Wednesday, October 11, 2017

A Bad Year For the Bay

Researchers say the total amount of oxygen-deprived dead zones in Chesapeake Bay this summer was the worst since 2014.

In June, federal scientists predicted a bigger-than-average oxygen-deprived zone. It turns out they were correct.

Researchers with the Virginia Institute of Marine Science who study bay hypoxia said Monday that the total amount of dead zones this summer increased by 10 percent over last year. The increase came despite a drop in the overall duration and maximum extent of dead zones compared with 2016.

The institute has used a real-time, three-dimensional forecast model since 2014 to gauge various hypoxia metrics in the bay. Researchers estimated there were 919 cubic kilometers of hypoxia during 2017. That’s larger than the 833 cubic kilometers in 2016, 757 cubic kilometers in 2015 and 918 cubic kilometers in 2014.
Which, curiously, is greater than the whole volume of Chesapeake Bay according to Wikipedia...

Bay Volume = Surface area (11,601 sq km) X Average depth (6.4 m = 0.0064 km) = 74.2 km3. So what's wrong here? A cubic kilometer is a lot of water.

Earlier reports this year, admitted partial, indicating the Bay was beating predictions, are now shown to be incorrect.

As when the Bay has a good year, I urge caution before over interpreting the results. Bay hypoxia is almost 100% driven by river flow and river flow timing. There are still plenty of nutrients left to feed the algae that lead to the hypoxia, and it's likely to be a long time before nutrient inputs drop enough to change that.

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