Recent trends of SST in the Western Mediterranean basins from AVHRR Pathfinder data (1985–2007)

Abstract

Keywords:sea surface temperature Western Mediterranean climate change warming trends Mediterranean warming AVHRR-NOAA seasonal and temporal variability Climate change in the Mediterranean region cannot be understood without taking into account changes in the Mediterranean Sea, which is an important source of moisture and heat for the Mediterranean climate system. Many research papers have been published in the last two decades increasing our knowledge about long-term trends and inter-annual variability of temperature and salinity in the Western Mediterranean. Although recent changes have been better documented, there remain uncertainties because different results are obtained depending on the period of time analyzed or the geographic region selected. This paper analyses the regional, seasonal and decadal variability of sea surface temperature in the Western Mediterranean basins (Northern (Ligurian Sea and Gulf of Lions), Balearic, Algerian and Alboran) by means of thermal satellite images. Monthly data from the PO.DAAC (Physical Oceanography Distributed Active Archive Center) have been processed for the period . Results show an averaged warming linear trend of 0.03°C/yr. This rate is higher during the spring (0.06°C/yr) in all the basins and the highest values were registered in the Northern basin in June. The study suggests that an early warming of the Sea is occurring in all the basins during the spring, with an increment of 0.5-1°C in the mean SST of April, May and June over the two decades studied. The analysis of thermal anomalies confirms the warming trend with a dominance of negative anomalies during 1985-1996 and a dominance of positive anomalies during the last decade (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007). Intense anomalies are more frequent in the Northern basin.

New Evidence of Mediterranean Climate Change and Variability from Sea Surface Temperature Observations

“…Other recent trends' estimates provide values of 0.036 ± 0.003 • C/year from 1993 to 2017 [21], 0.036 ± 0.003 • C/year from 1982 to 2016 [22] and 0.035 ± 0.007 • C/year from 1982 to 2012 [20], over the Mediterranean Sea. Trends' estimates we found in the Mediterranean sub-basins and the adjacent Northeastern Atlantic box agree with previous findings, e.g., the value of 0.031 ± 0.007 • C/year from 1985 to 2007 in the western Mediterranean Sea [18], about 0.045 • C/year in the Aegean Sea [23] and about 0.025 • C/year in the Atlantic area near Gibraltar from 1985 to 2008 [54], about 0.033 • C/year in the Ionian Sea and about 0.042 • C/year in the Levantine basin from 1982 to 2012 [20]. These trends are quite similar to our estimates within the indicated confidence interval.…”

“…Based on the 4 km Advanced Very High Resolution Radiometer (AVHRR) Pathfinder SST dataset [16], the author of [17] estimated a mean warming trend of 0.03 ± 0.008 • C/year in the western Mediterranean Sea and 0.05 ± 0.009 • C/year in the eastern basin from 1985 to 2006. Analogous results were obtained in [18], where a mean warming trend of 0.031 ± 0.003 • C/year in the western Mediterranean Sea from 1985 to 2007 was found. These authors [18] also evidenced a significant seasonal variability in the SST trend, observing the highest warming rate in spring, approximately 0.065 ± 0.012 • C/year, and much lower warming rates, approximately 0.02 • C/year or less, during the other three seasons.…”

“…Analogous results were obtained in [18], where a mean warming trend of 0.031 ± 0.003 • C/year in the western Mediterranean Sea from 1985 to 2007 was found. These authors [18] also evidenced a significant seasonal variability in the SST trend, observing the highest warming rate in spring, approximately 0.065 ± 0.012 • C/year, and much lower warming rates, approximately 0.02 • C/year or less, during the other three seasons. Based on Reynolds' SST reanalysis [19], a satellite-based gap-free (optimally interpolated) SST dataset on a 0.25 • grid, the authors of [20] found a mean warming trend of 0.035 ± 0.007 • C/year during a 31-year period (1982-2012) over the Mediterranean Sea, ranging from 0.016 ± 0.001 • C/year in winter to 0.038 ± 0.109 • C/year in spring.…”

Multiscale variability in the Balearic Sea: An altimetric perspective

“…We can speculate that there is a similar link between temporal variability in frontal activity and EKE in our study region, but further investigation is beyond the scope of this study. We note however that spatial variability of SST in the Balearic Sea has been found to be maximum in autumn, with low values in winter and spring [ López García and Camarasa Belmonte , ].…”

“…However, up to the present, there have been no long‐term mesoscale variability studies focused on the Balearic Sea, which occupies a central position within the western Mediterranean (WMED) (Figure ) and is described as a transition region between the northern (Gulf of Lions (GoL)) and southern (Algerian Sea) components of the so‐called Western Basin cyclonic gyre [e.g., López García et al ., ; Millot , ; Millot and Taupier‐Letage , 2005]. Indeed, in comparison with these latter regions, the Balearic Sea experiences the largest temperature range over the annual cycle [ López García and Camarasa Belmonte , ].…”