The northern European shelf as an increasing net sink for CO 2

Becker, Meike; Olsen, Are; Landschützer, Peter; Omar, Abdirhaman; Rehder, Gregor; Rödenbeck, Christian; Skjelvan, Ingunn

We developed a simple method to refine existing open-ocean maps and extend them towards different coastal seas. Using a multi-linear regression we produced monthly maps of surface ocean inline-formulafinline-formulaCO2 in the northern European coastal seas (the North Sea, the Baltic Sea, the Norwegian Coast and the Barents Sea) covering a time period from 1998 to 2016. A comparison with gridded Surface Ocean inline-formulaCO2 Atlas (SOCAT) v5 data revealed mean biases and standard deviations of 0 inline-formula± 26 inline-formulaµatm in the North Sea, 0 inline-formula± 16 inline-formulaµatm along the Norwegian Coast, 0 inline-formula± 19 inline-formulaµatm in the Barents Sea and 2 inline-formula± 42 inline-formulaµatm in the Baltic Sea. We used these maps to investigate trends in inline-formulafinline-formulaCO2, pH and air–sea inline-formulaCO2 flux. The surface ocean inline-formulafinline-formulaCO2 trends are smaller than the atmospheric trend in most of the studied regions. The only exception to this is the western part of the North Sea, where sea surface inline-formulafinline-formulaCO2 increases by 2 inline-formulaµatm 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 the expected trends. Consistently, the pH trends were smaller than expected for an increase in inline-formulafinline-formulaCO2 in pace with the rise of atmospheric inline-formulaCO2 levels. The calculated air–sea inline-formulaCO2 fluxes revealed that most regions were net sinks for inline-formulaCO2. Only the southern North Sea and the Baltic Sea emitted inline-formulaCO2 to the atmosphere. Especially in the northern regions the sink strength increased during the studied period.



Becker, Meike / Olsen, Are / Landschützer, Peter / et al: The northern European shelf as an increasing net sink for CO2. 2021. Copernicus Publications.


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