Sea ice in the Arctic Ocean is in rapid decline. This reduction in ice extent and thickness has resulted in a longer open water season and higher marine productivity. Until recently, phytoplankton blooms on continental shelves were thought to be restricted to waters free of sea ice.
However, during the summer of 2011 in the Chukchi Sea, a large phytoplankton bloom was observed for the first time beneath fully consolidated pack ice and extended from the ice edge to >100 km into the pack. This has been made possible by a thinning sea ice cover with more numerous melt ponds over the past decade that has enhanced light penetration through the sea ice into the upper water column.
These and other observations suggest that phytoplankton blooms are currently widespread on nutrient-rich Arctic continental shelves and that past estimates of annual primary production in waters where under-ice blooms develop are ~10-fold too low. These massive phytoplankton blooms represent a marked shift in our understanding of Arctic marine ecosystems and their early timing can potentially disrupt lifecycle strategies of both resident and migratory Arctic species.