Ablation from calving and surface melt at lake-terminatingBridge Glacier, British Columbia, 1984–2013

The Cryosphere

M.Chernos¹  M.Koppes¹  R. D.Moore¹ 

DOI  :  10.5194/tc-10-87-2016

学科分类：地球科学(综合)

来源: Copernicus Publications

【 摘 要 】

Bridge Glacier is a lake-calving glacier in the Coast Mountains of BritishColumbia and has retreated over 3.55 km since 1972. The majority of thisretreat has occurred since 1991. This retreat is substantially greater thanwhat has been inferred from regional climate indices, suggesting that it hasbeen driven primarily by calving as the glacier retreated across anoverdeepened basin. In order to better understand the primary drivers ofablation, surface melt (below the equilibrium line altitude, ELA) and calving were quantified during the2013 melt season using a distributed energy balance model (DEBM) andtime-lapse imagery. Calving, estimated using areal change, velocitymeasurements, and assuming flotation were responsible for 23 % of theglacier's ablation below the ELA during the 2013 melt season and were limitedby modest flow speeds and a small terminus cross-section. Calving and surfacemelt estimates from 1984 to 2013 suggest that calving was consistently asmaller contributor of ablation. Although calving was estimated to beresponsible for up to 49 % of the glacier's ablation for individual seasons,averaged over multiple summers it accounted between 10 and 25 %. Calving wasenhanced primarily by buoyancy and water depths, and fluxes were greatestbetween 2005 and 2010 as the glacier retreated over the deepest part ofBridge Lake. The recent rapid rate of calving is part of a transient stage inthe glacier's retreat and is expected to diminish within 10 years as theterminus recedes into shallower water at the proximal end of the lake. Thesefindings are in line with observations from other lake-calving glacierstudies across the globe and suggest a common large-scale pattern incalving-induced retreat in lake-terminating alpine glaciers. Despiteenhancing glacial retreat, calving remains a relatively small component ofablation and is expected to decrease in importance in the future. Hence,surface melt remains the primary driver of ablation at Bridge Glacier and thus projections of future retreat should be more closely tied to climate.

【 授权许可】

Unknown