Impacts of chromophoric dissolved organic material on surface ocean heating in the Chukchi Sea

Abstract

Recent observations show visible light attenuation in the Arctic Ocean to be greater than previously assumed. High attenuation observed during the period prior to ice melt and increased phytoplankton production, was attributed primarily to the high levels of absorption by chromophoric dissolved organic material (CDOM) present in these waters. Preliminary evidence suggests this material is produced by ice algae in the early spring. Optical data from the Chukchi shelf system collected in the spring and summer of 2002, were used to model energy absorption in the mixed layer by both dissolved and particulate material. In the spring, absorption by CDOM was responsible for increasing the energy absorbed in the mixed layer by 40% over pure seawater. Thus CDOM absorption represents a significant factor in the heating budget of Arctic surface waters. The energy absorbed by CDOM has the potential to account for 48% of the springtime ice melt driven by water column heating. With continued warming, negative feedback due to loss of ice algae habitat could slow down heating effects in the spring. However, terrestrial input of CDOM to the Arctic is postulated to increase due to the release of organic carbon from thawing permafrost. Coupled with the loss of the highly reflective sea ice cover during the spring and summer, CDOM absorption may become increasingly influential in the heating budget of Arctic surface waters.