Seasonal land-ice-flow variability in the Antarctic Peninsula

Abstract

Abstract. Recent satellite-remote sensing studies have documented the multi-decadal acceleration of the Antarctic Ice Sheet in response to rapid rates of ice-sheet retreat and thinning. Unlike the Greenland Ice Sheet, where historical, high-temporal-resolution satellite and in situ observations have revealed distinct changes in land-ice flow within intra-annual timescales, observations of similar seasonal signals are limited in Antarctica. Here, we use high-spatial- and high-temporal-resolution Copernicus Sentinel-1A/B synthetic aperture radar observations acquired between 2014 and 2020 to provide the first evidence for seasonal flow variability of the land ice feeding George VI Ice Shelf (GVIIS), Antarctic Peninsula. Our observations reveal a distinct austral summertime (December–February) speed-up of ∼0.06±0.005 m d−1 (∼ 22±1.8 m yr−1) at, and immediately inland of, the grounding line of the glaciers nourishing the ice shelf, which constitutes a mean acceleration of ∼15 % relative to baseline (time-series-averaged) rates of flow. These findings are corroborated by independent, optically derived velocity observations obtained from Landsat 8 imagery. Both surface and oceanic forcing mechanisms are outlined as potential controls on this seasonality. Ultimately, our findings imply that similar surface and/or ocean forcing mechanisms may be driving seasonal accelerations at the grounding lines of other vulnerable outlet glaciers around Antarctica. Assessing the degree of seasonal ice-flow variability at such locations is important for quantifying accurately Antarctica's future contribution to global sea-level rise.

Drainage and refill of an Antarctic Peninsula subglacial lake reveal an active subglacial hydrological network

“…Regional increases in Antarctic Peninsula surface melting have been reported by Abram et al (2013), andTuckett et al (2019) show that delivery of surface meltwater to the bed of Antarctic Peninsula outlet glaciers triggers increased basal water pressure resulting in rapid seasonal ice flow accelerations (up to 100 % greater than the annual mean). For glaciers discharging into ice shelves, ocean forcing has also been shown to influence seasonal flow rates at, and immediately inland of, the grounding line (Boxall et al, 2022).…”

Continent-scale mapping reveals a rise in East Antarctic surface meltwater

“…Our data demonstrate that surface meltwater is abundant on grounded ice around Antarctica (Fig. 1; Extended Data Table 1), where it could induce transient 2 and seasonal 47 accelerations in ice motion, as is common in West Greenland 48 , the High Arctic 49 and in mountain settings 16 . We expect that such surface-to-bed connections will become more common around Antarctica as surface melting increases.…”

“…Robust linear regression was used in MATLAB (https://uk.mathworks.com/help/stats/robustfit.html), which is less sensitive to outliers than standard linear regression. This enabled us to better assess the statistical relationship for each individual mode of climatic variability, without results being skewed by anonymously high or low melt years, which could have been strongly influenced via teleconnections with other climatic modes 47 .…”

Short- and long-term variability of the Antarctic and Greenland ice sheets

“…In the GrIS and AIS, the drainage of surface melt to the bed is inferred to subsequently influence ice dynamics through connections to the subglacial hydrological system [75][76][77] . Generally, however, the impact of hydrodynamic coupling on ice motion for grounded ice is uncertain 75,78 .…”