Institut Mediterrani d’Estudis AvançatsEsporles · Mallorca · SPAIN

A study of potential effects of climatic change on the ecosystems of the Mediterranean Sea: The Alboran Sea case

J. Solé1,2, J. Zavala-Garay2; J. Wilkin2, F. Werner2, J. Tintoré1

(1) IMEDEA (CSIC-UIB). Miquel Marques 21, Esporles, Mallorca. Spain(2) IMCS (Rutgers University). 71 Dudley road, New Brunswick (NJ). USA

AbstractWe study the inter-annual variability of the circulation in the Alborán Sea. We use ROMS forced by ERA-40 reanalysis and climatological boundary conditions from the Mediterranean Forecast System (MFS) to identify global change scenarios. These scenarios are characterized by the duration and intensity of the main oceanic structures usually formed in this area (Alboran gyres and Almeria-Oran front). For each one, we study the adjustment processes between Modified Atlantic Water (MAW, S < 36) and denser Mediterranean Water (MW, S>37). The interaction of this two major water masses is particularly important in the Eastern Alboran area, where the Almeria-Oran front is a major dynamical boundary (1,5 sigma-t difference). We analyze the dynamical relevance of mesoscale and sub-mesoscale eddies in the variability of the mean structures and the effects of this variability in the ecosystem behaviour.

Alboran Sea Mean dynamics

The dynamics of Alboran Sea is dominated for three main features: the two gyres and the Almeria-Oran front. These have a strong impact in the ecosystem behaviour in the area. The induced upwelling in the frontal zone and gyres enhances the primary production.

Introduction

The Mediterranean Sea is a complex ocean system in which several temporal and spatial scales (basin, sub-basin and mesoscale) interact to form a highly variable general

circulation. Signals of interannual variability have been reported in several places of the Mediterranean Sea. The region is densely populated by eddies, fronts and small currents whose evolution, driven by the internal ocean dynamics, can lead to fluctuations in the currents and in the water mass distributions, independently of the atmospheric forcing. The extent to which interannual variability in the Mediterranean Sea can be induced by this intrinsic internal dynamics and how this dynamics affect the chlorophyll pattern distribution in the Mediterranean remains an open question. Here we show the preliminary results of ROMS simulations for a sub-domain of the Mediterranean Sea, the Alboran sea.

Bibliography:

Fasham, M. J. R., H. W. Ducklow, and S. M. McKelvie, 1990: A nitrogen-based model of plankton dynamics in the oceanic mixed layer, J. Mar. Res., 48, 591-639.

Fennel, K., J. Wilkin, J. Levin, J. Moisan, J. O'Reilly, and D. Haidvogel, 2006: Nitrogen cycling in the Middle Atlantic Bight: Results from a three-dimensional model and implications for the North Atlantic nitrogen budget, Global Biogeochem. Cycles, 20, GB3007,doi:10.1029/2005GB002456

M. Vargas-Yanez, F. Plaza, J. Garcıa-Lafuente, T. Sarhan, J.M. Vargas, P. Velez-Belchi, 2002. About the seasonal variability of the Alboran Sea circulation. J. Mar. Sys. 35, 229-248.

Discussion:

Here we have shown the first preliminary results of the simulations using ROMS in the Alboran Sea area. The model is forced with the output climatology of MFS (Nemo) model as boundary conditions and the ERA-40 reanalysis as meteorological forcing. This area is specially interesting not only for the strong signature of the ocean features but also for the impact of the gyres and fronts on the ecology of the area. Taking this in to account we try to model the long term evolution of the

coupled physical-biological system. As a first approach we used the Bio-Fasham model to study the plankton spatial and time evolution. The first year simulation of the physical variables in ROMS shows a good agreement with the mean behaviour reported in the literature.

Evolution of the surface temperature in the first year of simulation:

Evolution of the surface salinity in the first year of simulation:

Evolution of the surface (5m) nitrate within the first year of simulation:

Evolution of the surface (5m) phytoplankton in the first year of simulation:

Evolution of the surface (5m) zooplankton within the first year of simulation:

Vertical view (crossing the strait) of nitrate within the first year of simulation:

Vertical view of temperature :

Vertical view of salinity:

Vertical view (crossing the strait ) of phytoplankton within the first year of simulation: