Resumen de Warming and salting in the western Mediterranean during the second half of the 20th century: inconsistencies, unknowns and the effect of data processing
Manuel Vargas Yáñez, F. Moya, Elena Tel, Mª Carmen García Martínez, Etienne Guerber
Many papers that have appeared since the late 1980s have reported trends for the salinity and temperature of the upper, intermediate and deep layers within the western Mediterranean. The review of these works shows that the figures reported depend on the period of time considered. In some cases, opposite results are obtained by different studies dealing with the same period of time. These results make it difficult to assess the mean trends of these variables during the second half of the 20th century and to distinguish long-term changes from decadal and multi-decadal variability. In order to determine the origin of these discrepancies, we analyse temperature and salinity profiles from MEDAR/2002 in three areas of the western Mediterranean: the Gulf of Lions, the Balearic Islands and the Alboran Sea. We use data analysis methods that have all been tested and used previously in the literature. Our results show that the scarcity of data makes trend estimations very sensitive to the data analysis methods, questioning the robustness of such estimations and showing the suitability of systematic sampling for studying long-term changes. We attempt to provide temperature and salinity trends from 1950 to 2000 for the three aforementioned regions, which show a higher degree of uncertainty than the previous studies. Long-term temperature and salinity increases for this 50-year period are within the intervals [0.02°C, 0.19°C] and [0.01, 0.1] for deep waters, [0.06°C, 0.38°C] and [0.01, 0.26] for LIW, and [0, 0.45°C] for the upper layers. No salinity change has been observed for the upper layer.
