Global warming? Yes, but there is an area of the Earth where the temperature is not only not increasing, it is decreasing: it is the “cold blob” (literally “cold spot”), a part ofAtlantic Oceanjust south of Greenland And Icelandwhich is getting colder, year after year.
But, unfortunately, it is far from good news: it could be the result of the weakening of ocean currents, as emerges from research led by Potsdam Institute for Climate Impact Research (Germany), and may be close to a tipping point.
This area of the Earth had already been known for some time and several hypotheses had already been formulated in an attempt to explain the unusual phenomenon in a global trend of increasing temperatures. Previous research actually attributed the cause to greater heat dispersion from the sea surface, but the hypothesis of a weakening of ocean currents had already been put forward in the past.
©Geophysical Research Letters
However, the new research decided to support the modeling with observational data to try to resolve the debate, in particular observation-based reanalysis data for ocean heat content and surface fluxes, including satellite and temperature measurements, and then combining them with established climate models.
The study was conducted with quality reanalysis data dating back to 1955 and satellite data to 1993, which allowed the team to determine changes over many decades, and also included a heat balance analysis, which quantified the balance between heat entering and exiting the cold blob.
Their results highlighted that cooling in the “cold spot” is a deep ocean phenomenon, driven by changes in ocean heat transport, and not just by changes in surface temperature: the data showed that surface heat loss actually decreased in the cold spot area, contradicting the hypothesis of greater heat loss from the sea surface.
©Geophysical Research Letters
The “fulcrum”, according to scientists, lies in theAtlantic Southern Overturning Circulation (AMOC), a system of ocean currents that moves warm surface water from the tropics northward and cold, dense water southward.
The AMOC plays a fundamental role in regulating the Earth’s climate and redistributing heat. And if this weakens, the result is the arrival of a smaller quantity of hot water in the area calledcold blob“, which is precisely the point at which the current releases its heat and transfers it to the atmosphere. The hypothesis is also strengthened by previous studies which highlight how the current has slowed down since the pre-industrial era.
If all this were further confirmed, concerns about the climate on our planet, already notoriously threatened by human activities, would be further strengthened.
©Geophysical Research Letters
A further weakening of the Atlantic Thermohaline Circulation (AMOC) could have important repercussions on future climate for millennia – the authors of the study write – given that the AMOC is known to have a turning point beyond which it is likely to stop
With consequences that are scary to even imagine.
The study was published on Geophysical Research Letters.
Sources: Phys.org / Geophysical Research Letters
