Synoptic climatology and recent climate trends at Lake El'gygytgyn.

We developed a synoptic climatology for Lake El'gygytgyn, Chukotka Russia, and explored modern climate trends affecting air temperatures there to aid in paleoclimate reconstructions of a 3.6 million year old sediment core taken from the lake. Our self-organized mapping (SOM) approach identified 35 synoptic weather patterns, based on sea level pressure, that span the range of synoptic patterns that influence the study domain over the 1961-2009 NCEP/NCAR reanalysis period. We found strong seasonality in modern weather patterns, with summer weather primarily characterized by weak low pressure systems over the Arctic Ocean or Siberia and winter weather primarily characterized by strong high pressures over the Arctic Ocean with strong low pressures in the Pacific Ocean. In general the primary source of variation in air temperatures came from the dominant patterns in each season, which we identify in the text, and nearly all of the dominant weather patterns here have shown increasing temperatures. We found that nearly all of the warming in mean annual temperature over the past 50 years (about 3 °C) occurred during sub-freezing conditions on either side of summer (that is, spring and fall). Here we found that the most summer-like weather patterns (low pressures to the North) in the shoulder seasons were responsible for much of the change. Finally we compared the warmest 15 years of the record (1995-2009) to the coolest (1961-1975) and found that changes in thermodynamics of weather were about 3 to 300 times more important than changes in frequency of weather patterns in controlling temperature variations during spring and fall, respectively. That is, in the modern record, general warming (local or imported) is more important by orders of magnitude than changes in storm tracks in controlling air temperature at Lake El'gygtgyn, and we conclude with a discussion of how these results may be relevant to the paleoclimate reconstruction efforts. [ABSTRACT FROM AUTHOR]