An irreversible shift in the chemical make-up of the Arctic Ocean driven by climate change is disrupting the region’s food chain, a study suggests.

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Key nutrient
Nitrate is vital for the growth of plankton at the base of the Arctic food chain, and reduced levels of the nutrient limit the amount of life the ecosystem can support, the team says.

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Ice losses
Their analysis reveals a clear shift from 2009 onwards, with nitrate levels in waters leaving the Arctic falling steadily. The drop in nitrate levels coincided with a drastic reduction in Arctic sea ice that began around the same time, the team says.

The extensive loss of sea ice ramped up a process that converts nitrate to nitrogen gas – called benthic denitrification – in shallow continental shelves that underly nearly half of the Arctic Ocean, the team says.

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Since the change in nutrient conditions is driven by ongoing sea ice loss, it is very unlikely the Arctic Ocean will ever revert to its previous state, researchers say.

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