Temperatures in parts of the North Atlantic Ocean are soaring off the charts, with an “exceptional” marine heat wave happening off the coasts of the United Kingdom and Ireland, sparking concerns about impacts on marine life.
Marine Heat Wave
Parts of the North Sea are experiencing a category 4 marine heat wave – defined as “extreme” – according to the National Oceanic and Atmospheric Administration. In some areas, water temperatures are up to 5 degrees Celsius (9 Fahrenheit) hotter than usual. Global oceans have been exceptionally warm for months. April and May saw the highest ocean surface temperatures for those two months since records began in 1850. The regional picture is even more stark, according to the UK Met Office: Temperatures in the North Atlantic in May were around 1.25 degrees Celsius (2.25 Fahrenheit) above average.
The heatwave is “very exceptional,” said Mika Rantanen, a researcher at the Finnish Meteorological Institute. It is “currently the strongest on Earth,” he told CNN. Richard Unsworth, an associate professor of biosciences at Swansea University in the UK and a founding director of Project-Seagrass, called the Atlantic heat wave “totally unprecedented.” Risks are high for marine species, such as fish, coral and seagrass – many of which adapted to survive within certain temperature ranges. Hotter water can stress and even kill them.
The El Nino Effect
El Niño, which tends to have a warming effect globally, is expected to drive temperatures even higher this year. And other factors may also play a role, including a lack of dust from the Sahara, which usually helps cool the region by reflecting away sunlight. “Weaker than average winds have reduced the extent of dust in the region’s atmosphere potentially leading to higher temperatures,” said Albert Klein Tank, the head of the Met Office Hadley Centre, in a statement.
Weaker winds may also have helped increase temperatures, as strong westerly winds typically cool the ocean surface, Rantanen said. Another potential driver of ocean heat could be anti-pollution regulations which require ships to cut sulfur in their fuel, reducing aerosols in the atmosphere. While these aerosols have a negative impact on human health, they also have a cooling impact by reflecting away sunlight.
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