Ice-dominated Arctic deltas

Arctic deltas are ice-dominated systems that modulate river fluxes from permafrost terrain to the ocean. This Review provides an overview of the controls, seasonality and processes that give Arctic deltas their unique morphodynamics and the influence of climate change on their future evolution. Arctic deltas form the critical interface between the Arctic landscape and the ocean. They filter freshwater, sediment, carbon and biochemical fluxes from approximately 14 million km(2) of northern permafrost terrain. This Review highlights the unique controlling factors, seasonality and morphodynamic processes affecting Arctic deltas. Arctic deltas are 'ice-dominated systems' that are affected by land ice, permafrost and sea ice. They are strongly seasonal and are frozen for 7-9 months of the year. Permafrost limits channel migration. Arctic deltas experience ice jam floods, inducing biochemical exchange with thermokarst lakes. Transport under sea ice creates shallow prodelta ramps. Open-ocean conditions that promote marine reworking of river deposits are short-lived in the Arctic. A data compilation of Arctic deltas highlights that sediment and carbon fluxes are substantially lower than for lower-latitude deltas, with the exception of Greenlandic deltas. Arctic delta morphodynamics are also markedly subdued, with land-water conversion about eightfold less than in low-latitude deltas, probably owing to the unique ice processes occurring in Arctic deltas, which result in preferential floodplain and submarine sedimentation. Future trajectories of controlling factors indicate that Arctic deltas will transition away from being dominated by ice. The open-water season is expanding most rapidly, with wave energy predicted to increase threefold by 2100. Arctic deltas will thaw and experience increased wave influence, with poorly understood consequences for delta morphodynamics and carbon cycling. Process studies under transitional conditions are needed to develop predictive models further.

Automated summary

Arctic deltas are ice-dominated systems that are influenced by land ice, permafrost, and sea ice. They are highly seasonal and frozen for most of the year. The sediment and carbon fluxes in Arctic deltas are lower compared to deltas in lower latitudes, and their morphodynamics are also subdued. Climate change will cause Arctic deltas to transition away from ice dominance, leading to unknown consequences for their morphodynamics and carbon cycling.