The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Polynyas (nonlinearly shaped openings enclosed in sea ice) are vital components of both physical and biological systems in ice-covered seas. Little is known about polynya-tide interactions in fjords, particularly in the Pangnirtung Fjord, a seasonally ice-covered fjord located on the southern Baffin Island, Nunavut, Canada. The Fjord is home to an indigenous community of about 1500 people, and it connects to Cumberland Sound via a shallow sill (~20 m). A small (4km x 2km) recurring polynya has been observed near the sill location. The large tidal range in the Fjord (up to 6.7 m) suggests a need to test the tidally forced polynya hypothesis in which tidal flows over the sill inject heat to the surface waters. However, the lack of observations in this remote location has so far prevented a quantitative investigation of the polynya-tide interaction. In this study, we demonstrate the new technological capacity of the SWOT (Surface Water and Ocean Topography) mission for high-resolution mapping of small recurring polynya in an Arctic fjord. We achieve this using daily data during the 1-day-repeat (calibration/validation) orbit phase from the KaRIn instrument (Ka-band wide-swath synthetic aperture Radar Interferometer) on board the SWOT satellite. We compare and validate the SWOT's daily sea surface heights and ice conditions with tide-gauge derived water levels and MODIS optical images, respectively. Our analysis seems to support the tidally forced polynya hypothesis in the Pangnirtung Fjord.

tide,polynya,fjord,Arctic,SWOT