Australia: The Land Where Time Began

A biography of the Australian continent 

Pine Island, Thwaites, Smith, and Kohler Glaciers , West Antarctica – Widespread, Rapid Retreat – 1992-2011

In this paper Rignot et al., (2011) present the results of their study that involved measuring the grounding line retreat of glaciers that drain the Amundsen Sea sector of West Antarctica by the use of the Earth Remote Sensing (ERS – ½) satellite radar interferometry from 1992 to 2011. The retreat measured for the Pine Island Glacier was 31 km at its centre, most of the retreat occurring between 2005 and 2009 when the glacier was ungrounded from its ice plain. The retreat of the Thwaites Glacier was 14 km along its fast-flow core and along the sides, 1 to 9 km. At the Haynes Glacier the retreat was 10 km along its flanks. The glaciers that retreated the most was the Smith/Kohler Glaciers, with a retreat of 35 km along its ice plain, and they also found that ice shelf pinning points of this glacier are vanishing. Regions of retrograde bed elevation which had been mapped at high spatial resolution with a mass conservation technique that removes residual ambiguities from prior mapping were the locations where these retreats occurred. They found no major bed obstacles upstream of the grounding line position is 2011 that would prevent further retreat of the glaciers and the drawdown of the entire basin.

Conclusion

Based on 20 years of ERS- 1/2 data the authors documented continued, rapid retreat of Pine Island, Thwaites, Haynes, Smith and Kohler glaciers, all of which drain a large sector of West Antarctica on a retrograde, bed below sea level, and such configurations have been indicated to be unstable by ice sheet numerical models (e.g., Favier et al., 2014; Katz & Worster, 2010; Parizek et al., 2013), unless normal and tangential buttressing could significantly increase, which is considered to be unlikely. The authors say the retreat is proceeding along thinning sectors that are fast-flowing and accelerating, and are bound to unground from the bed when they reach floatation. They found no major obstacle in the bed upstream from the 2011 grounding line that would be capable of preventing further grounding line retreat farther to the south. Their conclusion is that this section of West Antarctica is in the process of undergoing marine ice sheet instability that will, in future decades to centuries, contribute significantly to sea level rise.

Sources & Further reading

1. Rignot, E., J. Mouginot, M. Morlighem, H. Seroussi, and B. Scheuchl (2014), Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011, Geophys. Res. Lett. 41, 3502–3509, doi:10.1002/2014GL060140