Abstract
The West Antarctic Peninsula (WAP) is a highly productive marine ecosystem where extended periods of change have been observed in the form of glacier retreat, reduction of sea-ice cover and shifts in marine populations, among others. The physical environment on the shelf is known to be strongly influenced by the Antarctic Circumpolar Current flowing along the shelf slope and carrying warm, nutrient-rich water, by cold waters flooding into the northern Bransfield Strait from the Weddell Sea, by an extensive network of glaciers and ice shelves, and by strong seasonal to inter-annual variability in sea-ice formation and air–sea interactions, with significant modulation by climate modes like El Niño–Southern Oscillation and the Southern Annular Mode. However, significant gaps have remained in understanding the exchange processes between the open ocean and the shelf, the pathways and fate of oceanic water intrusions, the shelf heat and salt budgets, and the long-term evolution of the shelf properties and circulation. Here, we review how recent advances in long-term monitoring programmes, process studies and newly developed numerical models have helped bridge these gaps and set future research challenges for the WAP system.This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.
Highlights
The West Antarctic Peninsula (WAP) has undergone significant warming in the twentieth century, with observed changes reaching 3◦C over the period 1955–2004 [1], as well as warming of the surface ocean of approximately 1◦C [2] in the same period
The former is associated with the Antarctic Circumpolar Current (ACC), and the latter with the Antarctic Peninsula Coastal Current (APCC), a strong, narrow current forced by freshwater discharge and downwelling-favourable winds near the coast [42]
A consistent body of research shows that small ocean eddies are critical to explain the supply of Upper Circumpolar Deep Water (UCDW) [33,38,58,59], while Lower Circumpolar Deep Water (LCDW) probably results from a more steady overflow into deep troughs on the shelf [33]
Summary
The West Antarctic Peninsula (WAP) has undergone significant warming in the twentieth century, with observed changes reaching 3◦C over the period 1955–2004 [1], as well as warming of the surface ocean of approximately 1◦C [2] in the same period. A more recent study using repeated hydrography along the Drake Passage shows that this export of Weddell Water along the north slope of Elephant Island is probably a result of wind-driven modulation on the Weddell Sea, with relatively warmer, saltier waters being exported to the WAP when wind stress becomes more cyclonic over the gyre [32] The fate of this current has not been determined, but there is no evidence of it reaching Boyd Strait or the central. The near-surface circulation on the central WAP is characterized by flow towards the northeast along the outer shelf and slope, and towards the southwest, following the coast, near the shore (figure 1) The former is associated with the ACC, and the latter with the Antarctic Peninsula Coastal Current (APCC), a strong, narrow current forced by freshwater discharge and downwelling-favourable winds near the coast [42]. At least four large banks are evident in the mid-shelf bathymetry between Adelaide and Anvers Islands, suggesting that multiple such retention areas are likely to exist, this requires further study
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