Interannual variability of air-sea CO 2 fluxes and carbonate system parameters in the East Siberian Sea

Abstract

Over the past couple of decades it has become apparent that air-land-sea interactions in the Arctic have a substantial impact on the composition of the overlying atmosphere (ACIA, 2004). The Arctic Ocean is small (only ~4% of the total World Ocean), but it is surrounded by offshore and onshore permafrost which thaws at increasing rates under warming conditions releasing carbon dioxide (CO2) into the water and atmosphere. This work summarizes data collected from three expeditions in the coastal-shelf zone of the East Siberian Sea (ESS) in September 2003, 2004 and late August–September 2008. It is proposed that the western part of the ESS represents a river- and coastal erosion-dominated ocean margin that is a source for atmospheric CO2. It receives substantial river discharge that also adds organic matter, both dissolved and particulate. This in combination with significant input of organic matter from coastal erosion makes this region being of dominantly heterotrophic character. The eastern part of the ESS is a Pacific water-dominated autotrophic area. It's a high-productive zone, which acts as a sink for atmospheric CO2. The year to year dynamics of partial pressure of CO2 in the surface water as well as the sea-air flux of CO2 varied substantially. In some years the ESS shelf can be mainly heterotrophic and serve as strong source of CO2 (year 2004). Another year significant part of the ESS, where gross primary production exceeds community respiration, acts as a sink for the atmospheric CO2 and the net CO2 flux into the atmosphere is weak (year 2008). High variability of carbon system parameters observed in the ESS shelf is determined by many factors such as riverine runoff, advection of waters from adjacent seas, coastal erosion, primary production/respiration etc. The dynamics of the CO2 sea-air exchange is determined by ocean processes but also by atmospheric circulation which hence has a significant impact on the CO2 sea-air exchange. In this contribution the sea-air CO2 fluxes were evaluated in the ESS based on measured carbonate system (CS) parameters data and annual sea-to-air CO2 fluxes were estimated. It was shown that the total ESS shelf is a net source of CO2 for the atmosphere at a range from 0.5×1012 to 3.3×1012 g C.