Channelized Melting Drives Thinning Under a Rapidly Melting Antarctic Ice Shelf

Abstract

Ice shelves play a vital role in regulating loss of grounded ice and in supplying freshwater to coastal seas. However, melt variability within ice shelves is poorly constrained and may be instrumental in driving ice shelf imbalance and collapse. High‐resolution altimetry measurements from 2010 to 2016 show that Dotson Ice Shelf (DIS), West Antarctica, thins in response to basal melting focused along a single 5 km‐wide and 60 km‐long channel extending from the ice shelf's grounding zone to its calving front. If focused thinning continues at present rates, the channel will melt through, and the ice shelf collapse, within 40–50 years, almost two centuries before collapse is projected from the average thinning rate. Our findings provide evidence of basal melt‐driven sub‐ice shelf channel formation and its potential for accelerating the weakening of ice shelves.

How Accurately Should We Model Ice Shelf Melt Rates?

“…For purpose of discussion, we adopt terminology from Khazendar et al (2016) and Gourmelen et al (2017) and refer to them (in east-to-west order) as Pope, Smith,Kohler East,and Kohler West (Figure 3a). For purpose of discussion, we adopt terminology from Khazendar et al (2016) and Gourmelen et al (2017) and refer to them (in east-to-west order) as Pope, Smith,Kohler East,and Kohler West (Figure 3a).…”

“…Smith, Pope, and Kohler Glaciers are three narrow interconnected ice streams in the Amundsen sector of West Antarctica, which drain into Crosson and Dotson Ice shelves. For purpose of discussion, we adopt terminology from Khazendar et al (2016) and Gourmelen et al (2017) and refer to them (in east-to-west order) as Pope, Smith, Kohler East, and Kohler West (Figure 3a). Although their contribution to ice flux from the continent is ∼7-8 times smaller than that of Thwaites and Pine Island Glaciers (Shepherd et al, 2002), their observed thinning rates are even larger than that of these bigger ice streams (McMillan, Shepherd, Sundal et al, 2014).…”

“…This drop in buttressing may be related to submarine melt-induced thinning, which can decrease buttressing (e.g., Shepherd et al, 2004). High melt rates have been observed for both Dotson and Crosson in recent years (Depoorter et al, 2013;Gourmelen et al, 2017;Lilien et al, 2018;Miles et al, 2016;Randall-Goodwin et al, 2015;Rignot et al, 2013). Between 2003 and 2008, Dotson and Crosson had net average thinning rates of 3.1 and 6.5 m/a, respectively ; and both have had strong thinning trends for the last two decades (Paolo et al, 2015).…”

“…Estimates of melt rates under Amundsen ice shelves have typically been area-averaged or area-integrated; either because estimates are based on hydrographic measurements (e.g., Jacobs et al, 2011;Miles et al, 2016;Randall-Goodwin et al, 2015;Rignot et al, 2013) or because the spacing of satellite altimetry tracks does not allow for spatially resolved measurement (Paolo et al, 2015;Pritchard et al, 2012). However, a number of studies have found spatially resolved measurements through high-resolution remote sensing methods (Berger et al, 2017;Dutrieux et al, 2013;Gourmelen et al, 2017), showing that melt rates can differ widely from their areal average at spatial scales on the order of kilometers.…”

Estimating Spring Terminus Submarine Melt Rates at a Greenlandic Tidewater Glacier Using Satellite Imagery

“…Several studies have quantified SMR by accounting for ice flux divergence and surface mass balance of floating ice shelves and tongues (e.g., Rignot and Jacobs, 2002;Depoorter et al, 2013;Enderlin and Howat, 2013;Rignot et al, 2013;Gourmelen et al, 2017). This approach has generated SMRs up to 0.11 m d −1 beneath ice shelves in Antarctica (Rignot and Jacobs, 2002) and ranging from 0.03 ± 0.02 to 2.9 ± 0.65 m d −1 beneath floating glacier tongues in Greenland (Enderlin and Howat, 2013).…”