Tuesday, November 03, 2015

Pteropods in the news, again

Abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean : Nature Climate Change : Nature Publishing Group: Ocean acidification may lead to seasonal aragonite undersaturation in surface waters of the Southern Ocean as early as 2030 (ref. 1). These conditions are harmful to key organisms such as pteropods, which contribute significantly to the pelagic foodweb and carbon export fluxes in this region. Although the severity of ocean acidification impacts is mainly determined by the duration, intensity and spatial extent of aragonite undersaturation events, little is known about the nature of these events, their evolving attributes and the timing of their onset in the Southern Ocean. Using an ensemble of ten Earth system models, we show that starting around 2030, aragonite undersaturation events will spread rapidly, affecting ~30% of Southern Ocean surface waters by 2060 and & greater than 70% by 2100, including the Patagonian Shelf. On their onset, the duration of these events will increase abruptly from 1 month to 6 months per year in less than 20 years in & greater than 75% of the area affected by end-of-century aragonite undersaturation. This is likely to decrease the ability of organisms to adapt to a quickly evolving environment. The rapid equatorward progression of surface aragonite undersaturation can be explained by the uptake of anthropogenic CO2, whereas climate-driven physical or biological changes will play a minor role.
 The Sydney Morning Herald report on this notes:
"What surprised us was really the abruptness at which this
under-saturation [of calcium carbonate-based aragonite] occurs in large
areas of the Southern Ocean," Axel Timmermann​, a co-author of the study
and oceanography professor at the University of Hawaii told Fairfax
Media. "It's actually quite scary."

Since the Southern Ocean is already close to the threshold for shell-formation, relatively
small changes in acidity levels will likely show up there first, Professor Timmermann said: "The background state is already very close to corrosiveness."
And of course, the "let's burn coal to make poor people rich and airconditioned into safety" crowd never address the point that their tactic will only accelerate potential food chain collapse in the oceans.

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