Variability of temperature and chlorophyll of the Iberian Peninsula near costal ecosystem during an upwelling event for the present climate and a future climate scenario

- To study temperature and phytoplankton distributions during upwelling events in present climate conditions and in a future climate scenario.
- The reinforcement of the southward wind component induces a significant increase of the intensity of the and the westward currents.
- The reinforcement of the southward wind component induces a offshore spread of the near coast upwelled cold layer and a rise of the temperature of the warm layer.
- The reinforcement of the southward wind component induces significant changes in the Chl-a near coastal distribution patterns.
- The reinforcement of the westward or the eastward wind components shows no significant changes in both temperature and Chl-a patterns.

Understanding the importance and the implication of the climate changes on coastal areas may be one of the major issues for this and next centuries. Climate changes may, indeed, impact the nearshore marine ecosystem, as coastal areas are very sensitive to the strength and the variability of the meteorological forcings.The main purpose of this work is to study temperature and phytoplankton distributions along the Portuguese near coastal zone during upwelling events in the present climate conditions and in a future climate scenario. The SRES-A2 IPCC scenario has been considered.We have used a three-dimensional model for coastal and shelf seas, including the following sub-models: hydrodynamical/physical, biological, sediment and contaminant. The forcings are provided by the interactions at the air-sea, considering the wind intensity and direction with the help of the WRF model (Weather Research and Forecast Model) and the coupled atmosphere-ocean model ECHAM5/MPI-OM.Results show that, for the future climate scenario, there is a reinforcement of the southward wind. The responses of the coastal ecosystem corresponds to the reinforcement of both, the southward (up to 10 cm/s) and the westward (up to 6 cm/s) induced upwelling currents. This, in turn generates an enlargement of the near coast upwelled cold layer, extending up to 60 km, as well as the rise of the warm layer temperature (up to 2.0 °C) and the spreading of the phytoplankton offshore. Significant changes in both the Chl-a vertical and the horizontal distribution patterns have been observed, as the nutrient supply to the upper layers depends on the strength of the upwelling, the bottom topography and orography of the coastal. These results confirm that changes in the strength and eventually the frequency of the upwelling favourable wind impact the phytoplankton distribution, which can have significant effect in the distribution and population of the upper level of the trophic chain of the coastal ecosystem.

Surface temperatures (first row) and surface Chl-a concentration (second row) differences between the wind forcing scenarios ((a) the intensification of the southward wind component (2 m/s); (b) the intensification of the westward wind component (1 m/s); (c) the intensification of the eastward wind component (1 m/s)) and the REF. Superimposed to the maps, are plotted the respective surface current differences are also shown in each figure.