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480 points riffraff | 6 comments | | HN request time: 0.849s | source | bottom
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taylorlapeyre ◴[] No.44461488[source]
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).

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1. irthomasthomas ◴[] No.44463052[source]
As water is more dense than ice, wouldn't the sea level drop when the ice shelf melts?
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2. Matumio ◴[] No.44463122[source]
Only one way to find out... float some ice cubes in a glass of water and observe.

(Edit: I'm back to report the results. There was either no change in the water level, or a change below my measurement tolerance ;)

(Edit2: Here is a more serious take of that experiment: https://skepticalscience.com/Sea-level-rise-due-to-floating-...)

replies(1): >>44464733 #
3. _fizz_buzz_ ◴[] No.44463137[source]
Floating ice will displace exactly as much water as it does when it melts to water. Ice that melts on a land mess such as Greenland and Antarctica will raise the ocean level when it melts.
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4. irthomasthomas ◴[] No.44464733[source]
Ok that makes sense thanks.
5. Avshalom ◴[] No.44465525[source]
Not sea ice obviously but there are places where sea level is "dropping" https://en.m.wikipedia.org/wiki/Post-glacial_rebound
6. belorn ◴[] No.44466077[source]
Floating ice will actually increase the ocean a tiny bit as it melts into water because the ice has lower salinity than the ocean. Its comparable to around 3% of ice that melts on a land.