The strong warming of the Atlantic Ocean highlights the shortcomings of the measurement system

• 

  Helen Ecker

  Climate and Energy Editor

More and better Atlantic thermometers are needed to monitor ocean warming. The weather in Holland and other Western European countries is strongly determined by the warm Gulf Stream in this ocean. Since the beginning of March, the oceans, particularly the Atlantic, have shown unexpectedly very high surface temperatures. To the west of Ireland, the water at the surface is four to five degrees warmer than ever before.

Climate scientists tell NOS that this heat is “abnormal,” “very special,” and “has not been previously discussed with colleagues as a possibility.” They think it has nothing to do with the natural El Niño variability. researchers have There is no definitive explanation For the current development as well as the possible consequences are unknown.

The unusually high surface temperature of the Atlantic Ocean sheds light on the current ocean temperature measurement system and, in particular, on its shortcomings. The desire for more gauges at sea is widespread. “There’s always a lot of attention to the warming of the atmosphere, but the ocean is actually more important. Because 90 percent of the extra heat from the increase in greenhouse gases goes into the sea,” says Professor Caroline Katzman of TU Delft. .

If this were not the case, the Earth would be dozens of degrees warmer now. The temperature in the oceans is measured by satellites and so-called Argo buoys. Satellites measure only at the surface, while buoys go into the depths. There are about 4,000 such buoys around the world, automatic buoys that float with the current at a certain depth. Every ten days or so, they dive and soar through the water, recording temperature and salinity for the top two kilometres.

When this float reaches the surface, it transmits its data to scientists via satellite and then descends back below the surface of the water. According to the man who coordinates the Dutch contribution to this global measurement system with public data, Andreas Sterl of KNMI, there are parts of the ocean where very few measurements are actually made.

“In the warm Gulf Stream, for example, the differences are significant. So we would like to have more of those floaters there. Holland can make a bigger contribution to this,” says Stirle. Katzman agrees: “Three such floats have been active over the past month in that now very warm area, and together they made ten measurements.” Changes in the warm Gulf Stream may have a significant impact on Dutch weather, in addition to global warming.

Scientists would also like to know if the extra heat is now traveling north across the ocean, which could have consequences for ice in the Arctic region. Katzman: “It depends very much on whether it’s just surface water, or whether it’s a symptom of warmer water hundreds of meters deeper. In the latter case, a lot of the excess heat could go north, but if that’s the case Only the upper class, it’s not too bad.”

This is why scientists want to do more research on the influence of ocean currents. At the Royal Netherlands Institute for Research of the Sea, NIOZ in Texel, they recently purchased a new instrument: the glider. It can be controlled from shore to scout certain currents. In June, these gliders were deployed to the North Sea for the first time.

However, New Zealand Institute researcher Vemke de Young cautioned against being overly optimistic about the glider. “They are modern instruments, but they cannot go deeper than a kilometer, while we would also like to learn more about the deeper ocean. Also, gliders only move at 25 centimeters per second, which is too slow for large-scale research.” She’s also hoping for better and better Argo floats and other measuring instruments.