One scientist’s life on a boat tracking how the climate and ocean are linked

Maria S. Merian research vesselRV Maria S. Merian leaving Saint John's harbour on 8 July 2023 accompanied by a pilot. (Image: Pburka. CC BY-SA 4.0, Link)

Our seas are doing us an enormous favour by removing additional carbon from the atmosphere, but we don’t understand all the details of this process at the surface, or how this may change in the future.

By Helen Czerski
Courtesy of Guardian News & Media Ltd.

In this north-west corner of the Atlantic, between the southern tip of Greenland and Newfoundland, in winter — in the cold and continually stormy weather — we can live inside a particular scientific phenomenon for many weeks. We’re here to learn about a process that is fundamental to the way our planetary engine ticks. All around us, the ocean is taking a deep breath — literally. Cooling between late November and February causes a deep mixing between surface waters and the waters at depth, facilitating a vital transport of gases. I’m part of the UK contingent of an international team of scientists here to study how that happens.

The connected global ocean is an engine, a dynamic 3D system with internal anatomy that is constantly doing things that shape the world we take for granted. It is a huge reservoir for heat and gases: carbon dioxide (CO2), oxygen, nitrogen and more. And where the sea’s vast surface touches the atmosphere, these gases can be transferred in both directions, changing their concentrations in the water and the air.

Near the equator, for example, CO2 comes out of the water to rejoin the atmosphere, while up here in the high latitudes, it goes the other way. These processes are not currently balanced — the ocean is taking in extra CO2 because we have increased the atmospheric concentration by burning fossil fuels and altering the land surface.

A data-collecting buoy, made by members of the mechanical engineering workshop at University College London, is deployed in the Labrador Sea.

A data-collecting buoy, made by members of the mechanical engineering workshop at University College London, is deployed in the Labrador Sea. (Photo: Courtesy of Helen Czerski)

The ocean breathing that happens here in the Labrador Sea is particularly important because this is one of the few areas where its surface is sometimes directly connected to its depths. Over most of the global ocean, the top layer of water (usually a few tens of meters thick) floats on colder, denser water underneath, staying quite separate.

Related: And now we’re changing ocean currents — threatening to disrupt and worsen global weather

But in this corner of the north Atlantic in winter, the surface water cools so much that the continual storms can mix the top layer a long way downwards. It’s like an open plughole into the deep ocean — anything that enters the sea here can just keep going down — and this forms a crucial part of what’s called the “overturning circulation,” the slow global shunting of seawater between the surface and the depths. One of the consequences is that animals that live about two-thirds of a mile below the surface and never see the sun’s light, from the petite lanternfish to the giant squid, can still breathe oxygen.

Read the full article on The Guardian: