Atmospheric inputs in the Mediterranean Sea


The atmosphere is an essential element in the continent-sea coupling. The climate evolution could affect the aeolian transport and consequently it could modify the intensity and the inputs pathway to the sea. The aerosols particles in suspension in the atmosphere are important for the world climate. Locally, these particles originating from the anthropogenic activities (industry, car traffic, …) can affect the public health. The most important source of pollution in the open ocean zone as well as in the coastal zone is represented by the atmospheric inputs processes. These inputs lead to specific problems for the ecosystem with harmful consequences on ecologically sensitive areas like the Mediterranean coastal zones. In this case, the Mediterranean Sea, a semi-enclosed basin with particular hydrodynamic circulation and a strong seasonal variability with a short residence time, is an ideal study area. These inputs are an important impact on biological production especially during oligotrophic condition. In addition, the intensification of anthropogenic emissions introduces into the atmosphere a high amount of toxic elements for the marine ecosystem as lead, cadmium and mercury.

The atmospheric inputs are well contrasted and mainly due to two sources: anthropogenic from the north of Europe and lithogenic from the North Africa (Saharan dusts). Some previous projects have already focused on the impact of the atmospheric dusts on the marine biogeochemistry in the Mediterranean Sea: DYFAMED, EROS 2000, MATER, ADIOS, DUNE, OPERA, MELISSA. However, some issues on the long term evolution of atmospheric inputs are still unresolved in the NW Mediterranean Sea:

– Quantitative stock of the atmospheric fluxes at the air-sea interface

– Anthropogenic vs natural inputs

– Regional scale of inputs and coastal-open ocean gradient

– Deposition mechanism

– Impact of inputs in the seawater (dissolution, biodisponibility, …)

– Fertilization effect and contamination: the choice of tracers is important to observe such process (Na for marine signal, Al for lithogenic signal and Cd for anthropogenic signal)

 

In the context of MISTRALS, this topic is strongly associated to the CHARMEX project which aims to assess the present and future state of the atmospheric environment in the Mediterranean Basin, and of its impacts on the regional climate, air quality, and marine biogeochemistry (impact on the Fe, P and Hg inputs). Consequently, in the MOOSE project, it appears important to observe such inputs evolution in contrasted sites (natural vs anthropogenic) around the NW Mediterranean border to cover a large mesoscale atmospheric inputs. This is essential to better constrained chemical atmospheric model in the NW Mediterranean Sea. For this reason, dry and wet deposition is a crucial parameter as well as aerosols to constrain nutrients (influencing the biological production) and contaminants (public impact) inputs.

In the perspective of anthropogenic climate change, models predict profound changes concerning the regime and intensity of precipitation in the Mediterranean region (e.g. Gibelin and Déqué, 2003) that may have profound implications on the atmospheric fluxes and forms of the deposition (dry vs. wet; particulate vs. dissolved) and directly impact the bioavailability of elements reaching the seawater and their potential effect on biological productivity.

 

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