UNIVESRITY OF ATHENS, OCEAN PHYSICS AND MODELING GROUP Monitoring and modeling the Eastern Mediterranean circulation and its climatic variability S. Sofianos and OPAM group EastMed Symposium, November 17-20, 2014 Limassol, CYPRUS
POEM contribution in understanding the dynamics of the Eastern Mediterranean was multiple: A coherent picture of the basin circulation and stratification Introduction of spatio-temporal variability Generation scientific and technical capacity to further advance the research Based on these: Regional and/or process oriented studies for understanding the dynamics controlling the circulation and water mass formation New observational and modeling strategies produced new data enabling the investigation at different spatial and temporal scales A variety of modeling tools enabled the investigation of mechanisms controlling the spatial and temporal variability A growing and strengthening monitoring/forecasting system
How variable and sensitive are the thermohaline cells of the Eastern Mediterranean? What is the response of the Eastern Mediterranean and its sub-basins to the various mechanisms that are forcing the observed variability? Which are the mechanisms controlling the variability and enhancing the sensitivity of the Eastern Mediterranean thermohaline circulation?
1 o /20 Sub-regional modeling NORTH AEGEAN AEGEAN - LEVANTINE 1 o /60 1 o /30 ARPERA Forcing
Hydrographic Surveys Observational data 1 st Cruise: 1 to 10 March 2005 44 CTD stations Float Deployment in: Lemnos basin east Cretan basin 2 nd Cruise: 3 to 13 February 2006 47 CTD stations Float Deployment in: Chios basin central Cretan basin Five Float Deployments Eatsern Mediterranean Database (historical and new oceanographic data)
Long-term time series Deep-water variability Georgiou, S., A. Mantziafou, S. Sofianos, I. Gertman, E. Özsoy, S. Somot and V. Vervatis, 2014: Climate Variability and Deep Water Mass Characteristics in the Aegean Sea, Atmos. Res., 152, 146-158, DOI: 10.1016/j.atmosres. 2014.07. 023.
Adriatic Surface Variability Levantine 1.36 o C/cent 0.55 o C/cent 0.09 o C/cent 0.56 o C/cent 0.49 o C/cent Axaopoulos, P., Sofianos, S., 2009: Long term variability of the sea surface temperature in the Mediterranean Sea, AIP Con. Proc., DOI: 10.1063/1.3322579.
Even more complex sub-basin surface variability Horizontal distribution of the satellitederived SST annual linear trend (C/yr) in the Aegean Sea over (a) 1985 2008, (b) 1985 1992, and (c) 1992 2008. Aegean Sea basin-average yearly mean satellite-derived SST variations and linear trend over 1985 2008. Skliris, N., Mantziafou, A., Sofianos, S., Gkanasos, A., 2010: Satellitederived variability of the Aegean Sea ecohydrodynamics, Continental Shelf Research, 30 (5), pp. 403-418.
Subsurface spatio-temporal variability Vervatis, V. D., S. Sofianos, and A. Theocharis, 2011: Distribution of the thermohaline characteristics in the Aegean Sea related to water mass formation processes (2005-2006 winter surveys), J. Geophys. Res., doi:10.1029/2010jc006868.
Water mass formation variability Annual formation rate (in Sv) of intermediate/dense water in the Aegean (black), sub-basins (blue: north Aeg., green: central Aeg., red: south Aeg.) and Levantine (magenta) for different thresholds. Grey dashed line indicates average value over the 1961 2000 period.
Atmospheric forcing variability Anomalous winter (NDJF), with respect to 1960 2000 reference period, of net heat flux Q0 (in Wm-2), for the periods: pre-emt 1960 1969 and 1970 1986, EMT 1987 1993, and post-emt 1994 2000. Superimposed anomalous wind stress (scaled in 0.01 N m-2). Negative (positive) values denote loss (gain) for the ocean.
Surface and lateral buoyancy fluxes Annual cumulative impact of the surface, lateral, thermal and haline buoyancy terms (see Eq. (4) terms in m 2 s -3 ) on the basin buoyancy content evolution, for the Aegean (black) Levantine (magenta) Seas. Negative (positive) values denote loss (gain) for the ocean. Vervatis V. D., S. S. Sofianos, N. Skliris, S. Somot, A. Lascaratos and M. Rixen, 2013: Mechanisms controlling the thermohaline circulation pattern variability in the Aegean Levantine region. A hindcast simulation (1960 2000) with an eddy resolving model, Deep-Sea Research I, 74, 82 97.
River inflow variability (a simple modeling approach) S (300 m) S (300 m) Skliris N., S. Sofianos and A. Lascaratos, 2007: Hydrological changes in the Mediterranean Sea in relation to changes in the freshwater budget: A numerical modelling study, Journal of Marine Systems, 65, 400-416.
Nile damming impact on the salinity of the Levantine basin Additional cooling impact (1965 1975)
0.08 0.06 BSW inflow variability Inflow(Sv) 0.04 0.02 0-0.02-0.04-0.06 EXP EXP EXP EXP V 29/8 24/9 20/10 14/11 10/12 5/1 31/1 26/2 24/3 18/4 14/5 9/6 5/7 31/7 26/8 20/9 Time(Hours) Kine&c Energy of mean flow(m 2 /s 2 ) Velocity(m / s) Mavropoulou, A. M., S. Sofianos, A. Mantziafou, and E. Jarosz, 2014: The influence of Black SeaWater inflow and its synoptic time-scale variability in the North Aegean Sea hydrodynamics, Geophysical Research Abstracts, Vol. 16, EGU2014-6612-1, 2014, EGU General Assembly, Vienna 2014.
38.65 North Aegean Sea Salinity 38.6 Salinity(Psu) 38.55 EXP I 38.5 EXP II EXP III EXP IV EXP V EXP VI 38.45 Aug/08 Oct/08 Nov/08 Dec/08 Jan/09 Feb/09 Mar/09 Apr/09 May/09 Jun/09 Jul/09 Aug/09 Sep/09 Oct/09 Time(Days)
Advection of variability Annual isopycnal surfaces of sigma-theta 29.21 kg m3 over 1986 1994. Contour colors depict the depths [10 200:200:3000] (in meters) of the isopycnal surface 29.21 kg m3.
and feedbacks
Cyclonic Periods: 1965-1972, 1983-1984 1993-1999 Anticyclonic Periods: 1972-1982, 1985-1993 1997-1999 anticyclonic cyclonic Eastern boundary intermediate flow Ravdas M., S. Sofianos, A. Mantziafou, and V. Vervatis, 2013: The Dynamics of the Ionian Sea and its climatic implication: Interannual simulation for the period 1960-2000, Geophysical Research Abstracts, Vol. 15, EGU2013-4909, 2013, EGU General Assembly, Vienna 2013.
Hotspots of thermohaline circulation variability Transects of Θ( C), S, σθ (kg/m3 ) and oxygen concentration (ml/lt), of 17 CTD stations during the winter of 2006 at the eastern side of the North Central Aegean (NAg CAg); Vervatis, V. D., S. Sofianos, and A. Theocharis, 2011: Distribution of the thermohaline characteristics in the Aegean Sea related to water mass formation processes (2005-2006 winter surveys), J. Geophys. Res., doi:10.1029/2010jc006868.
Conclusions: o The Eastern Mediterranean exhibits very large spatio-temporal variability. o The variability and water mass formation processes are related to both surface (mostly heat flux and momentum flux) and lateral forcing (mostly salt flux). o Interbasin exchange changes dramatically the stratification. o Feedback mechanisms are influencing the basin-scale heat and freshwater budget. o Hotspots of deep water formation processes (e.g. eastern-central Aegean). Stratification pattern (mainly due to lateral advection) coincides with areas of intense surface forcing. o Need for synthesizing Thank you!