Gas exchange of CO2 and O2 in partially ice-covered regions of the Arctic Ocean investigated using in situ sensors

Abstract

Sea surface CO2 dynamics are not well characterized in the Arctic Ocean (AO). Most data are from ship-based studies during the low-ice period (May-September) and obtained from near shore areas because of accessibility. More CO2 data are needed to improve models for predicting the future of the carbon cycle in the region and its relationship to ocean acidification. Air-sea gas exchange rates are complicated by the presence of ice. Consequently gas exchange rates have a larger uncertainty in the AO compared to other ocean regions. To provide more information about CO2 dynamics and gas exchange in the AO, in situ time-series data have been collected from the Canada Basin during late summer to autumn of 2012. Partial pressure of CO2 (pCO2), dissolved O2 (DO) concentration, temperature, and salinity were measured at ∼6-m depth under little ice and multi-year ice on two ice-tethered profilers (ITPs) for 40-50 days. The pCO2 levels were always below atmospheric saturation whereas DO was almost always slightly above saturation. Although the two ITPs were on an average only 222 km apart, one was further south and had 14 ± 12% ice cover; whereas the more northern ITP had 63 ± 16% ice cover. Consequently the two data sets differed significantly in external forcings. Modeled variability of CO2 and DO estimate that gas exchange would significantly alter sea surface pCO2 in the low ice cover record but minimally in the more extensively ice-covered region. If these conditions extended over the entire AO, the total uptake of atmospheric CO2 would be 28.6 Tg C yr-1 and 15.4 Tg C yr-1 under low and high ice-covered conditions, respectively.