Chris just mentioned Hurricane Dean's cold wake, and I'm reminded that there may be some potentially helpful implications for the fisheries of the region. I recently explained the concept of "dead zones": oxygen-free ocean regions characterized by a dense layer of warm water settled on top of colder water. This stratification, called a thermocline, keeps oxygen from filtering through the water column--resulting in massive areas of oceans devoid of marine life. The Gulf of Mexico has been experiencing an enormous dead zone every year, exacerbated by runoff from fertilizers and animal waste in the Mississippi and Atchafalaya River Basins.
In the wake of Hurricane Katrina, however, scientists found dissolved oxygen in areas that had none the preceding week. Coincidence?
As Chris's post hints, the winds of strong hurricanes create gigantic waves and help mix surface waters downwards while bringing colder nutrient rich waters upward (similar to a natural process called upwelling). So it's possible that Hurricane Dean has helped get rid of stratification, meaning that dissolved oxygen will be redistributed throughout the water column from top to bottom.
Whether this helps out the Gulf, of course, will depend upon how much of the cold wake lingers in the Caribbean, rather than extending further northward.
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So, some aspect of a hurricane may actually be helpful and positive?
Linda,
Definitely...hurricanes and tropical storms often deliver rainfall to regions in great need of it. Their impacts aren't *entirely* negative....
So, can we at least all agree that the Al Gore's poster, with the hurricane coming out of the smokestack, was both silly and propagandistic?
But wouldn't this overturning also hold the potential to bring up deeper water richer in dissolved carbon and hence the possibility of adversely affecting the sea as a global carbon sink and increasing PCO2 in the atmosphere?
Or ... maybe I've had too much caffeine today. :)
Dave,
Admittedly, I don't know much about deep ocean carbon or its vertical distribution in oceans, but expect that the other nutrients brought to the surface will allow for increased productivity which will then fix and potentially sink more carbon. Of course, that depends on what the currents are doing, etc. I also expect the CO2 flux at the oceanic-atmospheric interface is relatively slow compared to other processes.
Sheril,
Nor do I claim to be an expert. But I do know that increasing CO2 input into the oceans comes with its own risks. For example, in increased acidification of the oceans, and the attendent risk this has especially on the growth of calcifying organisms (corals, mollusks, radiolarians, etc.).
We agree wholeheartedly here. I spend much time working on ocean acidification.
For those outside of marine biology: While the uptake of CO2 by oceans may help mitigate the climatic effects of CO2 emissions, a decrease in pH will have dangerous impacts on calcifying organisms. Decreased concentration of the carbonate ion will cause structures made of calcium carbonate to become vulnerable to reduced calcification/enhanced dissolution. This will affect organisms like corals, coccolithophore algae and pteropods.
The full ecological consequences of these changes are unknown, but we do know calcifying species will be adversely impacted and in turn, humans will be affected. Organisms may suffer directly through reproductive or physiological effects, or indirectly through trophic cascades.
That said, recent interest in carbon sequestration through mechanisms like iron fertilization frighten me tremendously. I'm sure I'll be posting more on ocean acidification soon...
Thanks for your comments Sheril. Love your blog.
And the other guy who blogs here sometimes is OK too. :)
P.S.: I wrote radiolarians but I actually I meant coccolithophorids/foraminifera...but you knew that already.