West Antarctic surface melt event of January 2016 facilitated by föhn warming

Abstract

The Ross Ice Shelf (RIS) buttresses ice streams from the Antarctic continent and restrains the grounded ice sheet from flowing into the ocean, which is important for the stability of the ice sheet. In recent decades, West Antarctic ice shelves, including the RIS, have experienced more frequent surface melting during summer. We investigated the role of warm, descending föhn winds in a major melt event that occurred on the RIS in January 2016. Only a few summer melt events of this magnitude have been observed since 1979. Backward trajectories from the area of earliest melting were constructed using the Antarctic Mesoscale Prediction System to investigate the dominant mechanisms at the beginning of the melt event, mainly from 10 to 13 January. Analysis was conducted over two distinct areas. The föhn effect contributed around 2–4 °C to the surface temperature increase over the coastal mountains of Marie Byrd Land and around 1 °C over the much lower Edward VII Peninsula. Most of the föhn warming was caused by isentropic drawdown of air aloft. On 10 January, the second‐most important contributor for both mountain ranges was the thermodynamic mechanism. On 11 January, the second‐most important mechanism was the sensible and radiative heat flux. This study contributes to a better understanding of surface melt events over the RIS and benefits research associated with the stability of West Antarctic ice shelves.

Atmospheric Rivers, Warm Air Intrusions, and Surface Radiation Balance in the Amundsen Sea Embayment

“…and the narrow Edward VII Peninsula (∼600 m a.s.l.) can block or redirect the airflow from the Ross and Amundsen Seas (Zou et al., 2019). In the PIG region, the JM is the highest local topographic feature and has an average elevation of ∼774 m, and the occurrence of foehn wind events has not yet been well established.…”

Recent Near-surface Temperature Trends in the Antarctic Peninsula from Observed, Reanalysis and Regional Climate Model Data

“…This period is also chosen to have a common period consistent with the RCM simulations (see section 2.3). We focus on the annual as well as summer (December−January−February, DJF) and autumn (March−April−May, MAM) time scales, as both large-and local-scale events can cause temperatures to rise above freezing, resulting in surface melting during these seasons (e.g., Nicolas et al, 2017;Bozkurt et al, 2018;Carrasco, 2018;Zou et al, 2019). Note that Larsen Ice Shelf station includes a low percentage of observations between 1990 and 1995 to perform the analysis; therefore, we have omitted the data between those years for this station.…”

“…In addition to surface observations and reanalysis products, a number of regional weather and climate model simulations have been employed over the Antarctic continent, particularly over West Antarctica and the Antarctic Peninsula. These modeling studies mainly consisted of the dynamical downscaling of boundary conditions provided by reanalysis, and covered a broad of spectrum of applications such as surface mass balance analysis (Lenaerts et al, 2012;van Wessem et al, 2014;Agosta et al, 2019), characterizing surface climate patterns and variability (van Wessem et al, 2015;Deb et al, 2018), and foehn events (Steinhoff et al, 2014;Elvidge et al, 2015;Bozkurt et al, 2018;Datta et al, 2019;Zou et al, 2019).…”

AWARE: The Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment

“…Moreover, the recent work of Pollard et al (2015) and DeConto and Pollard (2016) indicates an important role for direct atmospheric forcing on ice shelf hydrofracturing in West Antarctica. Parameterizations for ice shelf hydrofracturing and the MICI in coupled climate models are still in their early stages; actual field data are required for model testing and refinement, and for attribution of surface melting events to specific atmospheric processes such as warm air intrusion (Nicolas and Bromwich 2011;Scott et al 2019), cloud all-wave surface radiation enhancement (Bennartz et al 2013;Hu et al 2019), or foehn winds (e.g., Elvidge et al 2015;Zou et al 2019).…”