Ocean Dynamics

, Volume 66, Issue 11, pp 1449–1466 | Cite as

Hydrodynamic features of the South Aegean Sea as derived from Argo T/S and dissolved oxygen profiles in the area

  • Dimitris Kassis
  • Evangelia Krasakopoulou
  • Gerasimos Korres
  • George Petihakis
  • George S. Triantafyllou
Article

Abstract

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.

Keywords

Greek Argo POSEIDON system Dissolved oxygen Deep convection Cretan Sea Myrtoan Sea 

Notes

Acknowledgments

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.

References

  1. Astraldi M, Balopoulos S, Candela J, et al. (1999) The role of straits and channels in understanding the characteristics of Mediterranean circulation. Prog Oceanogr 44:65–108. doi:10.1016/S0079-6611(99)00021-X CrossRefGoogle Scholar
  2. Balopoulos ET, Theocharis A, Kontoyiannis H, et al. (1999) Major advances in the oceanography of the southern Aegean Sea–Cretan Straits system (eastern Mediterranean. Prog Oceanogr 44:109–130. doi:10.1016/S0079-6611(99)00022-1 CrossRefGoogle Scholar
  3. Bergamasco A, Malanotte-Rizzoli P (2010) The circulation of the Mediterranean Sea: a historical review of experimental investigations. Adv Oceanogr Limnol 1:11–28. doi:10.1080/19475721.2010.491656 CrossRefGoogle Scholar
  4. Broecker WS, Peng T-H (1974) Gas exchange rates between air and sea1. Tellus 26:21–35. doi:10.1111/j.2153-3490.1974.tb01948.x CrossRefGoogle Scholar
  5. Cardin V, Gacic M, Nittis K, et al. (2003) Sub-inertial variability in the Cretan Sea from the M3 A buoy. Ann Geophys 21:89–102. doi:10.5194/angeo-21-89-2003 CrossRefGoogle Scholar
  6. Cardin V, Civitarese G, Hainbucher D, et al. (2015) Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation? Ocean Sci 11:53–66. doi:10.5194/os-11-53-2015 CrossRefGoogle Scholar
  7. Clarke RA, Coote AR (1988) The formation of Labrador Sea Water. Part III: the evolution of oxygen and nutrient concentration. J Phys Oceanogr 18:469–480. doi:10.1175/1520-0485(1988)018<0469:TFOLSW>2.0.CO;2 CrossRefGoogle Scholar
  8. de Boyer Montégut C, Madec G, Fischer AS, et al. (2004) Mixed layer depth over the global ocean: an examination of profile data and a profile-based climatology. J Geophys Res Oceans 109:C12003. doi:10.1029/2004JC002378 CrossRefGoogle Scholar
  9. Garcia HE, Gordon LI (1992) Oxygen solubility in seawater: better fitting equations. Limnol Oceanogr 37:1307–1312. doi:10.4319/lo.1992.37.6.1307 CrossRefGoogle Scholar
  10. 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
  11. Ignatiades L (1998) The productive and optical status of the oligotrophic waters of the Southern Aegean Sea (Cretan Sea), Eastern Mediterranean. J Plankton Res 20:985–995CrossRefGoogle Scholar
  12. Ignatiades L, Psarra S, Zervakis V, et al. (2002) Phytoplankton size-based dynamics in the Aegean Sea (Eastern Mediterranean. J Mar Syst 36:11–28. doi:10.1016/S0924-7963(02)00132-X CrossRefGoogle Scholar
  13. Kara AB, Rochford PA, Hurlburt HE (2000) An optimal definition for ocean mixed layer depth. J Geophys Res Oceans 105:16803–16821. doi:10.1029/2000JC900072 CrossRefGoogle Scholar
  14. Kassis D, Schroeder K, Bossano R, et al (2013) Multi parametric moorings upgrade with new sensors and expansion. PERSEUS ProjectGoogle Scholar
  15. Kassis D, Korres G, Petihakis G, Perivoliotis L (2015) Hydrodynamic variability of the Cretan Sea derived from Argo float profiles and multi-parametric buoy measurements during 2010–2012. Ocean Dyn 65:1585–1601. doi:10.1007/s10236-015-0892-0 CrossRefGoogle Scholar
  16. Kihm C, Körtzinger A (2010) Air-sea gas transfer velocity for oxygen derived from float data. J Geophys Res Oceans 115:C12003. doi:10.1029/2009JC006077 CrossRefGoogle Scholar
  17. 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
  18. Klein B, Roether W, Kress N, et al. (2003) Accelerated oxygen consumption in eastern Mediterranean deep waters following the recent changes in thermohaline circulation. J Geophys Res Oceans 108:8107. doi:10.1029/2002JC001454 CrossRefGoogle Scholar
  19. Körtzinger A, Send U, Wallace DWR, et al. (2008) Seasonal cycle of O2 and pCO2 in the central Labrador Sea: atmospheric, biological, and physical implications. Glob Biogeochem Cycles 22:GB1014. doi:10.1029/2007GB003029 CrossRefGoogle Scholar
  20. 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
  21. Malanotte-Rizzoli P (2001) Systems in the Mediterranean Sea. In: Steele JH, Thorpe SA, Turekian KK (eds) Encyclopedia of ocean sciences. Academic Press, Oxford, pp. 605–612CrossRefGoogle Scholar
  22. Malanotte-Rizzoli P, Manca BB, d’Alcala MR, et al. (1999) The Eastern Mediterranean in the 80s and in the 90s: the big transition in the intermediate and deep circulations. Dyn Atmos Oceans 29:365–395. doi:10.1016/S0377-0265(99)00011-1 CrossRefGoogle Scholar
  23. Monterey G, Levitus S (1997) Seaonal variability of mixed layer depth for the world ocean. Natl. Oceanic and Atmos, Admin, Silver Spring, MdGoogle Scholar
  24. Nilsen JEØ, Falck E (2006) Variations of mixed layer properties in the Norwegian Sea for the period 1948–1999. Prog Oceanogr 70:58–90. doi:10.1016/j.pocean.2006.03.014 CrossRefGoogle Scholar
  25. Nittis K, Zervakis V, Perivoliotis L, et al. (2001) Operational monitoring and forecasting in the Aegean Sea: system limitations and forecasting skill evaluation. Mar Pollut Bull 43:154–163. doi:10.1016/S0025-326X(01)00055-8 CrossRefGoogle Scholar
  26. Nittis K, Tziavos C, Thanos I, et al. (2003) The Mediterranean moored multi-sensor array (M3 A): system development and initial results. Ann Geophys 21:75–88CrossRefGoogle Scholar
  27. Nittis K, Perivoliotis L, Korres G, et al. (2006) Operational monitoring and forecasting for marine environmental applications in the Aegean Sea. Environ Model Softw 21:243–257. doi:10.1016/j.envsoft.2004.04.023 CrossRefGoogle Scholar
  28. 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
  29. 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
  30. Petihakis G, Triantafyllou G, Allen IJ, et al. (2002) Modelling the spatial and temporal variability of the Cretan Sea ecosystem. J Mar Syst 36:173–196. doi:10.1016/S0924-7963(02)00186-0 CrossRefGoogle Scholar
  31. Petihakis G, Drakopoulos P, Nittis C, et al. (2007) M3A system (2000–2005)—operation and maintenance. Ocean Sci 3:117–128. doi:10.5194/os-3-117-2007 CrossRefGoogle Scholar
  32. Poulain P, Barbanti R, Font J, et al. (2007) MedArgo: a drifting profiler program in the Mediterranean Sea. Ocean Sci 3:379–395CrossRefGoogle Scholar
  33. 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
  34. Schroeder K, Millot C, Bengara L, et al. (2013) Long-term monitoring programme of the hydrological variability in the Mediterranean Sea: a first overview of the HYDROCHANGES network. Ocean Sci 9:301–324. doi:10.5194/os-9-301-2013 CrossRefGoogle Scholar
  35. 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
  36. SoHelMe, Papathanassiou E, Zenetos, A (eds) (2005) State of the Hellenic Marine Environment. HCMR Publ 2005 360Google Scholar
  37. Souvermezoglou E, Krasakopoulou E (2000) Chemical oceanography in the Cretan Sea: changes associated to the transient. Mediterr Mar Sci 1:91–103CrossRefGoogle Scholar
  38. 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
  39. 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
  40. Souvermezoglou E, Krasakopoulou E, Pavlidou A (1999) Temporal variability in oxygen and nutrient concentrations in the southern Aegean Sea and the straits of the Cretan Arc. Prog Oceanogr 44:573–600. doi:10.1016/S0079-6611(99)00045-2 CrossRefGoogle Scholar
  41. 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
  42. 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
  43. Theocharis A, Balopoulos E, Kioroglou S, et al. (1999a) A synthesis of the circulation and hydrography of the South Aegean Sea and the straits of the Cretan Arc (March 1994–January 1995. Prog Oceanogr 44:469–509. doi:10.1016/S0079-6611(99)00041-5 CrossRefGoogle Scholar
  44. Theocharis A, Nittis K, Kontoyiannis H, et al. (1999b) Climatic changes in the Aegean Sea influence the eastern Mediterranean thermohaline circulation (1986–1997. Geophys Res Lett 26:1617–1620. doi:10.1029/1999GL900320 CrossRefGoogle Scholar
  45. Theocharis A, Klein B, Nittis K, Roether W (2002) Evolution and status of the Eastern Mediterranean Transient (1997–1999. J Mar Syst 33–34:91–116. doi:10.1016/S0924-7963(02)00054-4 CrossRefGoogle Scholar
  46. 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
  47. Velaoras D, Krokos G, Nittis K, Theocharis A (2014) Dense intermediate water outflow from the Cretan Sea: a salinity driven, recurrent phenomenon, connected to thermohaline circulation changes. J Geophys Res Oceans 119:4797–4820CrossRefGoogle Scholar
  48. Velaoras D, Krokos G, Theocharis A (2015) Recurrent intrusions of transitional waters of Eastern Mediterranean origin in the Cretan Sea as a tracer of Aegean Sea dense water formation events. Prog Oceanogr 135:113–124CrossRefGoogle Scholar
  49. 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
  50. 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
  51. Zervakis V, Nittis K, Perivoliotis L, Tziavos C (2002) A comparison of model predictions to observations of seasonal variability and circulation in the Eastern Mediterranean. Glob Atmosphere Ocean Syst 8:151–172CrossRefGoogle Scholar
  52. Zodiatis G (1991) The hydrological conditions and the circulation in the Cretan Sea during late summer 1987. In: Annales Geophysicae. pp 233–238Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Institute of Oceanography, Hellenic Centre for Marine ResearchAnavyssosGreece
  2. 2.Department of Naval Architecture and Marine EngineeringNational Technical University of AthensAthensGreece
  3. 3.Department of Marine SciencesUniversity of the AegeanMytileneGreece

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