Assessing the subglacial lake coverage of Antarctica

Abstract

ABSTRACT. Lakes beneath the Antarctic Ice Sheet are known to decrease traction at the ice base and therefore can have a great impact on ice dynamics. However, the total extent of Antarctic subglacial lakes is still unknown. We address this issue by combining modeling and remote-sensing strategies to predict potential lake locations using the general hydraulic potential equation. We are able to reproduce the majority of known lakes, as well as predict the existence of many new and so far undetected potential lakes. To validate our predictions, we analyzed ice-penetrating radar profiles from radio-echo sounding flights acquired over 1994-2013 in Dronning Maud Land, East Antarctica, and this led to the identification of 31 new subglacial lakes. Based on these findings, we estimate the total number of Antarctic subglacial lakes to be ∼1300, a factor of three higher than the total number of lakes discovered to date. We estimate that only ∼30% of all Antarctic subglacial lakes and ∼65% of the total estimated lake-covered area have been discovered, and that lakes account for 0.6% of the Antarctic ice/bed interface.

Antarctic Topographic Realizations and Geostatistical Modeling Used to Map Subglacial Lakes

“…This is comparable to the Dowdeswell and Siegert () and Goeller et al () estimates, which were 54,000 km 2 and 77,000 ± 18,000 km 2 , respectively, though neither study generated a map of lake locations. The Dowdeswell and Siegert () and Goeller et al () estimates are likely within range of ours because they use the ratio of lakes intercepted by airborne radar flight lines as a constraint on surface area. Our estimate is an order of magnitude smaller than Livingstone et al (), which estimated 2.7%, or 350,000 km 2 .…”

“…Although the Bedmap2 topography generated larger lakes and a greater cumulative surface area, the smooth topography had a greater number of lakes. The smooth topographic simulations yielded more than twice as many expected lakes as the Bedmap2 topography and more than 15 times as many lakes as the Goeller et al () model.…”

“…We evaluated lake accuracy at different cutoff thresholds. Matches were determined using both a 5‐km search radius, as used in Goeller et al (), and a 20‐km search radius. The 20‐km search radius was used to account for topographic variability in the simulations that may have shifted lake positions.…”

“…This interpolation created unrealistically smooth bed topography. Bedmap2 contains regions with bed elevation uncertainty of up to 1,000 m (Fretwell et al, 2013), and interpolation artifacts from the smoothing process likely biased continental-scale models of subglacial lake size distribution toward larger lakes (Goeller et al, 2016;Livingstone et al, 2013). This bias is exacerbated by the 5-km grid resolution used in the Goeller et al (2016) model (more than half of known lakes are shorter than 5 km Dowdeswell & Siegert, 1999).…”

“…The Livingstone et al (2013) and Goeller et al (2016) models relied on Bedmap2 bed topography (Fretwell et al, 2013), which was generated by combining all available radar measurements of topography and interpolating between measurements. This interpolation created unrealistically smooth bed topography.…”