Abstract
Abstract. We present conventional and swath altimetry data from CryoSat-2, revealing a system of subglacial lakes that drained between June 2013 and January 2014 under the central part of Thwaites Glacier, West Antarctica (TWG). Much of the drainage happened in less than 6 months, with an apparent connection between three lakes spanning more than 130 km. Hydro-potential analysis of the glacier bed shows a large number of small closed basins that should trap water produced by subglacial melt, although the observed large-scale motion of water suggests that water can sometimes locally move against the apparent potential gradient, at least during lake-drainage events. This shows that there are important limitations in the ability of hydro-potential maps to predict subglacial water flow. An interpretation based on a map of the melt rate suggests that lake drainages of this type should take place every 20–80 years, depending on the connectivity of the water flow at the bed. Although we observed an acceleration in the downstream part of TWG immediately before the start of the lake drainage, there is no clear connection between the drainage and any speed change of the glacier.
Highlights
The Amundsen Sea embayment is one of the fastestchanging part of Antarctica, with large changes since at least the 1990s (Rignot, 2008)
The combination of radar observations and estimated melt rates led to a map of geothermal heat flux, based on the assumption that the basal water system was in equilibrium with steady-state melt rates (Schroeder et al, 2014)
The spatial correlation between relatively high driving stress in the lower trunk and the hypothesized channelized drainage system has led to speculation that the character of the basal water system plays a role in the stability of the glacier and that changes in this water system could lead to accelerated grounding-line retreat (Schroeder et al, 2013)
Summary
The Amundsen Sea embayment is one of the fastestchanging part of Antarctica, with large changes since at least the 1990s (Rignot, 2008). The bed of TWG has been mapped in detail, allowing mapping of basal shear stress and potential subglacial water-flow paths. These reveal abundant basal meltwater production, estimated at about 3.5 km yr−1 and averaging ∼ 19 mm yr−1 (Joughin et al, 2009). The spatial correlation between relatively high driving stress in the lower trunk and the hypothesized channelized drainage system has led to speculation that the character of the basal water system plays a role in the stability of the glacier and that changes in this water system could lead to accelerated grounding-line retreat (Schroeder et al, 2013)
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