MEOM - DRAKKAR main

The observations collected during the World Ocean Circulation Experiment (WOCE) program have clearly demonstrated that the state of the ocean is constantly changing at global and regional scales. In addition to an important year to year variability, these recent data show possible climate drifts over the last decades in many regions of the world ocean and strongly suggest that changes at every scales are tightly interconnected. The increase of anthropogenic CO2 in the atmosphere may trigger even more dramatic changes in the future, as shown by the coupled model experiments conducted for the IPCC assessment (Intergovernmental Panel on Climate Change, IPCC 2001). One striking feature of these model results is that some (but not all) predict a collapse of the thermohaline circulation (THC) in the Atlantic, and the variations in strength of the Atlantic THC are thought to have a considerable influence on the exchanges with the other basins of the world ocean. An important aspect of the WOCE legacy, extensively discussed in the recently published book Ocean Circulation and Climate (2001), is that understanding the role of the ocean in climate requires, in addition to an accurate description of the general circulation, a full understanding of its variability, a topic embraced by its follow-on program Climate Variability and Predictability (CLIVAR). The DRAKKAR project is motivated by open questions related to the variability of the circulation and water mass properties during the past and future decades, and its effects on climate through the transport of heat and the uptake of atmospheric anthropogenic CO2. Our regions of interest are primarily (but not exclusively) the Atlantic Ocean and the Nordic Seas. To understand and predict global changes in the atmosphere-ocean-ice system, the carbon cycle, and marine ecosystems, and also to improve the outcomes of operational oceanography, require numerical ocean/sea-ice circulation models capable of realistically representing the physical ocean processes relevant to these multidisciplinary applications. To achieve the best possible scientific results, these model simulations require a wide spectrum of competence and important computational resources, which can be best found within a co-ordinated effort. The project proposes to join the efforts of several research teams in France, Germany, Russia and Finland to carry on a community modelling effort which will implement and manage a hierarchy of ocean model configurations, from which it will carry out co-ordinated realistic simulations of the ocean circulation at regional and global scales, at resolutions high enough to insure dynamical consistency over a wide range of resolved scales (from eddy to global, from day to decade).
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One primary concern of DRAKKAR is related to the circulation and the day-to-decade variability in the North Atlantic Ocean, as driven by the atmospheric forcing, by interactions between processes of different scales, by exchanges between basins and regional circulation features of the North Atlantic (including the Nordic Seas), and by the influence of the world ocean circulation (including the Arctic and Southern Oceans). Those scientific questions underlie the French contribution and the German SFB460 project. DRAKKAR is also concerned by the role of the changing ocean circulation in ecosystem dynamics, and in climate through the transport of heat and the uptake of atmospheric CO2.

The scientific approach of the teams participating to DRAKKAR mainly relies upon numerical simulations. Therefore, the project is concerned by building a state of the art hierarchy of embedded model configurations, able to provide continued and systematic development and assessment of the ocean model components used in ecosystem, carbon cycle, and climate studies as well as in regional and operational oceanographic applications. With theses concerns, the groups participating to the project have identified several priority objectives.

To build state of the art community model configurations. A hierarchy of embedded model configurations of different grid resolution should make possible to carry out realistic, long term (several decades) simulations of the ocean and sea-ice circulation and variability at regional and global scale, and to perform sensitivity studies investigating key dynamical processes (requiring especially high resolution) and their impact at larger scales. The DRAKKAR model configurations will be used by the participating research teams to address their scientific objectives.

To provide a relevant, four-dimensional description of the atmospherically driven world ocean circulation and variability over the last 50 years and to extract dominant patterns and modes of variability. Obtained from multiple-decades high resolution simulations carried out with various configurations, this description will allow (in the limits of model accuracy) to study the regional impacts of the global oceanic variability during this period, and to identify remote interactions between the North Atlantic and the World Ocean. It is also expected to contribute to the interpretation of the changes noticed in past and future ocean observations.

To improve the representation of key processes in ocean circulation models. To achieve the best possible scientific results, ocean circulation models require a continuous improvement of numerical and physical parameterisations. The project will pursue continued development and sensitivity studies on atmospheric forcing fields and formulation of the surface boundary conditions, [representation] effects of topography and the bottom boundary layer, and sub-grid-scale parameterisation at medium resolution. One expects to achieve a significant improvement of the parameterisation of mesoscale and local key processes in future climate models.

To understand the role of regional [key] processes in the global oceanic circulation and variability. Using either open boundary conditions or regional grid refinement within a global or basin scale model configuration, it will be possible to identify the impact of the dynamics of a critical ocean region on the circulation characteristics of the Atlantic or the World oceans. Local grid refinement will provide dynamical consistency over a wide range of scales and allow to understand the underlying physics by studying scale interactions from eddy to basin or global. It will then be possible to establish dynamical links of variability between critical ocean regions and the general ocean. Priorities will be to understand the dominant mechanisms of the variability of the thermohaline circulation, of the basin-scale gyres, and of the most important regional circulation features in the Atlantic and the Nordic Seas. Special focus will be on the processes taking place within the North Atlantic and the Nordic Seas and their effect on the THC variability: freshwater and sea-ice cycles, intergyre exchanges, variability of mode waters, mesoscale features and transport, deep convection, deep water formation and export, boundary currents, deep overflows, exchanges across continental shelves, ...

To foster co-operative, multidisciplinary studies. The high degree of realism and the dynamical consistency that our model simulations aim at are favourable to co-operative multidisciplinary studies. Priorities will be given to study the effects of mesoscale processes on the uptake and spreading of anthropogenic CO2 and on the distribution of transient tracers, and to study the impact of the variability of the ocean circulation properties on the dynamics of large ecosystems (such as the upwelling of the Canaries or Benguela). Another specific objective of the project is to contribute to establish an integrated approach of marine studies, as the realistic prognostic simulations carried out in DRAKKAR appear complementary to the observing system which is presently being built up (ARGO, JASON) and to in-situ (sea-going) observation programs (SFB, OVIDE) with which a tight link will be maintained. Results from the project prognostic simulations relative to the last decade (1990's to present) will also complement the reanalyses from oceanic operational systems (MERSEA, MERCATOR) by providing dynamically-consistent, high-resolution descriptions of the circulation suitable to investigate key mechanisms and scale interactions.
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To permit participating research teams to achieve their scientific objectives, DRAKKAR proposes to carry out co-ordinated realistic simulations of the ocean circulation at regional and global scales, with pertinent atmospheric forcing and resolutions high enough to insure physical consistency over the range of scales which are dynamically important (i.e. from eddy to global, from day to decade).

As first objective, the project will build or improve a hierarchy of numerical model configurations, from global to regional scale, each based on the primitive equation ocean circulation code OPA (Madec et al, 1998) coupled to the multi-layered sea-ice code LIM (Fichefet et al, 1997). This system will include :

During the last decade, the DRAKKAR participating scientists fostered co-operative scientific activities within the Mast3 European project DYNAMO (Dynamics of North Atlantic Models), and between their national projects, CLIPPER in France and FLAME (Family of Linked Atlantic models) in Germany. The expertise gained through projects such as these also helped to build their capability to make significant contributions a the variety of modelling needs. However, the challenge of developing realistic ocean models required for the diverse range of applications can only be met by an effective integration and co-ordination of the activities and complementary expertise of every member of the group. This fact yielded the DRAKKAR concept. The structure proposed for DRAKKAR is inspired from the one successfully implemented in the CLIPPER project. An international project-team conducts the project activities. It has the charge to define details of the model configurations, to implement and to validate their various components. This team also defines model experiments to run, co-ordinates their execution by the participating groups, and organises the sharing of model results. To complement the role of the project-team, associate scientists from various laboratories are solicited to help define the experiments and to analyse the results. Their role is especially important to construct the multidisciplinary reach of the project, and to enhance the scientific value of the simulation outputs. The DRAKKAR project team is composed of the French former CLIPPER team and of the German FLAME team, both having a significant expertise in all the aspects of eddy resolving modelling of the ocean general circulation. The project team also includes individual research scientists at the Shirshov Institute of Oceanography (SIO) in Moscow, Dr. Gulev, who brings an essential expertise in air-sea fluxes and atmospheric marine boundary layer, and at the University of Helsinki, Dr. Beckmann, who brings an additional expertise in modelling of the high latitude ocean/sea-ice/ice-shelves system.
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The DRAKKAR numerical experiments are carried out by a project team, made of scientists and engineers from 8 research laboratories in Europe. Scientists and engineers participating to the project team are listed below :

Laboratory	Name	Position	Email
LEGI Grenoble Laboratoire des Ecoulements Géophysiques et Industriels	Bernard Barnier Jean-Marc Molines Thierry Penduff Jérôme Chanut Josiane Brasseur	CNRS Scientist CNRS Engineer CNRS Scientist Post-Doc Project Secretary	bernard.barnier@hmg.inpg.fr jean-marc.molines@hmg.inpg.fr thierry.penduff@hmg.inpg.fr jerome.chanut@hmg.inpg.fr josiane.brasseur@hmg.inpg.fr





LODYC Paris Laboratoire d'Océanographie Dynamique et de Climatologie	Gurvan Madec Claude Talandier	CNRS Scientist CNRS Engineer	gm@lodyc.jussieu.fr talandier@lodyc.jussieu.fr


LPO Brest Laboratoire de Physique des Océans	Anne-MarieTreguier Sébastien Theetten	CNRS Scientist CNRS Engineer	anne-marie.treguier@ifremer.fr sebastien.theetten@ifremer.fr


IFM Geomar Leibniz Institute of Marine Sciences Kiel	Claus Boening Joachim Dengg Arne Biastoch	Research Scientist Research Scientist Research Scientist	cboening@ifm-geomar.de jdengg@ifm-geomar.de abiastoch@ifm-geomar.de

SIO Moscow Shirshov Institut of Oceanography	Sergey Gulev	Research Scientist	gul@sail.msk.ru

UoH University of Helsinki	Aike Beckmann	Professor	aike.beckmann@helsinki.fi

Mercator-Ocean Operational Oceanography Toulouse	Corinne Derval Edmée Durand Elisabeth Rémy	Research Engineer Research Engineer Research Engineer	corinne.derval@mercator-ocean.fr edmée.durand@mercator-ocean.fr elisabeth.remy@mercator-ocean.fr

The concept of DRAKKAR is to integrate the skills and means of several research teams whose scientific objectives significantly overlap, in order to enhance their capabilities to develop state of the art numerical ocean circulation models. Such a collaborative effort, which requires an important commitment from each team, is expected to last longer than the typical duration of a scientific project such as DRAKKAR (2004-2007) or the German SFB460 (2002-2006), and is intended to serve the needs of new scientific projects in the future.

General scientific concern:
The recent changes in the North Atlantic Ocean at basin and regional scales: response to the atmospheric forcing, interactions between basin scale and regional circulation features of the North Atlantic (including the Nordic Seas), and influence of the world ocean circulation on the variability of the North Atlantic.
Objectives:

Approach:
High resolution model simulation of the ocean circulation and sea-ice at the world scale, and very high resolution model simulation of the circulation and sea-ice in the North Atlantic and the Nordic seas, over the period of most recent atmospheric re-analyses (i.e. from 1950 to 2000 and longer).

General scientific concern:
The circulation in the Atlantic Ocean, its variability from days to decades, its role in the ecosystem dynamics, and its effect on climate through the transport of heat and the uptake of atmospheric trace gases such as anthropogenic CO2.

Approach:
Development and application of a hierarchy of models, involving model versions of different resolution and geometry, with a range of different parameterisation concepts best suited for the variety of the scientific objectives. The presently available FLAME configurations are based on the MOM code. The one with the highest resolution is the 1/12° North Atlantic that should be integrated for years 1990-2003 in 2004. All new model configurations will be developed using the OPA code within DRAKKAR.

General scientific concern:
The physics of the interactions between the ocean the atmosphere, the links and feedback between the ocean and atmosphere climates.

Approach:
Statistical analysis of high resolution model simulations representative of the ocean variability in the last 50 years. Evaluation of the various estimates of air-sea flux fields and surface atmospheric variables, test and evaluation of atmospheric forcing parameterisation in ocean models.

General scientific concern:
Circulation and variability of the high latitude coupled ocean/ sea-ice system.

Approach:
Development and application of coupled ocean/sea-ice models, parameterisation of the effect of ice-shelves in the freshwater budget of the Antarctic Ocean and the inclusion of tidal effects in large scale climate models.