Introduction

State

The Central Arctic Ocean and the marginal seas such as the Chukchi, East Siberian, Laptev, Kara, White, Greenland, Beaufort, and Bering Seas, Baffin Bay and the Canadian Archipelago (Figure 36G.1) are among the least-known basins and bodies of water in the world ocean, because of their remoteness, hostile weather, and the multi-year (i.e., perennial) or seasonal ice cover. Even the well-studied Barents and Norwegian Seas are partly ice covered during winter and information during this period is sparse or lacking. The Arctic has warmed at twice the global rate, with sea-ice loss accelerating (Figure 36G.2, ACIA, 2004; Stroeve et al., 2012, Chapter 46 in this report), especially along the coasts of Russia, Alaska, and the Canadian Archipelago (Post et al., 2013). Changes in ice cover, ocean warming, altered salt stratification, alterations in water circulation and fronts, and shifts in advection patterns show that oceans within the Arctic are subjected to significant change, and may face even more change in future (Wassmann, 2011 and references within). The Central Arctic Ocean and the marginal seas are home to a diverse array of algae and animals, some iconic (e.g., polar bear), some obscure, and many yet to be discovered. Physical characteristics of the Arctic, important for structuring biodiversity, include extreme seasonality resulting in short growing seasons and annual to multi-annual ice cover. The Central Arctic Ocean has a deep central basin (>4000 m depth) surrounded by the most extensive shelves of all the world's oceans, and is characterized by extensive (albeit declining) ice cover for much of the year. This offers a vast number of different habitats created by the shape of the seabed, latitude, history of glaciations, proximity to the coastline and rivers, oceanic currents, and both the seabed and the ice as a substrate. Barriers for dispersal, such as the ice plug in the Canadian High Arctic, effectively separate stocks of some marine mammals (Dyke et al., 1996). Polynyas, which are open water areas surrounded by ice, provide important foraging and refuge areas and contribute to Arctic biodiversity. Differences in ice cover, mixing between warm- and cold-water currents, or currents with different nutrient content, create a mosaic of nutrient-poor areas which is reflected in species diversity (ABA, 2014, Figure 36G.3).