Eighteen-year record of circum-Antarctic landfast-sea-ice distribution allows detailed baseline characterisation and reveals trends and variability

Abstract

Abstract. Landfast sea ice (fast ice) is an important though poorly understood component of the cryosphere on the Antarctic continental shelf, where it plays a key role in atmosphere–ocean–ice-sheet interaction and coupled ecological and biogeochemical processes. Here, we present a first in-depth baseline analysis of variability and change in circum-Antarctic fast-ice distribution (including its relationship to bathymetry), based on a new high-resolution satellite-derived time series for the period 2000 to 2018. This reveals (a) an overall trend of -882±824 km2 yr−1 (-0.19±0.18 % yr−1) and (b) eight distinct regions in terms of fast-ice coverage and modes of formation. Of these, four exhibit positive trends over the 18-year period and four negative. Positive trends are seen in East Antarctica and in the Bellingshausen Sea, with this region claiming the largest positive trend of +1198±359 km2 yr−1 (+1.10±0.35 % yr−1). The four negative trends predominantly occur in West Antarctica, with the largest negative trend of -1206±277 km2 yr−1 (-1.78±0.41 % yr−1) occurring in the Victoria and Oates Land region in the western Ross Sea. All trends are significant. This new baseline analysis represents a significant advance in our knowledge of the current state of both the global cryosphere and the complex Antarctic coastal system, which are vulnerable to climate variability and change. It will also inform a wide range of other studies.

Landfast Ice Controls on Turbulence in Antarctic Coastal Seas

“…In 2016 the seasonal change in landfast ice cover for the Antarctic was ∼4 × 10 5 km 2 (Figure 5, Table 1), close to the climatological average cycle (Fraser et al, 2021). From the preceding boundary layer arguments, and with knowledge of wind stress and tidal currents, and using the pan-Antarctic PWP model simulations we have quantified: (a) The total tidal energy dissipated by the presence of a rigid ice lid; (b) the corresponding effective reduction in wind TKE entering the ocean due to landfast ice; (c) the comparative seasonal cycle of tide and wind sourced TKE in the SLIZ OSBL; and (d) the wind-induced heat flux into the OSBL of the SLIZ during a different calendar year (2010).…”

“…Unlike East Antarctica (Fraser et al, 2012), variability of landfast ice in other Antarctic sectors was poorly described until the recent availability of a circum-Antarctic dataset of landfast ice cover, a valuable 3 of 18 resource used in this article (Fraser et al, 2020). Positive trends in landfast ice extent have since been reported in the Dronning Maud Land, Western Indian Ocean, Australian and Bellingshausen Seas sectors (newly defined regions); all positive trends are significant (Fraser et al, 2021). Visual observations from Rothera Station (Figure 2) indicate that smooth, thermodynamically formed landfast ice covers Ryder Bay completely during most winter seasons with significant variability in the duration and extent of cover (Venables & Meredith, 2014).…”

Comment on tc-2022-94

“…In contrast to the three melt zones discussed above, patterns 3 and 6 show a clear melt-free region in the centre of the shelf, located between Masson Island and an area of fast ice that is near-permanent (Fraser et al, 2021). This central zone has a higher surface elevation (45-55 m above sea level) than its surroundings to the north and west (25-35 m) (Stephenson and Zwally, 1989;Howat et al, 2019), and cooler average summer temperatures (~0.5 K lower; Fig.…”

A Summary of United States Research and Monitoring in Support of the Ross Sea Region Marine Protected Area

“…These sea ice trends have important implications for altering the structure and dynamics of the Ross Sea ecosystem, including ocean access by air-breathing predators, primary productivity, and the numerical and functional relationships among higher trophic level species (e.g., [28,29]). Fast ice prevalence shows minimal discernable trend, though, at least in McMurdo Sound, the date of minimum fast ice extent has been occurring later and date of fast ice advance has been occurring earlier [30,31]. A slight reduction in fast ice seasonal persistence may be occurring in western McMurdo Sound [30].…”