Effects of the 2003 European heatwave on the Central Mediterranean Sea: surface fluxes and the dynamical response A. Olita1, R. Sorgente1, S. Natale2, S. Gaberšek2,*, A. Ribotti1, A. Bonanno3, and B. Patti3 1IAMC-CNR, Istituto per l'Ambiente Marino Costiero – Consiglio Nazionale delle Ricerche, c/o IMC Loc. Sa Mardini, 09170 Oristano, Italy 2Fondazione ONLUS Centro Marino Internazionale-IMC, Loc. Sa Mardini, 09170 Oristano, Italy 3IAMC-CNR, Istituto per l'Ambiente Marino Costiero – Consiglio Nazionale delle Ricerche, Via L. Vaccara 61, 91026 Mazara del Vallo (TP), Italy *now at: University of Ljubljana, Department of Mathematics and Physics, Jadranska 19, Ljubljana, 1000-SI, Slovenia
Abstract. The effects of the 2003 European heatwave on the sea surface layer of
the Central Mediterranean were studied using a regional 3-D ocean model.
The model was used to simulate the period 2000 to 2004 and its performance
was validated using remotely-sensed and in situ data. Analysis of the
results focused on changes in the Sea Surface Temperature (SST) and on
changes to the surface and sub-surface current field. This
permitted us to identify and quantify the anomalies of atmospheric and
sea surface parameters that accompanied the heatwave. The dominant annual
cycle in each variable was first removed and a wavelet analysis then
used to locate anomalies in the time-frequency domain.
We found that the excess heating affecting the sea surface in
the summer of 2003 was related to a significant increase in air
temperature, a decrease in wind stress and reduction of all
components of the upward heat flux. The monthly averages of the model
SST were found to be in good agreement with
remotely-sensed data during the period studied, although the ocean model
tended to underestimate extreme events. The spatial distribution of SST
anomalies as well as their time-frequency location was similar for both
the remotely-sensed and model temperatures. We also found, on the
basis of the period of the observed anomaly, that the event was
not limited to the few summer months of 2003 but was part of a
longer phenomenon. Both the model results and experimental data suggest
the anomalous heating mainly affected the top 15 m of ocean and was
associated with strong surface stratification and low mixing.
The skill of the model to reproduce the sub-surface hydrographic features
during the heatwave was checked by comparison with temperature and
salinity measurements. This showed that the model was generally in good
agreement with observations. The model and observations showed that the
anomalous warming also modified the currents in the region, most
noticeably the Atlantic Ionian Stream (AIS) and the Atlantic Tunisian
Current (ATC). The AIS was reduced in intensity and showed less
meandering, mainly due to the reduced density gradient and low winds,
while the ATC was enhanced in strength, the two currents appearing
to modulate each other in order to conserve the total transport of
Modified Atlantic Water.
Citation: Olita, A., Sorgente, R., Natale, S., Gaberšek, S., Ribotti, A., Bonanno, A., and Patti, B.: Effects of the 2003 European heatwave on the Central Mediterranean Sea: surface fluxes and the dynamical response, Ocean Sci., 3, 273-289, doi:10.5194/os-3-273-2007, 2007.