Giant icebergs² leave trail of carbon sequestration in their wake -- a month after they have passed Geographers³ analysed 175 satellite images of ocean colour which is an indicator⁴ of phytoplankton productivity at the ocean's surface Giant icebergs are responsible for storing up to 20 per cent of carbon in the Southern Ocean, a new study has found.

 

Pioneering research from the University of Sheffield's Department of Geography discovered melting water from giant icebergs, which contains iron and other nutrients⁵, supports hitherto unexpectedly high levels of phytoplankton growth.

 

This activity, known as carbon sequestration, contributes to the long-term storage of atmospheric⁶ carbon dioxide, therefore helping⁷ 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 which were at least 18 km 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 iceberg¹ passes.

 

Professor Bigg said: "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 radius⁸ of at least four-10 times the iceberg's length.

 

"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 flux⁹ 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 previously¹⁰ thought."

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