|From||Anne Marie Treguier <Anne.Marie.Treguier@ifremer.fr>|
|Date||Sat, 23 Jun 2012 19:21:41 +0200|
A post-doc position is open by CNRS for the EMBRACE European project:Coupled ocean-atmosphere processes in the North Atlantic basin: impact of oceanic meso-scale eddies
Contacts: Anne Marie Treguier and Julie Deshayes (CNRS, Laboratoire de Physique des Océans, Brest)
Description:Coupled global climate models are a necessary tool to understand past and present climate variability and build scenarios of future climate. These models are subject to systematic errors in the representation of climate processes and variability, which render climate projections uncertain. The objective of the EMBRACE project ( http://www.smhi.se/embrace/ ) is to reduce key systematic biases by improving the physical representation of critical processes. Regarding the climate of the North Atlantic, the challenge is to reproduce faithfully the major ocean fronts such as the Gulf Stream and the North Atlantic Current. One solution is to increase the horizontal resolution enough to explicitly resolve meso-scale eddies. The ocean components of global climate models used for IPCC, for the most part, do not resolve the eddies. This is a serious deficiency, as meso-scale eddies and associated fronts are the most energetic ocean components at time scales longer than one day. A new ocean model configuration, ERNA (Eddy Resolving in the North Atlantic), based on the NEMO system ( www.nemo-ocean.eu ) has been developed by J. Deshayes and collaborators in Brest. It combines a global low resolution model (comparable to the ocean component of current climate models) with an embedded high resolution North Atlantic nest using AGRIF (two-way nesting approach). Within EMBRACE, the ERNA configuration will be coupled to the atmospheric component of the CNRM-CM5 coupled climate model (a model of the CMIP project developed by CNRM-CERFACS). The atmospheric component (ARPEGE) allows stretching the grid to achieve higher resolution above the North Atlantic. The post-doc fellow will use this coupled model to explore at least one, but possibly both, of the following scientific questions: 1- The representation of ocean water masses, as well as their formation mechanisms by deep convection and subduction, presents systematic biases in climate models. The role of eddies in these processes is well established, but so far this role has been studied mainly in ocean simulations forced by atmospheric reanalyses, a procedure that often results in erroneous air-sea fluxes over eddy-rich regions. By using an ocean-eddy-resolving fully coupled model, it will be possible to assess the role of eddies in a more consistent air-sea interaction framework and understand better the impact of their absence for the biases of North Atlantic water mass ventilation in low resolution CMIP models. 2- The low resolution and absence of eddies generally results in a wrong location of major fronts in the North Atlantic in CMIP models. The wrong location of the North Atlantic Current leads to very large anomalous heat fluxes in the western North Atlantic, possibly impacting the weather over Europe. The ERNA configuration represents correctly these fronts when forced by a fixed atmosphere, and we expect a similar improvement in coupled mode. The higher resolution in both the ocean and atmosphere will allow to evaluate the impact of this bias reduction for North Atlantic weather regimes.
The 2-year position will start in September-November 2012 and the fellow will be located at the Ifremer centre near Brest. The post-doc project is a collaboration between the physical oceanography laboratory LPO (www.ifremer.fr/lpo) and CNRM in Toulouse (http://www.cnrm.meteo.fr/). The candidate must hold a PhD in fluid dynamics, oceanography or atmospheric sciences, and have an experience in numerical modelling. A knowledge of atmospheric and/or ocean models to be used in this project would be an advantage.
To apply, send a full resume, an application letter and the contact of 3 referees, preferably before July 15th, 2012 to firstname.lastname@example.org
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