The planet has been warming in recent times and, despite the fact that the surface of our oceans has absorbed much of the excess temperature in the atmosphere, induced by man (remember that approximately 90% of the heat absorbed by the Earth goes to the oceans ), as seawater circulates, a worrisome change is slowly making its way … into the depths. And even though they warm slowly, the heat causes the water molecules to expand, contributing to the rise in sea level. In addition, it also intensifies hurricanes.
Scientists from the US National Oceanic and Atmospheric Administration (NOAA) have detected a warming trend in some of the deepest and coldest parts of the South Atlantic Ocean. When analyzing ten years of temperature records in the Argentine basin from 2009 to 2019, experts have found that the four sites warmed between 0.02 and 0.04 degrees Celsius depending on the depth (the lowest measured depth was 1,360 meters and the deepest at 4,757 meters).
The seabed is heating up
The temperature records of the two deepest points revealed a clear warming trend during that decade. The waters at 4,540 meters below the surface warmed from an average of 0.209 ° C to 0.234 ° C, while the waters at 4,757 meters of depth went from approximately 0.232 ° C to 0.248 ° C. Although as we see it is much more weaker than in the upper ocean, he goes on to point out that as warm water rises, it takes a lot of heat to generate even a small increment of warming that deep.
That recorded warming may be a consequence of human-driven climate change, which has increased near-surface ocean temperatures, but it’s not really clear, because so little is known about the deepest and darkest parts of the ocean.
“The deep ocean, below about 2,000 meters, is difficult to observe,” says Chris Meinen, an oceanographer with the US National Oceanic and Atmospheric Administration in Miami. The deep sea is so difficult to reach that the temperature at any research site is typically taken only once every 10 years. However, Meinen’s team measured hourly temperatures from 2009 to 2019 using seafloor sensors at four points in the Argentine Basin, off the coast of Uruguay with these results.
In other words, global warming can already be detected even from the bottom of the ocean.
“In years past, everyone used to assume that the deep ocean was inactive. That there were no changes ”, clarifies Meinen. “But every time we look, we find that the ocean is more complex than we think .”
How exactly this affects ecosystems or climate is not clear yet, but it is not exactly good news.
“I hope this will lead to a new analysis of several of these historical data sets to try to see what we can say about the variability of the deep ocean temperature,” concludes the expert.
Referencia: C.S. Meinen et al. Observed ocean bottom temperature variability at four sites in the northwestern Argentine Basin: Evidence of decadal deep/abyssal warming amidst hourly to interannual variability during 2009–2019. Geophysical Research Letters. Vol. 47, September 28, 2020. doi: 10.1029/2020GL089093.
