Climate contradictions at sea – new findings from R/V Skagerak
The oceans are known as the Earth's largest carbon sink - but new studies show that this is not the whole truth. Using the research vessel R/V Skagerak, researchers from the University 91̽»¨ have made new discoveries in some of the world's most unique regions of the ocean.
Between glaciers and the deep seabed, a complex interplay between greenhouse gases and the world's oceans is taking place - a game that could affect the climate of the future.
New results from data collected on board the R/V Skagerak show that while the oceans absorb carbon dioxide, they can also release powerful greenhouse gases such as methane and nitrous oxide.
"It's like a double edged sword. Carbon dioxide goes down into the ocean, but at the same time other gases such as nitrous oxide and methane can come out from the ocean and amplify the greenhouse effect," says Isaac Santos, Professor of Marine Chemistry at the Department of Marine 91̽»¨s.
Skagerak - a mobile research platform
The R/V Skagerak is the university's most advanced marine research platform. In 2023, researchers sailed north to Iceland and Greenland to study what happens in the transition zone between melting glaciers and the sea.
"This ship is just the right size: not too expensive to run, but big enough to carry all the equipment and our graduate students and international colleagues," says Isaac Santos.
Nitrous oxide from fjords - less than feared, but not insignificant
The laughing gas is not a joke. One kg of nitrous oxide has a climate impact equivalent to 300 kg of carbon dioxide.
One of the new studies measured the amount of nitrous oxide emitted from six fjords. The results show that many fjords, especially in Greenland, act as sinks rather than sources of nitrous oxide.
"Surprisingly, Greenland fjords actually showed a net uptake of nitrous oxide from the atmosphere. This is related to large meltwater plumes from the glaciers diluting nutrients and lowering the pH," says Tobia Politi, lead author of the study.
But that's not the whole story. In fjords with salmon farms, higher emissions were found. This is because nutrient leaching from the farms drives nitrous oxide production through microbial processes in the bottom sediments.
"Our measurements show that fjords globally account for up to 13 percent of total nitrous oxide emissions from coastal zones. Our expeditions allowed for an update of the global budget " says Isaac Santos.
Melting glaciers affect greenhouse gas balance
A related study focused on glacial lagoons and coastal seas in southern Iceland. One kilogram of methane has the same climate impact as 80 kilogram of carbon dioxide. The Iceland rapidly melting glaciers release methane, but at the same time the ocean's ability to absorb carbon dioxide is such that it remains a net carbon sink. The researchers found high methane emissions near the glacier, but further out to sea, carbon dioxide uptake dominated.
"This shows how important it is to understand the role of the whole ocean in the greenhouse gas balance - from the ice to the deep sea. The R/V Skagerak is the perfect platform to sample shallow waters and the deep ocean at the same time," says Wilma Ljungberg, a PhD student at the Department of Marine 91̽»¨s at the University 91̽»¨.
Data shaping future climate policy
The expeditions have already produced several scientific papers, and the data is now being used for PhD projects and international collaborations.
"This is exactly the kind of research that shows why it is so important to have our own research vessel. Skagerak is not just a ship - it is a floating laboratory that is shaping the next generation of Swedish marine scientists," says Isaac Santos.
As the climate warms and glaciers melt faster, there is an urgent need to understand how these changes affect the role of the oceans in regulating the climate.
"The unique findings from R/V Skagerak expeditions help to fill important knowledge gaps - and put the University 91̽»¨ on the map as a leading centre for marine climate research," says Isaac Santos.
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Text: Agnes Faxén