Modelling the response of the Lambert Glacier–Amery Ice Shelf system, East Antarctica, to uncertain climate forcing over the 21st and 22nd centuries

Y Gong,A J Payne,S L Cornford

doi:10.5194/tc-8-1057-2014

Y Gong, A J Payne + Show 1 more

Open Access

https://doi.org/10.5194/tc-8-1057-2014

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Journal: The Cryosphere	Publication Date: Jun 18, 2014
Citations: 36	License type: CC BY 3.0

Affiliation: University of Bristol, University of Lapland

Abstract

Abstract. The interaction between the climate system and the large polar ice sheet regions is a key process in global environmental change. We carried out dynamic ice simulations of one of the largest drainage systems in East Antarctica: the Lambert Glacier–Amery Ice Shelf system, with an adaptive mesh ice sheet model. The ice sheet model is driven by surface accumulation and basal melt rates computed by the FESOM (Finite-Element Sea-Ice Ocean Model) ocean model and the RACMO2 (Regional Atmospheric Climate Model) and LMDZ4 (Laboratoire de Météorologie Dynamique Zoom) atmosphere models. The change of ice thickness and velocity in the ice shelf is mainly influenced by the basal melt distribution, but, although the ice shelf thins in most of the simulations, there is little grounding line retreat. We find that the Lambert Glacier grounding line can retreat as much as 40 km if there is sufficient thinning of the ice shelf south of Clemence Massif, but the ocean model does not provide sufficiently high melt rates in that region. Overall, the increased accumulation computed by the atmosphere models outweighs ice stream acceleration so that the net contribution to sea level rise is negative.

Highlights

Climate change can affect an ice sheet by altering its mass balance directly through surface accumulation and melting, or indirectly through melting and refreezing on the ice shelf– ocean interface and the consequential dynamic thickening and thinning (van den Broeke et al, 2009; Williams et al, 2011; Huybrechts and de Wolde, 1999)
Given that the melt rate close to the grounding line is usually considered to be important (Walker et al, 2008; Gagliardini et al, 2010), we considered this source of error by constructing one further set of calculations (HadCM3/A1B/None/FESOM+), where the HadCM3/A1B/FESOM melt data is extrapolated into any newly floating regions by setting the melt rate there to the maximum value found in the original data within 100 km
We used the BISICLES adaptive mesh ice sheet model to compute its response to changes in surface mass balance and sub ice-shelf melt-rate anomalies provided by two high-resolution atmosphere models (RACMO2 and LMDZ4) and one high-resolution ocean model (FESOM), in turn driven by two global climate models (HadCM3 and ECHAM5) and two future emissions scenarios (E1 and A1B)

Summary

Introduction

Climate change can affect an ice sheet by altering its mass balance directly through surface accumulation and melting, or indirectly through melting and refreezing on the ice shelf– ocean interface and the consequential dynamic thickening and thinning (van den Broeke et al, 2009; Williams et al, 2011; Huybrechts and de Wolde, 1999). Mass change over the ice sheet will in turn affect the global sea level (van den Broeke et al, 2009): the rate of sea-level rise due to the present-day mass loss from Antarctica is about 0.25 mm a−1 for 2000–2011 (Shepherd et al, 2012). These concerns motivate the application of numerical models that attempt to simulate the current state of ice sheets and their response to future climate forcing. 50 % of the mass (around 46.4 ± 6.9 Gt a−1) leaves the ice shelf through basal melting (Wen et al, 2010), with the remainder lost through calving events at the northern edge (Yu et al, 2010)

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