to the plate values will provide the one-year-in-ten frequency. PLATE 36B - DEGREE DAYS BELOW O°F IN ALASKA Degree days below zero, based on mean monthly temperatures, are a measure of climatic severity. Most equipment can be operated without serious problem down to about O°F. Below that temperature, the difficulties increase rapidly and winter operations require special techniques. The southern part of the state has no degree days below zero since no month has a mean temperature below that temperature. Winter temperatures fluctuate around the mean and actual temperatures do, of course, fall below zero. The number of degree days below zero increases steadily from south to north and reaches a maximum of about 1900 along the Arctic coast. Degree days below zero are a measure of long-term cold weather and should not be confused with extreme low temperatures. Plate 28 shows that the lowest temperatures are found along the Canadian border. However, in the north the low mean annual temperature and a relatively high seasonal tempera- ture amplitude result in the maximum degree days below zero. Source: U.S.W.B. (1965) A. HEATING DEGREE DAYS IN ALASKA B. DEGREE DAYS BELOW O°F IN ALASKA Note: DATA IS GENERALLY FROM LOW-LYING COASTAL AND RIVER VALLEY AREAS, IT IS PROBABLY NOT VALID FOR HIGHER ELEVATIONS, Environmental Atlas of Alaska 4/78 PLATE 36 Building design criteria shown in Plate 37 were developed by the Corps of Engineers, U. S. Army, and represent the only statewide list of such criteria available. The values shown are for specific points, generally military installations, and should be used with caution in nearby areas with different conditions--such as wind and snow. Incorporated cities and boroughs often have their own building codes, which should be used if available. , The design criteria shown--seismic probability, wind loads, snow loads, absolute minimum and maximum temperatures, pre- vailing wind, and maximum annual precipitation--provide general information on which an engineer can design. Other information in this atlas, such as heating degree days, should also be of value. However, successful building design in the subarctic and arctic parts of Alaska requires site investigation and the services of an engineer competent in the specialized conditions of the north. Permafrost, in particular, is widespread (see Plate 9) and must be considered in building design. The penalty for neglecting it is often complete failure of structures. Source: Corps of Engineers (1958) RIA IN ALASKA SEISMIC PROBABILITY OF STRUCTURAL DAMAGE Bettles (20/40 : ZONE RICHTER SCALE -63|85 ' Minor 3.0-4.5 —_ __ 20. 20 |30 2 =~ Moderate 4.5 -6.0 te) ’ 3 Major 6.0 -8.8* 10.7 j DESIGN DESIGN WIND LOAD P.S.F. SNOW LOAD P.S.F FanNirbonks 20 PSE MIN” // 20 PSE MIN. (aopax sl 29 Sof N8.7 7 . ABS. —— Ass 66 1)\ Big Detta | temp +66] 99) [98) o a : MIN. TEMP. az MAX. TEMP. PREVAILING MAX . ANNUAL WIND PRECIPITATION jorthway *88 IS MAXIMUM MAGNITUDE ep loip a6 15. parrevoiln Anchorage ! : ECORDED ON THE RICHTER 30/40 \-37| BI g 326 + Lay : Nove 'SoricheT” ai) ey SN Pp Hr -—" Environmental Atlas of Alaska — 74/78 STED BIBLIOGRAPHY Alaska Crop and Livestock Reporting Service. 1968. 1967 Alaska agricultural statistics. Alaska Crop Livestock Report Service, Palmer, Alaska. 25 pp. Alaska International Rail and Highway Commission. 1961. Transport requirements for the growth of northwest North America. Vol. 2. Research report by Battelle Memorial Institute on an integrated transport system to encourage economic development of northwest North America. U. S. 87 Congress, lst session, Committee on Interior and Insular Affairs, House Document 176, Vol. 2 Arctic Environmental Information and Data Center, University of Alaska. Alaska Regional Profiles, Vol I-VI, Anchorage, Alaska. Arctic Institute of North America. 1963. The arctic basin. (J. E. Sater, Coordinator). Tidewater Pub- lishing Corporation, Centreville, Maryland. 319 pp. Arkin, M. A. 1971. Windchill (Equivalent Temperatures), Environmental Information Summaries C-3, U. S. Department of Commerce. Silver Spring, MD. Bilello, M. A. 1967. Relationships between climate and regional variations in snow-cover density in North America, in Physics of snow and ice. Proc. International Conference Low Temperature Science, Sapporo, Japan. Clark, T. H. and C. W. Stearn. 1960. The geological evolution of North America. Ronald Press Co., New York. 434 pp. Cold Regions Research and Engineering Laboratory and U. S. Army Engineer District, Alaska. Design data for construction in Alaska. Hanover, New Hampshire. CRREL Report 76-35. 40 pp. + Append. Corps of Engineers, Alaska District, U. S. Army. 1958. Design data for military construction in Alaska. U. S. Army Corps of Engineers, District Engineer, Alaska District. Coulter, H. W., D. M. Hopkins, T. M. V. Karlstrom, T. L. Péwé, C. Wahrhaftig, and J. R. Williams. 1965. Map showing extent of glaciation in Alaska. U. S. Geological Survey Miscellaneous Geologic Inventory Map 1-415. Davis, T. N. and C. Echols. 1962. A table of Alaskan earthquakes, 1788-1961. University of Alaska Geophysical Institute Research Report 8. 44 pp. Ferrians, 0. J., Jr. 1965. Permafrost map of Alaska. U. S. Geological Survey Miscellaneous Geologic Inventory Map 1-445. Feyerherm, A. M., L. D. Bark, and W. C. Burrows. Undated, about 1965. Probabilities of sequences of ‘wet and dry days in Alaska. Agricultural Experiment Station Kansas, North Central Region. Research Pub- lication 161. 55 pp. Flint, R. F. 1957. Glacial and pleistocene geology. John Wiley Sons, Inc., New York. 553 pp. Gilluly, J., A. C. Waters, and A. 0. Woodford. 1968. Principles of geology, 3rd ed. W. H. Freeman and Co., San Francisco and London. 687 pp. Hopkins, D. M. 1959. Some characteristics of the climate in forest and tundra regions in Alaska. Arctic, 12(4):215-220. Hutchison, 0. Keith. 1968. Alaska's Forest Resource. U. S. Forest Service Resource Bulletin PNW 19. 74 pp. Johnson, H. A. and H. T. Jorgenson. 1963. The land resources of Alaska. University Publishers, New York. 551 pp. Kimble, H. T. and Dorothy Good (eds.). 1955. Geography of the northlands. American Geographic Society Special Publication 32. 534 pp. Norwood, G. and R. J. Cross. 1968. Alaska water re- sources, a strategic national asset. Address to the Seminar on the Continental Use of Arctic Flowing Rivers, Washington Water Research Center, Pullman, Washington. 29 pp. Orth, D. J. 1967. Dictionary of Alaska place names. U. S. Geological Survey Professional Paper 567. 1084 pp., 12 maps. Rogers, G. W. 1962. The future of Alaska. Johns Hopkins Press, Baltimore. 311 pp. Scott, R. F. 1964. Heat exchange at the ground surface. U. S. Army Cold Regions Research and Engineering Labora- tory, Hanover, New Hampshire. Report II - Al. 49 pp. + Append. Searby, H. W. 1968. Climates of the States: Alaska. Environmental Data Service, ESSA. Climatology of the United States No. 60-49. Searby, H. W. 1968. Freeze-thaw cycle in the coastal arctic of Alaska. U. S. Weather Bureau. Technical Report. 21 pp. Searby, H. W. 1968. Climate along a pipeline from the arctic to the Gulf of Alaska. U. S. Weather Bureau Technical Memorandum. Searby, H. W. 1969. Coastal weather of the Gulf of Alaska. U. S. Weather Bureau. Technical Report. 35 pp. Siple, P. A. and C. F. Passel. 1945. Measurements of dry atmospheric cooling in subfreezing temperatures. Proc. American Philosophical Society, 89(1):177-199. U. S. Army, Alaska. 1965. Reference handbook of Alaska. USARAL Pamphlet 381-1. U. S. Army Office of the Chief of Engineers. 1963. Terrain evaluation in arctic and subarctic regions. Engineering Manual EM 1110-1-377. 115 pp. U. S. Coast and Geodetic Survey. 1961. Coastline of the United States. U. S. Government Printing Office, Washington. U. S. Coast and Geodetic Survey. 1962. United States coast pilot 8, Pacific coast, Alaska. U. S. Government Print. Office, Washington. 246 pp. U. S. Coast and Geodetic Survey. 1964. United States coast pilot 9, Pacific and arctic coasts. U. S. Govern- ment Printing Office, Washington. 248 pp. U. S. Coast and Geodetic Survey. 1966. Tidal current tables, 1966. Pacific coast of North America and Asia. U. S. Government Printing Office, Washington. 254 pp. U. S. Coast and Geodetic Survey. 1966. The Prince William Sound, Alaska, earthquake of 1964 and after- shocks. Vol. 1. U. S. Government Printing Office, Washington. 263 pp. U. S. Coast and Geodetic Survey. 1966. Hydrographic chart 9302: Bering Sea. U. S. Coast and Geodetic Survey, Washington. U. S. Coast and Geodetic Survey. 1967. Hydrographic chart 9000: San Diego to Aleutian Islands and Hawaiian Archipelago. U. S. Coast and Geodetic Survey, Washington. U. S. Coast and Geodetic Survey. 1967. Hydrographic chart 9400: arctic coast of Alaska. U. S. Coast and Geodetic Survey, Washington. U. S. Geological Survey. 1958. Landscapes of Alaska, their geologic evolution. (H. Williams, ed.). Uni- versity of California Press. 148 pp. U. S. Geological Survey. 1964. Mineral and water re- sources of Alaska. U. S. 88 Congress 2d session, Committee on Interior and Insular Affairs, Committee Printing. 179 pp. U. S. Navy Hydrographic Office. 1958. Oceanographic atlas of the polar seas. Part II, Arctic. U. S. Navy Hydrography Office, Washington. U. S. Weather Bureau, 1965. Climatic summary of the United States, supplement for 1951 through 1960: Alaska. Climatography of the U. S., No. 86-43. 68 pp. U. S. Weather Bureau and U. S. Navy Hydrographic Office. 1961. Climatological and oceanographic atlas for mariners. Vol. II, North Pacific ocean. U. S. Government Printing Office, Washington. Watson, C. E. 1959. Climates of the states: Alaska. U. S. Weather Bureau, Climatography of the U. S., No. 60-49. 24 pp.