The Effect of Foehn‐Induced Surface Melt on Firn Evolution Over the Northeast Antarctic Peninsula

Abstract

Surface meltwater ponding has been implicated as a major driver for recent ice shelf collapse as well as the speedup of tributary glaciers in the northeast Antarctic Peninsula. Surface melt on the NAP is impacted by the strength and frequency of westerly winds, which result in sporadic foehn flow. We estimate changes in the frequency of foehn flow and the associated impact on snow melt, density, and the percolation depth of meltwater over the period 1982–2017 using a regional climate model and passive microwave data. The first of two methods extracts spatial patterns of melt occurrence using empirical orthogonal function analysis. The second method applies the Foehn Index, introduced here to capture foehn occurrence over the full study domain. Both methods show substantial foehn‐induced melt late in the melt season since 2015, resulting in compounded densification of the near‐surface snow, with potential implications for future ice shelf stability.

Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica

“…For both near-surface temperature and wind speed, the statistics for the summer period (DJF) are very similar to the statistics for the whole year. Our results show very similar model skills compared to other simulations in the same region (Deb et al, 2018;Lenaerts et al, 2017) or at coarser resolution over the whole ice sheet . We now assess the simulated SMB compared to the SMB from Medley et al (2013Medley et al ( , 2014 derived from airborne radar over the period 1980-2011.…”

“…This corresponds to the large-scale features described by Hosking et al (2013) but is here described for the SMB of individual drainage basins. By contrast, longitudinal migrations of the ASL are not the main driver of surface melting variability, as previously noted by Deb et al (2018). Summers tend to be associated with high surface melt rates when the Amundsen-Bellingshausen region experiences blocking, i.e.…”

“…d −1 (as in Datta et al, 2019) gives a mean underestimation of 4.8 d per year compared to observation from Nicolas et al (2017), while a threshold of 3 mm w.e. d −1 (as in Deb et al, 2018;Lenaerts et al, 2017) gives a mean underestimation of 4.9 d per year. This underestimation is less pronounced (0.8 to 0.9 d per year depending on the threshold) when using Picard et al (2007) as a reference.…”

“…Interannual and decadal variability in the tropical Pacific affects air temperature (Ding et al, 2011), snowfall (Bromwich et al, 2000;Cullather et al, 1996;Genthon and Cosme, 2003), sea ice extent (Pope et al, 2017;Raphael and Hobbs, 2014) and upwelling of circumpolar deep water favoring ice shelf basal melting (Dutrieux et al, 2014;Steig et al, 2012;Thoma et al, 2008) in West Antarctica. Recent studies found concurrences between El Niño events and summer surface melting over West Antarctic ice shelves (Deb et al, 2018;Nicolas et al, 2017;. These connections are generally explained in terms of Rossby wave trains excited by tropical convection during El Niño events and inducing an anticyclonic anomaly over the Amundsen Sea (Ding et al, 2011).…”

“…Medley and Thomas (2019) found similar patterns for the SAM trends and the reconstructed snow accumulation trend over 1801-2000. By contrast, the temperatures above the melting point over the Amundsen ice shelves were found to be largely insensitive to the polarity of the SAM (Deb et al, 2018). The SAM phase has also been suggested to influence the ENSO teleconnection to the south Pacific: in-phase ENSO and SAM events (i.e.…”