Title: Temperature, salinity and associated sea level changes in the Mediterranean Sea under global warming
1Temperature, salinity and associated sea level
changes in the Mediterranean Sea under global
warming scenarios
- Marta Marcos and Mikis Tsimplis
2Objectives
- Examine the T and S changes in the Mediterranean
Sea as predicted by the climate models - Understand steric sea level changes associated
with T and S variations
3Outline
- Models (global and regional) and data bases
- Comparison of T and S for the 20th century
- Projections of T, S for the 21st century
- Associated steric sea level changes
- Conclusions
4Models output and data
IPCC models used in this work
5Models output and data
Atmosphere-Ocean Regional Climate Model coupled
to a global variable resolution atmosphere model
with 50 km resolution over the Mediterranean
basin and forced by river runoff and influxes
from the Atlantic Ocean and the Black
Sea Resolution 1/8 x 1/8 and 43 vertical
levels Simulations SRES A2 scenario for the
21st century Hindcast for 1961-2000
(Somot et al., 2006 )
MEDAR database Yearly gridded T and S
climatology with 0.2ºx0.2º and 25 vertical levels
(Rixen et al., 2005)
6Models output and data
Parameterization of the Strait of Gibraltar
7Models output and data
Some climate change scenarios
Committed climate change scenario This scenario
assumes that concentrations are kept fixed at
year 2000 levels. Therefore, the committed
sea-level rise is the increase in sea surface
level associated with the historical changes in
greenhouse gases to date and the associated
trends in ocean temperature and ocean
volume. SRES A1B scenario The AOGCMs are run up
to year 2100 using the projected concentrations
forcing agents derived from the standard SRES A1B
scenario. This scenario describes a rapid
economic growth and the introduction of new and
more efficient technologies. The increase in
emissions is decelerated in the mid 21st
century. SRES A2 scenario In this scenario the
AOGCMs are run up to year 2100 using the
projected concentrations of greenhouse gases and
sulphates derived from the standard SRES A2
scenario. This scenario assumes a heterogeneous
world with regionally economic development,
implying a continuous increase of gases
emissions. Climate of the 20th century Includes
changes in the forcing according to historical
data
8Methodology
- Monthly T and S data are extracted from the
global models for the domain -15º to 36ºE and 30º
to 47º N - T and S given by the models for the 20th century
are compared with MEDAR data base - Steric sea level is computed for each grid point
as the vertical integration of the specific
volume anomaly from surface to bottom -
- Steric sea levels are obtained for each global
model and each scenarios and for the regional
model as well - The influence of T and S on steric sea level are
also estimated separately -
- Steric sea level does not account for the
changes in sea level induced by changes in the
barotropic circulation
9Changes in T S during the 20th century
Average T and S yearly time series in the
Mediterranean for the layer 0-100 m
10Changes in T S during the 20th century
Average T and S yearly time series in the
Mediterranean for the layer 0-100 m
11Changes in T S during the 20th century
Intermediate waters 100-500m
12Changes in T S during the 20th century
Deep waters 700-2000m
13Projected changes in T and S
Temperature
Salinity
Committed climate change scenario
0-500 m layer
SRES A2 scenario
14Associated steric sea level
SRES A2 scenario
Change in regional model 13 cm
Average MSL 5.9 cm
S constant
T constant
Average MSL 36.8 cm
Average MSL -30.9 cm
15Associated steric sea level
Differences in Western and Eastern basins
SRES A2 scenario
Western basin
Eastern basin
Average MSL 3.7 cm
Average MSL 10.1 cm
Change in regional model EASTERN 11 cm WESTERN
18 cm
16Associated steric sea level
Average steric sea level rise at the end of the
21st century respect to year 2000 (in cm)
Global average corresponds to thermal expansion
17Conclusions
- Climate models often provide unrealistic values
for T and S in the Mediterranean Sea - Global and regional models predict warming and
salinification of the Mediterranean Sea during
the 21st century. The effects on sea level rise
are opposite. - The worst scenario in the Mediterranean predicts
an average sea level rise due to steric changes
of at most 30 cm plus contributions of mass
addition - Coastal values and high resolution regional
models spatial variations of sea level changes
reflect also the barotropic changes in the
circulation. Regional models with high resolution
and describing different scenarios are needed to
improve estimates.
18Conclusions
- Total sea level rise steric dynamic changes
mass addition atmospheric effects - Steric in the Med 30 cm max.
- Atmospheric effects -2 cm max.
- Mass addition -7 to 18 cm globally (IPCC AR4)
- Sea level rise in the worst case scenario 46 cm
averaged over the Med according to the AOGCMs