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Ice-cold hotspots

Nature Reports Climate Change, page 32 (2007) | Download Citation

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Image: © Henry A Ruhl

Rising global temperatures are causing Antarctic ice shelves to disintegrate, creating thousands of free-drifting icebergs in the nearby Weddell Sea. A novel study has now found that these migrant icebergs serve as hot spots of ocean life, enhancing local primary production, which could increase the export of organic carbon to the deep sea.

Kenneth L. Smith Jr of the Monterey Bay Aquarium Research Institute and colleagues sampled two icebergs — one 0.1 km2and the other 30.8 km2 in aerial surface area — and their surrounding waters in the Weddell Sea during austral spring 2005. They found a zone of enhanced marine life, including significantly increased phytoplankton, chlorophyll, krill and seabirds, extending almost 4 km from both icebergs.

The 'hotspots' of marine activity surrounding the icebergs thrive on land-based minerals and organic matter released from the icebergs as they melt. Using iceberg population estimates from NASA satellite imagery, Smith and colleagues calculated that around 40% of surface waters in the region have enhanced productivity owing to this additional fertilizer. Climate models should include the influence of icebergs when calculating how much carbon the ocean sequesters, say the researchers.

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https://doi.org/10.1038/climate.2007.28

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