Two different paradigms of the Mediterranean Oscillation (MO) teleconnection index have been compared in this work: station-based definitions obtained by the difference of some climate variable between two selected points in the eastern and western basins (i.e., Algiers and Cairo, Gibraltar and Israel, Marseille and Jerusalem, or south France and Levantine basin) and the principal component (PC) approach in which the index is obtained as the time series of the first mode of normalised sea level pressure anomalies across the extended Mediterranean region. Interannual to interdecadal precipitation ( ), evaporation ( ), - , and net heat flux have been correlated with the different MO indices to compare their relative importance in the long-term variability of heat and freshwater budgets over the Mediterranean Sea. On an annual basis, the PC paradigm is the most effective tool to assess the effect of the large-scale atmospheric forcing in the Mediterranean Sea because the station-based indices exhibit a very poor correlation with all climatic variables and only influence a reduced fraction of the basin. In winter, the station-based indices highly improve their ability to represent the atmospheric forcing and results are fairly independent of the paradigm used. 1. Introduction The Mediterranean Sea (Figure 1(a)), a semi-enclosed basin that extends over 3000？km in longitude and over 1500？km in latitude with an area of ？m2, communicates with the Atlantic Ocean through the Strait of Gibraltar and with the Black Sea through the Turkish Bosphorus and Dardanelles Straits. An Atlantic inflow through the Strait of Gibraltar is necessary to balance the freshwater and salt budgets since evaporative losses ( ) are not balanced by precipitation ( ) and river runoff ( ). The circulation in the Mediterranean Sea is influenced to a large extent by the heat and freshwater air-sea exchanges which depend on the meteorological and oceanic conditions [1] and they also play a key role in dense water formation and hence in the Mediterranean Thermohaline Circulation [2]. As a consequence, they affect the characteristics of the Mediterranean water masses and then may potentially influence the Atlantic Ocean circulation via changes in the properties of the Mediterranean Outflow [2–5]. For these reasons, the improvement of our knowledge of heat and water budgets and their long-term variability is a challenge for the scientific community of the Mediterranean region and is thought to be crucial to understand the Mediterranean circulation and climate and their evolution under climate
References
[1]
M. Tsimplis, V. Zervakis, S. A. Josey, et al., “Changes in the oceanography of the Mediterranean Sea and their link to climate variability,” in Mediterranean Climate Variability Amsterdam, the Netherlands, P. Lionello, P. Malanotte-Rizzoli, and R. Boscolo, Eds., vol. 4 of Developments in Earth and Environmental Sciences, pp. 227–282, Elsevier, 2006.
[2]
J.-P. Béthoux, B. Gentili, and D. Tailliez, “Warming and freshwater budget change in the Mediterranean since the 1940s, their possible relation to the greenhouse effect,” Geophysical Research Letters, vol. 25, no. 7, pp. 1023–1026, 1998.
[3]
R. A. Potter and M. S. Lozier, “On the warming and salinification of the Mediterranean outflow waters in the North Atlantic,” Geophysical Research Letters, vol. 31, no. 1, Article ID L01202, 2004.
[4]
V. Artale, S. Calmanti, P. Malanotte-Rizzoli, G. Pisacane, V. Rupolo, and M. Tsimplis, “The Atlantic and the Mediterranean Sea as connected systems,” in Mediterranean Climate VariabilityAmsterdam, the Netherlands, P. Lionello, P. Malanotte-Rizzoli, and R. Boscolo, Eds., vol. 4 of Developments in Earth and Environmental Sciences, pp. 283–323, Elsevier, 2006.
[5]
C. Millot, J. Candela, J.-L. Fuda, and Y. Tber, “Large warming and salinification of the Mediterranean outflow due to changes in its composition,” Deep-Sea Research, vol. 53, no. 4, pp. 656–666, 2006.
[6]
G. T. Walker and W. E. Bliss, “World weather V. Memories of the royal meteorological,” Society, vol. 44, pp. 53–84, 1932.
[7]
H. van Loon and J. C. Rogers, “The see-saw of winter temperatures between Greenland and northern Europe. Part I: general descriptions,” Monthly Weather Review, vol. 106, pp. 296–310, 1978.
[8]
A. G. Barnston and R. E. Livezey, “Classification, seasonality and persistence of low-frequency atmospheric circulation patterns,” Monthly Weather Review, vol. 115, no. 6, pp. 1083–1126, 1987.
[9]
J. W. Hurrell, Y. Kushnir, G. Ottersen, and M. Visbeck, The North Atlantic Oscillation: Climate Significance and Environmental Impact, vol. 134 of Geophysical Monograph Series, 2003.
[10]
S. A. Josey, S. Somot, and M. Tsimplis, “Impacts of atmospheric modes of variability on Mediterranean Sea surface heat exchange,” Journal of Geophysical Research C, vol. 116, no. 2, Article ID C02032, 2011.
[11]
V. P. Papadopoulos, H. Kontoyiannis, S. Ruiz, and N. Zarokanellos, “Influence of atmospheric circulation on turbulent air-sea heat fluxes over the Mediterranean Sea during winter,” Journal of Geophysical Research C, vol. 117, no. 3, Article ID C03044, 2012.
[12]
V. Papadopoulos, S. Josey, A. Bartzokas, S. Somot, S. Ruiz, and P. Drakopoulou, “Large-scale atmospheric circulation favoring deep –and intermediate- water formation in the Mediterranean Sea,” Journal of Climate, vol. 25, pp. 6079–6091, 2012.
[13]
H. Kutiel and Y. Benaroch, “North Sea-Caspian pattern (NCP)—an upper level atmospheric teleconnection affecting the Eastern Mediterranean: identification and definition,” Theoretical and Applied Climatology, vol. 71, no. 1-2, pp. 17–28, 2002.
[14]
H. Kutiel, P. Maheras, M. Türke？, and S. Paz, “North Sea - Caspian Pattern (NCP)—an upper level atmospheric teleconnection affecting the eastern Mediterranean—implications on the regional climate,” Theoretical and Applied Climatology, vol. 72, no. 3-4, pp. 173–192, 2002.
[15]
M. Gündüz and E. ？zsoy, “Effects of the North Sea Caspian pattern on surface fluxes of Euro-Asian-Mediterranean seas,” Geophysical Research Letters, vol. 32, Article ID L21701, 2005.
[16]
M. Brunetti and H. Kutiel, “The relevance of the North-Sea Caspian Pattern (NCP) in explaining temperature variability in Europe and the Mediterranean,” Natural Hazards and Earth System Science, vol. 11, no. 10, pp. 2881–2888, 2011.
[17]
M. Conte, A. Giuffrida, and S. Tedesco, “The Mediterranean Oscillation, impact on precipitation and hydrology in Italy,” in Conference on Climate Water, pp. 121–137, Publications of the Academy of Finland, Helsinki, 1989.
[18]
H. Kutiel, P. Maheras, and S. Guika, “Circulation indices over the Mediterranean and Europe and their relationship with rainfall conditions across the Mediterranean,” Theoretical and Applied Climatology, vol. 54, no. 3-4, pp. 125–138, 1996.
[19]
P. Maheras, E. Xoplaki, and H. Kutiel, “Wet and dry monthly anomalies across the Mediterranean basin and their relationship with circulation, 1860–1990,” Theoretical and Applied Climatology, vol. 64, no. 3-4, pp. 189–199, 1999.
[20]
N. Supi？, B. Grbec, I. Vilibi？, and I. Ivan？i？, “Long-term changes in hydrographic conditions in northern Adriatic and its relationship to hydrological and atmospheric processes,” Annales Geophysicae, vol. 22, no. 3, pp. 733–745, 2004.
[21]
J. Jacobeit, S. Seubert, and A. Dünkeloh, “Links of the Mediterranean Oscillation to mid-latitude and tropical climate dynamics,” Proceedings of the 2nd ESF MedCLIVAR Workshop: Connection between Mediterranean and Global Climate Variability, Toulon, France, 2007, http://www.medclivar.eu/workshop_2.html.
[22]
T. T？rnros, “On the relationship between the Mediterranean Oscillation and winter precipitation in the Southern Levant,” Atmospheric Science Letters, vol. 14, no. 4, pp. 287–293, 2013.
[23]
J. P. Palutikof, “Analysis of Mediterranean climate data: measured and modelled,” in Mediterranean Climate: Variability and Trends, H. J. Bolle, Ed., Springer, Berlin, Germany, 2003.
[24]
M. Brunetti, M. Maugeri, and T. Nanni, “Atmospheric circulation and precipitation in Italy for the last 50 years,” International Journal of Climatology, vol. 22, no. 12, pp. 1455–1471, 2002.
[25]
K. Suselj and K. Bergant, Mediterranean Oscillation Index, Geophysical Research Abstracts 8, 02145 European Geosciences Union, 2006.
[26]
D. Gomis, M. N. Tsimplis, B. Martín-Míguez, A. W. Ratsimandresy, J. García-Lafuente, and S. A. Josey, “Mediterranean Sea level and barotropic flow through the Strait of Gibraltar for the period 1958–2001 and reconstructed since 1659,” Journal of Geophysical Research C, vol. 111, no. 11, Article ID C11005, 2006.
[27]
E. Kalnay, M. Kanamitsu, R. Kistler et al., “The NCEP/NCAR 40-year reanalysis project,” Bulletin of the American Meteorological Society, vol. 77, no. 3, pp. 437–471, 1996.
[28]
D. Pettenuzzo, W. G. Large, and N. Pinardi, “On the corrections of ERA-40 surface flux products consistent with the Mediterranean heat and water budgets and the connection between basin surface total heat flux and NAO,” Journal of Geophysical Research C, vol. 115, no. 6, Article ID C06022, 2010.
[29]
J. W. Hurrell, “Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation,” Science, vol. 269, no. 5224, pp. 676–679, 1995.
[30]
F. Criado-Aldeanueva, F. J. Soto-Navarro, and J. García-Lafuente, “Seasonal and interannual variability of surface heat and freshwater fluxes in the Mediterranean Sea: budgets and exchange through the Strait of Gibraltar,” International Journal of Climatology, vol. 32, no. 2, pp. 286–302, 2012.
[31]
S. A. Josey, “Changes in the heat and freshwater forcing of the eastern Mediterranean and their influence on deep water formation,” Journal of Geophysical Research C, vol. 108, no. 7, 2003.
[32]
K. Schroeder, S. A. Josey, M. Herrmann, L. Grignon, G. P. Gasparini, and H. L. Bryden, “Abrupt warming and salting of the Western Mediterranean Deep Water after 2005: atmospheric forcings and lateral advection,” Journal of Geophysical Research C, vol. 115, no. 8, Article ID C08029, 2010.
[33]
M. Herrmann, F. Sevault, J. Beuvier, and S. Somot, “What induced the exceptional 2005 convection event in the northwestern Mediterranean basin? Answers from a modeling study,” Journal of Geophysical Research C, vol. 115, no. 12, Article ID C12051, 2010.
[34]
K. E. Trenberth, “Signal versus noise in the Southern Oscillation,” Monthly Weather Review, vol. 112, no. 2, pp. 326–332, 1984.
[35]
J. W. Hurrell and H. Van Loon, “Decadal variations in climate associated with the North Atlantic oscillation,” Climatic Change, vol. 36, no. 3-4, pp. 301–326, 1997.
