Speed variability of Wordie Bay outlet glaciers driven by subglacial hydrology

The Antarctic Peninsula (AP) accelerating mass loss is dominated by ice dynamics [1]. The most up-to-date research reveals a widespread increase in discharge from glaciers on the west coast of the Antarctic Peninsula since 2018 [2]. The western AP is roughly divided by Brabant and Anvers islands of the Palmer Archipelago between the cooler waters of the Bransfield Strait to the north and the warmer Circumpolar Deep Water (CDW) to the south. The warm ocean water is widely accepted to be the main driver for acceleration of marine-terminating ice streams by a reduction of the resistive force due to ocean-driven ice shelf thinning, ice shelf disintegration, terminus retreat and increasing ice damage [3, 4].

In addition to the long-term ice dynamics for decades, short-term seasonal speed variability on the grounded ice sheet of AP have been reported that an average summer speed-up of 12.4% for tidewater glaciers in western AP [5] and 15% for glaciers feeding into the George VI Ice Shelf [6]. Current research links these speed fluctuations with seasonal ocean warming and surface melt [5], however the seasonality of speed varies between years and regions. Changes in subglacial hydrology can have large effects on glacier dynamics, including reductions in basal friction and short-term accelerations of ice flow, but until now these changes have remained challenging to detect.

In our study, we focused on the dynamics and driving mechanisms of outlet glaciers that flow into Wordie Bay on western AP. After the Wordie Ice Shelf break-up, these former tributary glaciers have significantly increased their flow speed and dynamically thinned. The mainstream Fleming Glacier is currently one of the fastest outlet glaciers on western AP. We use high-resolution digital elevation model (DEM) data from the TanDEM-X mission and Reference Elevation Model of Antarctica (REMA), and the radar depth sounder (RDS) data from the Center for Remote Sensing and Integrated Systems (CReSIS) mission to detect new subglacial lakes. We also use time-series DEMs to estimate subglacial lake height anomalies and analyze how subglacial lake filling and drainage processes affect glacier surface velocities. To further explore the basal conditions of sliding, we invert for time-series basal drag distribution with the Ice-sheet and Sea-level System Model (ISSM) using high resolution geometry and velocity data from remote sensing.

 

Reference:

• Otosaka, I.N., et al., Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020. Earth Syst. Sci. Data, 2023. 15(4): p. 1597-1616.
• Davison, B.J., et al., Widespread increase in discharge from west Antarctic Peninsula glaciers since 2018. The Cryosphere, 2024. 18(7): p. 3237-3251.
• Cook, A.J., et al., Ocean forcing of glacier retreat in the western Antarctic Peninsula. Science, 2016. 353(6296): p. 283-286.
• Wallis, B.J., et al., Ocean warming drives rapid dynamic activation of marine-terminating glacier on the west Antarctic Peninsula. Nature Communications, 2023. 14(1): p. 7535.
• Wallis, B.J., et al., Widespread seasonal speed-up of west Antarctic Peninsula glaciers from 2014 to 2021. Nature Geoscience, 2023. 16(3): p. 231-237.
• Boxall, K., et al., Seasonal land-ice-flow variability in the Antarctic Peninsula. The Cryosphere, 2022. 16(10): p. 3907-3932.