Seaglider and Float Observations Beneath Dotson Ice Shelf, West Antarctica

In Antarctica and Greenland, interactions between Oceans and Ice sheets are crucial to the regulation of the global overturning circulation and the current acceleration of ice flow into the ocean and associated global sea-level rise. Satellite and moored ocean observations demonstrate with increasing temporal and spatial resolution that the interaction is complex, and occurs on broad ranges of scales. But the establishment of clear relationships between ocean and ice sheet will remain elusive until we obtain direct, sustained in-situ observations beneath and near the ice shelves. Three Seagliders and four EM-APEX floats sampled oceanic properties near and under the Dotson ice shelf in West Antarctica in January 2018, with observations continuing through the winter into summer 2018/2019. Observed water properties generally confirm expected features of under ice shelf circulation, with deep inflowing warmer water on the eastern side of the cavity and shallower outflowing meltwater on the western side. However, initial analysis of the hundreds of kilometers of tracks already obtained also reveal new and potentially important features for ice/ocean interactions: (i) past bathymetric inversion from airborne gravity observations suffered significant biases, and a predicted under-ice shelf ridge seemingly blocking access for warmer deep waters to the ice grounding line does not in fact exist; (ii) large variability along the ice shelf calving front is associated with mesoscale intrusions of open ocean water in the ice cavity; and (iii) near ice water properties and stratification do vary greatly, showing large mixed layers in some locations, and strong stratification up to within a meter of the ice in others. These preliminary observations are only a tantalizing glimpse at the potential the technology developed for this project offers for future explorations.