Hydrodynamic features of the South Aegean Sea as derived from Argo T/S and dissolved oxygen profiles in the area
In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013–July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.
KeywordsGreek Argo POSEIDON system Dissolved oxygen Deep convection Cretan Sea Myrtoan Sea
This work has been supported by the Greek Argo project funded by the National Strategic Reference Framework (NSRF) 2007–2013.
The POSEIDON I and II projects were funded by the Financial Mechanism of the European Economic Area and the Hellenic Program of Public Investments.
The “Policy-oriented marine Environmental Research for the Southern European Seas” (PERSEUS) project was funded by the EU FP7 Theme “Oceans of Tomorrow”.
We would also like to thank the GIS and Remote Sensing Lab of HCMR—Institute of oceanography and all the people of the POSEIDON team (technicians and scientists) who contributed to this effort.
- Gotsis-Skretas O, Pagou K, Moraitou-Apostolopoulou M, Ignatiades L (1999) Seasonal horizontal and vertical variability in primary production and standing stocks of phytoplankton and zooplankton in the Cretan Sea and the straits of the Cretan Arc (March 1994–January 1995. Prog Oceanogr 44:625–649. doi: 10.1016/S0079-6611(99)00048-8 CrossRefGoogle Scholar
- Kassis D, Schroeder K, Bossano R, et al (2013) Multi parametric moorings upgrade with new sensors and expansion. PERSEUS ProjectGoogle Scholar
- Klein B, Roether W, Manca B, Theocharis A (2000) The evolution of the Eastern Mediterranean climatic transient during the last decade: the tracer viewpoint. In: Briand F (ed) In The Eastern Mediterranean Transient, CIESM Workshop Series, vol. 10, pp. 21–25Google Scholar
- Krokos G, Aarts G, Velaoras D, et al. (2014) On the continuous functioning of an internal mechanism that drives the Eastern Mediterranean thermohaline circulation: the recent activation of the Aegean Sea as a dense water source area. J Mar Syst 129:484–489. doi: 10.1016/j.jmarsys.2013.10.002 CrossRefGoogle Scholar
- Monterey G, Levitus S (1997) Seaonal variability of mixed layer depth for the world ocean. Natl. Oceanic and Atmos, Admin, Silver Spring, MdGoogle Scholar
- Ntoumas M, Kassis D, Potiris M, et al. (2011) Activities of the calibration laboratory at HCMR-Crete—progress and challenges. In: Dahlin H, Flemming N, Petersson S (eds) Proceedings of the sixth international conference on EuroGOOS. EuroGOOS Office, Sopot, pp. 15–22Google Scholar
- Pavlidou A, Kontoyiannis H (2011) Dissolved oxygen and nutrient dynamics in East Mediterranean Sea (Aegean, Ionian and Levantine Seas). In: EGU2011–9115. Geophysical Research AbstractsGoogle Scholar
- Roether W, Schlitzer R (1991) The Mediterranean Sea Eastern Mediterranean deep water renewal on the basis of chlorofluoromethane and tritium data. Dyn Atmos Oceans 15:333–354. doi: 10.1016/0377-0265(91)90025-B
- Sofianos S, Theocharis A, Vervatis V (2007) Changes in the Aegean Sea thermohaline characteristics in the post-EMT period. Rapp Comm Int Mer Mediterr 38:200Google Scholar
- SoHelMe, Papathanassiou E, Zenetos, A (eds) (2005) State of the Hellenic Marine Environment. HCMR Publ 2005 360Google Scholar
- Souvermezoglou E, Dagre P, Nakopoulou H, et al (1989) Distribution of nutrients and oxygen in the Eastern Mediterranean Sea. In: Proceedings of the UNESCO/IOC Second Scientific Workshop, Trieste, Italy, POEM Sci Repts pp 85–102Google Scholar
- Souvermezoglou E, Krasakopoulou E, Pavlidou A (1996) Recent modifications of nutrient and oxygen exchanges through the straits of the Cretan Arc. In: Proceedings TOS A Scientific Meeting. p 34Google Scholar
- Theocharis A, Georgopoulos D, Zodiatis G (1988) Late winter hydrological characteristics and circulation of the Cretan Sea (S. Aegean), EGS XIII General Assembly, Bologna, Italy, March 1988Google Scholar
- Theocharis A, Georgopoulos D, Lascaratos A, Nittis K (1993) Water masses and circulation in the central region of the Eastern Mediterranean: Eastern Ionian, South Aegean and Northwest Levantine, 1986–1987. Deep Sea Res Part II Top Stud Oceanogr 40:1121–1142. doi: 10.1016/0967-0645(93)90064-T CrossRefGoogle Scholar
- Triantafyllou G, Petihakis G, Allen IJ (2003) Assessing the performance of the Cretan Sea ecosystem model with the use of high frequency M3A buoy data set. In: Annales Geophysicae. pp 365–375Google Scholar
- Vervatis VD, Sofianos SS, Theocharis A (2011) Distribution of the thermohaline characteristics in the Aegean Sea related to water mass formation processes (2005–2006 winter surveys)Google Scholar
- Zervakis V, Georgopoulos D (2002) Hydrology and circulation in the North Aegean (Eastern Mediterranean) throughout 1997 and 1998. Mediterr. Mar Sci 3:5–19Google Scholar
- Zodiatis G (1991) The hydrological conditions and the circulation in the Cretan Sea during late summer 1987. In: Annales Geophysicae. pp 233–238Google Scholar