Friday, July 24, 2015

Halfway Update

Hi everyone,

We are a little more than halfway finished with our Gulf of Alaska Cruise! You’ve seen us writing about the tools we’ve been using, and we’ve been tweeting and blogging about the scenery and wildlife. Today we sailed into the Copper River plume to take some more measurements, and this line was really a combination of both—great data and great scenery.

The Copper River is home to one of the more famous salmon runs in Alaska. I’ve actually been to Chitina to fish there with my dad, and I can vouch for how good the catch can be! As one of North America’s largest wetlands, the Copper River Delta also hosts a large variety of seabirds, and gets its name from large copper deposits historically mined by native Alaskans. The area is a vital natural resource for Alaska. We're interested in the Copper River waters because of what they bring into the coastal ocean. As the largest river that empties into the Gulf of Alaska, it actually delivers about 1630 m3/s. That's enough water to fill about 50 large shipping containers every second!

In this picture, you can see the water from the Copper River plume meeting the offshore seas. The different color comes from the sediment that washes out of the delta. A number of glaciers drain directly into this river, and they are famous for grinding rock into a very fine powder—some folks call it rock flour. These fine sediments are very light and don’t easily sink to the bottom, which is why they stay suspended and change the river's color. (You can see two glaciers in the background at the upper right. That's right-- the glacial ice is blue!)

Sediments in Alaska—and the rivers that carry them—are unusually low in carbonates, a naturally occurring molecule that can moderate ocean pH and protect against ocean acidification. When rivers flow out to the coastal seas, they dilute the concentration of carbonates in seawater, and thereby increase the vulnerability of these areas to ocean acidification. On top of the river water, glacial melt and rock flour by themselves can introduce a lot of chemical complexity to this process. It’s important for us to observe and monitor these areas so that we can better understand these natural vulnerabilities and predict ocean acidification impacts.

We've been working hard the last several days to process some of the data we've collected throughout the first half of this cruise. Keep an eye out for new posts coming soon! Until then, may you have fair winds and following seas;


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