19 June 2023

Marine heatwaves ‘catastrophic’ for ocean life, say scientists

19 June 2023

Marine heatwaves have a “catastrophic” effect on ocean ecosystems, leading to the devastation or replacement of certain species, scientists have said.

The North Sea is currently experiencing one of the most extreme heatwaves on Earth, being 4-5C higher than its usual temperature for this time of year.

It has been classified as category four, meaning extreme, by the US National Oceanic and Atmospheric Administration.

The North Atlantic is also experiencing record high temperatures for this time of year.

Scientists believe this is a result of human-induced climate change pushing up the baseline of warming so that added heat from short-term natural climate processes results in record temperatures.

The added heat can be devastating for ecosystems that have evolved to live within a specific temperature niche.

Professor Geraint Tarling, an ocean biologist at the British Antarctic Survey, (BAS) said: “The things in the North Sea adapted to the North Sea environment, which has its own level of variability, but if you’re pushing things well outside of that variability, physiologically, they’re not going to cope.”

He said the Arctic is probably experiencing the most rapidly rising number of marine heatwaves than anywhere else and that many polar species are being replaced by more temperature ones in a process called Atlantification.

“What happens there is that you get replacements, you get winners and losers, things that respond really well, mostly things from lower latitudes, more tropical latitudes, will actually find these conditions conducive and that will replace things that are normally there,” he said.

“These are the things that can move.

“We’ve also got things on the bottom that can’t and those could be extinction events, where the heatwave actually kills off a lot of things at once and it might take decades to replace them.

“So then you’re having a really catastrophic effect over a very short period of time.”

Professor Yueng-Djern Lenn, an oceanographer at Bangor University, said: “There is no escape from the heat for sea creatures, they can’t turn on the air conditioners, and this can exert heat stress on their bodies that can lead to death.

“We don’t know yet how long this UK event will last, but we would expect our marine ecosystems to not escape unscathed.

“If there isn’t enough of a break between such events, allowing the ecosystems time to recover, the only winners will be the open ocean swimmers in the short term.”

The BAS said it is committing the next 60 years of research to understanding how climate change affects the polar regions and how they in turn impact on the rest of the world.

They are using new technology, such as AI and autonomous vehicles, to document and understand the rapid changes now taking place in the Arctic and Antarctica, as well as how the warming atmospheres and oceans influence each other.

Professor Dame Jane Francis, director of the BAS, said: “What is happening in the polar regions affects us all.

“Humans are changing the climate in the areas where humans live.

“That impact is going all the way to the polar regions and it’s affecting the polar regions more than anywhere else in the world.

“Those melting glaciers, those big volumes of ice and rivers of ice that are coming off the land are melting much quicker than we ever thought they would.

“And as they do, so that water from from glaciers is changing the global sea level.”

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