Roles of Moist Static Energy Transport in the Changing Arctic System

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The Arctic system appears to be heading toward a new state that may be unprecedented, and there are no apparent feedbacks within the Arctic that can arrest the cohesive change. Can negative feedback mechanisms involving lower latitudes offset widespread reductions in permanent ice and corresponding changes in physical and biological components? Possible candidates are feedbacks related to horizontally transported moist static energy. The likely amplification of warming in the Arctic relative to lower latitudes implies that heat transport should decrease as the poleward temperature gradient relaxes, but how do the fluxes of moisture and potential energy respond? Can they offset the reduced heat transport? How is advection affected by large-scale climate features such as the El Nino Southern Oscillation and changes in tropical sea surface temperatures? In which regions and seasons are transports most affected? This activity will attempt to answer these questions using a new combination of data sources. The European Center for Medium-Range Weather Forecast Reanalysis (ERA-40) will be used in regions where radiosondes and other observations are plentiful south of 70?N. Over the Arctic, however, there is little information for the reanalyses to assimilate, which is responsible for large uncertainties in many parameters and observed discrepancies with independent measurements. To ameliorate this problem, new products derived from satellite retrievals will be merged with ERA-40 output to create a hybrid hemispheric data set. This effort will use this resource to investigate how horizontal energy fluxes have behaved during the past 23 years, a period during which the Arctic system underwent widespread change. The effort contributes to a system understanding by focusing on the primary energy source for the Arctic climate system, exploring its role as a possible mitigator of Arctic change, and investigating its relationships with the global climate system.The objectives and methods of this project are:1. Calculate daily mean fluxes of potential energy from satellite-derived temperature profiles for the Arctic region. Sensible heat and moisture fluxes have already been completed.2. Calculate daily mean energy and moisture fluxes from ERA-40 fields and merge them with satellite-derived fluxes for the region north of 70?N to create a hybrid data set for the entire Northern Hemisphere (NH).3. Investigate spatial and temporal patterns (annual and seasonal anomalies and trends, dominant modes of variability) in fluxes and convergences at several atmospheric levels throughout the NH using a variety of spatial statistical techniques and time series analysis.4. Relate observed changes in a variety of Arctic parameters to changes in horizontal fluxes and correlate energy advection with large-scale circulation patterns, such as the ENSO and NAO using multivariate correlation methods.