Abstract
Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine “icescape”, including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95–110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160–170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40–100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors.
Highlights
Better identification, quantification and understanding of change and variability in global sea ice coverage are increasingly recognised as a high priority in climate and ecological research
Seasonality here collectively describes the timings of annual sea ice advance and retreat and resultant duration at any given location – as opposed to sea ice extent, which is a descriptor of the area of ocean covered by sea ice above a threshold concentration
The dashed lines indicate the location of the Southern Boundary of the ACC (SB-ACC), and the dash-dotted line that of the Southern Antarctic Circumpolar Current Front, VAP Valdivia Abyssal Plain, and PET Princess Elizabeth Trough
Summary
Quantification and understanding of change and variability in global sea ice coverage are increasingly recognised as a high priority in climate and ecological research. The 110uE and 140uE transects bisect regions of predominantly earlier ice advance, later retreat and increasing duration (Figure 6), and are characterised by positive ice concentration trends across fairly extensive zones that are largely located mid-pack, with negative trends in the outer pack and coastal margins (Figure 7C–D).
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