par- 7 novembre 2012 - ( maj : 26 mars 2015 )
Date de début et de fin : octobre 2012 - septembre 2015
Financement : Bourse ministérielle (MENRT)
Climate variability in the Arctic and Antarctic is characterized by the most drastic changes compared to e.g. mid latitudes and tropics. Climate models project to continue the rapid Arctic warming and unprecedented loss of sea ice in 21st and 22nd centuries. Growing during the last decades winds in the Southern Ocean and amplification of the Southern Annular circulation Mode (SAM) impose a number of critically important climate signals in the Antarctica, such as feedbacking to the global climate. In this respect, it is critically important to quantify the mechanisms of the atmospheric moisture advection in high latitudes in the present and future climate in order to understand its role in changing Arctic and Antarctic energy and moisture balances and their impact on the changes of highlatitudinal temperatures, marine and continental ice and snow mass balance. This PhD project will contribute for understanding of mechanisms driving highlatitudinal climate variability and change and will provide novel tools for diagnostics of regional moisture balances to be applied to observational and reanalyzed data as well as to the results of model experiments. The main goal of the proposed project is to quantify the mechanisms driving the moisture advection to high latitudes in the present and future climate. At the first stage the methodology for the analysis of high latitudinal moisture advection will be developing. This methodology, originating from Trenberth (1997), Cullather and Bosilovich (2011) and Suarez (2011), will be enriched by the Reynolds’ decomposition of variables and will allow for a separate consideration of the mean meridional circulation and synoptic transients and, thus, the analysis of the source terms for different time and space scales. This methodology will be applied to the modern era reanalyses for the period from 1979 to 2012. This will allow to quantify the relative contribution of the two components into the Arctic and Antarctic moisture balance and to locate highlatitudinal regions where the role of different components dominates. Already at this stage we will obtain the ensemble of estimates of the Arctic and Antarctic moisture advection in modern reanlayses and will get the insights on the robustness of moisture advection estimates in different reanlayses. At the next stage it is suggested to use present climate simulations by IPCC climate models (with the emphasis on the French configurations such as CNRM-CM3 and IPSL-CM4 and their recent developments) in order to answer the questions, how capable state of the art climate models of replicating different mechanisms of the moisture transport in the Arctic and Antarctic. This activity will provide quantitative evaluations of the skills of the present climate models to adequately simulate highlatitudinal moisture balance and will help to guide climate model discrimination with respect to the model’s representation of the highlatitudinal moisture balances. Being armed with these estimates we will analyze the results of the model climate projections for the 21st and 22nd centuries performed under IPCC 4th and 5th Assessment reports. The main questions to be answered under this activity are (i) whether the projected changes in the global temperatures and associated trends in high latitudes are consistently linked to the Arctic and Antartic moisture advection and, if yes, (ii) what are the leading mechanisms behind this link. Answering these questions we will potentially understand why the climate projections in the Arctic and Antarctic being qualitatively robust, exhibit very strong quantitative spread (e.g. Holland and Bitz 2003, Bony et al. 2006).
Keywords : Water cycle in polar regions, moisture advection
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