The imbalance of glaciers after disintegration of Larsen-B ice shelf, Antarctic Peninsula

Abstract

The outlet glaciers to the embayment of the Larsen-B Ice Shelf started to accelerate soon after the ice shelf disintegrated in March 2002. We analyse high resolution radar images of the TerraSAR-X satellite, launched in June 2007, to map the motion of outlet glaciers in detail. The frontal velocities are used to estimate the calving fluxes for 2008/2009. As reference for pre-collapse conditions, when the glaciers were in balanced state, the ice fluxes through the same gates are computed using ice motion maps derived from interferometric data of the ERS-1/ERS-2 satellites in 1995 and 1999. Profiles of satellite laser altimetry from ICESat, crossing the terminus of several glaciers, indicate considerable glacier thinning between 2003 and 2007/2008. This is taken into account for defining the calving cross sections. The difference between the pre- and post-collapse fluxes provides an estimate on the mass imbalance. For the Larsen-B embayment the 2008 mass deficit is estimated at 4.34 ± 1.64 Gt a<sup>−1</sup>, significantly lower than previously published values. The ice flow acceleration follows a similar pattern on the various glaciers, gradually decreasing in magnitude with distance upstream from the calving front. This suggests stress perturbation at the glacier front being the main factor for acceleration. So far there are no signs of slow-down indicating that dynamic thinning and frontal retreat will go on

Detailed ice loss pattern in the northern Antarctic Peninsula: widespread decline driven by ice front retreats

“…In the published assessments based on laser altimetry (Shepherd et al, 2012), broad assumptions and large extrapolations are required to interpolate the data across the dissected and rugged peninsula region. Mass budget methods (Rignot et al, 2004(Rignot et al, , 2008Rott et al, 2011;Shepherd et al, 2012), which aim to difference outflowing ice flux and surface mass balance (SMB) for each glacier basin, have to date shown results that are difficult to reconcile with other studies of the same glaciers (Shuman et al, 2011;Berthier et al, 2012). This is primarily due to spatially coarse SMB estimates from Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Temperature and Wind Climate of the Antarctic Peninsula as Simulated by a High-Resolution Regional Atmospheric Climate Model

“…This resulted in the (partial) disintegration of multiple ice shelves that fringe the AP [e.g., Larsen A, Larsen B, and parts of the Wilkins Ice Shelf (Cook and Vaughan 2010)]. In turn, this led to the speedup and thinning of the grounded glaciers that feed into these ice shelves (Scambos 2004;Rott et al 2011) and consequently to an increased grounded ice discharge and contribution of AP glaciers to global sea level rise (Rignot et al 2004). Although the exact cause of AP ice shelf disintegration is still under debate, it is generally believed that the disintegration of Larsen A and B ice shelves was mainly driven by enhanced surface melt in response to stronger atmospheric westerlies in summer Marshall et al 2006), resulting in meltwater ponding and hydrofracturing (Scambos et al 2000; Van den Broeke et al 2005;Scambos et al 2009).…”

Modeling the instantaneous response of glaciers after the collapse of the Larsen B Ice Shelf

“…The breakup of the LBIS in February 2002 produced a stress perturbation which lead to profound dynamical changes and an imbalance of the remainder of the ice shelf and the upstream grounded ice [Scambos et al, 2004;Rott et al, 2011]. In order to simulate the abrupt change in forces and the repercussions on ice flow, the distribution of balanced stresses prior to the collapse of the ice shelf needs to be known.…”

“…The latter is a mosaic of ASTER scenes with unspecified acquisition dates between 2000 and 2009 and therefore possibly contaminated by a thinning signal that has been observed for some glaciers after the collapse of the ice shelf in 2002 [Rignot et al, 2004;Rott et al, 2011;Shuman et al, 2011;Berthier et al, 2012]. In order to correct this uncertainty and to obtain a surface elevation that is closer to the (unobserved) precollapse values, we applied a correction to the API-DEM, requiring the ice upstream of the 1995 grounding line to be at or below floatation.…”

“…Good satellite coverage before, during, and after the disintegration, complemented by ground-based measurements, made this one of the best documented large-scale events in recent history of the cryosphere. Observations of surface velocities and elevation showed that glaciers previously feeding the ice shelf (Figure 1), accelerated and thinned [Scambos et al, 2004;Rignot et al, 2004;Hulbe et al, 2008;Rott et al, 2011;Shuman et al, 2011], leading to an overall mass loss of about 8 Gt a −1 from 2001 to 2010 [Scambos et al, 2014] and an increased discharge of grounded ice into the ocean, which is still ongoing today [Berthier et al, 2012;Wuite et al, 2015]. The acceleration, thinning, and associated grounding line retreat has been complex in behavior and highly variable in time and space, with some tributaries reacting rapidly, others with delay, and some hardly at all [Scambos et al, 2014;Wuite et al, 2015;Khazendar et al, 2015].…”