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Climate Change Impacts on Sea Surface Temperature (SST)
in the Mediterranean Sea, and specifically,
the Levantine Basin
Yianna Samuel-Rhoads*, George Zodiatis,
Oceanography Centre, University of Cyprus, P.O.Box. 20537, 1678 Nicosia, Cyprus *rhoads.yianna@ucy.ac.cy
IPCC 2007: WG1-AR4 • Global SST increases: 0.3ºC -1.0ºC over the last millennium (Salinger, 2005). • Most rapid warming occurring over the past 30-40 years (Casey and Cornillon, 2001; Trenberth
et al., 2007). • Regional temperature increases reported in the Mediterranean Sea for each of its two sub-
basins(Bethoux and Gentili, 1999; Samuel-Rhoads et al., in prep; Skliris et al., 2011;Tsimplis and Rixen, 2002).
• Regional changes are out of phase, due to different processes affecting the climate of the two sub-basins (Artale et al., 2006; Korres et al., 2000; Reddaway and Bigg, 1996).
Objective
• Investigate the increase in SSTs due to climatic changes in the Mediterranean Sea and the Levantine Basin from 1982 until 2012, with the use of satellite remote sensing data.
Data sources (1) • SST data collected by the NOAA/NASA AVHRR radiometers and processed by the SST
Pathfinder program. • Global daily Level-3 (L3), version 5.2, from the night time pass (code numbers 1 and 4), at
4km resolution and equal-angle grid of 8192 pixels/360º from January 1, 1982 through December 31, 2012.
• Daily quality control flag files were obtained from the same source.
Methodology • All satellite data for the Mediterranean Sea and the Levantine Basin were sub-scened from
the global sets and bound by the following coordinates: • For the Mediterranean: 46 ºN to 30 ºN, and -5.5 ºE to 37 ºE. • For the Levantine: 37 ºN to 30 ºN, and 24 ºE to 37 ºE.
• Quality control flags were applied to the daily SST data for the Mediterranean Sea and the
Levantine Basin. Only pixels of highest quality were kept. • Annual averages were calculated for 1982 through 2012 across the Mediterranean Sea and
the Levantine Basin for SST. • Annual anomalies for the SST dataset were also obtained by calculating the overall mean for
the dataset during 1982-2012, and then subtracting the mean from each year of the corresponding dataset.
• To investigate the spatial and temporal variability in SSTs, empirical orthogonal function
(EOF) analysis was performed on the annual anomalies of SST. • Here we present only the first two modes that arise form the EOF analyses.
Mediterranean & Levantine Annual mean satellite SST
Mediterranean: 1982-2012 general increase: ~ 1.30°C 1982-2012 average: 21.08°C 0.042°C/year
World Oceans: 1985-2004: 0.017±0.005°C/year (Good et al., 2007) Since 1950s: 0.014°C/year (Scott et al., 2010) Since 1970s: 0.0048°C/year(Abraham et al., 2013)
Levantine: 1982-2012 general increase: ~ 1.33°C 1982-2012 average: 22.39°C 0.045°C/year
20.0
20.5
21.0
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22.0
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23.0
23.5 19
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1982
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1984
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1986
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1988
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1990
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1992
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1994
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1996
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1998
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2012
Ann
ual M
ean
SST
(ºC)
Year
Med
Lev
1985 1982 1983 1984
1986 1987 1988 1989
1990 1991 1992 1993
1994 1995 1996 1997
1998 1999 2000 2001
2002 2003 2004 2005
2006 2007 2008 2009
2010 2011 2012
1982 1983 1984 1985 1986 1987
1988 1989 1990 1991 1992 1993
1994 1995 1996 1997 1998 1999
2000 2001 2002 2003 2004 2005
2006 2007 2008 2009 2010 2011
2012
• Spatial eigenfunctions of mode 1 show that the annual SSTs across the entire Mediterranean share high positive eigenfunctions. → SSTs varied in a spatially coherent manner over time. → SST variability is characterized by a broad, basin-wide warming .
• The principal component (PC) of the same mode (PC1), depicts the time variation of the first mode. • PC1 of the annual data supports the fact that higher than average SSTs were observed across the
Mediterranean during the later part of the 31-year time period. • An asymmetry in the E-to-W direction is depicted in the spatial eigenfunctions of mode 2, creating a dipole
pattern of heating and cooling at interannual time scales.
Mode 1: 55.78% Mode 2: 8.45%
-2.0
-1.0
0.0
1.0
2.0
3.0
1982 1986 1990 1994 1998 2002 2006 2010 -2.0
-1.0
0.0
1.0
2.0
1982 1986 1990 1994 1998 2002 2006 2010
• Similarly, spatial eigenfunctions of mode 1 show that the annual SSTs across the entire Levantine share high positive eigenfunctions. → SSTs varied in a spatially coherent manner over time.
• PC1 of the annual data supports the fact that higher than average SSTs were observed across the Levantine during the later part of the 31-year time period.
-2.0
-1.0
0.0
1.0
2.0
1982 1986 1990 1994 1998 2002 2006 2010 -3.0
-2.0
-1.0
0.0
1.0
2.0
1982 1986 1990 1994 1998 2002 2006 2010
Mode 1 62.44% Mode 2 8.85%
Results
• We show an SST increase in the entire Mediterranean Sea and the Levantine Basin from 1982 to 2012, with higher than average SSTs occurring during the second half of the 31 year period (1998 onward).
• The Levantine Basin is warming at a slightly faster rate than the entire Mediterranean Sea (0.003°C/year) and SSTs in both are increasing at least more than 2 times as much as the global SSTs.
• SST variability is characterized by a broad, basin-wide warming (mode 1) occurring at interannual time scales, and a weaker dipole pattern that fluctuates at similar time scales (mode 2).
• The driving mechanisms of these changes need to be investigated, as they may be driven by changes in annual latent heat losses and by the variability in regional wind speeds.
• It will be valuable to investigate future trends in SSTs to determine whether the observed patterns represent a continued pattern of persistent warming or a new direction for the Mediterranean Sea and the Levantine Basin.