The last 30-year thermohaline variability in the ... - Medclivar

The last 30-year 30 year thermohaline
variability in the Mediterranean as a
useful input for continuing climatic
research in an ideal “test test-basin basin”
Tel Aviv, ISRAEL
Alexander Theocharis
Hellenic Centre for Marine Research, Greece
MedCLIVAR workshop
19-20 19 20 September 2011

Why the Mediterranean Sea?????
• The Mediterranean region has a long observational record of past
climate with both instrumental and proxy data revealing a variety variety
of
time and space scales of variability that demonstrate the complexity complexity
of the Mediterranean Climate System.
• The Mediterranean is considered, as a “miniature miniature ocean” ocean due to
analogies to the Ocean as far as the dynamical processes is
concerned. Many processes which are fundamental to the general
circulation of the world ocean also occur within the Mediterranean,
Mediterranean,
either identically or analogously.
• The Mediterranean Sea responds rapidly to external forcing.
• The Mediterranean as a semi-enclosed semi enclosed almost isolated mid-latitude mid latitude
oceanic basin surrounded by three nearby continents, Europe, Asia Asia
and Africa, is under the influence of large atmospheric systems and
their variability.
• Moreover, due to its location it is also profoundly naturally
influenced by the nearby continents, the neighboring Atlantic Ocean Ocean
and Black Sea.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Why the Mediterranean Sea?????
• Increasing human activities, such as urbanization in coastal areas, areas,
tourism, agriculture, maritime traffic, industry, fisheries,
aquaculture, river damming etc, exert considerable pressure on
coastal and marine environment.
• Therefore, changes in the Mediterranean are due both to natural and
anthropogenic factors.
• The role of the Mediterranean as a Laboratory test Basin for
studying Global Processes “(e.g. (e.g. multi-scale multi scale circulation, the
existence of closed thermohaline cells, “Conveyor Conveyor Belt”, Belt , deep water
formation processes etc), has been clearly revealed. Therefore, as
both a “miniature miniature” ocean and a “regional regional” sea, the
Mediterranean has been shown to record both global and
regional changes, and as such, is considered an important test
basin for studying multi-scale multi scale variability.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Why the Mediterranean Sea?????
• Since the beginning of the 20th century and up to late 80s the
Mediterranean was considered as an almost “steady steady state” state basin, with
some small scale variability and trends in T and S in the IW and DW.
• Furthermore, since the ‘90s 90s abrupt changes occurred so that the
Mediterranean is at present in a transitional state. Both long-term long term and
abrupt temperature and salinity changes affected the thermohaline
thermohaline
circulation of the entire basin.
• The Oceans play crucial role in modifying the climate. (i.e. Air-Sea Air Sea
interaction processes in the N. Atlantic influence the climate of of
Europe.)
• The Global importance of the Mediterranean is defined by its impact impact
on the Atlantic Thermohaline Circulation (Polar Convection Cells). Cells).
High salinity tongues and Meddies extend westward and northward
from Gibraltar in the intermediate and deep waters of the Atlantic Atlantic
Ocean. This salty water of Mediterranean origin may affect processes processes
and variability and even the stability of the thermohaline equilibrium equilibrium
state.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

The Mediterranean as a laboratory Basin
• All the above mentioned characteristics/
“advantages advantages” of the Mediterranean led to the
conclusion that this Sea is successfully considered
as an ideal test basin for climatic research.
• Monitoring (continuous data acquisition and
archiving) and modeling strategies (model
development), as well as closer cooperation of
scientists from pertinent fields are continuously
needed for better understanding the past and
present variability and predicting the future of the
Mediterranean region for the mankind benefit.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Mediterranean Thermohaline Circulation:
the traditional picture (I)
The excess evaporation over freshwater
input within the basin is balanced by a
two layer exchange at the Strait of
Gibraltar comprising a relatively warm,
fresh (15°C, 36.2psu) upper water
inflow and a relatively cool and saltier
(13.5°C and 38.4 psu) outflow to the
Atlantic. The transformation of the
inflowing Atlantic Water to
Mediterranean outflowing water within
the basin is made through a thermohaline
cell that involves the whole basin
and leads to the formation of the
Levantine Intermediate Water (LIW).
Chapter 4, MedCLIVAR book, 2006
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011
From Lascaratos et al., 1999

Mediterranean Thermohaline Circulation:
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the traditional picture (II)
In addition to the formation of
intermediate waters, deep water
formation takes place in distinct
parts of the basin and in particular
in the Gulf of Lions and the
Adriatic Sea. There exist two
internal closed thermohaline cells
one in the western and one in the
eastern sub-basin.
MedCLIVAR workshop
19-20 19 20 September 2011
From Lascaratos et al., 1999

Pressure (dbar)
0
-500
-1000
-1500
-2000
-2500
-3000
-3500
-4000
The pre-EMT pre EMT haline structure of the Eastern
780
M A W
779 778
777
773
L I W
761
760
E M D W
F/S METEOR 1987
-4500
0 200 400 600 800 1000 1200 1400 1600 1800
Tel Aviv, ISRAEL
758
756
751
Distance (km)
Mediterranean
723
726 727
728
729
734
L I W
E M D W
739
740
M A W
741
742
MedCLIVAR workshop
19-20 19 20 September 2011
39.05
39.00
38.95
38.90
38.85
38.80
38.75
38.70
38.67
38.66
38.50
38.00
37.50
During the 80’s many
intensive research
detailed field programs
run in the Mediterranean
Basins. These studies
confirmed the almost
“standard” vertical
structure of the Basin
(e.g. homogeneous DW)
, as known from the
beginning of the 20th
century,……

The multi-scaled multi scaled dynamical features in the
Mediterranean during the late 80s-early 80s early 90s
Malanotte-Rizzoli et al., 1999
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011
…....but also gave insight in
the dynamics and revealed
that the Mediterranean
circulation was dominated by
multi-scaled structures
variable in space and time.
Millot 1991, 1999

39.00
38.90
38.80
38.70
38.60
Salinity variability and trends in the eastern
Mediterranean (1910-1999)
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LIW
dS/dt = 0.00103 psu yr -1
N = 32, R 2 = 0.36
Ionian Sea
dS/dt = 0.00103 psu yr-1
N = 41, R 2 = 0.20
dS/dt = 0.0012 psu yr-1
N = 37, R 2 = 0.13
2000m
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
39.20
39.10
39.00
38.90
38.80
38.70
38.60
38.50
MedCLIVAR workshop
19-20 19 20 September 2011
dS/dt = 0.00125 psu yr-1
N = 24, R2 = 0.19
2000m
LIW
dS/dt = 0.0016 psu yr-1
N = 22, R2 = 0.27
Levantine Basin
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
During the last century several changes in the Mediterranean have been
documented. Trends in the temperature (T) and salinity (S) of the intermediate and
deep waters have been observed. Moreover sudden changes in the deep water
formation sites in the Eastern Mediterranean have been documented between 1987-
1995 that affected the DW of the entire eastern Mediterranean.

WMDW
From Tsimplis et al., 2006
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nEMDW
The EMT event
MedCLIVAR workshop
19-20 19 20 September 2011
Existing climatological data sets
indicate that the Mediterranean Sea
is not in a steady
state and is potentially very
sensitive to changes in atmospheric
forcing.
Shift of the main source of
DW from the Adriatic to the
Aegean (1987-1995)

Forcing Forcing Mechanisms
��A A series of abnormal
meteorological
conditions
•extended extended dry period
•exceptionally exceptionally cold
winters
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60
50
40
30
20
10
Precipitation (cm/yr)
0
1984 1986 1988 1990 1992 1994 1996
Winter Air Temperature
13.5
13
12.5
12
11.5
11
10.5
10
1984 1986 1988 1990 1992 1994 1996
��Long Long term changes in
fresh-water fresh water budget of
the basin (control of
major rivers) Hurrell, 1995
MedCLIVAR workshop
19-20 19 20 September 2011

Pressure (dbar)
-500
-1000
-1500
-2000
-2500
-3000
-3500
-4000
The evolution of the T/H structure of the eastern
Mediterranean during the 90s
0
780
M A W
779 778
777
773
L I W
E M D W
F/S METEOR 1987
761
760
758
-4500
0 200 400 600 800 1000 1200 1400 1600 1800
756
Distance (km)
Tel Aviv, ISRAEL
751
723
726 727
728
729
734
L I W
E M D W
739
740
M A W
741
742
1987
From Robinson, Theocharis et al.,
2001. Ocean Currents:
Mediterranean Sea Circulation.
Encyclopaedia of Ocean Sciences.
Publishers: Academic Press Ltd.,
London, 1689-1706.
39.05
39.00
38.95
38.90
38.85
38.80
38.75
38.70
38.67
38.66
38.50
38.00
37.50
Pressure (dbar)
Pressure (dbar)
MedCLIVAR workshop
19-20 19 20 September 2011
-500
-1000
-1500
-2000
-2500
-3000
-3500
-4000
-500
-1000
-1500
-2000
-2500
-3000
-3500
-4000
9
10 12 13
M A W
30
34
Old uplifted DW
(Adriatic origin)
EMDW
Adriatic
origin
F/S METEOR 1995
50 54
L I W / C I W
58 57
Deep/bottom waters
(Aegean origin)
(1991-95)
67 62 61 60 74 72 76
L I W
Old uplifted DW
(Adriatic origin)
0 200 400 600 800 1000 1200 1400 1600 1800 2000
78 7 6 5
Distance (km)
4 34 3 1 2
M A W
Old
uplifted
DW
(Adriatic
origin)
EMDW
(Adriatic
origin)
L I W / C I W
New deep Aegean
waters 1996-99
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Distance (km)
1995
L I W
77
Old uplifted DW
(Adriatic origin)
Deep/bottom
Aegean waters
1991-1995
1999
R/V AEGAEO 1999
39.05
39.00
38.95
38.90
38.85
38.80
38.75
38.70
38.68
38.65
38.50
38.00
37.50
39.05
39.00
38.95
38.90
38.85
38.82
38.80
38.75
38.70
38.65
38.50
38.00
37.50

The influence of the South Aegean on the Eastern
Mediterranean T/H structure
Contribution to the
intermediate layers
(100-500m) in
1991
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Contribution to the
deep layers
(>2000m) in 1991
MedCLIVAR workshop
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Contribution to the
layers between
intermediate and deep
(700-1100m) in 1987

Variability of the dissolved oxygen distribution
along the eastern Mediterranean (1987-1999) (1987 1999)
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Zonal sections of oxygen concentrations
takenby Meteor; 1987 (M5/6) (a), 1995
(M31/1) ( b), and 1999 (M44/4) (c)
(From Klein et al., 2003)
Since early 90s, the oxygenated young but poor
in nutrients AgDW have filled almost the entire
EM deep and bottom layers and as a
consequence the old waters poor in oxygen but
richer in nutrients have been uplifted towards
shallower depths….
MedCLIVAR workshop
19-20 19 20 September 2011

Pressure (dbar)
-500
-1000
-1500
-2000
-2500
-3000
-3500
-4000
The evolution of the T/H structure of the Ionian Sea
during the 90s
N S
23
0
24 28 29 30 31 32
ADW
R/V METEOR
January 1995
CDW
0 100 200 300 400 500 600
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Distance (km)
(a)
In 1997-98 no deep convection
(~400m) was reported in the
Adriatic, while in 1999 the
ventilation went deeper (~700m)
(Manca et al., 2002)
39.10
39.08
39.06
39.04
39.02
39.00
38.98
38.96
38.94
38.92
38.90
38.88
38.86
38.84
38.82
38.80
38.78
38.76
38.74
38.72
38.70
38.50
38.30
38.00
Pressure (dbar)
-500
-1000
-1500
-2000
-2500
-3000
-3500
-4000
MedCLIVAR workshop
19-20 19 20 September 2011
In 1995 the ADW appeared above
the deep and bottom CDW.
In 1998 the ADW circulated around
1000m (Theocharis et al., 2002)
27B 27A 27 28A 29 30 32
ADW
R/V AEGAEO
October 1998
C D W
0 100 200 300 400 500 600 700
Distance (km)
(b)
39.10
39.08
39.06
39.04
39.02
39.00
38.98
38.96
38.94
38.92
38.90
38.88
38.86
38.84
38.82
38.80
38.78
38.76
38.74
38.72
38.70
38.50
38.30
38.00

Tel Aviv, ISRAEL
Trends in the western Mediterranean:
Warming and salting of the TDW
(a) Pot. Temperature and Salinity
from moorings in Tyhrrenian
Sea (>3000 dbar) dbar
(b) Profiles of Pot. Temperature and
Salinity in Tyhrrenian Sea from
the MEDATLAS DATA BASE :
(1) 1987, (2) 1990, (3-6) (3 6) 1996, (7- (7
8) 2000
(c, d) Time evolution of the TDW
characteristics (squares and
circles). Trends reported in the
literature for WMDW in the
Algero-Provencial
Algero Provencial are
represented by solid lines
(Rohling and
Bryden, 1992) and dashed lines
(Bethoux and Gentili, Gentili,
1999).
(From Fuda and Millot, 2002)
MedCLIVAR workshop
19-20 19 20 September 2011
Potential temperature (°C)
Pressure (dBar)
Potential temperature (°C)
13.00
12.99
12.98
12.97
12.96
12.95
12.94
12.93
12.92
12.91
12.90
12.89
1500
2000
2500
3000
3500
13.00
12.95
12.90
12.85
12.80
12.75
12.70
12.65
1900
2
1997 1998 1999 2000 2001 2002
Year
1
c)
a)
b)
1920
3-4-5
6
1940
1960
7-8
12.80 12.90 13.00
Pot. temp. (°C)
1980
2000
1900
1-2
d)
1920
6
3-4-5
1940
7-8
38.45 38.55
Salinity (p.s.u.)
1960
1980
2000
38.51
38.50
38.49
38.48
38.47
38.46
38.45
38.50
38.45
38.40
Salinity (p.s.u.)
Salinity (p.s.u.)

Variability of the Mediterranean water around the
Spanish coast: Project RADIALES.
Baleares. 200m.
13.8
13.6
13.4
13.2
13.0
12.8
44.0
42.0
40.0
38.0
36.0
34.0
43.5
1994-2000
13.23 ± 0.04ºC
0.02 ± 0.02ºC/yr
St. 7
20 00m
10 00m
50 0m
20 0m
-4.0 -3.5 -3.0
MÁLAGA
M1
V1
V2
36.5 P1
P2
M2
M3
V3
200m P3
500m
-5.0 -4.5 -4.0 -3.5
-10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0
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SANTANDER
MURCIA
1994-2002
13.22 ± 0.04ºC
0.005 ± 0.02ºC/yr
1994 1996 1998 2000 2002
40.0
39.0
100 0m
20 0m
50 0m
1.0 2.0 3.0 4.0
38.0
37.8
37.6
BALEARES
200m
E9
1 000m
500m
37.4
2 000m
-1.2 -1.0 -0.8 -0.6 -0.4
temperature(ºC)
13.40
13.35
13.30
13.25
13.20
13.15
13.10
13.05
13.00
MedCLIVAR workshop
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13.23 ± 0.02ºC
0.02 ± 0.01ºC/yr
1992 1994 1996 1998 2000 2002
time(years)
Temperature in Málaga Bay at 200m (ECOMÁLAGA project).
(From Vargas-Yanez et al., 2002)

Variability of the Mediterranean water around the
Spanish coast (Atlantic Ocean): Project RADIALES.
Temperature and salinity of the maximum of salinity in
Station7 (Santander).
10.20
10.10
10.00
9.90
9.80
9.70
9.60
35.85
35.83
35.80
35.78
35.75
9.97 ± 0.04ºC
0.05 ± 0.02 ºC/yr
1994 1996 1998 2000 2002
35.79 ± 0.01
0.008 ± 0.005 yr -1
1994 1996 1998 2000 2002
(From Vargas-Yanez et al., 2002)
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44.0
42.0
40.0
38.0
36.0
34.0
MedCLIVAR workshop
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43.5
St. 7
20 00m
10 00m
50 0m
20 0m
-4.0 -3.5 -3.0
MÁLAGA
36.5 P1
P2
V1
M1 V2
M2 V3
M3
200m P3
500m
-5.0 -4.5 -4.0 -3.5
SANTANDER
MURCIA
1.0 2.0 3.0 4.0
BALEARES
-10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0
40.0
39.0
100 0m
38.0
37.8
37.6
20 0m
50 0m
200m
E9
1 000m
500m
37.4
2 000m
-1.2 -1.0 -0.8 -0.6 -0.4
Maximum depth sampled in each survey. Only casts
deeper than 900m are considered for this plot and for
the temperature and salinity analysis above.
max. depth sampled
1600
1500
1400
1300
1200
1100
1000
900
800
976 ± 14m
1994 1996 1998 2000 2002

Approach towards a networking project…. project
• In early 2000, the oceanographic community organized a rather
informal meeting in the frame of CIESM Congress and tried to
discuss ideas on the already observed changing status of the
Mediterranean, especially in the eastern Basin. The aim of this
initiative was to bring together not only the oceanographers of the
western and eastern Mediterranean, but mainly the atmospheric
and oceanographic community of the Mediterranean and Europe,
to work together under the auspices of an international
Organization, if possible.
• The idea of a project focused on the Mediterranean climate was
initially proposed by Paola Malanotte-Rizzoli Malanotte Rizzoli and Roberta Boscolo,
a couple of years later, to fill a gap in the Mediterranean area
which was not addressed in the initial CLIVAR implementation
plan. This proposal has been shared by a progressively larger
group of scientists and succeeded as coordinated scientific
activities under the CLIVAR umbrella and later on as the
networking ESF/MedCLIVAR program..
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Abrupt Changes Observed in the Deep Western
Mediterranean Sea between 2004 and 2006
Katrin Schroeder, Mireno Borghini, Borghini,
Stefania
Sparnocchia,
Sparnocchia,
Gian Pietro Gasparini
(MedCLIVAR workshop, Rhodes, 2008)
More recent observations have
shown further significant heat
and salt increases, both in the
deep and intermediate layers, in
several WMED sub-basins, which
have been attributed to the
propagation of the Eastern
Mediterranean Transient (EMT),
from the EMED to the WMED.
(Gasparini et al., 2005, DSR;
Schroeder et al., 2006, GRL)
LIW is the only eastern water mass found
also in the WMED. Therefore the signal of the
EMT propagation has to follow the LIW path.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

T, S, O evolution 2004-2005 2004 2005-2006 2006 along
2 w-e section in the western Mediterranean
Tel Aviv, ISRAEL
MedCLIVAR workshop
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From: K. Schroeder et al. 2008

New DW in the western Mediterranean 2004-2006
2004 2006
Classical WMDW structure (before 2005)
Tel Aviv, ISRAEL
Katrin Schroeder, Mireno Borghini, Borghini,
Stefania
Sparnocchia,
Sparnocchia,
Gian Pietro Gasparini
(MedCLIVAR workshop, Rhodes, 2008)
MedCLIVAR workshop
19-20 19 20 September 2011
Deep layer structure after DWF in
2004/2005 and then in 2005/2006

Tel Aviv, ISRAEL
Signature in the MOW
Garcia-Lafuente et al. (2007),
observing a θ decrease in the MOW
by the end of March 2005 and in
March 2006, have attributed it to a
remote signature of the deep
convection, which replenishes the
WMDW reservoir and raises its
interface with the water above,
making cooler water available for
suction. This happens almost every
year, with a drop in θ in early
spring, but in 2005 and 2006 a very
sharp decrease was registered.
MedCLIVAR workshop
19-20 19 20 September 2011
Garcia-Lafuente et al., 2007

Tel Aviv, ISRAEL
Open questions……
questions…….
Formulated during MedCLIVAR scientific meetings
– Has there been an EMT in the past?
– Relative role of the various phenomena recorded during the EMT
(exact processes)
– Relative role of atmospheric forcing vs LIW salt anomaly in the
recent WMDW formation
– Relative role of Atlantic inflow
– Relative role of Black Sea inflow in North Aegean formation
– Is there a major climatic / teleconnection feature that explains
the changes in trends recorded in the SST / MSL of the Med?
– In estimating MSL trends in the Mediterranean, we need to take
care of inhomogeneous land vertical motions.
– Connection of EMT to large scale atmospheric patterns?
– Reconstruction of MSL from both tide gauges and altimetry is
possible – minima in 1960s and 1970s might suggest previous
EMT-like EMT like phenomena (this is also supported by heat fluxes, SST
and numerical simulations)
– Evolution of MSL at the northern African coast
MedCLIVAR workshop
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Open questions……
questions…….
• Major areas of uncertainty include:
– We need to define how to assess the full range of
uncertainties
– The role of the Gibraltar remains to be determined
– The importance of Alpine glaciers melting in further
increasing the stratification
– The sensitivity to the role of vertical mixing processes
in ventilating the deep layers
– Need to improve our knowledge of the bottom
circulation to assess the model quality
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Open questions……
questions…….
Assess the effect on the Mediterranean Outflow Water (MOW)
toward the Atlantic Ocean and when this will be visible.
• Considering that in the EMED the EMT produced an uplifting of the the
old EMDW of about 500 m, what it is observing now in the WMED
seems to be significant as well (300 m displacement of the resident resident
WMDW in two years on average).
Analogy Analogy with with the the Strait Strait of of Sicily: Sicily:
• As it was the case of the EMO, probably the first effect would be be
a
MOW with a higher % of old WMDW �� decrease of θ and S ( (Garcia Garcia
Lafuente Lafuente et et al., al., 2007). 2007).
• Successively, if the new WMDW will be able to reach the Alboran
Sea an increase of θ and S is very likely.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Some open issues proposed by the Greek team….. team ..
More focus on the Atmosphere-Ocean
Atmosphere Ocean-Land Land interactions:
• More specifically, further studies of the NAO influence on
the atmospheric circulation, air sea heat exchanges and
precipitation.
• In addition, ship emission and related atmospheric
pollution studies, since most naval routes are lying
nearby heavily populated coastal areas.
• Along the same lines, the Saharan dust and several
biogenic emissions (e.g. DMS) have not been extensively
investigated as an additional circulation modifiers.
Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011

Tel Aviv, ISRAEL
MedCLIVAR workshop
19-20 19 20 September 2011