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Polar Ecosystems: The Arctic The Arctic is a deep basin & much of this sea is a permanently frozen ice cap. Marine ecosystems in the Arctic face the challenges of reduced sunlight under the ice & water that’s barely above freezing. For these reasons, diversity of organisms is limited under the permanent ice cap. Species that do live in these conditions have special adaptations. These include antifreezing compounds in their blood & extremely low metabolisms. Polar Ecosystems: The Arctic At the edge of the ice cap, however, life intensifies especially between March & September. As the sun melts ice in the spring, water flows off the ice, sinking into deep water. Warm currents from the south interact with the cold water at the continental shelf edges. This process churns up nutrients from the shelf bottom. This ecosystem flourishes from the churned up nutrients. Polar Ecosystems: The Arctic Extremely high productivity occurs along an arc in the North Pacific & across the North Atlantic from April to August. These waters support massive fisheries, marine mammals, & other organisms. Polar Ecosystems: The Antarctic Antarctica has a more extreme climate than the Arctic. Also, the Antarctic differs geographically from the Arctic. Antarctica, is a continent, not a frozen sea. It’s also not enclosed by the continental shelves of other continents. Instead, it has its own continental shelf. The deepest & broadest ocean ring surrounds the Antarctic. For these reasons, the Antarctic ecosystem has differences & similarities compared to the Arctic. Polar Ecosystems: The Antarctic During the winter, sea ice surrounding Antarctica freezes, adding an area about the size of North America. When summer comes, the melting of this sheet sets off an explosion of bioproductivity. Winds blowing along the coast result in Ekman Transport, which moves water away from the continent at the surface, causing upwelling in the area. Polar Ecosystems: The Antarctic This nutrient-rich deep water reaches the surface at the Antarctic Divergence. This is the largest nutrient-rich area on Earth. The Antarctic Divergence supports massive phytoplankton blooms from November through the southern summer. The copepod & krill populations are larger than any other species population found in any other ecosystem. Single krill swarms have been estimated as exceeding 100 million tons, which is more than the world’s annual commercial fish catch. Polar Ecosystems: The Antarctic The productive water zone extends northward until it meets the warm Atlantic, Indian, & Pacific waters. As in the Arctic, organisms living in the coldest Antarctic ecosystems have special adaptations. Because the Antarctic is a relatively isolated ecosystem, most species are specialized & found only in the Antarctic.