Relationships between varve thickness and climatic parameters and paleoclimatic reconstruction

Abstract

Varve thickness in Skilak Lake/ Alaska is correlated with mean annual temperature (r2=0.74) and inversely correlated mean annual cumulative snowfall (r 2=0.92) in the southern Alaska climatological division but not correlated with the mean annual precipitation (r 2=0.17) of this division. Varve thickness in Skilak Lake is sensitive to annual temperature and snowfall because Skilak Glacier/ the dominant source of sediment for Skilak Lake/ is sensitive to these climatic parameters. Varve thickness is also correlated with annual temperatures of the northern Alaska climatological division (r 2=0.75)/ State of California (r 2=0.41)/ State of Hawaii (r 2=0.46), western climatological division of Oregon (r 2=0.47), and the cities of Seattle (r 2=0.59) and North Head (r2=0.68)/ Washington; and Eureka, California (r 2=0.41). The correlation between varve thickness and annual temperature in these locations probably results from annual variations in the mean position and intensity of the semipermanent pressure systems of the North Pacific. Reconstructions of trends of annual snowfall in the southern Alaska climatological division and annual temperature in the southern and northern climatological divisions of Alaska and the cities of Seattle and North Head, Washington were made and for the years 1700-1906. These reconstructions are based on varve thickness in Skilak Lake and utilise the equations derived from the regression of varve thickness on the historic climatological data. These reconstructions suggest that annual snowfall in the southern Alaska climatological division during the 1700*s and 1800's was much greater than that of the early and mid-1900's. Two periods, 1770-90 and 1890-1906, show a marked decrease in annual snowfall. Reconstructed trends of annual temperatures for the northern and southern climatological divisions of Alaska and the cities of Seattle and North Head suggest that annual temperatures during the 1700 and 1800's were cooler than those of the early and mid-1900's. Two periods of relatively warm annual temperatures coincide with the periods of low annual snowfall that occured during these years. Reconstructions of annual snowfall and annual temperature based on glacial fluctations or tree-ring data suggest that reconstructions of snowfall and temperature based on varve thickness are valid, at least for the State of Alaska.