Light Transmittance through Arctic Sea Ice Cover

Observing and Understanding the Impacts of a Thinning and Retreating Sea Ice Cover on Light Propagation, Primary Productivity, and Biogeochemistry in the Pacific Arctic Region
Funding Agency: NASA Interdisciplinary Research in Earth Science Program
Collaborators: D. Perovich (ERDC-CRREL), C. Polashenski (ERDC-CRREL), B. Light (University of Washington), and J. Comiso (NASA GSFC)
Funding Period: 2014-2018

The Arctic sea ice cover is undergoing tremendous changes. There has been a pronounced decrease in the summer sea ice extent, an overall thinning of the ice, a lengthening of the summer melt season, and a fundamental shift to a primarily seasonal sea ice cover. Some of the greatest changes in the sea ice cover have been observed in the Chukchi and Beaufort seas, where there has been substantial loss of summer ice over recent decades. These changes in the physical system are profoundly affecting biological and biogeochemical systems as well. Results from the NASA-sponsored Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) program demonstrated how physical changes in the sea ice impact primary productivity and biogeochemistry by altering sunlight availability. Massive phytoplankton blooms in the water column were found directly beneath a melting (yet fully consolidated) sea ice cover in the central Chukchi Sea in July of 2010 and 2011. Unexpectedly high levels of nutrients and transmitted sunlight through the ice cover enabled these blooms to occur. Furthermore, subsequent laboratory experiments have demonstrated that this available sunlight is also sufficient for significant photodegradation of chromophoric dissolved organic matter (CDOM) in the water column beneath the ice, which has important implications for the absorption of sunlight and heat balance of the upper ocean. The overarching goal of this work is to determine the impact of physical changes in the sea ice cover of the Chukchi and Beaufort seas on biological productivity and biogeochemical cycling in waters beneath and associated with this ice cover. We proposed an interdisciplinary and multi-methodological approach to address this goal, with integration of field observations, satellite remote sensing, and process studies/broader modeling. Our geographic domain is focused in the Chukchi and Beaufort seas of the Pacific Arctic region, where profound replacement of multiyear sea ice with seasonal sea ice has taken place over recent decades.