Spatial variability and regional trends of Antarctic ice shelf surface melt duration over 1979–2020 derived from passive microwave data

Abstract

Passive microwave satellite observations are used to identify the presence of surface meltwater across Antarctica at daily intervals from July 1979 to June 2020, with a focus on ice shelves. Antarctic Peninsula ice shelves have the highest number of annual days of melt, with a maximum of 89 days. Over the entire time period, there are few significant linear trends in days of melt per year. High melt years can be split into two distinct categories, those with high melt days in Dronning Maud Land and Wilkes Land, and those with high melt days in the Antarctic Peninsula and the Bellingshausen Sea sector of West Antarctica. The first pattern coincides with significant negative correlations between melt days and spring and summer Southern Annular Mode. Both patterns also form the primary modes of spatial and annual variability in the dataset observed by Principal Component Analysis. Areas experiencing extended melt for the first time in years tend to show large decreases in subsequent winter microwave emissions due to structural changes in the firn. We use this to identify the impact of novel melt events, particularly over the austral summers of 1991/92 and 2015/16 on the Ross Ice Shelf.

Precursor of disintegration of Greenland's largest floating ice tongue

“…However, similar to the fact that WIS has not retreated further to date despite high number of annual melt days (Johnson et al, 2022) and JI's calving front retreat and acceleration has slowed down (Joughin et al, 2020), 79NG may retreat in episodes.…”

Seasonal land-ice-flow variability in the Antarctic Peninsula

“…Despite the seemingly close correspondence between surface meltwater forcing and the seasonal signals that we ob- serve at GVIIS' glaciers, satellite observations show that supraglacial meltwater presence and persistence are limited inland of Antarctica's grounding zone (Dirscherl et al, 2021;Johnson et al, 2022), and no obvious regional contrasts in melt exist near the grounding line of Alexander Island and Palmer Land (Trusel et al, 2013;Bell et al, 2018). At GVIIS, routine satellite observations have also revealed mi-nor trends of decreasing meltwater presence over most of the 21st century (Johnson et al, 2022), which is consistent with a previously documented, pervasive cooling of the Antarctic Peninsula from the late 1990s onwards (Turner et al, 2016;Adusumilli et al, 2018). Inland, we expect that melt rates will have similarly decreased but at a greater rate given the lapse rate associated with the Antarctic Peninsula's moun- tainous terrain.…”

“…Three decades of routine Earth observation have revealed the progressive decay of the Antarctic Ice Sheet, evinced by accelerated rates of ice thinning, retreat, and flow (Gardner et al, 2018;Konrad et al, 2018;The IMBIE Team, 2018;Rignot et al, 2019). This phenomenon has been ascribed to an array of atmospheric and oceanic forcing mechanisms impinging upon the continent (Rignot et al, 2004;Thoma et al, 2008;Cook and Vaughan, 2010;Joughin et al, 2012a;Steig et al, 2012;Dutrieux et al, 2014;Paolo et al, 2018), from which resulting land-ice losses are estimated to have totalled an average of ∼ 109 ± 59 Gt yr −1 between 1992 and 2017 (The IMBIE Team, 2018). Alongside satellite-altimetry-and gravimetry-based assessments of ice-mass change, this trend has partly been constrained by satellite-derived velocity measurements acquired sporadically throughout the year (Rignot et al, 2011a;Mouginot et al, 2012), under the implicit (and unverified) assumption that no discernible intra-annual (i.e.…”

Comment on tc-2022-94

“…These metrics are often reported at regional or continental scales and usually show large interannual variability, with only short-term or insignificant trends (e.g. Liu et al, 2006;Picard et al, 2007;Tedesco et al, 2007;Trusel et al, 2012;Zheng et al, 2018;Johnson et al, 2021). Studies which have focused on individual shelves have largely been restricted to the Antarctica Peninsula (e.g.…”