Summer greenhouse gases spatial variability from Svalbard and Norway fjords

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, its fluxes, and they stressed the importance to follow the non-CO₂ GHG with greater global warming potential.

The ocean plays a crucial role in climate regulation as a sink of anthropogenic CO₂, while surface seawater is naturally supersaturated in CH₄, and shallow coastal waters are a source of CH₄ to the atmosphere. However, the air-sea CO₂ and CH₄ fluxes are driven by different key processes depending on the region of the open or coastal ocean.

To improve the understanding of the processes driving the air-sea exchange of GHG, we investigate the CO₂ and CH₄ concentrations in open ocean and coastal areas affected by sea ice, glacier runoff and riverine inputs within the context of the European project GreenFeedBack. To do so, we measured CO₂ and CH₄ concentrations in surface water during a summer cruise (August 2024) conducted on board the RV Skagerak between Sweden, Norway and the Storfjorden in Svalbard. The data were obtained using a custom-made air-seawater equilibration system, that was connected to the vessel’s non-toxic seawater supply (equilibrator and Cavity Ring Down Spectrometer) and discrete sampling. We also investigated the depth distribution of CH₄ and carbonate system parameters.

Our first results show very high CH₄ concentration in surface seawater near marine-terminated glaciers in the Storfjorden, correlated with salinity gradient (but not the lowest salinity observed in Svalbard). In West-Svalbard, we found minimal CO₂ concentration correlated with low salinity, indicating a potential impact of freshwater discharge from the glaciers systems.