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

21.5

22.0

22.5

23.0

23.5 19

81

1982

19

83

1984

19

85

1986

19

87

1988

19

89

1990

19

91

1992

19

93

1994

19

95

1996

19

97

1998

19

99

2000

20

01

2002

20

03

2004

20

05

2006

20

07

2008

20

09

2010

20

11

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.

THANK YOU