Carbon Dioxide Exchange in the Coastal Ocean-Sea Ice-Atmosphere System

Based on climatic data consisting of routine measurements of carbon dioxide concentration at Barrow, Alaska, and on satellite data about sea ice area in eastern part of the Arctic Ocean, we hypothesize that ice conditions in the Arctic Ocean influence the long-term variability of atmospheric carbon dioxide concentration. Our data from ship observations in the Chukchi, Laptev, and East-Siberian Seas give some support to this hypothesis. We found that surface seawater in the ice-free Arctic shelf seas is mostly unsaturated in CO2 and therefore serves as a sink for atmospheric CO2. In contrast, during winter when the seas are ice-covered, the water beneath the sea ice is strongly oversaturated by CO2 and, respectively reverse CO2 flux to atmosphere. Note, that the coastal areas, strongly influenced by coastal erosion and the river input of terrestrial carbon (suspended and dissolved), are the sources of CO2 into the atmosphere year-round. Eddy-correlation and chamber measurements made on fast ice near Barrow during the summer provided some insights into the influence of sea ice on carbon dioxide exchange between the ocean and the atmosphere through sea ice. We infer that, in early summer, the absorption of atmospheric CO2 by the ice-covered ocean dominates. Our measurements also suggest the important role of melt ponds on gas exchange. The first results of continuous direct pCO2 measurements beneath fast ice (winter 2003) indicate the possible role of early photosynthesis on pCO2 decline.