Journal Article

Multi‐Decadal Record of Sensible‐Heat Polynya Variability From Satellite Optical and Thermal Imagery at Pine Island Glacier, West Antarctica

Savidge, Elena, Siegfried, Matthew R., Snow, Tasha

2023

Overview

Open ocean areas surrounded by sea ice and maintained by ocean heat, or sensible‐heat polynyas, are linked to key ice‐sheet processes, such as ice‐shelf basal melt and ice‐shelf fracture, when they occur near ice‐shelf fronts. However, the lack of detailed multi‐year records of polynya variability prevent assessing coupling between polynya and frontal dynamics. Here, we present the first multi‐decadal polynya area record (2000–2022) at Pine Island Glacier (PIG), West Antarctica, from thermal and optical satellite imagery. We found substantial interannual variability in polynya area, with consistencies in the timing of polynya opening, maximal extent, and closing. Furthermore, the largest polynya in our record (269 km2) occurred at PIG's western margin just 68 days before iceberg B‐27 calved, suggesting that polynya size and position may influence rifting dynamics. Our new data set provides a pathway to assess coevolving polynya and frontal dynamics, demonstrating the importance of building long‐term, year‐round polynya variability records. Plain Language Summary Persistent sensible‐heat polynyas are areas of open ocean surrounded by sea ice maintained by ocean heat. These surface features occur near ice‐shelf fronts at the coastal margins of Antarctica and therefore have the potential to impact ice‐shelf stability through heat transfer processes. However, our understanding of long‐term polynya variability remains limited due to the lack of multi‐year records documenting polynya evolution. Here, we use satellite imagery to measure polynya area near Pine Island Glacier (PIG) and build the first multi‐decadal record in Antarctica. We observed a large amount of year‐to‐year area variability from 2000 to 2022, with the largest polynya in our record (269 km2) occurring at the western edge of PIG just 68 days before a large iceberg calved from PIG. This correspondence suggests that polynya size and position may influence iceberg calving. Our new data set provides a pathway to assess potentially coupled ice and ocean processes, demonstrating the importance of building long‐term, year‐round polynya variability records. Key Points We generated a 22 years record of polynya area at Pine Island Glacier from satellite thermal and optical imagery Our data set shows high variability in sensible‐heat polynya area (0–322 km2) from 2000 to 2022 Large, marginal, and persistent sensible‐heat polynyas may reduce ice‐shelf buttressing and contribute to rift initiation and propagation

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Coastal fronts / Datasets / Frontal dynamics / Glaciers / Heat transfer / Ice calving / Ice shelves / Iceberg calving / Icebergs / Interannual variability / Ocean-atmosphere interaction / Oceans / Polynyas / Records / Rifting / Satellite imagery / Satellites / Sea ice / Standard deviation / Thermal imaging / Tidal fronts / Time series / Variability