Long-term analysis of satellite-derived Sea Surface Temperature (SST) and Ocean Colour (OC) in coastal waters of the Azores Archipelago

The present analysis is focused on the inshore waters surrounding all the nine islands of the Azores Archipelago (Northeast Atlantic). An area extending for 40 km from the coastline of each island was subjected to a 7-year study concerning Sea Surface Temperature (SST) and Ocean Colour (OC). One-km resolution MODIS/Aqua-derived monthly chlorophyll-a (Chl-a) concentration and 1-km resolution NOAA/AVHRR-derived monthly temperatures were acquired at the HAZO HRPT satellite station of the Azores and analysed for the period June 2002 - July 2008.
Remotely-sensed data turned out to provide precise and reliable indications on the surface thermal conditions and on the sub-surface Chl-a content within the restricted regions analysed. Both inter-annual and seasonal variability in SST was found within the Azorean region, with significant variations related to the geographic position of each group of islands (western, central and eastern groups). A largely marked seasonal variability of the Chl-a density was described with clear identification of a major peak occurring during springtime (April-May) and a lower increase in autumn. This secondary annual peak is characterised by consistent intensity variations mainly relating to the island and to the year considered. In particular, highest (25.4 ºC) and lowest (14.0 ºC) temperature values are found in Santa Maria (August 2003) and Pico (February 2002), respectively. Highest (1.07 mg/m³) and lowest (0.07 mg/m³) pigment concentrations are recorded in Faial (May 2003) and Pico (September 2004), respectively. Island geographic position relative to the mean water flow, topography and slope effect, coastal and predominant winds are some of the factors that underlie these distributions. This is particularly evident on OC results, which show highest variability and distinct geographic sectors of pigment concentration around single islands. Further analyses will be extended using in situ data.