Ninth International Conference on Permafrost ... - IARC Research

Climate Change in Permafrost Regions in North AmericaMaria K.GavrilovaMelnikov Permafrost Institute SB RAS, Yakutsk, RussiaIntroductionIn North America, permafrost occurs in three-fourths ofAlaska, half of Canada, and along the coasts and below icesheets in Greenland.MethodWeather station records have been used to analyze climatevariations during the last centuries. The method of 10-year moving averages has been used in the analysis, whichexcludes casual errors.Results and DiscussionFor the Barrow station (the northern coast of Alaska)which has a relatively long record spanning from the 1910sto 2000s, the change of air temperature in winter was withinthe limits of similar values of mean annual temperaturefor January (-25.8°С) from the 1920s to 1970s. Significantcooling occurred in the 1910s (up to-29°С). Then, intensivewarming was observed in the 1970s. The winter airtemperature lowered nearly to the long-term average in the1990s and began to increase again in the 2000s.Summer temperatures changed less, within the limits of±1–1.5°С. Warming was observed in the 1920s, coolingin the 1950s, and warming in the 1990s. The mean annualtemperature which dictates whether the ground is frozenor unfrozen varied within ±1–1.5°С. Significant warmingoccurred in the 1930s, cooling was observed from the 1940sthrough the 1970s, and rapid warming has occurred sincethe 1990s to the end of the century. The latter warming wasdue to increases in both winter and summer temperaturesobserved in the last decades.For Fairbanks (central Alaska), the length of the recordis 20 years shorter than at Barrow. Significant cooling ofwinter temperatures of up to -30° (the long-term average is-23.2°) in the 1960s–1970s and significant warming in thelate 1970s–1980s (up to -19°) are evident. In the 1990s and2000s, temperatures decreased to the long-term average.Summer temperatures were lower than the average fromthe 1930s to 1960s, and have been persistently higher thanthe average since the 1970s. Mean annual temperatures werebelow the long-term average of -2.9° prior to the mid 1970s(up to -4°С), and have been higher since the mid 1970s (upto -2°).St. Bethel (southwestern Alaska) shows nearly the samevariations as Fairbanks, but only with a smaller range.Mt. Washington is situated in southern Alaska, and recordsare available since 1940. A significant increase in wintertemperatures was observed from the mid 1940s to mid 1960s,when temperatures reached -12.5°С, while the long-termmean is -15°. Then, cooling occurred in the 1960s–1980s(up to -17°). This cooling was followed by warming fromthe mid 1980s to mid 2000s. The last warming, however,was less in magnitude than the warming of the 1950s. Then,temperatures began decreasing again.Summer temperatures are surprisingly stable, varyingwithin the limits of ±0.5°С. The mean annual temperaturealso varied more or less stable. Slight warming occurred inthe mid 1950s, extended cooling from the mid 1950s–1980sand a steady temperature increase in the 1990s. All thesevariations were within the range of ±0.5°С.Unfortunately, in northern Canada, meteorologicalobservations were begun later, and recent data, probably, arenot published.At the Alert station located on the most northern extremityof the Canadian Archipelago, observations were apparentlybegun in the 1950s and ended in the 1990s. During thisperiod, there were two peaks in winter temperatures: asmaller one in the 1950s and a larger one in the 1970s (-29°at the mean of -32°). Then temperatures began to decrease.Summer temperatures were above the long-term averagein the 1950s–1960s and have been below the average sincethe latter half of the 1980s. There has been a slight increasingtrend in recent years. The mean annual temperature varied±0.5°С.Along the northern coast of the continent (Aklavik station)there were alternating cold and warm winters within therange of typical variation. Unfortunately, only the data priorto the mid 1960s are available for us.For the Frobisher Bay station (Baffin Island) data areavailable from the 1940s to 2000s. Winter warming wasobserved in the 1960s and the 1980s, similar in magnitude(-24°, while the long-term mean is -26.5°). In the mid1940s, late 1980s and 1990s, winter temperatures loweredto -29°С.After significant cooling in the mid 1980s and in the 1990s,summer and mean annual temperatures have increased by1–1.5°С in the early 2000s.The longest record for the permafrost region at our disposalis from the Churchill station, where observations began inthe 1890s. January temperatures increased significantly inthe 1940s and, in similar magnitude, in the 1980s and the1990s. During these warmer periods, temperatures were-25° to -25.5°, while the long-term average is -27.2°С.Increases in summer temperature were observed in thesecond half of the 1930s and in the 1990s. The mean annualtemperature increased noticeably during the last decades ofthe 20th century, having reached -5.5° (the long-term normalis -7°С).Greenland stations, for which records are available, aresituated on the western coast. The longest record is from the81