CLIMATE OF ALASKA

 

TOPOGRPHIC FEATURES Alaska is the westernmost extension of the North American Continent. Its east-west span covers a distance of 2,000 miles, and from north to south a distance of 1,100 miles. The States coastline, 33,000 miles in length, is 50 percent longer than that of the conterminous United States. In addition to the Aleutian Islands, hundreds of other islands, mostly undeveloped, are found along the northern coast of the Gulf of Alaska, the Alaska Peninsula, and the Bering Sea Coast. Alaska contains 375 million acres of land and many thousands of lakes.

 

There are 12 major rivers plus three major tributaries of the Yukon, all of which drain two-thirds of the State. Four rivers, the Yukon, Stikine, Alek, and Taku, can be classed as major international rivers.

 

The two longest mountain ranges are the Brooks Range which separates the Arctic region from the interior and the Alaska-Aleutian Range which extends westward along the Alaska Peninsula and the Aleutian Islands, and northward about 200 miles from the Peninsula, then eastward to Canada. Other shorter but important ranges are the Chugach Mountains which form a rim to the central north Gulf of Alaska, and the Wrangell Mountains lying to the northeast of the Chugach Range and south of the Alaska Range. Both of these shorter ranges merge with the St. Elias Mountains, extending southeastward through Canada and across southeastern Alaska as the Coast Range. Numerous peaks in excess of 10,000 feet are found in all but the Brooks Range. The highest peak (20,320 feet above sea level) in the North American Continent, Mt. McKinley, is located in south-central Alaska. Many other peaks tower above 16,000 feet; however, nearly all of the inhabited sections of the State are at 1,000 feet elevation or less.

 

Permafrost is a major factor in the geography of Alaska. It is defined as a layer of soil at variable depths beneath the surface of the earth in which the temperature has been below freezing continuously from a few several thousands of years. It exists where summer heating fails to penetrate to the base of the layer of frozen ground. Permafrost covers most of the northern third of the State. Discontinuous or isolated patches also exist over the central portions in an overall area covering nearly a third of the State. No permafrost exists in the south-central and southern coastal portions including southeastern Alaska, the Alaska Peninsula, and the Aleutian chain.

 

CLIMATIC ZONES The geographical features already mentioned have a significant effect on Alaskas climate, which falls into five major zones. Reference is made to the section of maps at the back, specifically to the map showing geographical subdivisions of Alaska. The climate zones are: (1) a maritime Zone which includes southeastern Alaska, the south coast, and southwestern islands; (2) a maritime continental zone which includes the western portions of Bristol Bay and west-central zones. In this zone the summer temperatures are moderated by the open waters of the Bering Sea, but winter temperatures are more continental in nature due to the presence of sea ice during the coldest months of the year; (3) a transition zone between the maritime and continental zones in the southern portion of the Copper River zone, the Cook Inlet zone, and the northern extremes of the south coast zone; (4) a continental zone make up of the remainders of the Copper River and west-central divisions, and the interior basin; and (5) an artic zone, shown on the map as the arctic drainage division.

 

PRECIPITATION In the maritime zone a coastal mountain range coupled with plentiful moisture produces annual precipitation amounts up to 200 inches in the southeastern panhandle, and up to 150 inches along the northern coast of the Gulf of Alaska. Amounts decrease to near 60 inches on the southern side of the Alaska Range in the Alaska Peninsula and Aleutian Island sections. Precipitation amounts decrease rapidly to the north, with an average of 12 inches in the continental zone and less than 6 inches in the arctic region.

 

Snowfall makes up a large portion of the total annual precipitation. For example, Yakutat averages 216 inches of snow annually and has a total annual precipitation (rain plus water equivalent of snow) of about 130 inches. Along the arctic slope, Barrow receives an average of 29 inches of snow annually and a total annual precipitation of slightly more than 4 inches. Total snow depths on the ground are controlled by the temperature of an area. Fortunately, most of the areas of heavy snow have relatively mild temperatures which prevent total depths from becoming excessive. Present-day snow removal equipment is able to keep highways and airports operational.

 

Precipitation extremes are of interest. With reference to total amounts (both rain and snow) and based on existing records, the greatest annual precipitation occurred at MacLeod Harbor on Montague Island in the Gulf of Alaska with 332.29 inches in 1976. This station also holds the record for monthly totals with 70.99 inches in November 1976.

 

The record maximum for 24 hours occurred on December 29, 1955, in the city of Cordova (North Gulf of Alaska coast) with a measured amount of 14.13 inches. Snowfall extremes are all credited to a station at Thompson Pass, which is on the highway north of Valdez. The record measurements are: season (1952-53) 974.5 inches; month (February 1953) 298 inches; and 24-hour (December 1955) 62 inches.

 

TEMPERATURE Mean annual temperatures in Alaska range from the low 40s under the maritime influence in the south to a chilly 10 degrees a long the Arctic Slope north of the Brooks Mountain Range. The greatest seasonal temperature contrast between seasons is found in the central and eastern portion of the continental interior. In this area summer heating produces average maximum temperatures in the upper 70s with extreme readings in the 90s. The highest recorded temperature for the state is 100 degrees at Fort Yukon in June 1915. In winter the lack of sunshine permits radiation to lower temperatures to the minus 50s and occasionally colder for two or three weeks at a time. Average winter minimums in this area are 20 to 30 degrees below zero. The coldest temperature ever recorded in Alaska was minus 80 degrees at Prospect Creek on January 23, 1971.

 

Elsewhere in the state, temperature contrasts are much more moderate. In the maritime zone the summer to winter range of average temperatures in from near 60 to the 20s. In the transition zone, temperatures range from the low 60s to near zero; in the maritime-continental zones the range is from the low 60s to 10 below zero. The arctic slopes has a range extending form the upper 40s to 20 below zero.

 

Winter temperatures play a principal role in the flow of most of Alaskas rivers. Usually beginning in late October and extending into May (and sometimes early June for the northernmost steams), thick layers of ice form, permitting passage with all types of heavy equipment. In many areas construction work and oil exploration is done in winter because both the ground and the streams are frozen hard enough from the use of the heaviest of equipment. Several rivers cease to flow completely during the coldest months.

 

WIND A normal storm track along the Aleutian Island chain, the Alaska Peninsula, and all of the coastal area of the Gulf of Alaska exposes these parts of the state to a large majority of the storms crossing the North Pacific, resulting in a variety of wind problems. Direct exposure results in the frequent occurrence of winds in excess of 50 mph during all but the summer months. Shemya, on the western end of the Aleutian Islands, has experienced winds on an estimated 139 mph (estimated because the wind recorder pen could only record up to 128 mph). Wind velocities approaching 100 mph are not common but do occur, usually associated with mountainous terrain and narrow passes. For years, strong winds have taken their toll of both merchant and fishing vessels.

 

An occasional storm will either develop in or move into the Bering Sea then move north or northeastward, creating strong winds along the western coastal area. Because of the low flat ground in many places along the coast, these winds will cause flooding during the time the winds are blowing onshore. Winter storms moving eastward across the southern Arctic Ocean cause winds of 50 mph or higher along the arctic coast. Except for local strong wind conditions, winds are generally light in the interior sections.

 

Strong winds, or in fact any wind occurring in the areas of extreme winter cold, create a definite hazard to personnel exposed for even brief periods of time. For example, (using a wind chill chart developed by the U.S. Army) a temperature of a -13F and an accompanying wind of 15 mph equals conditions that would be experienced with a temperature of 49 F and no wind. If the temperature is a -49 F and the winds 10 mph, the resulting equivalent temperature is -81 F.

 

CLIMATE AND THE ECONOMY

TIMBER - wooded areas in the state total approximately 100 million acres of both commercial and non-commercial timber. Southeastern Alaska is and always has been the principal production area. Lumber and pulp mills are important contributors to the economy of that portion of the state. In south-central Alaska high, barren mountains and numerous glaciers limit the forests to about 10 to 20 percent of the total area. Some commercial logging has occurred in the Tyonek area on the northwest shore of Cook Inlet and in the Matanuska-Susitna Valley. Some forested land exists in the central interior and southwestern portions along major rivers like the Yukon and the Kuskokwim but, to date, has not been developed commercially. No commercial timber is found north of the Brooks Range or along the western coastal region. Western interior forested areas are limited to small isolated patches without permafrost.

 

FARMING It is estimated that statewide there are 18 to 20 million acres of land potentially suitable for cropland, but less than 20 thousand acres are actually under or have been under cultivation. The largest acreages are devoted to grass crops for hay, silage, and pasture. Rangelands are widespread in the Alaska mainland. Wind caribou herds foraging on portions of these lands have numbered in the hundreds of thousands and are an important source of protein in many Alaska villages. Cattle and sheep are raised in areas of the Kenai Peninsula, the Alaska Peninsula, and the Aleutian Islands, and small herds of reindeer are raised on the tundra lands of the Seaward Peninsula. Vegetable crops, especially potatoes, are also important, and limited mild production in the Matanuska Valley north of Anchorage and the Tanana Valley near Fairbanks provide fresh dairy products to local residents. Within the agricultural areas the growing season averages 80 to 110 days each year. This is a short growing season, but the daily potential of 16 to 19 hours of sunshine each day produces some of the finest and largest vegetables grown anywhere.

 

MINERAL Oil is by far the most important mineral product at this time. Current commercial production is at Prudhoe Bay, the Kenai Peninsula, and offshore Cook Inlet. Production from the Prudhoe Bay field is now at 750,000 barrels per day and is projected to reach 1.2 million barrels per day by the end of 1978. The trans-Alaska pipeline, completed in 1977, transports this crude petroleum from the Prudhoe Bay field on the North Slope of Alaska to a refinery at North Pole and to Valdez, a deepwater port in the northern Gulf of Alaska. The petroleum is then moved by oceangoing tankers to refineries in Alaska and the contiguous 48 states. Exploration for additional petroleum is in progress in several land areas and on the outer continental shelf from the Gulf of Alaska to the Beaufort Sea coast. Commercial gas wells are producing in the Barrow area and the Kenai Peninsula, and a large pipeline is expected to be built in the next 5 to 10 years to transport Prudhoe Bay gas to the lower 48 states.

 

Coal is mined in the Healy area, and several other large deposits have been located but are not commercially mined. Gold mining has resumed in the vicinity of Nome, bornite is mined in the vicinity of Kobuk, and platinum of the Bering Sea coast. All other types of mining area of a minor nature but are expected to develop as problems or transportation and production coasts are solved.

 

FISHING The fishing industry, which includes the taking of crab and shrimp, is another leading industry in Alaska. Commercial fishing occurs along the entire Alaska coast but is heaviest in the southeastern Bering Sea, along the Aleutian Islands, and around the coast of the Gulf of Alaska. Salmon have been the main product, but shellfish, particularly ding and tanner crab and shrimp, are becoming more important. A new fishery for bottom fish is emerging with the implementation of the U.S. zone of extended jurisdiction within 200 miles of the coast. Halibut have also long been an important part of the harvest. In recent years, at least one Alaskan port has been listed among the top 10 U.S. ports in terms of both pounds of fisheries products landed and total economic value of the landings.

 

TOURISM Out-of-state visitors have been increasing in number each year. Because of the airplane, tourism extends into nearly every part of the state. This is particularly true if game hunting is included. Hunting for bear, caribou, moose, and sheep draws hundreds of people to the state each year and contributes many thousands of dollars to the economy.