Major reversal in ocean circulation detected in the Southern Ocean

The deep-ocean vent south of Antarctica is real but small, on the order of a few-tenths Pg C yr⁻¹. The claim that it could double atmospheric CO₂ exaggerates the flux by three orders of magnitude relative to observed values and known physical limits.

The most optimistic estimate of deep-water outgassing south of 60 ° S is 0.36 Pg C yr⁻¹. Even if that rate tripled and persisted unabated, it would take more than 800 years to add 895 Pg C (which would be what it would require to justify the press release’s claims of “doubling”)

What the salinity reversal can do is:

- Expose ice shelves to warmer subsurface water, accelerating sea-level rise.

- Reduce the Southern Ocean’s role as a sink by a few tenths Pg C yr⁻¹, nudging the global ocean sink (~2.7 Pg C yr⁻¹) downward.

- Perturb atmospheric circulation patterns, with knock-on effects for the Atlantic overturning (but those links remain speculative).

The article says that deep water is warmer, afaik deep water is colder and surface water is hotter (https://en.wikipedia.org/wiki/Upwelling)?

A 2023 study https://www.sciencedaily.com/releases/2023/03/230330102327.h... observed slowdown in Antarctic overturning, in which cold water sinks down at the south pole and then spreads north in the deeper parts of the ocean.

The slowing of this process would cause deep ocean water to become warmer.

edit: the publication linked in the article https://www.pnas.org/doi/epub/10.1073/pnas.2500440122 makes this a bit clearer:

"In the polar Southern Ocean, cold, fresh surface waters overlay warmer, saltier deep waters (Fig. 2A). During winter, surface cooling and sea ice formation reduce stratification, allowing vertical mixing to transport heat upward, either melting sea ice from below or limiting its growth (8). However, decades of surface freshening strengthened stratification, trapping subsurface heat at depth, sustaining expanded sea ice coverage (7, 9) and limiting deep convection along with open-ocean polynyas (10). Here, we show that since 2015, these conditions have reversed: Surface salinity in the polar Southern Ocean has increased, upper-ocean stratification has weakened, sea ice has reached multiple record lows, and open-ocean polynyas have reemerged."

If deep water is now rising and releasing centuries of stored CO2, we're talking about a major shift in Earth's climate plumbing. Also wild that this only became visible thanks to a novel satellite processor

Most climate research studies provide a range from optimistic to pessimistic outlooks on climate impacts. It would be interesting to know how the studies from the last 30 years have fared. I have the feeling that rather the pessimistic estimates have come to pass.

I didn't know much about the Southern Ocean. For a quick update, YouTube has some good info https://www.youtube.com/watch?v=8VMSF28J9H4

Can someone explain in simple terms what this means? Like what is happening (like am 5) and what are the consequences of this.

Look at London. Draw a line west. Compare climates. Now do the same for New York and go East. Ocean currents are what keeps London warm and NYC cool.

So this is a huge deal. I’ve been down to the Southern Ocean, lectured all the way by scientists.

North of the Antarctic is the only place on earth where the sea can rotate completely around the world without hitting a land mass, and it is deemed the engine of the world’s oceans. Those oceans are what have absorbed most of the excess CO2 that we’ve emitted, and a lot captured has been buried in deep ocean. But the ocean warms, and can capture less CO2, and bad days are ahead.

This news signals not just a slowing in that absorption for an area, which not just sends more CO2 into the atmosphere, but has more terrifyingly unknown downstream implications for other ocean streams.

I asked for no more unprecedented world events in my lifetime.

Next up, AMOC collapse.

We thought the currents would run AMOC but got a SMOCdown instead?

Well as long as we keep pretending that the most conservative of the already downplayed IPCC estimates is the real trajectory we'll keep getting surprised over and over. It's not really a coincidence that most climate scientists are depressed.

If this is the very first time this part of the ocean has ever been imaged/studied, how do we know that this is unusual and not something that happens periodically?

Be warned, this article is misleading. The actual scientific paper shows a salinity‑driven weakening of stratification that likely allows more subsurface heat to reach the surface and melt sea ice. The article describes this as a complete overturning‑circulation reversal with dire carbon release consequences. These are claims that the paper itself does not make or substantiate. The paper actually does not use the words carbon or CO2 even once. The authors of the article took such liberties with this that I really believe this should be considered disinformation.