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Project OC1 – Mediterranean climate variability documented in oxygen isotope records from northern Red Sea corals
T. Felis, N. Rimbu, G. Lohmann, J. Pätzold
Annually banded reef corals from the northern Red Sea provide a high-resolution archive of past climate variations at the southeastern rim of the Mediterranean basin. Subseasonally resolved oxygen isotope records derived from the carbonate skeletons of these massive colonies robustly document seasonality and interannual to decadal climate variability. These proxy records of climate, supported by analyses of instrumental data and model simulations, reveal the prominent role of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) in controlling eastern Mediterranean/Middle East climate on seasonal, interannual to decadal and orbital timescales, most pronounced during winter. Variability at interannual periods of 5-6 yr evident in the coral records is indicative of AO/NAO-like atmospheric variability over the Northern Hemisphere and its influence on eastern Mediterranean/Middle East climate during the last centuries, the late Holocene and the last interglacial period. The coral oxygen isotope records, which are recording temperature and surface evaporation in the northern Red Sea, are linked via AO/NAO-controlled atmospheric circulation changes to variations in temperature and precipitation throughout the Mediterranean and Middle East region. Whereas the entire eastern Mediterranean/Middle East region experiences colder winters during the high-index state of the AO/NAO, the resulting changes in hydrologic balance have a more complex spatial pattern. More arid conditions in the northern Red Sea are accompanied by drier winters in the northeastern Mediterranean but by wetter winters along the southeastern rim of the Mediterranean Sea. This observation may raise difficulties for proxy-based reconstructions of eastern Mediterranean precipitation from the Levant, which is located in the transition zone between positive and negative precipitation anomalies. Compared to the AO/NAO, the atmospheric teleconnections of the El Niño-Southern Oscillation (ENSO) on eastern Mediterranean/Middle East climate, which are modulated by higher-latitude atmospheric circulation over the North Pacific-North Atlantic region, are weaker and non-stationary.
Figure 1: Correlation maps for the winter coral δ18O record from Ras Umm Sidd in the northern Red Sea (indicated by the red dot) and temperature (left) and precipitation fields (right) over land for January-February (1901–1995). During the AO/NAO high-index state, colder/more arid conditions in the northern Red Sea as inferred from coral δ18O are accompanied by colder conditions throughout the eastern Mediterranean/Middle East, as well as by drier conditions in the northeastern Mediterranean but by wetter conditions along the southeastern rim of the Mediterranean Sea. Correlations of r = 0.2 and higher are significant at the 95% confidence level. Modified from Rimbu et al. (2006) and Felis & Rimbu (2010). Coral data are from Felis et al. (2000). Temperature and precipitation data are from Mitchell and Jones (2005).
Publications
Felis, T, Rimbu, N (2010) Mediterranean climate variability documented in oxygen isotope records from northern Red Sea corals - A review. Global and Planetary Change, 71, 232-241 Reprint
Rimbu, N, Felis, T, Lohmann, G, Pätzold, J (2006) Winter and summer climate patterns in the European-Middle East during recent centuries as documented in a northern Red Sea coral record. The Holocene, 16, 321-330 Reprint