Sudden Heat Increase in North Atlantic Seas Could Have Devastating Effects

Scientists have warned that an extreme marine heat wave off the UK and Ireland coasts is posing a major threat to marine species. According to the official blog of the UK’s Met Office, the global sea surface temperatures for April and May of this year were the highest since records began in 1850.

Last month was the warmest May on record in the North Atlantic, with temperatures about 1.25 degrees Celsius higher than average over the 1961 to 1990 reference period.

“The extreme and unprecedented temperatures show the power of the combination of human-induced warming and natural climate variability like El Niño,” said Daniela Schmidt, a professor of earth sciences at the University of Bristol, as The Guardian reported. “While marine heatwaves are found in warmer seas like the Mediterranean, such anomalous temperatures in this part of the north Atlantic are unheard of. They have been linked to less dust from the Sahara but also the North Atlantic climate variability, which will need further understanding to unravel.”

The Met Office said El Niño will likely keep temperatures high, which can kill fish and other marine life.

“Heat, like on land, stresses marine organisms. In other parts of the world, we have seen several mass mortalities of marine plants and animals caused by ocean [heatwaves] which have caused hundreds of millions of pounds of losses, in fisheries income, carbon storage, cultural values and habitat loss. As long as we are not dramatically cutting emissions, these heatwaves will continue to destroy our ecosystems,” Schmidt said, as reported by The Guardian.

Humans also rely on the ocean for food, oxygen and carbon dioxide removal.

Factors such as lack of dust in the atmosphere and trade winds have also contributed to the increased ocean temperatures.

“Typically, airborne dust from the Sahara helps to cool this region by blocking and reflecting some of the sun’s energy; but weaker than average winds have reduced the extent of dust in the region’s atmosphere potentially leading to higher temperatures,” said professor Albert Klein Tank of the Met Office’s Hadley Centre in the Met Office blog.

The rising sea-surface temperatures could also influence hurricane season this year. Most North Atlantic hurricanes originate in the eastern tropical Atlantic, and warmer waters give tropical cyclones their energy. This year the Met Office forecast suggests that the number of cyclones and tropical storms in the North Atlantic basin will be above average.

 “We are getting indications from models of an Atlantic tropical storm development east of the Caribbean by the middle of next week. This would be highly unusual in this area so early in the season. June storms normally form further west in the Caribbean or Gulf of Mexico. The high sea-surface temperatures in the tropical Atlantic would likely be one of the main factors if this development did happen next week,” said Julian Heming, a Met Office tropical cyclone expert, in the blog.

On Friday, the Met Office published its most recent polar sea ice report, which found a well below average level of Arctic sea ice extent for this time of year, though still above record lows. It found Antarctic sea ice extent to be by far the lowest on record for the date recorded.

“Over recent decades we have seen a sustained loss in Arctic sea ice extent in every month of the year, but especially in late summer to early autumn. Although the current Arctic sea ice extent is considerably higher than the record low for the time of year, it is still well below the long-term average. Antarctic sea ice has been at very low levels since November 2016. This year we have seen Antarctic sea ice shrink to a record low-point for the time of year, following a second successive annual record minimum sea ice extent in February,” said Dr. Ed Blockley, leader of the Met Office’s Polar Climate Group, according to the blog.

In the Amundsen Sea, atypically low sea level pressure is likely at least partially the cause of the current low sea ice extent in the Antarctic. It has been associated with oscillations in sea surface temperatures in the tropical Pacific sea, as well as atmospheric pressure from the Southern Annular Mode and El Niño in the Southern Hemisphere, which the Met Office blog says is a main component of higher latitude climate variability in the southern hemisphere.

Dr. Dan Smale, who studies marine heat waves with the Marine Biological Association, was surprised by the North Atlantic sea-surface temperatures. “I always thought they would never be ecologically impactful in the cool waters around UK and Ireland but this is unprecedented and possibly devastating. Current temperatures are way too high but not yet lethal for [a] majority of species, although stressful for many… If it carries on through summer we could see mass mortality of kelp, seagrass, fish and oysters,” Smale said, as The Guardian reported.