Title: Arctic-Antarctic Parity in High-latitude Climate Sensitivity: the Hydrologic Cycle, Ocean Dynamics, and Meridional Energy Transports
Abstract: We begin to consider similarities between the Arctic and Antarctic response to CO2-forcing by analyzing changes in the Lagrangian aerial hydrologic cycle. In all seasons, the remote (i.e. non-local) moisture contribution to polar precipitation increases significantly in both hemispheres; this response closely follows the global hydrologic cycle response to CO2-doubling, where an increase in the moisture transport length scale increases the distance between moisture sources and sinks. In winter, on the other hand, the fraction of the polar precipitation from local moisture sources increases due to enhanced turbulent heat fluxes over areas of sea ice retreat. We show that these enhanced turbulent surface fluxes, in turn, are due to a poleward shift in the ocean heat flux convergence (OHFC), which pushes the winter sea ice edge poleward and increases local (polar) evaporation. Indeed, the primary role of this poleward shift in the OHFC is to enhance polar warming while damping extrapolar warming, thereby amplifying polar climate sensitivity. Radiative feedback analysis shows that changes in the OHFC warm polar surface temperatures while cooling the atmosphere aloft, thereby activating a positive lapse rate feedback in the high latitudes. These results suggest a fundamental asymmetry between oceanic and atmospheric energy transports in polar warming, and suggest a mechanism linking polar amplification to the partitioning of meridional energy transports into the high latitudes between the atmosphere and ocean.