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The Arctic’s land surface has large areas of wetlands that exchange moisture, energy, and momentum with the atmosphere. The authors use a mesoscale, pan-Arctic model simulating the summer of 1986 to examine links between the wetlands and arctic atmospheric dynamics and water cycling. Simulations with and without wetlands are compared to simulations using perturbed initial and lateral boundary conditions to delineate when and where the wetlands influence rises above nonlinear internal variability. The perturbation runs expose the temporal variability of the circulation’s sensitivity to changes in lower boundary conditions. For the wetlands cases examined here, the period of the most significant influence is approximately two weeks, and the wetlands do not introduce new circulation changes but rather appear to reinforce and modify existing circulation responses to perturbations. The largest circulation sensitivity, and thus the largest wetlands influence, occurs in central Siberia. The circulation changes induced by adding the wetlands appear as a propagating, equivalent barotropic wave. The wetlands anomaly circulation spreads alterations of surface fluxes to other locations, which undermines the potential for the wetlands to present a distinctive, spatially fixed forcing to atmospheric circulation. Using the climatology of artic synoptic-storm occurrence to indicate when the arctic circulation is most sensitive to altered forcing, the results suggest that the circulation is susceptible to the direct influence of wetlands for a limited time period extending from spring thaw of wetlands until synoptic-storm occurrence diminishes in midsummer. Sensitivities in arctic circulation uncovered through this work occur during a period of substantial transition from a fundamentally frozen to thawed state, a period of major concern for impacts of greenhouse warming on pan-Arctic climate. Changing arctic climate could alter the behavior revealed here.


DOI: 10.1175/JCLI4243.1



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