A benchmark dataset of in situ Antarctic surface melt rates and energy balance

Constantijn L Jakobs,Michiel R Van Den Broeke,C J P Paul Smeets,Carleen H Reijmer,J Melchior Van Wessem,Willem Jan Van De Berg,Luke D Trusel

doi:10.1017/jog.2020.6

Constantijn L Jakobs, Michiel R Van Den Broeke + Show 5 more

Open Access

https://doi.org/10.1017/jog.2020.6

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Abstract

AbstractSurface melt on the coastal Antarctic ice sheet (AIS) determines the viability of its ice shelves and the stability of the grounded ice sheet, but very few in situ melt rate estimates exist to date. Here we present a benchmark dataset of in situ surface melt rates and energy balance from nine sites in the eastern Antarctic Peninsula (AP) and coastal Dronning Maud Land (DML), East Antarctica, seven of which are located on AIS ice shelves. Meteorological time series from eight automatic and one staffed weather station (Neumayer), ranging in length from 15 months to almost 24 years, serve as input for an energy-balance model to obtain consistent surface melt rates and energy-balance results. We find that surface melt rates exhibit large temporal, spatial and process variability. Intermittent summer melt in coastal DML is primarily driven by absorption of shortwave radiation, while non-summer melt events in the eastern AP occur during föhn events that force a large downward directed turbulent flux of sensible heat. We use the in situ surface melt rate dataset to evaluate melt rates from the regional atmospheric climate model RACMO2 and validate a melt product from the QuikSCAT satellite.

Highlights

For most of the Antarctic ice sheet (AIS), the near-surface climate is too cold to allow for widespread or continuous summer melting, such as occurs in the lower ablation zone of the Greenland ice sheet (Bell and others, 2018)
The large uncertainty in QG is a result of taking radiation penetration into account; when it is accounted for, energy that would have been provided to the surface by SW↓ is instead absorbed in the subsurface, which is eventually provided to the surface through QG
SW↓ is slightly larger in the Antarctic Peninsula (AP), the higher precipitation amounts increase the surface albedo sufficiently to result in an SWnet similar to what is observed in Dronning Maud Land (DML)

Summary

Introduction

For most of the Antarctic ice sheet (AIS), the near-surface climate is too cold to allow for widespread or continuous summer melting, such as occurs in the lower ablation zone of the Greenland ice sheet (Bell and others, 2018). As ice shelves are present along ∼74% of the margins of the AIS (Bindschadler and others, 2011), the developments in the AP could serve as an analogue for future ice-shelf disintegration and ice-sheet destabilisation elsewhere in Antarctica when the climate continues to warm, with different roles for local and large-scale atmospheric circulation and ice dynamics (Nicolas and Bromwich, 2014; Fürst and others, 2016; Reese and others, 2018). That is why a robust quantification and understanding of contemporary Antarctic surface melt is essential for improving future predictions of AIS mass loss and sea level rise (Trusel and others, 2015; DeConto and Pollard, 2016)

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