Articles | Volume 8, issue 4
Research article
05 Dec 2017
Research article |  | 05 Dec 2017

The potential of using remote sensing data to estimate air–sea CO2 exchange in the Baltic Sea

Gaëlle Parard, Anna Rutgersson, Sindu Raj Parampil, and Anastase Alexandre Charantonis

Abstract. In this article, we present the first climatological map of air–sea CO2 flux over the Baltic Sea based on remote sensing data: estimates of pCO2 derived from satellite imaging using self-organizing map classifications along with class-specific linear regressions (SOMLO methodology) and remotely sensed wind estimates. The estimates have a spatial resolution of 4 km both in latitude and longitude and a monthly temporal resolution from 1998 to 2011. The CO2 fluxes are estimated using two types of wind products, i.e. reanalysis winds and satellite wind products, the higher-resolution wind product generally leading to higher-amplitude flux estimations.

Furthermore, the CO2 fluxes were also estimated using two methods: the method of Wanninkhof et al. (2013) and the method of Rutgersson and Smedman (2009). The seasonal variation in fluxes reflects the seasonal variation in pCO2 unvaryingly over the whole Baltic Sea, with high winter CO2 emissions and high pCO2 uptakes. All basins act as a source for the atmosphere, with a higher degree of emission in the southern regions (mean source of 1.6 mmol m−2 d−1 for the South Basin and 0.9 for the Central Basin) than in the northern regions (mean source of 0.1 mmol m−2 d−1) and the coastal areas act as a larger sink (annual uptake of −4.2 mmol m−2 d−1) than does the open sea (−4 mmol m−2 d−1). In its entirety, the Baltic Sea acts as a small source of 1.2 mmol m−2 d−1 on average and this annual uptake has increased from 1998 to 2012.

Short summary
Coastal environments and shelf sea represent 7.6 % of the total oceanic surface area. They are, however, biogeochemically more dynamic and probably more vulnerable to climate change than the open ocean. Whatever the responses of the open ocean to climate change, they will propagate to the coastal ocean. We used the self-organizing multiple linear output (SOMLO) method to estimate the ocean surface pCO2 in the Baltic Sea from remotely sensed measurements and we estimated the air–sea CO2 flux.
Final-revised paper