Final Activity Report Summary - EHAWC (European high arctic wetland change) Arctic wetlands are active in carbon and hydrological cycles and are both climatically sensitive ecosystems as well as important archives of past environmental conditions. To assess the carbon sequestration and hydrological sensitivity of High Arctic mires to climate variation, peat deposits from Svalbard, Norway were studied to determine their response to past climate. Our goal, to quantify carbon accumulation and determine surface wetness histories, is motivated by the question of whether High Arctic mires have been dynamic and sensitive to past climate variation. Peat cores and surface samples were collected in 2007 and 2008 at several low-elevation sites from the inner fjords of west-central Spitsbergen between 78 and 79N. Decadally-resolved indicators of peat decomposition together with high-resolution carbon assays and radiocarbon dating reveal that Arctic mires in Svalbard are highly sensitive to perturbation. Patterns in the rate of carbon accumulation included abrupt slowdowns/near-shutdowns of carbon accumulation that have persisted for centuries to surprisingly high sustained rates - as high as Eurasian sites much further south. For example, 6000-year old organic deposits at 79N show slowdown in carbon sequestration contemporaneous with the close of Holocene Thermal Maximum conditions, whereas, 1500-year-old deposits at 78N show renewed sequestration around AD 1500 following a multi-centennial hiatus. This highly-sensitive carbon sequestration response to past warming was shown to be strongly mediated by hydrological conditions, suggesting that future response in a warmer Arctic will have a strong reliance on the fate of local water and changes in the amount and seasonality of precipitation.