Monitoring iceberg A68 calved from the Larsen C IceShelf using satellite remote sensing

Abstract

Iceberg A68 calved from the Larsen C Ice Shelf, Antarctic Peninsula, in July 2017. In this study, we analyze the initial evolution of iceberg A68 in terms of changes in its area, drift speed, rotation, and freeboard using Sentinel-1 synthetic aperture radar (SAR) images and CryoSat-2 SAR/Interferometric Radar Altimeter observations. The study period extends from July 2017 to end of 2018. The area of the iceberg sharply decreased in mid-August 2017 and mid-May 2018 via large calving. The area of A68 decreased only 2% over 1.5 years. A68 was relatively stationary until mid-July 2018, while it was surrounded by the Larsen C Ice Shelf front and a high concentration of sea ice, and when its movement was interrupted by the shallow seabed. The iceberg passed through the front of the Larsen C Ice Shelf after July 2018, showing a higher drift speed and greater rotation. The freeboard of A68 decreased at an average rate of 0.80± 0.29 m/a during FebruaryNovember 2018, which could have been due to basal melting. The freeboard measured from CryoSat-2 could represent the returned signal from the snow surface on the iceberg. Based on this, the average rate of freeboard change was estimated at 1.62± 0.30 m/a during the study period considering an average rate of snow accumulation of 0.82±0.06 m/a predicted by reanalysis data from the Modern-Era Retrospective analysis for Research and Applications, Version 2.