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N. Atlantic, Mediterranean Sea temperature hit all-high, NOAA warns of marine heatwaves by Sept
The Unprecedented marine heatwave in July is not expected to come to an end. With North Atlantic recording its hottest ever temperature in July and the Mediterranean Sea hit an all-time high temperature of 28.7°C, America’s National Oceanic and Atmospheric Administration warned that half of the world’s oceans may experience marine heatwaves by September.
June saw the highest ever average global ocean surface temperatures, with local records being set from Ireland to Antarctica. In Florida, waters reached 38°C.
Marine heatwaves doubled in frequency between 1982 and 2016 and have become longer and more intense since the 1980s, found a 2021 study by the UN’s Intergovernmental Panel on Climate Change.
The latest heatwave is being driven by climate change, said Leticia Carvalho, the Head of Freshwater and Marine Ecosystems at the United Nations Environment Program (UNEP). As humanity burns fossil fuels, massive amounts of planet-warming greenhouse gasses are flooding into the atmosphere. Much of that heat is being absorbed by the ocean.
This not only results in higher marine temperatures, it also makes the ocean less effective at absorbing carbon dioxide, leaving more of the greenhouse gas to percolate in the atmosphere.
The climate crisis is being compounded by the natural El Niño climate pattern now underway, which is driving up sea temperatures in the Pacific Ocean.
There are other causes of the ocean heatwave, too. Weaker-than-average winds have reduced the amount of Saharan dust in the atmosphere, which usually reduces sea temperatures by blocking some of the sun’s energy.
Hotter marine temperatures can have a devastating effect on marine life, and there have been multiple mass mortalities of marine animals and plants due to ocean heatwaves.
Increased marine temperatures can be harmful on land too, causing extreme weather, such as storms and hurricanes.
As water temperatures rise – and average ocean temperatures have risen 1.5°C in the past century – marine ecosystems’ ability to absorb local temperature rises is reduced, further increasing the likelihood of more marine heatwaves.
“The ocean is a vital carbon sink,” Carvalho said. “It absorbs 90 per cent of the excess heat generated by carbon dioxide emissions and generates 50 per cent of the oxygen we need. It is the lungs of the planet, and regulates our climate. However, it is in serious peril and we need to immediately prioritize protection and restoration efforts.”
“The effects of ocean heatwaves are varied and extremely damaging,” said Carvalho. “We know severe temperature rises can lead to mass mortalities of sea life, increase ocean acidification and disrupt the currents that influence our weather patterns, potentially causing hundreds of millions of dollars in economic losses and posing a severe risk to global food security.”