UNIVERSITY OF BRISTOL (GB)
Arctic-SummIT will deliver, for the first time, a sea ice thickness product during summer months from the ESA Cryosat-2 satellite. As the extent of Arctic sea ice has declined at unprecedented speed over the past few decades, we have been able to view only limited snapshots of the ice cover’s thickness. Pan-Arctic observations of sea ice thickness have been obtained in recent years by satellite altimeters such as ICESat and Cryosat-2, but conventionally these data are only available during winter months. Our current understanding of basin-scale sea ice melting patterns during summer are limited to poorly-constrained ice-ocean model simulations, at a time when the ice cover is most dynamic, not to mention biological productivity and ice-ocean geochemical fluxes are most active. Moreover, advanced knowledge of ice conditions – thickness in particular – are critical for managing sustainable commercial enterprises, such as shipping and oil & gas extraction, in the northern polar seas.
This project will develop a novel algorithm for obtaining sea ice thickness from satellite altimetry, even as the ice is melting. The conventional technique for separating sea ice from water (i.e. leads within the ice pack) relies on classifying altimeter waveforms through the shape of echoes, but breaks down when meltwater ponds forming at the ice surface appear the same as leads. However, pilot research alongside partners from the Canadian Ice Service (CIS) has demonstrated that other characteristics of the Cryosat-2 echoes, particularly the calibrated backscatter coefficient of the radar, can separate ice from ocean regardless of the surface melting state. Arctic-SummIT will develop this exciting discovery into a rigorous method for measuring sea ice thickness during summer months. By the end of the project, a unique, pan-Arctic sea ice thickness product will be produced for July-September over the full Cryosat-2 data record: 2011-2018+, filling the summer ‘gap’ we have presently. Exchange of sea ice between the central Arctic Ocean and, for instance, the Canadian Arctic Archipelago (CAA) or Fram Strait will then be determined from the product of ice volume from Cryosat-2, and high-resolution ice drift speed obtained from Synthetic Aperture Radar (SAR) imagery including the ESA Sentinel-1 constellation and the Canadian Space Agency’s (CSA) RADARSAT-2. Seasonal ice volume fluxes will be made available to the academic community, alongside the new summer sea ice thickness product, through an online portal hosted via ESA at the University of Bristol.