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!