Ocean warming drives rapid dynamic activation of marine-terminating glacier on the west Antarctic Peninsula

Abstract

Ice dynamic change is the primary cause of mass loss from the Antarctic Ice Sheet, thus it is important to understand the processes driving ice-ocean interactions and the timescale on which major change can occur. Here we use satellite observations to measure a rapid increase in speed and collapse of the ice shelf fronting Cadman Glacier in the absence of surface meltwater ponding. Between November 2018 and December 2019 ice speed increased by 94 ± 4% (1.47 ± 0.6 km/yr), ice discharge increased by 0.52 ± 0.21 Gt/yr, and the calving front retreated by 8 km with dynamic thinning on grounded ice of 20.1 ± 2.6 m/yr. This change was concurrent with a positive temperature anomaly in the upper ocean, where a 400 m deep channel allowed warm water to reach Cadman Glacier driving the dynamic activation, while neighbouring Funk and Lever Glaciers were protected by bathymetric sills across their fjords. Our results show that forcing by warm ocean water can cause the rapid onset of dynamic imbalance and increased ice discharge from glaciers on the Antarctic Peninsula, highlighting the region’s sensitivity to future climate variability.

Widespread increase in discharge from West Antarctic Peninsula glaciers since 2018

“…Although the glaciers on the AP are small compared to their neighbours in other parts of West Antarctica, they are changing rapidly such that AP contributed 14 % of Antarctica's total mass loss from 1992 to 2020 (Otosaka et al, 2023). Previous work has linked warming subsurface ocean waters to widespread glacier retreat along the west AP (Cook et al, 2016) and more recent work has further shown an ocean-driven ice tongue collapse and acceleration of Cadman Glacier on the west AP (Wallis et al, 2023a). The observations presented in this study develop this understanding by showing a widespread, quasisynchronous acceleration of grounding line discharge along the west AP linked to a period of high air and subsurface ocean temperatures.…”

“…However, other 'low responders' do not always coincide with areas of shallow bathymetry and sometimes have responsive neighbouring glaciers. As in Wallis et al (2023a), these cases There is broad consistency in the timing of discharge trend changes amongst west AP glaciers (Figures 4 & 5). A vast majority of glaciers with significant discharge trend increases began to accelerate during the austral summer of 2020/2021 (Figure 5), though there is spread around this period (Figures 3 & 4d).…”

“…The majority of glaciers further north, which are not exposed to CDW, exhibit muted or no change in grounding line discharge trends (Fig 4c). There is variability in the timing and magnitude of glacier response along the coast, which will be governed by individual glacier geometry (Seehaus et al, 2018), proximal fjord bathymetry (Bao and Moffat, 2024;Wallis et al, 2023a) as well as the competition between distinct processes (e.g. crossshelf transport and modification of CDW vs transport of cold water from the Weddell Sea around the tip of the Peninsula) setting the subsurface ocean temperature (Moffat and Meredith, 2018;Venables et al, 2017).…”

“…More recently, a large and sustained acceleration and retreat of Cadman Glacier on the west AP has been documented (Wallis et al, 2023a). This acceleration and retreat began in 2018 during a period of anomalously high subsurface ocean temperatures on the continental shelf, due to an incursion of warm CDW.…”