CHANGES IN LEVANTINE INTERMEDIATE WATER PROPERTIES OBSERVED IN THE EASTERN LEVANTINE: 1995-2012 D. Hayes *, G. Zodiatis , G. Georgiou , E. Mauri , P. Poulain , R. Gerin , G. Notarstefano and P. Testor Oceanography Center, University of Cyprus - dhayes@ucy.ac.cy OGS, Trieste, Italy LOCEAN-IPSL/CNRS, Universite Pierre et Marie Curie, Paris, France Abstract Hydrographic data have been collected for 17 years in the northeastern Levantine by the Cyprus Basin Oceanography (CYBO) initiative of the Oceanography Center, University of Cyprus. Twenty-three cruises have covered the region extensively, and have shown significant changes in the salinity of the Levantine Intermediate Water (LIW: 250 m depth) from values of around 39.1 to 39.3 since 2007. Profiling float data since 2003 and glider data since 2009 show agreement. LIW temperature shows a very small change at the same time from all three platforms. Keywords: Intermediate waters, Levantine Basin 1 1 1 2 2 2 2 3 1 2 3 LIW is primarily formed in February and March in the cyclonic Rhodes Gyre [1]. It is signified by a sub-surface maximum in salinity, around 250 m. During and after buoyancy driven convection, LIW spreads laterally around the Levantine basin, eventually finding its way into the Western Mediterranean, and to the Atlantic Ocean. Salinity and temperature values at the time of formation are reported to be 38.95-39.1 and 15-16 deg C [2]. In this paper, the properties of LIW from 1995 to present is examined. Since 1995, the CYBO program has carried out 23 hydrographic cruises of up to ninety stations to 1000 m over 9 days (Fig. 1). For the last 10 years or so, profiling Argo floats have been deployed in earnest in the Mediterranean Sea [3]. While coverage is not the same every year, a significant portion of the region is covered in any given year. The last three years gliders have been used: over 4000 profiles have been collected, most to 1000 m (Fig. 1). The salinity and temperature at the depths of the LIW have been extracted from floats and gliders for the Eastern Levantine each year in order to be compared to the CYBO data. Fig. 1. Location map of standard Cyprus Oceanography hydrographic stations (zoom) and Cyprus glider fleet missions (2009-2012). Results from CYBO show a significant increase in LIW salinity and temperature from 39.0 to 39.15 and 15.4 to 16.0 deg, around 2009 (Fig. 2).The glider data (connected symbols) also show higher salinity and temperature in recent years, in agreement with CYBO. Maps of salinity at 200 m (Fig. 2) from floats also indicate a sudden change in LIW salinity around 2009, with the years before and after not exhibiting large-scale changes.These results could indicate a change is taking place on the fresh water budget of the Mediterranean. Besides the slow changes over the last century because of the damming of major rivers, it could be that different sites for LIW formation are favored in recent years. The geographic extent outside the eastern Levantine is not yet known, nor is the mechanism for this change. Further analysis of the in situ data, as well as model re-analyses will shed light on the mechanisms at work. Fig. 2. Time series of salinity (a) and temperature (b) at 250 m depth from cruises and from glider missions (lines) with +/- standard deviation. Profiling float values of salinity at 200 m for March 2006-2007 (c) and March 2009-2010 (d). References 1 - Lascaratos, A., and Nittis, K., 1998. A High-resolution Three-dimensional Numerical Study of Intermediate Water Formation in the Levantine Sea. J. Geophys. Res. 103, no. C9: 18497–18511. 2 - Lascaratos, A., Williams, R. G., and Tragou, E., 1993. A Mixed-layer Study of the Formation of Levantine Intermediate Water. J. of Geophys. Res. 98, no. 8: 14739–14749. 3 - Poulain, P.-M., Barbanti, R., Font, J., Cruzado, A., Millot, C., Gertman, I., Griffa, A., Molcard, A., Rupolo, V., Le Bras, S., and Petit de la Villeon, L., 2007. MedArgo: a drifting profiler program in the Mediterranean Sea. Ocean Sci., 3, 379-395. 212 Rapp. Comm. int. Mer Médit., 40, 2013 Powered by TCPDF (www.tcpdf.org) 1 / 1