Climatic variability during the last  90 ka of the southern and northern Levantine Basin as evident from marine records and speleothems |
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| Authors: | Ahuva Almogi-Labin Miryam Bar-Matthews Dan Shriki Elina Kolosovsky Martine Paterne Bettina Schilman Avner Ayalon Zeev Aizenshtat Alan Matthews |
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| Institution: | aGeological Survey of Israel, 30 Malchei Yisrael St., Jerusalem 95501, Israel;bEarth-Sciences Institute, Hebrew University, Jerusalem 91904, Israel;cInstitute of Chemistry, Hebrew University, Jerusalem 91904, Israel;dLSCE -CNRS-CEA Avenue de la Terrasse 91198 Gif sur Yvette, France |
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| Abstract: | The influence of the northern Atlantic and tropical monsoonal systems, as recorded by the River Nile, on the climate variability of the southeastern Mediterranean was studied in two cores taken by the R/V Marion Dufresne: one core taken SE of Cyprus representing the northern Levantine Basin (core 9501, 980 m water depth) and the other located ˜380 km further south, represents the southeastern Levantine Basin in an area influenced by the River Nile plume (core 9509, 884 m water depth). The study was performed at relatively high resolution using several proxies: δ18O of Globigerinoides ruber, sediment characteristics and index colour parameters in core sections representing the last 86 ka. A low-resolution alkenone sea surface temperature record was also measured. The time frame in both cores was mostly constrained by ‘wiggle’ matching with the nearby well-dated δ18O and δ13C record of the Soreq Cave, which is mainly influenced by the eastern Mediterranean water vapor. The sedimentary record of the southern core is strongly influenced by the River Nile contribution throughout the last 86 ka, as evidenced by the higher sedimentation rates compared with the northern core (20 cm/ka vs. 5 cm/ka), continuously darker sediment colour, and higher TOC values (0.6–0.9 vs. 0.25 wt% not including sapropels). During sapropels S1 and S3, present in both cores, the influence of the River Nile became more widespread, reaching as far as Cyprus. Yet, the influence of the River Nile remained stronger in the south, as evident by the higher TOC values in the southern core throughout the entire 90 ka period and the longer duration of S1 in the southern core. An anomalous low δ18O interval that is not recorded in western Mediterranean occurred between 58 and 49 ka in the Levantine Basin and is more developed in the northern core. This period correlates with D-O interstadial 14 and maximum northern hemisphere insolation during the lastglacial cycle, suggesting that the warming mainly impacted the northern Levant.The Eastern Mediterranean Sea and land area was considerably warmer than the western Mediterranean throughout the LGM – Holocene transition, and the δ18OG. ruber drop of 4.5‰ is significantly greater than the 3‰ shift found for the western Mediterranean δ18OG. bulloides, both differences reflecting an increased continental effect from the western to eastern Mediterranean. Comparison between the marine and the land δ18O records suggests that the origin of rain over the land is composed of mixed signal from the southern and northern Levantine Basin. The study of Δδ18Osea–land variations demonstrates that various factors have influenced the sea–land relationship during the last 90 ka. The ‘amount effect’ has an important influence on rainfall δ18O during interglacial periods (particularly sapropel periods), whereas during glacial periods, increased land distances and elevation differences arising from decrease in sea level may have brought about decrease in δ18O of rainfall due to Rayleigh distillation processes. These influences were superimposed on those of sea surface water δ18O changes brought about by continental ice melting, and the strong effects felt in the southern Levantine Basin of the high River Nile input during periods of enhanced monsoonal activity. |
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