Climate Change Impacts on
Sea Surface Temperature in the
Eastern Mediterranean, Levantine Basin
Yianna Samuel-Rhoads*, George Zodiatis,Daniel Hayes, Gregory Konnaris,
Georgios Georgiou, Marios Nikolaides
Oceanography Centre, University of Cyprus, P.O.Box. 20537, 1678 Nicosia, Cyprus*[email protected]
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).
• SSTs across the entire Mediterranean increasing twice as much as the SSTs of the global oceans (Samuel-Rhoads, et al., 2009; in prep; Zodiatis et al., 2010; 2011).
Objective
• Investigate the increase in SSTs due to climatic changes in the Eastern Mediterranean, Levantine basin from 1982 until 2012, with the use of satellite remote sensing data as well as with in-situ 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 throughDecember 31, 2012.
• Daily quality control flag files were obtained from the same source.
From mid 1990s until today, the OC-UCY has been conducting in-situ observations oftemperature during more than 24 multi-day oceanographic research cruises.
Since 2009, the OC-UCY has also been deploying 2 autonomous gliders for missions in theeastern Levantine. In-situ profiles from both of these types of excursions were used to studyseasonal and interannual variability in the Levantine basin from 1996-2012 at the surface layer(0-10m).
Data sources (2)• Ιn-situ SST data collected with CTD (Conductivity-Temperature-Depth) during oceanographic
research cruises CYBO, between 1996 until 2012, and with the two autonomous ocean gliders owned by OC-UCY, which were deployed between 2009 and 2012.
CYBO survey areaOC-UCY gliders
Gliders survey area March – July 2009
Methodology• All satellite data for the Eastern Levantine basin were sub-scened from the global sets and
bound by the following coordinates: 37 ºN to 30 ºN, and 24 ºE to 37 ºE.
• Quality control flags were applied to the daily SST Levantine data. Only pixels of highest quality were kept.
• Annual averages were calculated for 1982 through 2012 across the Eastern 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.
• Averages for the in-situ SST data from the CTD from 1996-2012 were calculated for the top 10 meters of the water column for each CYBO research cruise.
• Monthly averages for the SST data from the glider cruises from 2009-2012 were calculated for the top 10 meters of the water column, after removal of outliers.
Mediterranean & Levantine Annual mean satellite SST
Mediterranean:1982-2012 general increase: ~ 1.30°C1982-2012 average: 21.08°C0.042°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°C1982-2012 average: 22.39°C0.045°C/year
20,0
20,5
21,0
21,5
22,0
22,5
23,0
23,5
1981
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
Ann
ual M
ean
SST
(ºC)
Year
Med
Lev
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 Levantine 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 Levantine
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.
-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%
• Analyses of annual in-situ SST data (from CYBO cruises) for the first 10m depth from CTD casts : reveal similarities in SSTs to the ones recorded by satellites in the region since 1996.
• The average rate of increase of SSTs is 0.022°C/year, which is approximately half than the recorded by satellites 0.045°C/year rate of increase of Levantine SSTs.
• During 2010, the highest temperatures were recorded up to date, which were much higher than the recorded ones from 2003 (mean values for 2010 for SST=29.54°C)
Sat
ellit
e S
ST
(°C
)
17
19
21
23
25
27
29
21,5
22
22,5
23
23,5
1982 1986 1990 1994 1998 2002 2006 2010
In-s
itu S
ST
(°C
)
• Analyses of monthly in-situ SST data collected during glider expeditions from 2009 until 2012.• Calculated for the top 10 meters of the water column.• Depiction of monthly variability in SSTs in the Eastern Mediterranean Levantine basin. • However, the time series in some cases does not represent well the entire region of interest, as the gliders
may have been in an area with a local effect, which is then affecting the regional averages. • Further examination, processing and analysis of these data is needed.
Results
• We show an SST increase in the Levantine Basin from 1982 to 2012, with higher than average SSTs occurring during the second half of the 30 year period (1998 onward).
• 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).
• Satellite SST data are correlated with in-situ CTD SST data. • The warming in the Levantine, which is revealed by the satellite SST data, as well as by the
recorded increases in in-situ SST, occurred at interannual time scales. • The fact that in 2010 the highest insitu SSTs have been recorded so far, which were even
higher than the record values of 2003 seen by satellites, indicates that the increasing trend is expected to continue.
• 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.
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