1. ETESIAN WINDS AND COASTAL UPWELLING OVER THE NE AEGEAN SEA: MONITORING AND MODELING Yannis Androulidakis 1, Yannis Krestenitis 1, Villy Kourafalou 2 1.Laboratory of Maritime Engineering and Maritime Works, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 2. University of Miami / RSMAS, 4600 Rickenbacker Cswy. Miami, FL 33149 (iandroulidakis@rsmas.miami.edu; ynkrest@cvil.auth.gr; vkourafalou@rsmas.miami.edu)iandroulidakis@rsmas.miami.eduynkrest@cvil.auth.grvkourafalou@rsmas.miami.edu General Information Detection of upwelling events This research has been co ‐ financed by the European Union (European Social Fund–ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) ‐ Research Funding Program: THALES. Investing in knowledge society through the European Social Fund Lateral intrusions (LW) Implementation of North Aegean Hybrid Circulation Ocean Model (NAS-HYCOM; Androulidakis & Kourafalou, 2011) Model Domain – N. Aegean 1/50 o (2.2 km) 20 vertical hybrid layers Transformation of the vertical coordinates between isopycnal, sigma and cartesian Simulations 2002-2008 & 2013-2014 Parameterizations of BSW through the Dardanelles Straits Atmospheric forcing 2013-2014 (WRF-ARW V3.2.0 1/20 o x1/20 o ) Atmospheric forcing 2002-2008 (SKIRON 1/10 o x 1/10 o ) The oligotrophic Aegean Sea receives nutrients through upwelling and through the input of the fresher Black Sea Waters (BSW; Androulidakis et al., 2012a). Here we examine the interplay between these physical mechanisms over the North Aegean Sea, and the impact of the upwelling-favorable northerly winds (Etesian). The prevailing northerly winds influence especially the eastern coastal area and form a strong front due to occurring upwelling waters. Realistic mathematical simulations with Hybrid Circulation Ocean Model in tandem with measurements are used to investigate the impact of lateral inputs such as the BSW and Levantine Waters (LW) originating from the South on the upwelling processes. The speed of the Etesian winds is correlated with the surface temperature of the northeastern coastal region, especially over areas out of the BSW impact. Several summer events showed that the temperature difference between the upwelled and the ambient waters is strongly related with the upwelling depth. Model Description The western Lesvos coastal region in one of the major upwelling areas of North Aegean Sea. These upwelling waters influence the physical and biological characteristics of the near field and broader central area. The upwelled waters may flow over a bigger area, at the west side of Lesvos Island and up to the Chios Basin. The upwelled, deep and cold waters, enriched with nutrients, move to the surface and enhance the biological activity, enriching the fish-productivity of the coastal waters Model evaluation 2002–2008 & 2013-2014 buoy measurements from L1 station (Poseidon system & AegeanMarTech project) Cruise measurements (R/V “AEGAIO”, HCMR) Comparison with satellite SST images (MODIS & MyOcean) Sea Surface Temperature (SST) mean monthly variability from Lesvos Poseidon System measurements and the respective NAS-HYCOM simulations for the L1 station during 2002-2008, without the seasonal cycle. Willmot score skill: Ws=0.8 (SST comparison) Pearson correlation coefficient: r c =0.7 (SST comparison) Low and high SST peaks are well simulated by NAS-HYCOM Upwellign events (e.g. summer 2008) are detected on both in situ and model time-series under northerly winds NAS-HYCOM SST time-series at L1, L2, L3, L4, L5 stations Satellite SST images (MODIS) NAS-HYCOM SST distributions Vertical distribution of temperature along S1 section during P1 and P2 periods Detection of 2 periods (P1 & P2) with prevailing strong northerly winds (L1 station) during 2002 Pearson Correlation Coefficient between (a) SST at L1 station and (b) northerly wind speed (m/s) for each July-August period from 2002 to 2008 Summer of 2014 SST time-series from in situ buoy from AegeanMarTech project (thales- aegeanmartech.hcmr.g) and NAS-HYCOM during 2014 summer periods High correlation (upwelling) Low correlation (no upwelling) Vertical sigma–theta σ θ (kg/m 3 ) distribution from R.V. ‘‘AEGAIO’’ (HCMR) and the NAS-HYCOM simulations for 06/09/2005 (gray curve) and for 03/04/2006 (black curve) in Skyros Basin (Androulidakis et al., 2012b). BSW signal Upwelling Androulidakis Y., Kourafalou V., (2011), “Evolution of a buoyant outflow in the presence of complex topography: The Dardanelles plume (North Aegean Sea)”, Journal of Geophysical Research, Vol. 116, doi: 10.1029/2010JC006316 Androulidakis Y., Krestenitis Y., Kourafalou V. (2012a), "Connectivity of North Aegean circulation to the Black Sea water budget", Continental Shelf Research. DOI:10.1016/j.csr.2012.08.019 Androulidakis Y. Kourafalou V., Krestenitis Y., Zervakis V. (2012b),“Variability of deep water mass characteristics in the North Aegean Sea: The role of lateral inputs and atmospheric conditions”, Deep Sea Research Part I, vol 67, pp 55-72 Conclusions The physical characteristics of the BSW and LW over the upper and middle Aegean layers may affect the upwelling processes and enhance or confine the phenomenon. NAS-HYCOM described adequately the upwelling processes in agreement with satellite and in situ measurements Strong correlation between the wind state and the temperature of the surface waters over the eastern coastal regions during summer months Relation between the strong northerly winds and the appearance of colder deep waters near the surface. All Pearson correlation coefficients between the summer northerly wind speed and the SST time-series are lower than -0.6. The lower correlation is calculated for summer 2006 where the significantly strong winds are not related with the SST values; no upwelling events were observed during this summer period. This is possibly related to the intrusion of more saline and warm Levantine waters that increased the sigma–theta of the south North Aegean region in 2006.