Dynamic changes on the Wilkins Ice Shelf during the 2006–2009 retreat derived from satellite observations

Abstract

Abstract. The vast ice shelves around Antarctica provide significant restraint to the outflow from adjacent tributary glaciers. This important buttressing effect became apparent in the last decades, when outlet glaciers accelerated considerably after several ice shelves were lost around the Antarctic Peninsula (AP). The present study aims to assess dynamic changes on the Wilkins Ice Shelf (WIS) during different stages of ice-front retreat and partial collapse between early 2008 and 2009. The total ice-shelf area lost in these events was 2135 ± 75 km2 ( ∼ 15 % of the ice-shelf area relative to 2007). Here, we use time series of synthetic aperture radar (SAR) satellite observations (1994–1996, 2006–2010) in order to derive variations in surface-flow speed from intensity-offset tracking. Spatial patterns of horizontal strain-rate, stress and stress-flow angle distributions are determined during different ice-front retreat stages. Prior to the final break up of an ice bridge in 2008, a strong speed up is observed, which is also discernible from other derived quantities. We identify areas that are important for buttressing and areas prone to fracturing using in-flow and first principal strain rates as well as principal stress components. Further propagation of fractures can be explained as the first principal components of strain rates and stresses exceed documented threshold values. Positive second principal stresses are another scale-free indicator for ice-shelf areas, where fractures preferentially open. Second principal strain rates are found to be insensitive to ice-front retreat or fracturing. Changes in stress-flow angles highlight similar areas as the in-flow strain rates but are difficult to interpret. Our study reveals the large potential of modern SAR satellite time series to better understand dynamic and structural changes during ice-shelf retreat but also points to uncertainties introduced by the methods applied.

Recent dynamic changes on Fleming Glacier after the disintegration of Wordie Ice Shelf, Antarctic Peninsula

“…variations in wind stress or reduced freshwater fluxes from runoff and ice-shelf basal melt) until ∼ 8 years before break-up events took place in and 2009(Braun and Humbert, 2009Padman et al, 2012). Subsequent changes in ice dynamics and stresses leading to break-up have been observed (Rankl et al, 2017). On George VI Ice Shelf, surface lowering is linked to enhanced basal melt caused by an increased circulation of warmed circumpolar deep water (CDW) and a 13 % increase in ice flow was observed between 1992 and 2015 for its tributary glaciers (Hogg et al, 2017).…”

Remote Sensing of Antarctic Glacier and Ice-Shelf Front Dynamics—A Review

“…The high interest in the Larsen Ice Shelf can be attributed to the disintegration of Larsen A and Larsen B, as well as the huge calving events of Larsen C [102][103][104][105]. Also, for the Wilkins Ice Shelf, a strong retreat since the 1990s was detected on satellite imagery before its partial disintegration in 2008/2009, which resulted in many studies [106,107]. The disintegration of the Larsen ice shelves reduced the buttressing for the feeding glaciers, which accelerated and retreated beyond the grounding line.…”

Reply to reviewer comment

“…ice rises and rumples). Analyses of satellite imagery suggest that the ice shelf was temporarily grounded and stabilised at these pinning points until one of the next rapid break-up events took place (Doake and Vaughan, 1991;Reynolds, 1988;Vaughan, 1993;Vaughan and Doake, 1996). However, during phases of ice front retreat, instead of protecting the ice shelf against decay, ice rises that were embedded in the ice shelf appeared to behave as indenting wedges, contributing to weakening the ice shelf and accelerating break-up (Doake and Vaughan, 1991;Vaughan, 1993).…”

“…However, during phases of ice front retreat, instead of protecting the ice shelf against decay, ice rises that were embedded in the ice shelf appeared to behave as indenting wedges, contributing to weakening the ice shelf and accelerating break-up (Doake and Vaughan, 1991;Vaughan, 1993). It is likely that the collapse of Wordie Ice Shelf was triggered by a combination of amplified ablation due to rising air temperatures (Doake and Vaughan, 1991), enhanced tidal action as a consequence of relaxed seaice conditions in Marguerite Bay (Reynolds, 1988) and increased basal melt rates on ice shelves in the Bellingshausen . Surface velocities were derived from Sentinel-1 acquisitions acquired on 28 August and 9 September 2015.…”