Trends and time variability in the northern continental shelf of the western Mediterranean

Abstract

[1] Different works appearing during the last decade show that the western Mediterranean has suffered a temperature and salinity increase during the 20th century. Most of these works analyze long-term trends in Levantine Intermediate Water (LIW) and Western Mediterranean Deep Water (WMDW); those dealing with changes in shallow and coastal waters are very scarce. It is still an open question whether these changes are due to meteorological factors occurring in the western Mediterranean or if they are caused by the salinity increase of the water masses contributing to deep water formation. In this work we analyze the data obtained in the last decade of the 20th century (and longer time series in some cases) within the frame of six projects aimed at the systematic collection of hydrographic data at fixed stations in the northern sector of the western Mediterranean (mainly in coastal areas). We detect strong warming trends in those stations located in the continental shelf (and probably with no influence of the LIW). This result could indicate that changes observed in the WMDW cannot be explained only on the basis of changes imported from the eastern basin. Another striking result is that these trends are an order of magnitude higher than those reported for the rest of the century, indicating that the 1990s have been an exceptionally warm decade. On the other hand, time series affected by the LIW show a salinity increase, and in some cases this is not accompanied by the corresponding temperature increment, indicating that the LIW salinity increase could also be a factor to be taken into account.

Cannibalism among size classes of larvae may be a substantial mortality component in tuna

“…Given that one of our main findings is the temperature dependence of cannibalistic mortality, recruitment variability from year to year may be expected due to slight variations in temperature over the spawning season. In the long term, effects of piscivory on survival may become stronger if average surface tem peratures tend to increase in the Mediterranean as suggested in some studies (Salat & Pascual 2002, Vargas-Yáñez et al 2005.…”

Calentamiento y aumento de la salinidad en el Mediterráneo Occidental durante la segunda mitad del siglo XX: Inconsistencias, incertidumbres e influencia del procesado de datos

“…schröder et al (2006) considered that the acceleration of the deep water temperature and salinity trends after 1995 was caused by the influence of the eMT on the WMeD. Pinot et al (2002) reported the progressive disappearance of the Western intermediate Water (WiW) in the balearic sea from 1996 to 1998 and more recently an abrupt decrease of 0.14ºc was observed in the temperature of the newly formed WMDW during the winter of (Font et al, 2007lópez-Jurado et al, 2005) followed by a strong increase in the deep water temperature and salinity in the following winter (smith and bryden, 2007).…”

Range expansion of an invasive pufferfish, Lagocephalus sceleratus (Actinopterygii: Tetraodontiformes: Tetraodontidae), to the south-western Mediterranean

“…It is the second representative of Tetraodontidae found after the blunthead puffer, Sphoeroides pachygaster (Müller et Troschel, 1848) (see Hemida et al 2009). The observed increase of the mean annual temperature observed within the last several years in the Mediterranean waters (Béthoux et al 1990, Francour et al 1994, Vargas-Yáñez et al 2005) could possibly explain the recent spreading of Lessepsian migrants from the eastern to the western Mediterranean basin, and their progressive geographical dispersal (Koukouras et al 2010). In addition to the presently observed warming of the western basin, the changes in the main current circulation in the Mediterranean during the last few decades may also explain the recent spread of Red Sea species towards the western basin (see Francour et al 2010, Otero et al 2013.…”