June 20 – Disco Volante

Today’s Factismal: Ocean water has gotten 40% cloudier since 1950.

One way or another, we all depend on the ocean. It feeds us with fish, provides us with water thanks to storms, and transports heat from the equator to the  poles using currents and really, really big storms. But most importantly, the ocean takes up nearly a third of the carbon dioxide that is created on Earth. (The ocean puts out lots of CO2, but it takes in even more so that it is a net sink.)

When the ocean takes in CO2, it helps to keep the world cool.

When the ocean takes in CO2, it helps to keep the world cool.

The ocean removes CO2 from the air by two main methods. First, it just soaks in the CO2 much as  a sponge soaks in water and for much the same reason; there’s so much of it outside that some gets pushed inside. (In science-speak, that’s “the partial pressure of CO2 gas is higher in the atmosphere than it is in the ocean”.) When CO2 is absorbed by the oceans, it forms carbonic acid which is a weak acid that nonetheless can interact with a wide variety of things, including the calcium carbonate shells of coral and the mortar and cement holding bridges and piers together.

Bleached coral (My camera)

Bleached coral
(My camera)

The second way that the oceans remove CO2 is by the action of the critters that live in it. Tiny little bugs known as phytoplankton suck in the CO2 and use it during photosynthesis to make sugars and more phytoplankton; about half of all photosynthesis on Earth happens in the upper ocean waters. And those phytoplankton form the base of a food web that feeds little fish which feed bigger fish which feed huge fish which feed us. No phytoplankton means no fish tacos, sandwiches, and no soylent green! But those bugs need more than CO2 to grow; they also need light. And that’s where things aren’t looking too bright.

For reasons that are still unclear, the ocean waters have gotten cloudier over the past half century. That means that there is more debris and crud in the water, which means that less light makes it through to the phytoplankton. As a result, the phytoplankton can’t grow as quickly, which means that they absorb less CO2 and that there are fewer of them. That 40% decrease in light in the oceans has meant a 40% decrease in the plankton which has meant a decrease in both the amount of CO2 taken up and the number of fish that grow up.

Citizen scientists measuring the cocan's cloudiness with a Secchi disc (My camera)

Citizen scientists measuring the cocan’s cloudiness with a Secchi disc
(My camera)

But the most interesting thing about this is how we know that the oceans have gotten 40% cloudier. We know it thanks to citizen scientists like you. Citizen scientists have been using a flat black and white plate known as a Secchi disc to measure the visibility in the water. By taking measurements on boats and in streams and lakes, these citizen scientists have provided invaluable ground truth for scientists around the world! If you’d like to take part, then download the Secchi app and start measuring!

2 thoughts on “June 20 – Disco Volante

  1. Pingback: June 8 – Deep Blue | Little facts about science

  2. Pingback: June 24 – On Wings Of Eagles | Little facts about science

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