Active subglacial lakes and channelized water flow beneath the Kamb Ice Stream

Abstract

Abstract. We identify two previously unknown subglacial lakes beneath the stagnated trunk of the Kamb Ice Stream (KIS). Rapid fill-drain hydrologic events over several months are inferred from surface height changes measured by CryoSat-2 altimetry and indicate that the lakes are probably connected by a subglacial drainage network, whose structure is inferred from the regional hydraulic potential and probably links the lakes. The sequential fill-drain behavior of the subglacial lakes and concurrent rapid thinning in a channel-like topographic feature near the grounding line implies that the subglacial water repeatedly flows from the region above the trunk to the KIS grounding line and out beneath the Ross Ice Shelf. Ice shelf elevation near the hypothesized outlet is observed to decrease slowly during the study period. Our finding supports a previously published conceptual model of the KIS shutdown stemming from a transition from distributed flow to well-drained channelized flow of subglacial water. However, a water-piracy hypothesis in which the KIS subglacial water system is being starved by drainage in adjacent ice streams is also supported by the fact that the degree of KIS trunk subglacial lake activity is relatively weaker than those of the upstream lakes.

Thirteen years of subglacial lake activity in Antarctica from multi-mission satellite altimetry

“…Our results show that KT1 was the only lake of the three to exhibit dynamic behavior between 2003 and 2009, with height on the lake decreasing by 0.23 m a −1 after accounting for the 0.10 m a −1 regional thickening signal. All three lakes showed dynamic height changes during 2014, consistent with Kim and others (2016). The height changes on these lakes were abrupt: ice-surface height at KT1 and KT3 increased by 2.5 m and 1.7 m over 4 months, while the mean height of KT2 increased by 1.7 m in a single month (equivalent to >20 m a −1 ).…”

“…The extended record of surface-height anomalies has demonstrated that several, but not all, locations identified as active subglacial lakes continued to be active after the end of the ICESat mission in 2009. On Whillans, Kamb, MacAyeal, Institute, Thwaites, and Slessor ice streams, there were eight locations that exhibited large (>1 m) surface-height anomalies afor the period 2010–16, in addition to the 12 events previously reported using CryoSat-2 data (McMillan and others, 2013; Siegfried and others, 2014, 2016; Kim and others, 2016; Smith and others, 2017). Following existing literature (e.g.…”

“…3). KT1 is at the same location as KambTrunk 1 from Smith and others (2012), but its outline was refined by Kim and others (2016). KT2 and KT2 were discovered by Kim and others (2016), who derived activity time series with CryoSat-2 data, but did not assess any of the three regions during the ICESat period.…”

“…KT1 is at the same location as KambTrunk 1 from Smith and others (2012), but its outline was refined by Kim and others (2016). KT2 and KT2 were discovered by Kim and others (2016), who derived activity time series with CryoSat-2 data, but did not assess any of the three regions during the ICESat period. Our results show that KT1 was the only lake of the three to exhibit dynamic behavior between 2003 and 2009, with height on the lake decreasing by 0.23 m a −1 after accounting for the 0.10 m a −1 regional thickening signal.…”

“…These two altimeters have successfully been used for both identifying surface-height anomalies (e.g. Fricker and others, 2007; Smith and others, 2009; Kim and others, 2016) and constructing time series for known dynamic regions (e.g. Fricker and Scambos, 2009; Siegfried and others, 2016).…”