Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning

Abstract

During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise-meltwater pulses-took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A. This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat.

The GRISLI ice sheet model (version 2.0): calibration and validation for multi-millennial changes of the Antarctic ice sheet

“…Our approach is somehow similar to previous works (e.g. Ritz et al, 2001;Huybrechts, 2002;Pollard and DeConto, 2009;Greve et al, 2011;Golledge et al, 2014).…”

Palaeo-ice stream pathways and retreat style in the easternmost Amundsen Sea Embayment, West Antarctica, revealed by combined multibeam bathymetric and seismic data

“…1). Current LGM model simulations capture the locations and widths of palaeo-ice streams on the inner and middle shelf as mapped from bedforms (e.g., Larter et al, 2009;Nitsche et al, 2013), but considerable data-model mismatches remain on the outer shelf (Golledge et al, 2013(Golledge et al, , 2014. On the outer shelf of the eastern Amundsen Sea Embayment (ASE) in particular, model results reconstructing the widths of fast-flowing corridors deviate significantly from existing data constraints.…”

“…While some models reconstructing the ice sheet configuration at the Last Glacial Maximum (LGM;~23-19 cal. ka BP -calibrated kiloyears before present) have already included geological data (e.g., LeBrocq et al, 2011;Golledge et al, 2013Golledge et al, , 2014Jamieson et al, 2014), gaps are still significant in understanding West Antarctic Ice Sheet (WAIS) behaviour (e.g., Larter et al, 2014;The RAISED Consortium, 2014). …”

Antarctic ice rise formation, evolution, and stability

“…The most recent modeling attempts aimed at reconstructing the ice volume in Antarctica from the last deglaciation [Maris et al, 2014;Golledge et al, 2014] employ ice sheet models at relatively coarse resolutions, which questions whether they guarantee a coherent migration of the grounding line and hence the retreat of the ice sheet , a problem usually circumvented by applying a large amount of basal slipperiness as is the case in these model simulations. Furthermore, not all approximations to the Stokes equations are valid for transient evolution of Stokes problems, such as grounding lines or ice rises [Pattyn and Durand, 2013].…”