Vegetated coastal ecosystems like salt marshes are effective soil organic carbon sinks due to high rates of photosynthetic CO2 uptake, and storage of organic material under reducing soil conditions. At the same time, salt marshes emit only small amounts of the non-CO2 greenhouse gases N2O and CH4. Their biogeochemistry is characterised by a complex interplay of abiotic and biotic factors driven by periodical and episodical inundation with seawater. This complexity further increases when global change impacts like rising temperatures are taken into account. To study the impact of warming on an ecosystem scale, we measured land-atmosphere fluxes of CH4, N2O and CO2 at the MERIT (Marsh Ecosystem Response to Increased Temperature) field study site at Hamburger Hallig, Nordfriesland, Germany. This unique warming experiment enables passive aboveground and active belowground warming of +1.5°C and +3°C compared to ambient temperatures. We combined a closed chamber approach with in situ measurements of portable infrared gas analysers in biweekly campaigns during the main vegetation period from July 2020 to September 2021. Our findings show that greenhouse-gas fluxes of salt marshes strongly vary in time and space. Salt marshes of the Wadden Sea area show the ability to take up the strong greenhouse gases CH4 and N2O, emphasizing their important role in mitigating global warming. Land-atmosphere fluxes under experimentally warmed conditions are currently under analysis, aiming to elucidate the effect of future warmer temperatures and to clarify how changes through warming effects compare to preexisting spatial and temporal variability.