Melting ice caps may slow global warming

Huge amounts of dissolved iron being released into the oceans from melting ice sheets may cancel out some of the negative effects of global warming, a new study has claimed.
A newly-discovered source of oceanic bio-available iron could have a major impact on our understanding of marine food chains and global warming, researchers said.
The team found that summer melt-waters from ice sheets are rich in iron, which will have important implications on phytoplankton growth.
It is well known that bio-available iron boosts phytoplankton growth in many of Earth's oceans. In turn phytoplankton capture carbon - thus buffering the effects of global warming, researchers said.

The plankton also feed into the bottom of the oceanic food chain, thus providing a food source for marine animals.
The team, comprising researchers from the Universities of Bristol, Leeds, Edinburgh and the National Oceanography Centre, collected melt-water discharged from the 600 square km Leverett Glacier in Greenland over the summer of 2012, which was subsequently tested for bio-available iron content.

The researchers found that the water exiting from beneath the melting ice sheet contained significant quantities of previously-unconsidered bio-available iron.
This means that the polar oceans receive a seasonal iron boost as the glaciers melt.
"The Greenland and Antarctic Ice Sheets cover around 10 per cent of global land surface. Iron exported in icebergs from these ice sheets have been recognised as a source of iron to the oceans for some time. Our finding that there is also significant iron discharged in runoff from large ice sheet catchments is new," said lead author Jon Hawkings from the Bristol University.

"This means that relatively high iron concentrations are released from the ice sheet all summer, providing a continuous source of iron to the coastal ocean," said Hawkings.
Iron is one of the most important biochemical elements, due to its impact on ocean productivity.
Despite being the fourth most abundant element in Earth's crust, it is mostly not biologically available because it is largely present as unreactive minerals in natural waters.
Over the last 20 years there has been controversy over the role of iron in marine food chains and the global carbon cycle, with some groups experimenting with dumping iron into the sea in order to accelerate plankton growth - with the idea that increased plankton growth would capture man made CO2.

This work indicates that ice sheets may already be carrying out this process every summer.
Based on their results the team estimates that the flux of bio-available iron associated with glacial runoff is between 400,000 and 2,500,000 tonnes per year in Greenland and between 60,000 and 100,000 tonnes per year in Antarctica.
The finding was published in the journal Nature Communications.