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“Extreme event impact on 3 - D thermohaline structure variability in the Aegean - Levantine region” Sarantis Sofianos Ocean Physics and Modelling group University of Athens, Greece. 3 rd HyMeX workshop 1-4 June 2009 , Heraklion , GREECE. - PowerPoint PPT Presentation
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3rd HyMeX workshop 1-4 June 2009, Heraklion, GREECE
““ExtremeExtreme event impact on 3 event impact on 3--DD thermohaline structurethermohaline structure variability variability in the Aegeanin the Aegean--Levantine Levantine region”region”
Sarantis SofianosSarantis SofianosOcean Physics and Modelling groupOcean Physics and Modelling group
University of Athens, GreeceUniversity of Athens, Greece
• How robust is the thermohaline circulation pattern of the Eastern Mediterranean?
• What is the impact of long term (atmospheric and/or lateral) changes-variability on the thermohaline cells in the Eastern Mediterranean?
• How can extreme events alter the thermohaline circulation in the Aegean-Levantine region (and further downstream)?
• Combine data/models to evaluate the above.
Traditional SchemeTraditional Scheme
How typical is this scheme?How typical is this scheme?
Cretan Deep Waters (1000m)
Levantine Deep Waters (2000m)
S
S
EMTEMT
EMT SchemeEMT Scheme
Is this just a coincidence of forcing mechanisms or an indication Is this just a coincidence of forcing mechanisms or an indication of thermohaline cell sensitivity?of thermohaline cell sensitivity?
Cretan Deep Waters (1000m)
Levantine Deep Waters (2000m)
S
S
EMTEMT
??
Skliris, Sofianos, Lascaratos, JMS, 2007
Additional SchemeAdditional Scheme
What causes this type of variability?What causes this type of variability?
0.54 oC/cent
1.41 oC/cent
0.11 oC/cent
0.56 oC/cent0.49 oC/cent
0.83 oC/cent
1.41 oC/cent
0.54 oC/cent
0.90 oC/cent0.60 oC/cent
1880 1900 1920 1940 1960 1980 2000
18
19
20
SS
T(o C
)Mediterranean
Annual Mean SST
Filtered (5 years)
Trend=0.0041/y
1880 1900 1920 1940 1960 1980 2000
18
19
20
SS
T(o C
)
Mediterranean
Annual Mean SST
Filtered (10 years)
Trend=0.0041/y
Axaopoulos,MSc Thesis,Univ. Athens
Dominant period ~80 years
Long-term changesLong-term changes
Pre-conditioningPre-conditioning
Violent mixingViolent mixing
Sinking and spreadingSinking and spreading
… … communication with the rest of oceancommunication with the rest of ocean
D.W.F.PhasesD.W.F.Phases
Marshall and Schott, 1999
Effect of extreme Effect of extreme events (buoyancy events (buoyancy
loss rate)loss rate)
x = 440 km
y = 440 km
H = 1000 m
Η , r = 80km
Resolution:0.04o x 0.04o
(4,4 x 4,4 km)
Compare 1-D approach with 3-D results (1000 W/m2)
Forcing rates:100 W/m2
250 W/m2
500 W/m2
750 W/m2
1000 W/m2
1250 W/m2
1500 W/m2
2000 W/m2
Krokos, MSc Thesis, Univ. Athens
5days 10 days 15 days 20 days 25 days
5days 10 days 15 days 20 days 25 days
Pentration Depth
-1200
-1000
-800
-600
-400
-200
0
0 10 20 30 40 50 60
Days
Dep
th 1000W_5x5
(1-D) Theory (1000W/m^2)
N
BtH
2/12
Depth reached
0
100
200
300
400
500
600
700
0 5000 10000 15000 20000 25000
B*t (Days*W/m^2)
H (m
)
100
250
500
750
1000
1250
1500
2000
V. per D.B*t=12500
-1.00E+12
-5.00E+11
0.00E+00
5.00E+11
1.00E+12
1.50E+12
28.3 28.4 28.5 28.6 28.7 28.8 28.9 29 29.1 29.2 29.3
Density ( σ units )
Vo
lum
e (
kgr/
lt ) 500W/m^2
750W/m^2
1000W/m^2
1250W/m^2
1500W/m^2
2000W/m^2
The rate of buoyancy The rate of buoyancy loss is very important in loss is very important in
determining the final determining the final characteristics of the characteristics of the water mass formedwater mass formed
Effect of buoyancy Effect of buoyancy loss rate loss rate
db
PFG215 PFN206 PFG214 PFG212 PFN226 PFG222
14.4
14.2
13.612.5 14.4
13
0 50 100 150 200 250 300 350 400 450 500
0
100
200
Potential Temprature (oC)
13.3
13.914.2
14.2
0 50 100 150 200 250 300 350 400 450 500
500
1000
1500
10.02 11.5 13 13.6 14.2 14.6 15 15.4
PFG215 PFN206 PFG214 PFG212 PFN226 PFG222
37.838.5
38.95
38.1
38.75
38.8
0 50 100 150 200 250 300 350 400 450 500
0
100
200
Salinity (psu)
39.01
38.95 39.04
0 50 100 150 200 250 300 350 400 450 500
500
1000
1500
35.06 35.5 36 36.5 37 37.5 38.6 38.9
db 29.229
28.828.8
29.1
28.6
29.1
0 50 100 150 200 250 300 350 400 450 500
0
100
200
Distance (km)
Potential Density
29.45
29.2
29.45 29.2
0 50 100 150 200 250 300 350 400 450 500
500
1000
1500
27 28 28.2 28.4 28.6 29.15 29.4
4.5
4.84.8
4.4
4.5
4.8
4.3
0 50 100 150 200 250 300 350 400 450 500
0
100
200
Distance (km)
Oxygen Concentration (ml/l)
3.8
3.6
4.24.3
0 50 100 150 200 250 300 350 400 450 500
500
1000
1500
3.38 3.6 4 4.3 4.5 4.8 5.2
db
PFN226 PFN225 PFN218 PFN219 PFN220 PFN221
14 14.9
14.2
14.1
14.96
0 10 20 30 40 50 60 70 80 90
0
100
200
Potential Temprature (oC)
14.2
0 10 20 30 40 50 60 70 80 90
200
400
600
800
13.95 14.05 14.2 14.4 14.6 14.8 14.91
PFN226 PFN225 PFN218 PFN219 PFN220 PFN221
38.8538.93 39.03
38.87
0 10 20 30 40 50 60 70 80 90
0
100
200
Salinity (psu)
38.95
38.9338.91
0 10 20 30 40 50 60 70 80 90
200
400
600
800
38.83 38.87 38.91 38.95 38.99 39.03
db
29.1829.1
29.1629.14
0 10 20 30 40 50 60 70 80 90
0
100
200
Distance (km)
Potential Density
29.21
29.2
29.1929.18
0 10 20 30 40 50 60 70 80 90
200
400
600
800
29.06 29.08 29.1 29.12 29.14 29.16 29.18 29.2
4.424.42
0 10 20 30 40 50 60 70 80 90
0
100
200
Distance (km)
Oxygen Concentration (ml/l)
4.1
4.15
4.3
0 10 20 30 40 50 60 70 80 90
200
400
600
800
4.05 4.15 4.25 4.35 4.4 4.45Vervatis, Sofianos and Theocharis, 2009
ARPERA (~1o/10)
ALERMO (~1o/30)OO
PPAAMMEEDD88
1960-2001+
Extreme Extreme EventsEvents
• How robust is the thermohaline circulation pattern of the Eastern Mediterranean?
Less than we thought
• What is the impact of long term (atmospheric and/or lateral) changes-variability on the thermohaline cells in the Eastern Mediterranean?
▪ Changes the preconditioning ▪ Induces different behavior of extreme events
• How can extreme events alter the thermohaline circulation in the Aegean-Levantine region (and further downstream)?
Crucial in determining the thermohaline cell structure
• Combine data/models to evaluate the above: Beyond the idealized approach
Thank you!Thank you!