Monday, February 11, 2008

Natural ocean thermostat may limit warming

I'm skeptical about the ocean thermostat, but new research says natural processes may act to limit ocean temperature increases.

Where ocean waters are already very warm, 88 degrees F in the Western Pacific warm pool, scientists have found relatively little additional temperature increase even as surrounding waters warmed substantially. Could this mean that there is a natural ocean "thermostat" that prevents temperatures from rising much above 88 degrees F?

How would this putative thermostat work? According to a press release at NSF.gov:
Researchers have speculated about several processes that could regulate ocean temperatures. As surface waters warm, more water evaporates, which can increase cloud cover and winds that cool the surface. In some areas, warming alters ocean currents in ways that bring in cooler waters. In addition, the very process of evaporation removes heat.

Corals have survived better in the warm pool in recent years, avoiding the widespread coral bleaching that harmed corals elsewhere. Does this mean that corals are safe? Corals that are adapted to cooler water may not survive even if maximum temperature is somehow limited to around 88 degrees F.

Oh, one more thing. That unpleasant global warming thing may defeat the ocean thermostat anyway. Models suggest substantial temperature increase even in the warm pool as CO2 in the atmosphere continues to rise. It could be that the models don't capture the thermost effect, or that CO2 increases overwhelm the hypothesized thermostat.

2 comments:

Simon Donner said...

The new research is an important contribution to the scientific discourse on ocean warming. The coral reefs within the west pacific warm pool - the warm area of ocean described in the paper - have experience fewer bleaching events than coral reefs elsewhere. However, the data in the new research paper also suggests those coral reefs are more sensitive to temperature fluctuations (bleaching at temperature "anomalies" of less than 0.5 deg C, as opposed to the 1-2 deg C thought to cause bleaching elsewhere). Perhaps the corals may be adjusted to the less variable thermal environment, such that a small increase in temperatures is enough to cause widespread bleaching? What the new research makes clear is there are many questions left to task.

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