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Melting icebergs help to slow global warming

Melting icebergs are doing their own bit to halt the onward march of global warming.

By releasing iron into the Southern Oceans, melting icebergs are fuelling the growth of plankton - which help to remove a substantial amount of CO2 from the atmosphere.

Iron is an essential nutrient, a lack of which limits the growth of plant life in the Southern Ocean.  The main source of this iron is believed to be from atmospheric dust, but new evidence from the University of Leeds shows that icebergs could provide at least as much absorbable iron into the ocean.

Supporting evidence from the Weddell Sea in the Southern Ocean shows that iron from melting icebergs acts as a fertilizer for plant life in the surrounding ocean. This in turn reduces the level of C02 in the atmosphere - the main cause of climate change. 

"We've found a new source of iron delivery into the Southern Ocean, in the form of iron nanoparticles embedded in icebergs," says Prof Rob Raiswell, a professor of sedimentary geochemistry at the University of Leeds. 

"This source has previously been overlooked because the iron in glacial sediments was assumed to be too inert for plankton to use, but we have discovered iron oxide nanoparticulates that can be easily absorbed."

The research, funded by a Leverhulme Emeritus Fellowship and published in the journal Geochemical Transactions, used samples from icebergs and glaciers in Antarctica which were analysed using high resolution microscopy and chemical extraction methods to identify the iron nanoparticles.  The data allowed Leeds scientists to quantify the rates of nanoparticle iron supply from icebergs and assess the significance of these rates compared to other sources of iron

The results suggest that icebergs have a time-honoured method of reducing rising CO2 levels. 

"We have reason to think that the iceberg delivery of nanoparticulate iron oxides during the last Ice Age (18000-21000 years ago) was a significant factor in maintaining the cold climate and the associated low C02 concentrations.  And if icebergs mitigated against climate warming in the past they should have the capacity to do so in the near future," comments Raiswell.

For further information: 

Please contact the University of Leeds Press Office on +44 (0)113 343 4031 or email

Notes to editors:

1. Professor Rob Raiswell is available for interview.  He is a Leverhulme Emeritus Professor of sedimentary geochemistry in the School of Earth and Environment at the University of Leeds.

2. This research was funded by a Leverhulme Emeritus Fellowship.

3. The full text of the original research paper Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt, published in Geochemical Transactions, is available on request. 

4. The University of Leeds is one of the largest higher education institutions in the UK with more than 30,000 students from 130 countries. With a turnover approaching £450m, Leeds is one of the top ten research universities in the UK, and a member of the Russell Group of research-intensive universities.

5. The School of Earth and Environment at the University of Leeds has more than 60 academic staff, 35 support staff and over 50 Postdoctoral Research Fellows and Associates. It focuses on a multidisciplinary approach to understanding our environment, studying the Earth from its core to its atmosphere and examining the social and economic dimensions of sustainability.


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