As global warming leads to a hotter planet, the Arctic region is experiencing uncharacteristically warmer temperatures. This has raised hopes that the warmer temperatures might hasten a phytoplankton bloom leading to more productive waters that support fish and other animals.
But a team of scientists led by Princeton University and the Max Planck Institute for Chemistry disagrees. In the current issue of the journal Nature Geoscience, they suggest that under a global warming regime, open Arctic waters will experience more intense nitrogen limitation, likely preventing a rise in productivity.
Plankton need more than just sunlight to grow and thrive. They need abundant nutrients, such as nitrogen, which are typically supplied by deeper, denser waters. But the Arctic Ocean receives an influx of salty Pacific waters, which flows through the Bering Strait. These waters flow over the denser water layers, keeping nutrients at greater depths and limiting them from reaching upper levels.
By examining fossilized plankton from the past, the researchers found that during warmer periods, such as after the last Ice Age, nitrogen was subsumed under less dense water layers. With the Earth warming, a similar scenario will likely play out — limiting the amount of vital nutrients like nitrogen from reaching surface waters.