Drivers of recent ice speed variability on Cook West Glacier, East Antarctica

Changes in flow speed of large Antarctic outlet glaciers are a key indicator of the stability of the ice sheet. West Antarctica, primarily along the Amundsen Sea facing coast, is known to be in dynamic imbalance and losing significant mass, but a less clear picture exists in East Antarctica. Observing ice dynamic change in East Antarctica, and identifying its drivers, will allow us to better constrain estimates of future ice mass loss.

The Cook Glacier system in George V Land drains a large volume of ice from the Wilkes Subglacial Basin. This is one of the largest regions in East Antarctica susceptible to the marine ice sheet instability and contains 3-4m of sea level rise equivalent. Cook Glacier has two distinct flow units: Cook West Glacier (CWG), which has a readily calving ice front near the grounding line; and the slower but larger Cook East Glacier (CEG), which flows into an extensive ice shelf.

By offset tracking of high-resolution imagery from the Sentinel-1 synthetic aperture radar satellites, we generate a dense data cube of ice velocity observations in this region from 2015-2024. In this period, ice speeds on CWG have followed a sinusoidal pattern (with an approximately 2-year period), superimposed on a positive linear trend. Meanwhile, neither this variability nor trend have been observed on CEG, where the speed of grounded ice has been stable through the study period.

To investigate drivers of this speed variability on CWG we compare our dense time series of ice speed observations with climate reanalysis data. We present the propagation and timings of speed change along CWG and using the Copernicus Marine Service Global Ocean Physics reanalysis and ECMWF ERA5 atmospheric reanalysis, investigate correlation of this variability with environmental variables including wind speed, air temperature, ocean temperature, sea surface height, and surface pressure.