Research from the University of Sheffield’s Department of Geography has revealed that melting water from giant icebergs, which contains iron and other nutrients, supports unexpectedly high levels of phytoplankton growth.
This activity, known as carbon sequestration, contributes to the long-term storage of atmospheric carbon dioxide, therefore helping to slow global warming.
During the study, which is the first of its kind on this scale, a team of scientists led by Professor Grant Bigg analysed 175 satellite images of ocean colour – which is an indicator of phytoplankton productivity at the ocean’s surface – from a range of icebergs in the Southern Ocean that were at least 18km in length.
The images from 2003-2013 showed that enhanced phytoplankton productivity, which has a direct impact on carbon storage in the ocean, extends hundreds of kilometres from giant icebergs, and persists for at least one month after the iceberg passes.
‘This new analysis reveals that giant icebergs may play a major role in the Southern Ocean carbon cycle.
‘We detected substantially enhanced chlorophyll levels, typically over a radius of at least four-10 times the iceberg’s length.’
The Southern Ocean plays a significant part in the global carbon cycle, and is responsible for approximately 10% of the ocean’s total carbon sequestration through a mixture of biologically driven and chemical processes, including phytoplankton growth.
‘The evidence suggests that assuming carbon export increases by a factor of five-10 over the area of influence and up to a fifth of the Southern Ocean’s downward carbon flux originates with giant iceberg fertilisation.
‘If giant iceberg calving increases this century as expected, this negative feedback on the carbon cycle may become more important than we previously thought.’
Previous studies have suggested that ocean fertilisation from icebergs makes relatively minor contributions to phytoplankton uptake of CO2.
However this research, published on Monday in Nature Geoscience, shows that melting water from icebergs is responsible for as much as 20% of the carbon sequestered to the depths of the Southern Ocean.
Click here to see the full study in the journal Nature Geoscience.
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