Scientists discover new variability in iron supply to the oceans with climate implications

National Oceanography Centre (UK): The supply of dissolved iron to oceans around continental shelves has been found to be more variable by region than previously believed – with implications for future climate prediction.  Iron is key to the removal of carbon dioxide from the Earth’s atmosphere as it promotes the growth of microscopic marine plants (phytoplankton), which mop up the greenhouse gas and lock it away in the ocean. 

A new study, led by researchers based at the National Oceanography Centre Southampton, has found that the amount of dissolved iron released into the ocean from continental margins displays variability not currently captured by ocean-climate prediction models. This could alter predictions of future climate change because iron, a key micronutrient, plays an important role in the global carbon cycle.

Previously assumed to reflect rates of microbial activity, the study found that the amount of iron leaking from continental margins (the seafloor sediments close to continents) is actually far more varied between regions because of local differences in weathering and erosion on land. The results of the study are published this week in Nature Communications.

“Iron acts like a giant lever on marine life storing carbon,” says Dr Will Homoky, lead author and postdoctoral research fellow at University of Southampton Ocean and Earth Science, which is based at the Centre. “It switches on growth of microscopic marine plants, which extract carbon dioxide from our atmosphere and lock it away in the ocean.”

...But how much can this one factor really affect changes in the Earth’s climate? Dr Homoky explains: “Model simulations indicate that the presence or absence of iron supply from continental margins may be enough to drive Earth's transition between glacial and interglacial periods,” he says. “Therefore these findings could certainly have implications for global climate modelling – to what extent, is yet to be determined....

A phytoplankton bloom off the Japanese coast, via NASA