Relationships of Lemon Creek Glacier, Alaska and North Cascade glaciers mass balance to climate indices

The relationship of glacier annual mass balance to atmsopheric circulation is a focus of continuing research to better understand the synoptic controls of mass balance. In this study we relate both the longest record in North America, and the most extensive regional record in North America to ten separate climate indices. The glaciers range in latitude from 59o north to 48o north provides an opportunity to better define the limit of significant influence of both Arctic systems in the temperate martime Pacific Northwest, and of tropical circulation on the temperate and polar regions. Anova is used to develop the most accurate model for mass balance estimation for each region.

The Annual balance measurements on the Lemon Creek Glacier, Alaska (59oN) conducted by the Juneau Icefield Research Program from 1953 to 1998 provide a continuous 46-year record. This is the longest glacier mass balance record in North America. These data have been verified by repeat geodetic mapping of the glacier in 1957, 1995 and 1998. The mean annual balance of the 46-year record is -0.48 m/a, a loss of at least 24.7 m of ice thickness for the entire period. The mean annual balance decreased from –0.23 m/a from 1953-1975, to –0.65m/a from 1975-1991, and finally –1.12 m/a from 1992-1998.

In the North Cascades of Washington annual mass balance records from ten glaciers over a 19-year period by the North Cascade Glacier Climate Project represent the most extensive regional network of glacier mass balance observations in North America. The mean annual balance from 1984-2002 has been –0.28 m/a.

The key indices Arctic Oscillation (AO), Pacific Decadal Oscillation (PDO), Aleutian Forcing Index (AFI), North Atlantic Oscillation (NAO), Southern Oscillation Index (SOI), Pacific Northwest Index (PNI), North Pacific Index (NP), Pacific North American Index (PNA), East Pacific (EP), and West Pacific (WP). Some of the indices prove to be redundant in the models. Key findings are: 1) Pacific Decadal Oscillation is the single most powerful predictor of glacier mass balance. 2) The Arctic Oscillation Index has a significant impact on mass balance of the Lemon Creek Glacier, but not North Cascade glaciers. 3) That a power coefficient of 0.997, and R-squared of 0.48, and a mean error of +0.24 m/a can be achieved for Lemon Creek Glacier with a best model of four coefficients PDO, AFI, AO and year. Year was accidentally included in the initial run, and after removal model performance declined. Year is obviously a proxy, in this case likely the continuing increase in global and particularly Alaskan temperatures. 4) That the best fit model for North Cascade glaciers includes SOI, PDO, and PNI 5) That as other researchers have noted the lack of influence of the SOI on glacier mass balance in Alaska, but the North Cascade glaciers are influenced.