The heat wave under the sea that worries scientists

The month of June and the first days of July were the warmest on record, according to the World Meteorological Organization.

Residents of the southern United States and southern Europe have experienced sweltering temperatures, numerous heat warnings, wildfires and a serious deterioration in air quality.

However, records have not only been broken on land, but also in the water.

The global ocean surface temperatures were higher than any other month of June on record, according to a report from the Copernicus Climate Change Service, with particularly high North Atlantic satellite readings.

Last month also set a record with the National Office of Oceanic and Atmospheric Administration (NOAA) for the largest difference between expected and actual temperatures.

The water temperatures around Florida in particular were particularly warm.

Researchers also tracked an ongoing major marine heat wave off the west coast of the US and Canada that formed in May.

While the heat wave in the Northeast Atlantic has now subsided, according to scientific NGO Mercator Ocean International, another in the western Mediterranean appears to be strengtheningespecially around the Strait of Gibraltar.

Extreme sea temperatures have also been observed around Ireland, the United Kingdom and the Baltic Sea, as well as areas near New Zealand and Australia. More recently, scientists suspect a possible heat wave south of Greenlandin the Labrador Sea.

“We have these huge marine heat waves in different parts of the ocean that develop unexpectedly very early in the year, very strong and over large areas,” said Karina von Schuckmann, an oceanographer at Mercator Ocean.

“Without Precedents”

Carlo Buontempo, director of the European Union’s Copernicus Climate Change Service, scientists say expect large temperature swings in the Pacific Oceanassociated with the El Niño weather pattern, a phase of global warming that has just begun, though NOAA has been tracking a major heat wave in the Gulf of Alaska that has been offshore since 2022.

But what we’re currently seeing in the North Atlantic, really “unparalleled”says Buontempo.

Scientists are still trying to unravel all the causes.

Short-term changes in regional oceanic and atmospheric circulation patterns can create the conditions for periods of intense sea heat over weeks, months and even years.

But increase in the long term in ocean temperatures caused by an increase in greenhouse gas emissions is a key factor in recent heat waves.

Close to 90% excess heat generated by anthropogenic climate change stored in the oceanand in the past two decades, the rate of heat accumulation in the Earth’s climate system has doubled.

A 2021 report from the Intergovernmental Panel on Climate Change (IPCC) found that marine heat waves had doubled and reversed in frequency between 1982 and 2016 more intense and longer since the 1980s.

Another possible contributing factor is the volume of aerosols in the atmosphere, which have a mild cooling effect. But this seems to have diminished due to efforts to clean up shipping.

More recently there has been something unusual lack of Sahara dustwhich normally provides cooling.

everything could be worse

Today’s heat waves at sea are even possible worsen. While experts don’t believe El Niño itself is the cause of the North Atlantic event, the WMO expects it to contribute to global warming.

Experts are concerned that heat waves at sea could ocean life, fisheries and weather patterns.

Record high temperatures for the west coast of Australia during the summer of 2010/2011 resulted in a “devastating” fish mortality And destroyed kelp forests, and the coastal ecosystem has fundamentally changed.

Several years later, an unprecedented marine heat wave, caused by climate change and amplified by a strong El Niño, led to the worst coral bleaching seen on the Great Barrier Reef in 2016.

Marine heat waves can cause coral bleaching and have already contributed to the stress coral reefs face. reef ecosystems Worldwide.

High temperatures can cause coral polyps to expel the zooxanthellae living in their tissues, making them white and more vulnerable to disease and other threats.

In the Mediterranean Sea, exceptional temperatures between 2015 and 2019 caused repeated mass deaths of important species such as corals and algae. A recent study described marine heat waves of this type as “pervasive stressors for global marine ecosystems.”

Marine heat waves also facilitate the proliferation of invasive species.

For example, Japanese kelp proliferated in New Zealand when a marine heat wave in the Tasman Sea in 2017-2018 wiped out the area’s native kelp.

much to learn

Dan Smale, marine ecologist at the UK Marine Biological Association and member of the International Task Force on Marine Heat Waves, says that “short and fast strokes” they don’t give species time to redistribute, and those at the limit of what their bodies can carry are particularly at risk.

But even around the British coast, which is not considered an extreme environment and where scientists expect ecosystems to gradually change, a marine heat wave could be deadly if it lasts all summer.

However, there’s still a lot to learn about the impact of marine heatwaves compared to those on land because they’re harder to monitor and long-term data isn’t available, Smale says.

“The information that satellites have been giving us since the early 1980s is fantastic … the problem is when we try to move on,” he says.

warm oceans for a while

A significant drop in numbers phytoplankton it has already been seen in the North Atlantic, something Mercator Ocean attributes to recent heat waves.

Spring flowering is crucial as it provides most of the energy needed to maintain the marine food chain in the area and contributes substantially to global CO2 uptake from the oceans.

The economy of regional fisheries can also be affected.

A heat wave in the Northwest Atlantic in 2012 caused warm-water-preferring species to move north and migrate early, changing when and how much catch could be obtained.

The North Atlantic Ocean is also a major cause of extreme weather.

Increased ocean surface temperatures can lead to hurricanes, although it remains to be seen whether the El Niño phenomenon will exacerbate or mitigate this effect next year.

On the other hand, the warmth of the North Atlantic is the main factor behind the alternating cycle between sdrought and abundant rainfall in Central Africa.

Overall, experts say the persistence of recent marine heat waves is a worrying sign of how climate change is playing out alongside terrestrial heat waves, unusual snowpack melting in the Himalayas and sea ice loss.

Von Schuckmann says that even if people stopped pumping CO2 into the air tomorrow, oceans would continue to warm for years to come.

“I worry as a climate scientist that we are further away than we thought.”