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Oceans marked 365 straight days of record-breaking global surface sea temperatures this week, fuelling concerns among international scientists that climate change could push marine ecosystems beyond a tipping point.
The consistent climb in temperatures reached a peak on Wednesday when the new all-time high was set for the past 12 months, at 21.2C.
The world’s seas have yet to show any signs of dropping to typical, seasonal temperatures, with daily records consecutively broken since they first went off the charts in mid-March last year, according to data from the US National Atmospheric and Oceanic Administration and the Climate Reanalyzer research collaboration.
Driven by human-caused climate change and amplified by the cyclical El Niño weather phenomenon that warms the Pacific Ocean, this exceptional heat has bleak implications.
Richard Spinrad, the US under secretary and administrator of Noaa, said this week that the warming would have “rather dramatic impacts on major storms, on ecosystems”.
Noaa warned earlier this month that the world was on the brink of experiencing its fourth global mass coral reef bleaching event.
The US agency’s Coral Reef Watch introduced three new bleaching alert levels as several regions, particularly in the eastern Pacific and Greater Caribbean, experienced such extreme heat stress that it was no longer sufficiently captured by the old scale.
Scientists further worry that the coming Atlantic hurricane season has the potential to be devastating because of this sustained heat, even as the El Niño system weakens to give way to the opposing La Niña weather cycle that results in a cooling effect.
Spinrad said that, historically, the hurricane season started at the beginning of June and ended in November, but this pattern had shifted, with areas of the central Atlantic far warmer for March than normal.
“If you look at the record, we are seeing certainly tropical cyclones forming earlier than June 1, and we’re seeing systems extending well beyond the end of November. So that, hurricane season has certainly become longer both on the front and the back,” he said.
The world’s oceans absorb 90 per cent of the excess heat and energy released by greenhouse gas emissions that are trapped in the Earth’s system and are the cause of climate change.
The largest carbon sink in the northern hemisphere is the Atlantic Ocean, where the circulation of water helps ensure that temperatures on land are regulated.
There was “a lot of concern”, Spinrad said, about what is described as the conveyor belt of circulation in the oceans, known as the Atlantic Meridional Overturning Circulation, which may be slowing because of excess heat, with unknown consequences for habitable conditions on Earth.
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