Of all the regions in the world, the Arctic is perhaps the most sensitive to climate change, since air temperatures at high latitudes have risen two to three times faster compared to the rest of the world [1,2,3]. This amplified temperature rise has already led to apparent changes around the Arctic, such as reductions in snow cover, shown in Figure 1, an earlier onset of the growing season [4] and permafrost degradation [5,6].

Next to these changes on land, the Arctic Ocean has also seen drastic and very apparent changes. Sea ice extent in the Arctic has diminished by approx. 45000 km²/year [7], also shown in Figure 1, with an all-time low in 2007 [8,9], while at the same time sea-ice thickness has decreased by ~50% in 40 years [10].

These changes in the ocean and on land are not isolated processes and in all probability influence each other. Recent studies have suggested that the decline in sea ice has increased land surface temperatures [11], influenced weather patterns [12] and affected plant growth in the Arctic [13].

From a carbon cycling perspective, this interaction between ocean and land is important since it is also expected to influence the exchange of greenhouse gases in the Arctic. For example, an Arctic ocean with less sea-ice could lead to higher Arctic air temperatures and changes in precipitation. Since methane emissions are sensitive to changes in temperature and water availability, this would subsequently affect emissions. However, up till now no study has conclusively been able to confirm these connections, which have been obscured by a lack of circumpolar measurements.

Then again, there are studies that suggest that processes in the Arctic are directly linked to variations in the atmospheric methane concentration [14,15] and ocean-land interactions might help in understanding and clarifying these patterns. For that reason, the aim of my project is to assess how the mechanism of ocean-land interaction impacts greenhouse gas exchange in the Arctic, with an emphasis on methane emissions.

To achieve this, a better understanding of the drivers of greenhouse gas exchange in the Arctic is needed. This research focuses on observed and modeled changes in circumpolar greenhouse-gas exchange, and identifies signals that indicate influences from a changing ocean-land interaction, in combination with the direct influence of sea ice on the greenhouse gas exchange of the Arctic Ocean. By zooming in on how a changing sea-ice extent affects circumpolar greenhouse gas exchange, we will achieve a better understanding of the functioning of the system as a whole .

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