| Summary: | Funds are provided to better understand how rapidly the extra summer heat absorbed in the Arctic Ocean in recent years is lost, where it goes, how precipitation patterns change, and what the feedbacks of these changes are on fall ice production. These objectives will be addressed through a series of carefully crafted regional atmospheric modeling studies. The Weather Research and Forecasting (WRF) model will be used in a domain covering the Arctic Ocean at a resolution of 60 km with a nested 20-km grid in the Pacific sector. Model evaluation will be performed using observations from SHEBA, Barrow, Eureka, and Tiksi as well as a new 2-m air temperature data set and a new compilation of quality-controlled radiosonde soundings. Lateral boundary conditions for the model will be taken from the ERA-Interim Reanalysis for the years 1989 ? 2010. Paired experiments will be run for the fall of each year (September ? December) in which the prescribed sea ice is set to either low-ice or high-ice conditions, defined as the 25th or 75th quantile of the observed ice concentration over the same period. The focus of study will be the difference for these paired runs in atmospheric properties such as temperature, stratification, precipitation, and the components of the heat budget of the atmospheric column. Composite analysis and heat budget calculations for different regions will be employed and the yearly difference fields will be related to the large-scale circulation as represented by the Arctic Oscillation. The implications of the different atmospheric conditions from the low-ice and high-ice runs will then be explored with a separate dynamic-thermodynamic Lagrangian ice model to determine if the ice growth in the fall and early winter is sufficient in the low-ice case to replenish the ice lost in the summer and if this replenishment has suffered in recent years due to winter warming. The results of this study will provide a first step in understanding the consequences of the dramatic and anomalous reductions in arctic sea ice extent observed in recent years.
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