Sub-ice Phytoplankton Blooms
Regions of the Arctic Ocean that permit a sub-ice bloom in July, 2006-2015One of the most striking scientific discoveries in the modern era occurred in June, 2011 in the Chukchi Sea of the Arctic Ocean. Kevin Arrigo and colleagues observed a massive phytoplankton bloom underneath a region of the ocean that was fully covered by sea ice. The levels of chlorophyll in this bloom rivaled the highest levels ever recorded in the worlds oceans!
Typically, sea ice is optically thick enough so that the little light that reaches the ocean underneath it does not support photosynthesis. The thinning sea ice, and the existence of sea ice melt ponds, have been suggested as a possible explanation: as the ice thins, more light can pass through it without being attenuated. And melt ponds do not reflect as much sunlight as does bare sea ice, so more can be transmitted to the ice base.
Working with Sarah Iams, David Rees Jones, and a group from the Center for Polar Ocean Meteorology, we developed and tested a model for the timing and initiation of these blooms under sea ice (submitted pdf here). We found that the thinning of sea ice has lead to the potential for sub-ice blooms that can extend as far as the North Pole in June and July, covering nearly a third of the Arctic Basin, during periods several months before ice retreats and sunlight reaches the open water.