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Could midlatitude moisture be driving the Arctic midtropospheric amplification of warming?

Under rising greenhouse gases concentrations, the Arctic troposphere is warming faster than anywhere else in the extratropics. This phenomenon, known as ‘Arctic amplification’, is observable in the whole atmospheric column and is more pronounced near the surface. Near-surface Arctic warming has been attributed to reduced sea ice cover and increased ocean heat transports. Midtropospheric Arctic warming, on the other hand, has been linked to intensified atmospheric heat transport driven by midlatitude surface warming. The mechanisms by which the atmospheric dynamic amplifies the midlatitude surface warming and transports it into the Arctic have surprisingly received little attention, especially since projected twenty-first century Arctic midtropospheric warming from coupled atmosphere-ocean simulations tend vary widely across models.

In this presentation, I show that the spread in Arctic midtropospheric warming among models can be explained by a simple conceptual model of atmospheric dynamics. I apply this simple conceptual model to the Representative Concentration Pathway 4.5 (RCP4.5) scenario of the Coupled Model Intercomparison Project phase 5 (CMIP5) and briefly discuss how it applies to reanalyses.