The ocean is as important to the climate as the atmosphere

FOr Homo sapiens, an arid land species, discussions of climate and how it’s changing revolve around what’s going on in the atmosphere. This is a dangerously narrow approach, as the atmosphere is one of two fluid systems operating above the Earth’s solid surface. The other, Ocean, is in many ways the more important of the pair.

It is this ocean circulation that, by redistributing heat, limits the temperature difference between the tropics and the poles to about 30 °C. If the atmosphere alone was responsible for moving heat, that difference would be something like 110°C. And, when it comes to anthropogenic global warming, the problem would be far greater without the buffering effect of the ocean.

The ocean not only absorbs heat that would otherwise remain in the air, it also swallows up a third of the carbon dioxide emitted by human activity. While this makes seawater more acidic (or, strictly speaking, less alkaline), which can harm some marine species, most CO₂ The inclusion ends up in the abyss, where it can produce no greenhouse effect, and where it is likely to remain for many centuries.

The poverty of human understanding of ocean circulation, as compared to that of the atmosphere, is therefore lamentable. And this Hope Susan Lozier of the Georgia Institute of Technology, who was also last year’s president of the American Geophysical Union, hailed the meeting as an excellent lament on the matter.

Oceanographers discovered in the late 20th century that the system’s engine room is in the North Atlantic. Here, in a process called the Atlantic Meridional Overturning Circulation (amoc), water moving upward from the tropics cools, thus increasing in density, until it becomes so heavy that it begins to sink, requiring more water to move from the south to replace it. is pulled up. After descending for 3 km, it turns itself towards south.

Although some ocean overturning of this kind occurs elsewhere, 90% of it occurs in the North Atlantic. And it is the North Atlantic inversion that drives what is often described as a planet-spanning conveyor belt of connected currents.

That, at least, is the conventional thinking. But Dr. Lozier considers this a bad analogy. A conveyor belt conveys an image of smooth and linear progress. This belt, however, jerks everywhere, making it very hard to figure out what’s going on.

A smoothly running belt should only be checked occasionally to check if it has a varying rate of progress. So when, in 2005, a paper in Nature Reported 30% decline in volume, based on five relevant shipborne surveys conducted since 1957 amoc There was serious concern between 1992 and 2004. If such a decline continues, it will alter weather patterns by altering the planet’s heat distribution, particularly over Europe. It will also reduce the rate at which CO₂ taken to the deep sea.

As it happened, however, 2004 was a turning point in the observations of what was going on, as it saw the beginning of the deployment of a set of recording equipment now known as Fast amoc, These oversee the Atlantic a few degrees north of the Tropic of Cancer, the part of the world where the survey was reported. Nature The paper was done. Fast amoc was joined in 2014 by an Arctic counterpart, OSNAPInversion in the Subpolar North Atlantic Program.

The result is the finding that the reversal rate can vary, apparently randomly, by up to six times over the course of a year. described a decline in Nature The paper was an artifact of a bad data set.

another discovery of OSNAP It turns out that the details of where the reversal occurs in the North Atlantic are not exactly what the models predicted. Most of the turnover occurs on the east side of the ocean, not the west, as previously believed. While this doesn’t make much sense in the grand scheme of climate change, it’s another example of how poorly people understand what’s happening in the ocean.

next step for OSNAP To look at carbon dioxide uptake is to expand your remit. More systematic studies are taking place in other parts of the ocean as well, as land-husbanding humans are finally paying proper attention to the hitherto neglected 71% of the planet’s surface, which they delight to call “Earth”. But what can really be called a “sea”.

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