Stabilization of Ocean structure : is this the end of our planetary thermostat?

12/04/21

Last March, a study carried out by the French National Council for Scientific Research (CNRS) and the French Institute for Marine Research (IFREMER) was published in the journal Nature. Reporting on fifty years of research, it reveals that the structure of the Ocean is becoming increasingly stable, and that this is happening six times faster than expected. This stabilization, which is directly caused by global warming, could well challenge the Ocean's role as a natural thermostat, greatly accentuating the consequences of climate change. Here are a few explanations. 


The Ocean is stabilizing

The study published by the two French laboratories, which arises from international collaboration, is based on temperature and salinity readings carried out in several oceanic areas between 1970 and 2018. These 50 years of observations reveal that a radical change of ocean structure is taking place. The Ocean, which is usually extremely dynamic and in constant motion, is becoming more stable, with surface water mixing less and less with deep water. The cause? Climate change!


Surface waters are warming as a result of the increase in atmospheric temperatures, and their salinity level is dropping due to increased precipitation and the melting of glaciers. This lowers their density. Conversely, deep water has a high density. Since their physical characteristics differ, the two layers of water mix together much less easily. And this involves a great many risks. 


The Ocean's regulatory role called into question

The Ocean has always acted as a climate thermostat and this role is greatly strengthened today, since the Ocean absorbs 90% of excess heat and a quarter of CO2 emissions linked to human-induced global warming. Normally, when it mixes with cold deep water, surface water heated by the atmosphere cools again, regulating the temperature on Earth.

However, the fundamental change in Oceanic structure is slowing down this exchange: the surface water layers are no longer reaching the deep layers, and consequently the Ocean's capacity for absorbing heat and CO2 is diminishing more and more. This raises atmospheric temperature, further warming the surface water. The exchange between the two layers is slowed down even more, increasingly altering the Ocean's regulatory effect. A vicious circle of warming is taking place.


Towards an aggravation of meteorological disasters


And that's not all! Beyond accentuating the effects of global warming, rising sea temperatures may well increase the frequency and severity of extreme weather events, such as tropical cyclones. These are fed by the heat emanating from the Ocean: the higher the temperature, the more the hurricane turns and absorbs water, the greater the risk of it becoming violent and generating catastrophes. These are all phenomena that will increasingly impact ecosystems and our lifestyles.

We alone are responsible for this situation and, once again, this new study must encourage us to continue our efforts to preserve the marine environment.

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