Parts of the North Atlantic are setting winter heat records, allowing species ranging from swordfish to jellyfish to thrive beyond their normal ranges in a shift linked by many scientists to global warming.
Temperatures in Arctic waters off northern Europe at the tail end of the Gulf Stream, for example, are about 6.7 Celsius, the highest for early January since records began in the 1930s, according to Norway’s Institute of Marine Research.
The world’s oceans are already in a warming trend that could alter fish stocks, perhaps damaging coral reefs that are vital nurseries for tropical species while boosting northern stocks of cod or herring.
A type of Black Sea jellyfish seems to have become established off Scandinavia, perhaps flushed out of the ballast tanks of visiting ships and now able to survive because of less chilly waters in winter.
Norway’s Institute of Marine Research said 18 tropical swordfish had been seen off Norway since 1967 and sightings were becoming more frequent. Four were spotted in 2006 alone, including a 22 kg specimen caught on November 14.
In recent years, salmon have been seen swimming north of the Bering Straits between Russia and Alaska, and jellyfish plagued Mediterranean beaches in 2006. Over-fishing and destruction of habitats is also disrupting marine life.
Many scientists link high global air and water temperatures in recent months to an El Nino weather event warming the eastern Pacific, and to global warming stoked by burning fossil fuels.
The longer-term warming trend is affecting all oceans. “The Indian Ocean has had an overall warming trend attributed to the overall warming of the oceans,” said Nerilie Abram of the Australian National University.