Seeds of Change: Investigating the Impact of Antarctic Basal Channel and Persistent Polynya Co-Evolution on Ice Shelf Stability

Funding Program: NASA Cryospheric Science
Start Date: 1 February 2022
End Date: 31 January 2025
Collaborating Institutions: University of Colorado Boulder, University of Manitoba, University of St Andrews, University of Berkeley

Ice shelves and their tributary glaciers that drain Antarctica account for almost the entirety of net mass loss from the Antarctic Ice Sheet, the source of the greatest uncertainty in 21st-century sea-level rise projections. Nearly half of the glacier ice that reaches the ocean to form floating ice shelves is lost to basal melting by the ocean. This melting varies substantially in time and space as a result of complex climate, ocean, and ice interactions, making projections of future ice loss difficult. In particular, enhanced localized basal melt rates can incise ice-shelf basal channels that may structurally weaken ice shelves. Many of these channels convey water sourced from the upstream locations where the channels form to the edge of the ice shelf. This outflow often includes residually warm ocean water with enough heat to maintain local sea icefree ocean conditions seasonally or year-round for small areas near the ice front, known as persistent polynyas. The water in these polynyas represents a mixture between the ocean water mass that initiated basal melt and the melt content entrained as the water exits the ice shelf cavity. Variability in these features over time, as a result of climate and oceanographic changes, provides insight into ice-shelf evolution (e.g., strain and melt rates) and the processes that can weaken ice shelves. However, mapping of basal channels and their impact on ice-shelf evolution are limited. Further, direct in situ outflow measurements are sparse and little work has explored the use of remote sensing for this task.

In this project led by postdoctoral scholar Dr. Tasha Snow, we will use optical and thermal infrared imagery from the Landsat 7 through 9, Aqua and Terra, Sentinel-2, and Sentinel-3A/B instrumentation in a multi-sensor and multi-modal data fusion investigation that will assess the characteristics variability of the persistent polynya ice-ocean features in Antarctica. Data from field observations and ICESat-2 laser altimetry will be examined using modern machine learning approaches and cloud-based, open-sourced workflows. The proposed work is organized around three specific goals:

1. Automate persistent polynya detection and characterization for community use;
2. Optimize Landsat, MODIS, and Sentinel-3 SST retrievals to build year-round upper ocean temperature records for multiple Antarctic basal channel outflows; and
3. Assess ice shelf and water outflow co-evolution using a data fusion framework for deriving ice shelf and ocean parameters.