Climate and surface mass balance of coastal West Antarctica resolved by regional climate modelling

Jan T M Lenaerts,J Melchior Van Wessem,Robert Mulvaney,Hannes Konrad,Willem Jan Van De Berg,Luke D Trusel,Julien P Nicolas,Stefan R M Ligtenberg,Rebecca J Tuckwell,Anna E Hogg,Elizabeth R Thomas,Brooke Medley

doi:10.1017/aog.2017.42

Abstract

ABSTRACTWest Antarctic climate and surface mass balance (SMB) records are sparse. To fill this gap, regional atmospheric climate modelling is useful, providing that such models are employed at sufficiently high horizontal resolution and coupled with a snow model. Here we present the results of a high-resolution (5.5 km) regional atmospheric climate model (RACMO2) simulation of coastal West Antarctica for the period 1979–2015. We evaluate the results with available in situ weather observations, remote-sensing estimates of surface melt, and SMB estimates derived from radar and firn cores. Moreover, results are compared with those from a lower-resolution version, to assess the added value of the resolution. The high-resolution model resolves small-scale climate variability invoked by topography, such as the relatively warm conditions over ice-shelf grounding zones, and local wind speed accelerations. Surface melt and SMB are well reproduced by RACMO2. This dataset will prove useful for picking ice core locations, converting elevation changes to mass changes, for driving ocean, ice-sheet and coupled models, and for attributing changes in the West Antarctic Ice Sheet and shelves to changes in atmospheric forcing.

Highlights

The West Antarctic Ice Sheet (WAIS) comprises an ice volume equivalent to ∼4.3 m of sea level (Fretwell and others, 2013)
RACMO2 combines the representation of atmospheric dynamics of the High Resolution Limited Area
The general wind field is largely dominated by katabatic flow originating from the interior ice sheet (Fig. 2)

Summary

Introduction

The West Antarctic Ice Sheet (WAIS) comprises an ice volume equivalent to ∼4.3 m of sea level (Fretwell and others, 2013). Most of the ice on the WAIS is grounded well below sea level on bedrock that slopes down from the coast to the interior ice sheet, designating it as a ‘marinebased ice sheet’ (Thomas, 1979). Fast-flowing ice streams transport accumulated snow and firn from the high interior to the coast, supplying mass to floating ice shelves. The diminishing support from their ice shelves led to considerable speed-up of the ASE glaciers (Mouginot and others, 2014), grounding-line retreat (Park and others, 2013; Scheuchl and others, 2016), and upstream propagation of thinning into the interior (Konrad and others, 2017), manifesting in a by 77% increased solid ice discharge from this area (Mouginot and others, 2014). Numerical simulations of future glacier dynamics drive the speculation that this observed imbalance will be followed by rapid, widespread and potentially irreversible deglaciation of the ASE region (Joughin and others, 2014)

Methods

Results

Conclusion