The life cycle of small- to medium-sized icebergs in the Amundsen Sea Embayment

Abstract

An object-based method for automatic iceberg detection has been applied to Advanced Synthetic Aperture Radar images in the Amundsen Sea Embayment (ASE), Antarctica. The images were acquired between 1 January 2006 and 8 April 2012 under varying meteorological, oceanographic and sea-ice conditions. During this time period, the icebergs were counted (average 1370 ± 50) and their surface area was estimated (average 1537.5 km 2). The average surface area was about 2.5 times larger than the annual calved area (620 km 2), indicating that the average iceberg age in the ASE is about 2.5 years, which was confirmed by observed residence times based on drift tracks. Most of the ASE icebergs were less than 1500 m long, and almost 90% of them were smaller than 2 km 2. The proportion of small-and medium-sized icebergs (84.4%) was significantly higher than in the open ocean, where large icebergs (>10 km 2) account for nearly the whole iceberg surface area. The opposite was true for the freshly calved icebergs in the ASE. The data indicate that the creation of icebergs in the ASE is dominated by steady small-to medium-scale calving from ice shelves fringing the embayment. In addition, rare calving events of giant icebergs occur on a decadal timescale. There is also some import of icebergs from the Bellingshausen Sea further east along the coast, in particular after large calving events there.

The geochemical and mineralogical fingerprint of West Antarctica's weak underbelly: Pine Island and Thwaites glaciers

“…ages match the previously observed 40 Ar/ 39 Ar age peak offshore from the Cosgrove Ice Shelf; Figures 4, 5). This is supported by recently published iceberg trajectories, documenting that icebergs calved along this coast drift SSW-wards into central PIB before turning westwards (Mazur et al, 2019).…”

“…the area north of ca. 73° S, they turn westwards and continue to drift in a westerly direction across the shelf (Mazur et al, 2019).…”

“…In contrast, icebergs sourced from the Dotson and Crosson ice shelves are directed westwards immediately after calving (Mazur et al, 2019), ruling out eastward transport of IRD from there (Figure 4). Mukasa and Dalziel, 2000) and in the Ellsworth-Whitmore Mountains (~170-210 Ma K-Ar whole rock and U-Pb zircon; Craddock et al, 2017).…”

“…Iceberg drift across the Amundsen Sea shelf is generally directed westwards and driven by surface ocean currents, wind and sea-ice drift, with a strong bathymetric control for deepkeeled icebergs (Mazur et al, 2017(Mazur et al, , 2019.…”

Changes in the Area, Thickness, and Volume of the Thwaites B30 Iceberg Observed by Satellite Altimetry and Imagery

“…The advent of satellite remote sensing greatly increased our capability to study icebergs. A wide range of studies have employed repeat satellite imagery to track changes in iceberg area (Bouhier et al, 2018;Budge and Long, 2018;Han et al, 2019;Li et al, 2018;Mazur et al, 2019;Scambos et al, 2008). The most common approach to measure iceberg thickness is using satellite altimeter measurements of their freeboard, which began in the late 1980's (McIntyre andCudlip, 1987).…”