| Abstract/Description or Keywords |
Bridge Glacier is a lake-terminating glacier in the Coast Mountains of British Columbia and has retreated over 3.55 km since 1972, with the majority of the retreat having occurred since 1991. This retreat is out of proportion to surface melt inferred from regional climate indices, suggesting that it has been driven primarily by calving as the glacier retreated across an over-deepened basin. In order to better understand the primary drivers of mass balance, the relative importance of surface melt and calving is investigated during the 2013 melt season using a distributed energy balance model and time-lapse imagery. Calving is responsible for 23% of the mass loss during the 2013 melt season, and is limited by modest flow speeds and a small terminus cross-section. Calving and summer balance estimates over the last 30 years suggest that calving is consistently a smaller contributor of mass loss relative to surface melt. Although calving is estimated to be responsible for up to 49% of ice loss for individual seasons, averaged over multiple summers it typically accounts for 10 to 25%. Calving has been driven primarily by buoyancy and water depths, and fluxes were greatest between 2005 and 2010 as the glacier retreated over the deepest part of Bridge Lake. These losses are part of a transient stage in the glacier's retreat, and are expected to diminish as the terminus recedes into shallower water. Surface melt is the primary driver of ice loss at Bridge Glacier, and future mass loss and retreat is dependent on governing climatic conditions. |
