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par5zmi4gy · Wysłany: Czw 5:37, 31 Mar 2011

Warming is happening at such a rapid rate – particularly in the Arctic – that species adapted to ice and Arctic conditions have no recourse but retreat. Bering Sea ice melt is averaging three weeks early, and the cold pool is contracting. Since early 1980’s, the southern edge of the cold pool – which both defines the transition zone between arctic and subarctic communities, and supports the specialized bottom-dwelling ecosystem – has retreated 230 km (143 miles) northward.
Fish and shellfish distribution is largely controlled by temperature. Each species prefers a specific temperature range, shunning (if possible) deviation from that range.
Of course [link widoczny dla zalogowanych], marine ecosystems are very dynamic [link widoczny dla zalogowanych] with natural warm and cold cycles periodically flip-flopping a region’s dominant species. There are signs, however, that the overall warming underway in the Bering Sea may swamp these natural pendulums.
Basic Oceanography
This diversity is not strictly a function of upwelling and summer sunlight, however; the region’s winter ice also plays a role. Within the Bering itself, each winter’s ice cover creates a pool of cold bottom water on the continental shelf. This “cold pool” lingers throughout the summer and supports a specialized seafloor ecosystem, including much of Alaska’s highly profitable crab fisheries.
Deadliest Catch is an award winning documentary series following Alaskan crab boats and their crews as they fish for king crab and Opilio crab. Theirs is a dangerous profession, made so by the waters they fish: a tempest-ridden marginal sea in the very throes of climate change.
Read on
Is Climate Change Affecting Grey Whale Reproduction and Survival?
Captain Phil Harris on Discovery Channel Deadliest Catch
Humboldt Squid Invade Gulf of California
The world's most extensive eelgrass bedsAt least 450 species of fish, crustaceans, and mollusks50 species of seabirds25 species of marine mammals
The Bering Sea is a northern extension of the North Pacific Ocean. North of the Aleutian Islands, sandwiched between western Alaska and eastern Russia [link widoczny dla zalogowanych], it is the world's third-largest semi-enclosed sea. Like other high-latitude marginal seas, much of the Bering Sea freezes during the Arctic winter.
Sea level in the Bering Sea is approximately 0.5 meters higher than the Arctic Ocean, causing a mean northward transport through the Bering Strait up into the Arctic. This northward flow is fed by nutrient rich slope waters of the Bering Slope Current, itself the eastern boundary current of the Bering Sea Gyre. (The Bering Sea Gyre is a large cyclonic current system in the Aleutian Basin). These nutrient rich waters well upwards from depth, shoal over the Bering’s large, shallow, northern shelf, and fuel the region’s seasonal phytoplankton blooms – the foundation of the region’s food web.
What Does Climate Change in the Bering Sea Mean?
Bering Sea Fisheries and Climate Change
The Bering Sea’s broad, shallow continental shelf is home to a rich variety of plants and animals. They include:
The challenge with climate ch
At present, the U.S. Bering Sea fishery constitutes approximately 40% of the U.S. and about 5% of the world harvest of fish and shellfish.
The sub-arctic species are following suit. Two decades of data show at least 45 fish species have shifted their centers of distribution north since the early 1980’s.
Welcome to the Bering Sea.
Bering Sea Productivity
The Bering Sea