The northern European shelf as increasing net sink for CO2

• Main Authors: Becker, Meike, Olsen, Are, Landschützer, Peter, Omar, Abdirhaman, Rehder, Gregor, Rödenbeck, Christian, Skjelvan, Ingunn
• Format: Text
• Language: English
• Published: 2020
• Subjects: Barents Sea
• Online Access: https://doi.org/10.5194/bg-2019-480; https://www.biogeosciences-discuss.net/bg-2019-480/

We developed a simple method to refine existing open ocean maps towards different coastal seas. Using a multi linear regression we produced monthly maps of surface ocean f CO 2 in the northern European coastal seas (North Sea, Baltic Sea, Norwegian Coast and in the Barents Sea) covering a time period from 1998 to 2016. A comparison with gridded SOCAT v5 data revealed standard deviations of the residuals 0 ± 26 μatm in the North Sea, 0 ± 16 μatm along the Norwegian Coast, 0 ± 19 μatm in the Barents Sea, and 2 ± 42 μatm in the Baltic Sea.We used these maps as basis to investigate trends in f CO 2 , pH and air-sea CO 2 flux. The surface ocean f CO 2 trends are smaller than the atmospheric trend in most of the studied region. Only the western part of the North Sea is showing an increase in f CO 2 close to 2 μatm yr −1 , which is similar to the atmospheric trend. The Baltic Sea does not show a significant trend. Here, the variability was much larger than possibly observable trends. Consistently, the pH trends were smaller than expected for an increase of f CO 2 in pace with the rise of atmospheric CO 2 levels. The calculated air-sea CO 2 fluxes revealed that most regions were net sinks for CO 2 . Only the southern North Sea and the Baltic Sea emitted CO 2 to the atmosphere. Especially in the northern regions the sink strength increased during the studied period.