Abstract
Abstract. The annual surface mass balance records of the Lemon Creek Glacier and Taku Glacier observed by the Juneau Icefield Research Program are the longest continuous glacier annual mass balance data sets in North America. Annual surface mass balance (Ba) measured on Taku Glacier averaged +0.40 m a−1 from 1946–1985, and −0.08 m a−1 from 1986–2011. The recent annual mass balance decline has resulted in the cessation of the long-term thickening of the glacier. Mean Ba on Lemon Creek Glacier has declined from −0.30 m a−1 for the 1953–1985 period to −0.60 m a−1 during the 1986–2011 period. The cumulative change in annual surface mass balance is −26.6 m water equivalent, a 29 m of ice thinning over the 55 yr. Snow-pit measurements spanning the accumulation zone, and probing transects above the transient snow line (TSL) on Taku Glacier, indicate a consistent surface mass balance gradient from year to year. Observations of the rate of TSL rise on Lemon Creek Glacier and Taku Glacier indicate a comparatively consistent migration rate of 3.8 to 4.1 m d−1. The relationship between TSL on Lemon Creek Glacier and Taku Glacier to other Juneau Icefield glaciers (Norris, Mendenhall, Herbert, and Eagle) is strong, with correlations exceeding 0.82 in all cases. doi:10.5065/D6NZ85N3
Highlights
The Juneau Icefield Research Program (JIRP) is the longest ongoing program of its kind in North America, facilitating arctic and alpine education and expeditionary training in the fields of climate science, glaciology and glacial geology
This paper reports on three data sets: (1) annual surface mass balance (Ba) record of the Taku and Lemon Creek glaciers, including their annually calculated equilibrium line altitude (ELA) and accumulation area ratio (AAR), as well as evaluation of validation and potential errors; (2) probing transects above the transient snow line (TSL; snow line at time of observation) in 1984, 1998, 2004, 2005 and 2010; and (3) satellite image-determined transient snow line observations and rate of rise on Lemon Creek and Taku glaciers and TSL variations on six glaciers of the Juneau Icefield from 1995–2011 (Eagle, Herbert, Lemon Creek, Mendenhall, Norris and Taku)
7 Conclusions The annual surface mass balance record from Lemon Creek Glacier and Taku Glacier illustrates a decline in Ba mass balance for both glaciers after 1985
Summary
The Juneau Icefield Research Program (JIRP) is the longest ongoing program of its kind in North America, facilitating arctic and alpine education and expeditionary training in the fields of climate science, glaciology and glacial geology. JIRP has examined the surface mass balance of the Juneau Icefield since 1946, with principal efforts focused on Lemon Creek Glacier and Taku Glacier. This database is the longest direct measurement of surface mass balance in North America. M. Pelto et al.: Juneau Icefield Mass Balance Program 1946–2011 sustained positive annual mass balance is out of equilibrium and will tend to thicken and advance. It is crucial that we continue to maintain the invaluable climate–glacier data set and provide it to the World Glacier Monitoring Service (WGMS)
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