| Summary: | 19 páginas, 8 figuras [EN] In this chapter, trends in the longest available series of oceanographic variables on the Galician coast are analysed. Sea surface temperature and air temperature over the sea were obtained from the ICOADS project, which compiled observations on board opportunity ships from the end of the 18th century. These temperatures increased at a rate of about a tenth of degree per decade. The increase is larger and more significant in sea surface temperature than in air temperature over the sea and is comparable to the trend obtained in the average global temperature. Variability observed in temperature is correlated with variability in the atmospheric forcing of the Atlantic Ocean described by the teleconnection index NAO (North Atlantic Oscillation) and with the interdecadal oscillation that has been described in the entire Atlantic Ocean basin (AMO, Atlantic Multidecadal Oscillation pattern). Since cycles of upwelling-downwelling are fundamental for the dynamics of coastal circulation in Galicia, the trend in upwelling-favourable winds was studied. The upwelling index series calculated from geostrophic winds at 43º N 11ºW shows a tendency of reduction of upwelling in the last decades (from 1966), especially evident in a seasonal analysis. This trend is also apparent in surface winds obtained from COADS project. A time series of temperature and salinity of subsurface waters near the Galician coast was constructed and waters in the 27.1 isopycnal, close to the thermocline, were analysed. No significant linear trend was observed, but interannual and decadal variability were evident, with an alternation of periods of warmer and saltier waters with periods of less saline waters. Taking the 80s as the origin for analysis of trends would lead to the conclusion that temperature and salinity of these waters have increased, but the inspection of the entire series reveals that variability is more complex. The change in trend in oceanic and atmospheric circulation patterns over the Atlantic observed in ...
|
|---|