Wintertime Polynya Structure and Variability From Thermal Remote Sensing and Seal-Borne Observations at Pine Island Glacier, West Antarctica

Abstract

Antarctica's ice shelves play a critical role in modulating ice loss to the ocean by buttressing grounded ice upstream. With the potential to impact ice-shelf stability, persistent polynyas (open-water areas surrounded by sea ice that occur across multiple years at the same location) at the edge of many ice-shelf fronts are maintained by winds and/or ocean heat and are locations of strong ice-ocean-atmosphere interactions. However, in situ observations of polynyas are sparse due to the logistical constraints of collecting Antarctic field measurements. Here, we used wintertime (May-August) temperature and salinity observations derived from seal-borne instruments deployed in

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

“…By location, the west polynya was largest on average (mean: 33 km 2 ; range: 269 km 2 ), followed by east (mean: 7 km 2 ; range: 110 km 2 ), other (mean: 6 km 2 ; range: 111 km 2 ), and mid (mean: 2 km 2 ; range: 19 km 2 ). Our observation that the western polynya had the largest mean areal extent is consistent with previous polynya observations covering shorter time periods (e.g., Bindschadler et al., 2011; Mankoff et al., 2012; Savidge, Snow, et al., 2023) and with both modeled and observed intensified outflow from the PIGIS cavity along the western shear margin (e.g., Nakayama et al., 2021; Thurnherr et al., 2014). We note that the other polynya category differs from the other three frontal polynyas (west, mid, east) in that it occurs offshore, not at the calving front edge (e.g., Figure S8 in Supporting Information ).…”

“…These observations suggest not only that polynya variability may influence ice dynamics, but also that large calving events can influence polynya dynamics (e.g., Cape et al., 2014). Therefore, polynya variability may be indicative of both: (a) ocean‐driven basal melt (e.g., Savidge, Snow, et al., 2023; Zheng et al., 2021), and potentially (b) rift initiation processes (i.e., precursor to calving)—two processes that are roughly equally responsible for all of the mass loss observed in Antarctica (Greene et al., 2022; Rignot et al., 2013; Walker et al., 2013).…”

“…Depending on plume volume and buoyancy, and local upper ocean stratification, these plumes sometimes reach the surface and can deliver enough heat to melt sea ice and form persistent, sensible‐heat polynyas. Sensible‐heat polynyas, which require a heat supply to form, are therefore surface expressions of subsurface ice‐ocean interactions that, when large enough, can be detected from visible (e.g., Alley et al., 2016), thermal (e.g., Bindschadler et al., 2011; Mankoff et al., 2012; Savidge, Snow, et al., 2023), and microwave (e.g., Markus & Burns, 1993; Massom et al., 2001) remote sensors. However, thermal and visible satellite images have spatial resolutions ∼10–200 times finer than passive microwave, making them ideal for monitoring the km‐scale sensible‐heat polynyas found at PIG.…”