A pan-arctic river delta carbon and nitrogen stock estimation

The land-ocean interface in the Arctic is a sensitive environment facing severe changes due to rising global air temperatures. In particular, Arctic river deltas are rapidly changing permafrost landscapes which will become more dynamic due to sea-level rise, longer thaw periods, changes in river discharge, increased storm-surge flooding and thawing permafrost. As a result, previously frozen river delta deposits are becoming available for microbial decomposition as permafrost thaws. However, very few studies have focused on Arctic deltas and estimates of deltaic carbon stocks are even more limited. Therefore, we compiled 140 soil cores (new and already published soil cores), consisting of more than 1400 samples from 17 different deltas around the Arctic Ocean. In addition, we mapped the spatial extent of more than 250 Arctic deltas in order to accurately assess the carbon and nitrogen stock estimations for Arctic deltas. Our study shows that Arctic river delta deposits contain a considerable amount of carbon and nitrogen. The ongoing thaw and degradation of these permafrost deposits resulting from global climate warming might release additional carbon and nitrogen with implications for Arctic waters and biogeochemical cycles. The additional export of terrestrial carbon and nitrogen will alter biogeochemical processes not only in the nearshore zone, but throughout the Arctic Ocean. With this study we will improve our understanding of changing terrestrial carbon and nitrogen deposits and their contribution to a changing Arctic Ocean.