21 Polar and ice-edge marine systems

Cold, seasonal and dominated by ice, the two polar regions are similar in many ways. Oceanographically, however, they are very different. The Arctic is a deep basin surrounded almost completely by extensive shallow continental shelves and continental land masses. Large river systems (Chapter 2) discharge significant volumes of fresh water and sediment into the Arctic basin, some of them carrying substantial pollution, and exchange with the Pacific and Atlantic Oceans is highly constrained. In direct contrast, the Antarctic is a single isolated land mass surrounded on all sides by a deep ocean contiguous with the three great ocean basins (Fig. 21.1). Climate change has been identified as the key environmental trend in both polar regions, with the most likely effect in the marine environment being mediated through changes in sea-ice dynamics (Clarke & Harris 2003) (Table 21.1). The polar regions play a critical role in the