Remote Rupert Bay in northern Quebec is a place where the majesty and dynamism of fluid dynamics is regularly on display. With several rivers pouring into this nook of James Bay, the collision of river and sea water combines with the churn of tides and the motion of currents past islands to make swirls of colorful fluid that could impress even the most jaded of baristas.

As they wind through the boreal forests and wetlands of Northern Quebec, the rivers that flow into Rupert Bay often carry water stained brown with tannins and lignins, chemical substances found in plants. Tannins and lignins from roots, leaves, seeds, bark, and soil can leach into the water and give it a yellow, brown, or even black color. (The same process gives tea its dark color.)

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NASA Earth Observatory, October 2016