Grounding line retreat of Pope, Smith, and Kohler Glaciers, West Antarctica, measured with Sentinel‐1a radar interferometry data

Abstract

We employ Sentinel‐1a C band satellite radar interferometry data in Terrain Observation with Progressive Scans mode to map the grounding line and ice velocity of Pope, Smith, and Kohler glaciers, in West Antarctica, for the years 2014–2016 and compare the results with those obtained using Earth Remote Sensing Satellites (ERS‐1/2) in 1992, 1996, and 2011. We observe an ongoing, rapid grounding line retreat of Smith at 2 km/yr (40 km since 1996), an 11 km retreat of Pope (0.5 km/yr), and a 2 km readvance of Kohler since 2011. The variability in glacier retreat is consistent with the distribution of basal slopes, i.e., fast along retrograde beds and slow along prograde beds. We find that several pinning points holding Dotson and Crosson ice shelves disappeared since 1996 due to ice shelf thinning, which signal the ongoing weakening of these ice shelves. Overall, the results indicate that ice shelf and glacier retreat in this sector remain unabated.

Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years

“…One possible non-geophysical explanation is that the radar mosaic includes data from a period significantly earlier than 2008 for area of the second peak. East Kohler and Smith glaciers also show extensive speedups throughout their length, with increases of > 100 m yr −1 reaching more than 40 km inland likely driven by increased ocean melt rates and subsequent grounding-line retreat Scheuchl et al, 2016). Patterns of velocity change for Pope and Kohler glaciers are more complex, with slowing of up to 100 m yr −1 near the grounding line and increased speed by ∼ 50 m yr −1 upstream reaching 40-80 km inland.…”

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

“…2). The grounding-line position of Smith Glacier was relatively stable from 1992 to 1996, but it then retreated substantially in the 18 years following Scheuchl et al, 2016). By contrast, the grounding line of Kohler experienced limited retreat (∼ 0.2 km yr −1 ) from 1996 to 2011 and subsequently re-advanced to near its 1996 position by 2014 .…”

“…(c) Ice-bottom elevation relative to the EGM2008 geoid, which represents bed elevation over grounded ice. minology for these tributaries has varied in the literature, and we adopt the names used in Scheuchl et al (2016) for consistency and clarity. The largest grounding-line retreat (> 2 km yr −1 ) occurred in the area where the branches of Smith Glacier flow together before splitting into their respective shelves (Fig.…”

Glacier change along West Antarctica's Marie Byrd Land Sector and links to inter-decadal atmosphere–ocean variability

“…GL advance or retreat on the order of ≥10 2 -10 3 m. These uncertainties broadly match the positional errors reported in other satellite-based GL detection studies (cf. Brunt et al, 2010Brunt et al, , 2011Joughin et al, 2016;Scheuchl et al, 2016). Additional confounding variables such as diurnal tidal variability and atmospheric forcing -previously recognized as important controls on GL migration over much shorter temporal baselines (Anandakrishnan et al, 2003;Fricker et al, 2009;Brunt et al, 2010) -are assumed to be negligible over the timescales we consider (cf.…”

“…Observations of the ice streams and glaciers draining into this sector, in particular Pine Island Glacier and Thwaites Glacier, have revealed rapid grounding-line retreat (cf. Park et al, 2013;Rignot et al 2014;Scheuchl et al, 2016), pronounced icedynamic thinning (Pritchard et al, 2009Konrad et al, 2017), ice-flow-speedup Gardner et al, 2018), and large ice-shelf melting rates (Depoorter et al, 2013;Rignot et al, 2013;Paolo et al, 2015;Gourmelen et al, 2017a). These phenomena have been attributed to oceanic and atmospheric forcing impinging on the West Antarctic margin (e.g.…”