Abstract
Predicting the impact of global warming on polar marine ecosystems requires the combined efforts of climate modelers and marine ecologists. A subset of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) climate model output for emission scenario ‘Special Report on Emission Scenarios’ (SRES) A1B (doubling of CO 2 from 360 and stabilizing at 720 after 2100) was used to identify the time period at which globally8 averaged surface air temperature will have increased by 2°C above pre8industrial levels. Criteria used to identify a subset of the better IPCC AR4 climate8model outputs for emissions8scenario A1B are provided, and an ensemble of models is selected to examine impacts on cetaceans in the Southern Ocean. The potential impacts of the predicted change in Southern Ocean sea8ice extent, concentration and seasonality, water masses, ocean circulation and frontal positions on resident cetacean populations (i.e. Antarctic minke whales Balaenoptera bonaerensis ) and migratory cetaceans are examined for the time of 2°C warming. Varying with specific Southern Ocean sector, Antarctic minke whales are expected to lose 5830% of ice8associated habitat in the Antarctic by the year of 2°C warming (i.e., 2042 for the ensemble average). Migratory cetaceans will travel farther (~385° latitude) to reach important Southern Ocean fronts where they forage. The potential impact of the southward displacement of Southern Ocean fronts and watermass boundaries (i.e. Polar Front and Southern Boundary of the ACC) is a reduction and compression of the frontal8associated habitat of Southern Ocean cetaceans around Antarctica. As these frontal features are seasonally important to migratory cetaceans (i.e., blue whale Balaenoptera musculus , humpback whale Megaptera novaeangliae , fin whale Balaenoptera physalus , and sperm whale Physeter macrocephalus ), it suggests a compression and reduction of valuable foraging habitat. The loss of 5830% of ice cover is expected to reduce the availability of krill Euphausia superba upon which resident and migratory cetaceans, and the Antarctic ecosystem.
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