There may be a plus side to melting polar ice caps: British scientists suggest they could hold the key to stemming global warming.
According to research published in the journal Nature Communications, summer meltwaters from polar ice sheets are rich in iron, which are critical for phytoplankton growth. And what do phytoplankton do? They capture carbon dioxide emissions that scientists say are contributing to global warming.
“This study shows that glacier meltwater can contain iron concentrations that are high enough to significantly stimulate biological productivity in oceans that otherwise are oftentimes limited in the element iron that is essential to most living organisms,” wrote a team of UK scientists led by John Hawkings of the University of Bristol.
Researchers collected meltwater discharged from Greenland’s Leverett Glacier during the summer of 2012, which was then tested for bioavailable iron content. Scientists found that water being discharged beneath the melting ice sheet was rich in iron — iron that was previously unavailable to plankton populations. As more ice sheets melt, plankton populations could boom.
The Ice sheets of Greenland and Antarctica cover about 10 percent of the globe’s land surface and their coastlines harbor active ecosystems which are limited in iron, according to scientists. But as more ice begins to melt with rising global temperatures, more iron will be released from the ice sheets, fueling phytoplankton growth and leading to the capturing of more carbon dioxide.
“Iron exported in icebergs from these ice sheets have been recognised as a source of iron to the oceans for some time,” wrote Hawkings and his fellow researchers. “Our finding that there is also significant iron discharged in runoff from large ice sheet catchments is new.”
“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,” the researchers added.
Previous research has established that bioavailable iron boosts phytoplankton in other oceans. Melting ice could fuel more phytoplankton, which would absorb more carbon dioxide and stem some of the effects of global warming. Scientists noted that phytoplankton also feed on the bottom of the ocean, which would provide more food sources for other marine animals.
Hawkings found that the amount iron from glacier runoff is 400,000 and 2.5 million metric tons per year in Greenland and between 60,000 and 100,000 metric tons in Antarctica — the combined average of these estimates weighs the same as 125 Eiffel Towers and about 3,000 fully-laden Boeing 747s.
“This is a substantial release of iron from the ice sheet, similar in size to that supplied to the oceans by atmospheric dust, another major iron source to the world’s oceans,” the researchers wrote. “At the moment it is just too early to estimate how much additional iron will be carried down from ice sheets into the sea. Of course, the iron release from ice sheet will be localised to the Polar Regions around the ice sheets, so the importance of glacial iron there will be significantly higher.”
“Researchers have already noted that glacial meltwater run-off is associated with large phytoplankton blooms – this may help to explain why,” they added.
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