Modeling group activity

 

For more information contact : ivane.pairaud@ifremer.fr

 

Aim

A modeling-group was structured as a transversal axis of the program.

The first task was dedicated for the identification of the modeling advances achieved during the first years of the Mermex program (increase in models’ complexity, coupling of the different compartments, new types of models and configurations, validation of the simulations). This work resulted in the writing of a synthesis included in the MERMEX review (MERMEX Group, 2011).

A second meeting focusing on physical-biogeochemical coupled models was held in December 2013. This was an opportunity to bring together the modelers from the different institutes working on the different actions of Mermex on the Mediterranean Sea. Presentations and discussions focused on the state of the art of modeling activities with regards to Mermex unanswered questions and on the future model developments. Several links appeared between the activities within the Mermex framework and the developments emerging from other programs (Hymex, Simed, COMODO and AMICO, PERSEUS among others). An important gap was identified concerning the availability of biogeochemical data spatial and temporal resolution. As it is very important to enhance our ability to reproduce the biogeochemical functioning of the Mediterranean Sea at the regional scale, a MOOSE representative (L. Mortier) was invited to strengthen the link between modelers and field researchers.

 

Results

During the past years, modeling activities came in support to observational activities, both for guiding the sampling strategies and for process studies (in particular through WP1-DEWEX, WP3- RIVERS/C3A/CASCADE and WP2-SPECIMED actions). Field data and satellite observations from DEWEX and RIVERS projects were used for model/observation comparison, and for the calibration of coupled or forced multi-compartments models (including hydrodynamics, sedimentary processes, biogeochemistry and chemistry).
Several issues were (or are being) investigated with these models, among which cascading and dense water formation influence on ecosystem, impact of climate change on ecosystem, influence of extreme events on the sedimentary processes, characterization and quantification of the carbon export, or the amount of pollution transferred from a urban city to the sea. New kinds of models emerged for the High Trophic Levels (ecological models, ecological niche models, bio-energy models). Listing of the different model configurations showed the strong diversity of the models used. This allows comparing the differing strategies and numerical schemes, and the influence of mesh refinement from basin scale to regional and very local scale configurations. Hence it should be noted that Low Trophic Level models are very difficult to validate but a strong effort is presently being done in order to improve model skill assessment by the use of rigorous statistical tools for comparison with data and by the extension of these comparisons to several state variables of the model (in addition to chlorophyll concentrations).
The use of data collected in the framework of MERMEX or MOOSE for comparison with model and toward process-oriented studies will increase in the second phase of the program. More interactions with the MOOSE observational community will also improve the spatial and temporal cover of data needed for model validation. Specific experiments are needed in order to enhance the models’ ability to mimic the ecosystems’ behavior (including laboratory or mesocosm experiments), and the MERMEX modeling community will play a role in their definition.


Interactions with other communities (HYMEX, CHARMEX mainly) are at play at the basin scale in the framework of the transversal SIMED action involving hydrodynamics, biogeochemistry and air-sea interactions.

The MERMEX modeling group also took part to the integrated regional climate modeling workshop organized by Mistrals in early 2015, as the use of coupled ocean-atmosphere model scenarios allowed to study the response of pelagic and benthic ecosystems to climate change. Actually, there is a transversal action « climate change and impact in Mediterranean sea ».