Southern Ocean Lighter? Are We SOL?

From way down south, David Fogarty of Reuters brings us yet another uplifting climate change story - this time about the freshening of the deep waters of the Southern Ocean. Yeah, they're getting less dense (lighter).

So?

Well, if they get too fresh, it's possible part of the oceanic thermohaline circulation could weaken or shut down entirely. This would not be good, as this circulation serves to transfer heat from the tropics to the higher latitudes. Because of it, the north Atlantic region (especially northern Europe) does not have the same frigid winters as does Siberia, and has average temperatures up to 5 degrees C higher than they should be. 

Here's a short article from 2003 by Robert B. Gagosian of the Woods Hole Oceanographic Institution (WHOI) about the possibility of abrupt climate change due to circulation changes in the world's oceans.

Last May I posted an item about the freshening of the North Atlantic Ocean, and also posted a DoD-funded report by Peter Schwartz and Doug Randall about the climatic change and social upheaval such an event would cause. It's a short report (< 30 pages) but if you don't want to read it, let me summarize it thusly: We're SOL.

From The Reuters article:

Voyage leader Steve Rintoul said his team found that salty, dense water that sinks near the edge of Antarctica to the bottom of the ocean about 5 km (3 miles) down was becoming fresher and more buoyant.

So-called Antarctic bottom water helps power the great ocean conveyor belt, a system of currents spanning the Southern, Pacific, Indian and Atlantic Oceans that shifts heat around the globe.

"The main reason we're paying attention to this is because it is one of the switches in the climate system and we need to know if we are about to flip that switch or not," said Rintoul of Australia's government-backed research arm the CSIRO.

"If that freshening trend continues for long enough, eventually the water near Antarctica would be too light, too buoyant to sink and that limb of the global-scale circulation would shut down," he said on Friday.

Cold, salty water also sinks to the depths in the far north Atlantic Ocean near Greenland and, together with the vast amount of water that sinks off Antarctica, this drives the ocean conveyor belt.

This system brings warm water into the far north Atlantic, making Europe warmer than it would otherwise be, and also drives the large flow of upper ocean water from the tropical Pacific to the Indian Ocean through the Indonesia Archipelago.

If these currents were to slow or stop, the world's climate would eventually be thrown into chaos.

"We don't see any evidence yet that the amount of bottom water that's sinking has declined. But by becoming fresher and less dense it's moving in the direction of an ultimate shutdown."

What's disturbing about this story is that there is now evidence that deep water freshening is occurring in the southern latitudes, too.  Freshening will be exacerbated by the melting of ice in the polar regions. So although global warming may be the ultimate culprit, it will produce colder temperatures in the north Atlantic region but warmer temperatures (and likely droughts) in the African equatorial regions.

Let me put in a word for the Schwartz-Randall report: whether you like it or not, it's the kind of study - "thinking about the unthinkable" - that needs to be done. I have inquired about the existence such a study on the potential desiccation of the Southwest USA and its ramifications but have been unable to ascertain who, if anyone, is looking at various scenarios. I suspect there are some people doing this kind of work somewhere, even if it's in the bowels of the Pentagon.

It's not the kind of work a lot of people would want to see publicized.

"Some cause happiness wherever they go; others, whenever they go." -- Oscar Wilde

Comments

[solfilm]

Hm.. Quite interesting read actually, thanks for the good read! :)