As giant icebergs bob across the open seas they leave behind a trail of nutrient-rich meltwater, sparking new life in the world’s remotest and least hospitable oceans. This in turn means more carbon is taken from the atmosphere and stored below the waves. Massive icebergs may be a symptom of climate change—but they can also help keep it in check.
“Giant” icebergs are technically those at least 18 kilometers in length. At any one time several dozen are afloat in the Southern Ocean, and individually they can survive for up to a decade. They make up roughly half of the ice discharged from Antarctica, so around 1000km3 per year—equivalent to the annual flow of the Congo River.
However these icebergs come in fits and starts. Some years hardly any break off, whereas five of the biggest icebergs recorded in the satellite era broke off into the Southern Ocean during 1999–2003.
So a big iceberg year can have a huge impact. In fact, during previous ice ages huge “iceberg armadas” from Northern Hemisphere ice sheets are believed to have redirected the Gulf Stream—albeit thanks to melting on a slightly larger scale.
It’s clear then that meltwater from giant icebergs can directly impact circulation of the Southern Ocean, and the climate above it. However, in a recent paper in Nature Geoscience, colleagues at the University of Sheffield and I have shown there is also a significant impact on the carbon sink, and hence the rate of exchange of CO2 between the ocean and atmosphere.
Why Icebergs Mean Oceans Store More Carbon
