The water in the North Atlantic has become extremely much warmer. An area of sea ice the size of Argentina is gone from Antarctica. – Completely outside of everything we have expected, says the climate scientist.
This heat map shows how the sea surface temperatures deviate from normal on 31 August this year. The sea areas to the west of the North Atlantic are more than five degrees warmer than usual. Photo: Screenshot NOAA Coral Reef Watch
sea view
Several days before the end of the month, it was clear that July would be the hottest month ever recorded on the globe. By a good margin.
This summer it has been tight between the news about scorching heat waves, bathing temperatures more common in a hot tub, huge forest fires and deadly downpours. The weather has been extreme.
Climate scientists have been warning about the consequences for years.
– Shocking, but not surprising, says director Gavin Schmidt at NASA’s Goddard institute to the Washington Post about what is now unfolding.
– The weather is just as wild as expected in a world that is 1.2 degrees warmer than before, says Bjørn Hallvard Samset at the Cicero Center for Climate Research.
But this summer, two phenomena still made researchers around the world jump in their seats. Or as the seasoned NASA leader says: “It made me raise an eyebrow.”
Here’s what triggered the reaction:
The Mystery of the North:
Temperatures in the North Atlantic have been record high since March. On 1 August, the temperature was a full degree higher than the previous peak.
The heat center has moved from off the UK in June to the coast off Newfoundland. There, the temperature at the end of July was a full 5–10 degrees above normal:
Temperatures in the sea have large natural fluctuations, and will rise as a result of global warming. Surface temperatures in the world’s oceans have been measured at their highest ever recorded this summer.
At the end of July, over 38 degrees were measured in the water in Florida.
– Like swimming in soup, said one bather.
The Mediterranean was too record hot, with an average temperature of 28.7 degrees. It is 0.5 degrees higher than the previous peak.
But the heat wave in the North Atlantic stands out.
– This is completely outside of everything we have experienced in the past and what we expect even when we take climate change into account, says Samset.
Scientists are struggling to find out what is driving the heat wave. This may be due to a combination of several possible explanations:
Warmer air temperaturesWeaker winds that blow less sand from the Sahara out across the Atlantic, and cause more sunlight to hit the sea surface The weather phenomenon El Niño, which with its high temperatures in the Pacific Ocean affects weather patterns worldwide, and Less pollution from ships
Marine gasoline contains less sulfur than before. It is good for the environment, and produces less acid rain. But sulfur also has a cooling effect, since it forms larger particles in the atmosphere that reflect more sunlight, making the clouds whiter.
– It’s a nice hypothesis, but I have a hard time seeing how it can have such a big contribution, says Samset.
Academically interesting = disturbing
He believes the extreme heat in the North Atlantic is most likely due to minor changes in how the ocean flows.
Global warming is caused by the earth absorbing more energy from the sun than what flows out. 90 percent of this energy is found in the oceans. Thus, small changes in ocean currents can have a large impact on temperatures.
During El Niño, for example, less warm water is transported from the surface down into the depths. As a result, hot water accumulates on the surface.
– But we do not know what these changes in the Atlantic are due to. It’s not El Niño. It may sound vague. That makes it academically exciting, but also disturbing, says Samset.
2. The mystery in the south
Also from the other side of the globe, in Antarctica, there are now measurements that make the researchers open their eyes:
Here, the sea ice is at its lowest extent for this time of year since measurements began 45 years ago. A full 1.6 million square kilometers less than the previous record, which was set last year:
In total, an ice-covered area roughly the size of Argentina is missing.
The extent of the sea ice fluctuates both with the season and from year to year, and has previously also shown an increasing tendency. But in recent years, the ice sheet has shrunk, before making a steep decline in 2022 and plummeting in 2023.
The ice level is now so extremely low that, according to the researchers, with natural variation, it statistically only happens once in several million years.
But with climate change, it no longer makes sense to talk about “normal circumstances”.
– We partially expect that when the water in the Southern Ocean gets warmer, it will be more difficult for the ice to freeze until late in the autumn. But the pace of the melting is completely unexpected, says Samset.
Could the volcano be to blame?
Here, too, the researchers are struggling to understand what drives the melting.
– The change we are seeing now is so extreme that something radical has happened in the last two years, and especially this year, says glacier researcher Ted Scambos at the University of Colorado Boulder to CNN.
What can this “radical” be?
Warmer waters in the Southern Ocean may play a role. Changes in wind conditions can affect. Last year’s eruption from the undersea volcano Hunga Tonga is also mentioned as a possible factor.
This satellite image shows the eruption from Hunga Tonga in January 2022. Photo: AP / NTB
sea view
Generally, volcanoes have a cooling effect since particles ejected into the atmosphere reflect sunlight. But most water vapor came from Hunga Tonga, which has a warming effect. However, Samset does not believe this explains the steep fall.
– It doesn’t seem like it will have that big of an effect. Then we would have seen it in the temperatures in the southern hemisphere, he explains.
Tipping over the edge?
Several scientists are now asking questions about whether the sea ice in Antarctica has reached such a critically low level that it is losing its ability to recover.
– The sea ice has a natural average, where it freezes in winter and thaws in summer. It may be that it is now so reduced that the entire cut moves down. It has never happened before in our history, but it is a bit early to say, says Samset. He believes that 2024 will provide a good indication of where development is headed.
What will the effect be, if the sea ice in Antarctica shrinks permanently?
– It will affect wildlife locally. For the world as a whole, it can cause climate change to go even faster because the sea captures more heat in the summer, says Samset.
Further north, the fear is that global warming will cause the northernmost part of the Gulf Stream, called the AMOC, to collapse. In that case, it would be a tipping point that would lead to large and sudden changes in the climate system. A Danish study has recently pointed out that this may happen sooner than previously expected.
However, Samset says there is no indication that the heat wave in the Atlantic Ocean can tip us over this critical point.
– We don’t expect it to happen at the temperatures we have now, but we expect it to happen when it gets very hot, around five to six degrees worldwide, says Samset.
He says the beginning of this may be similar to what we have seen in the Atlantic Ocean this summer. But at the same time you would have seen that the sea began to flow more slowly.
– No one who follows this has shouted any warning about it now, he says.
2023-08-03 20:28:43
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