Abstract :
[en] Since the beginning of the industrial era, the atmospheric greenhouse gases (GHG) have increased continuously (around +50% for carbon dioxide (CO2) and +150% for methane (CH4), for the two most important), causing the current climate change. In November 2023, the World Meteorological Organization (WMO) highlighted once again there are still significant uncertainties about the carbon cycle and its fluxes, and stressed the importance to follow the non-CO2 GHG with greater global warming potential.
The subpolar North Atlantic Ocean is a major CO2 sink, whereas the continental shelf and fjords show more spatial-temporal variability and poor regional coverage of sea-air CO2 flux data due to the lack of in-situ observational data. While surface seawaters are naturally supersaturated in CH4, the Arctic region (including Southern Greenland fjords) is subject to rapid warming and, therefore, is susceptible to substantial CH4 release into the atmosphere, further exacerbating global warming.
To improve our knowledge, it is essential to increase observational efforts to reduce uncertainties on the ocean CO2 sink and monitoring CH4 levels in high-latitude surface waters where changes have already been observed. To do so, we measured CO2 and CH4 concentrations and calculated their fluxes, in surface water during a summer cruise (July-August 2023) conducted on board the RV Belgica in the subpolar North Atlantic Ocean, between Iceland and Southern Greenland Fjords. The data were obtained using a custom-made air-water equilibration system, that was connected to the vessel’s non-toxic seawater supply (equilibrator and Cavity Ring Down Spectrometer) and discrete sampling.
