Abstract
Lake CookE2, upstream of Cook Glacier in East Antarctica is an ‘active’ subglacial lake, which experiences episodic discharge and recharge of basal water. Although around 130 active lakes are known to exist, the majority are not able to be identified by radar sounding techniques, suggesting they are ephemeral and/or distributed stores of small amounts of water rather than permanent significant singular features. Airborne ice-sounding radar data from Lake CookE2, a known ‘active’ subglacial lake, reveal a bright and flat ice-bed interface, providing clear evidence of deep (>10 m) water surrounded by elevated topography, however. The data reveal the lake area is ~46 km2; 3 times less than a previous estimated (145 km2) from ICESat surface altimetry, indicating a possible bias in identifying subglacial lake area from surface depressions. Using time-series altimetry from ICESat, Cryosat-2 data, and the Reference Elevation Model of Antarctica, we re-estimate the lake discharged ~2.93 km3 of water (or ~63.8 m in lake level) between February 2006 and January 2011. Subsequently, the ice surface over the lake rose steadily and experienced a mean uplift of ~11 m between January 2011 and November 2016, indicating continuous recharge with total volume increase of ~0.51 km3. The lake is recharging at a rate of ~1.33 m/year, which means it will take another ~39 years to reach the lake level that triggered the previous discharge.
Highlights
Lake CookE2, located at the head of Cook Glacier in Wilkes Land (Figure 1), is an “active” Antarctic subglacial lake
The unbroken nature of the basal reflector indicates that the water must be at least 10 m deep (Gorman and Siegert, 1999), confirming Lake CookE2 as a deep-water subglacial lake
We have confirmed, using ice-penetrating radar data, that Subglacial Lake CookE2 in East Antarctica is similar in its physiography to many stable deep-water lakes that are contained by steep-sided topography
Summary
Lake CookE2, located at the head of Cook Glacier in Wilkes Land (Figure 1), is an “active” Antarctic subglacial lake. Evidence for this is drawn from the significant surface depression that occurred during 2006–2008 (Smith et al, 2009), interpreted as a sudden loss of basal water. The ice surface lowered by ∼70 m in just 2 years (Mcmillan et al, 2013), due to the largest discharge of basal water measured in Antarctica far. Surface depressions with such an amplitude are captured by satellite altimetry and/or InSAR techniques (Flament et al, 2014). 129 active subglacial lakes have been identified in Antarctica according to this interpretation, and they featured in the latest inventory of Antarctic subglacial lakes (Wright and Siegert, 2012).
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