Phytoplankton, reducing greenhouse gases or amplifying Arctic warming?

Phytoplankton, commonly known as plant plankton that remove carbon dioxide from the atmosphere through photosynthesis, are potentially a key driver of Arctic warming under greenhouse warming, a study reveals.

Scientists with Pohang University of Science and Technology (POSTECH), Max Planck Institute for Meteorology (MPI-M), and Korea Institute of Ocean Science and Technology (KIOST), presented on Monday, April 20, in Proceedings of National Academy of Sciences (PNAS) Online, the geophysical impact of phytoplankton that triggers positive feedbacks in the Arctic warming when the warming-induced melting of sea ice stimulates phytoplankton growth. The paper is titled “Amplified Arctic warming by phytoplankton under greenhouse warming.”

When the Arctic sea ice melts away due to greenhouse warming, the ocean surface albedo inevitably decreases, reducing the amount of solar energy reflected back from the earth and ultimately resulting in warmer ocean surface. As phytoplankton growth is subject to factors such as temperature, light, and nutrients, the explosive growth of phytoplankton follow when both the warming-induced melting and shortwave radiation penetrating the ocean increase.

The new study has confirmed that it is the beginning of the geophysical feedback by which chlorophyll and the related pigments in phytoplankton absorb solar radiation and in turn raise the sea surface temperature even further. Using a coupled ocean-atmosphere model, the authors have revealed that the additional positive feedback in the Arctic can amplify Arctic warming by as much as 20%.

Read more