OSLO (Reuters) - 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 (44.06 Fahrenheit), 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.
“The global oceans have been warming since the middle 1970s and several studies have shown that the warming can be attributed to a human-produced signal,” said James Hurrell of the U.S. National Centre for Atmospheric Research.
Off New York this week, rescuers guided eight dolphins into open water after they became stranded in a shallow cove, apparently because unusually warm waters meant fish on which they feed were staying closer to the coast.
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 (49 lb) specimen caught on November 14.
“There have been many record high temperatures in recent months,” said Jan Aure, a researcher at the Institute. “The climate regimes are changing and moving northwards.”
In Lista by the North Sea, for example, water temperatures were a record 8.5C (47.3F), 2-3 degrees (4-5 F) above normal for January.
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.
Abram said droughts in Indonesia and perhaps Australia might become more frequent as a result of changing ocean and monsoon conditions.
Not all is gloom, however. In a sign of how higher temperatures might help some fish stocks, a period of warmer waters in the 1920s allowed cod to spawn off Greenland and let a new stock break away from Icelandic waters. In the cooler 1960s, cod were unable to reproduce off Greenland and the stock collapsed.