Decadal changes in temperature and salinity of Central Waters off Western Iberia

Abstract Historical in-situ data were used to investigate decadal changes in temperature and salinity of Central Waters off the Western coast of Iberian Peninsula between 1955 and 2016. Two sources of historical profiles were used: the collection of profiles from campaigns between 1978 and 2007 available at MARE - Marine and Environmental Sciences Centre of the Faculdade de Ciencias da Universidade de Lisboa (FCUL), and the World Ocean Database for the period 1955–2016. To investigate the decadal changes, time series of annual means of properties were constructed based on the historical profiles and two objective analysis products. At depths characteristic of Central Waters (200–400 m), data suggests two colder periods, centered around 1965 and 1980, followed by a warmer period centered around 2008. The salinity tends to follow the temperature behavior but it is notable a period of high salinity also in early 1970s. The isopycnal of 27.1 kg m −3 lay around 200–400 m and was deeper in the recent warm and saline period. The salinity (and temperature) of this isopycnal fluctuated, with three crests centered around early 1970s, early 1990s and late 2000s. The observed variability was linked to air-sea heat and freshwater fluxes, and the possible mechanisms involved are discussed.