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Modeling studies predict that changes in radiocarbon (C-14) reservoir ages of surface waters during the last deglacial episode will reflect changes in both atmospheric C-14 concentration and ocean circulation including the Atlantic Meridional Overturning Circulation. Tests of these models require the availability of accurate C-14 reservoir ages in well-dated late Quaternary time series. We here test two models using plateau-tuned C-14 time series in multiple well-placed sediment core age-depth sequences throughout the lower latitudes of the Atlantic Ocean. C-14 age plateau tuning in glacial and deglacial sequences provides accurate calendar year ages that differ by as much as 500-2500years from those based on assumed global reservoir ages around 400years. This study demonstrates increases in local Atlantic surface reservoir ages of up to 1000years during the Last Glacial Maximum, ages that reflect stronger trades off Benguela and summer winds off southern Brazil. By contrast, surface water reservoir ages remained close to zero in the Cariaco Basin in the southern Caribbean due to lagoon-style isolation and persistently strong atmospheric CO2 exchange. Later, during the early deglacial (16ka) reservoir ages decreased to a minimum of 170-420 (14)Cyears throughout the South Atlantic, likely in response to the rapid rise in atmospheric pCO(2) and Antarctic temperatures occurring then. Changes in magnitude and geographic distribution of C-14 reservoir ages of peak glacial and deglacial surface waters deviate from the results of Franke et al. (2008) but are generally consistent with those of the more advanced ocean circulation model of Butzin et al. (2012).

The 14C reservoir age of ocean surface waters shows small-scale spatial and temporal variations. Accordingly, correct estimates of reservoir ages are crucial for any reconstruction of a precise radiocarbon-based chronology of marine sediments. To meet this target in the mid- and low- latitude Atlantic we obtained both 14C reservoir ages and an absolute age model for the glacial-to-deglacial sections of four marine sediment cores by means of the ‘14C Plateau Tuning Technique’. This method is independent of any common conversion scheme of 14C ages. The resulting empiric reservoir ages were compared with reservoir age estimates based on model simulations., Radiokarbon (14C) Reservoiralter mariner Oberflächenwässer zeichnen sich durch starke örtliche wie zeitliche Unterschiede aus. Folglich sind korrekte Angaben über Reservoiralter wesentlich, um mittels der Radiokarbonmethode ein exaktes Altersmodel für marine Sedimente zu erstellen. Die vorliegende Arbeit dient dem Versuch, erstmals durchgehende Zeitserien der planktischen Reservoiralter für die mittleren und niedrigen Breiten des Atlantiks bereit zu stellen, die den Zeitraum des letzten Hoch- und Deglazials abdecken. Dafür wurde die Methode des 14C-Plateau-Tunings an vier marinen Sedimentkernen eingesetzt, eine Technik, die nicht an die konventionellen Ansätze der Konversion von 14C-Altern in „Kalender-Alter “ gebunden ist. Durch sie erhält man einerseits ein absolutes Altersmodell, andererseits die den einzelnen Altern zugehörigen örtlichen 14C Reservoiralter. Diese empirischen Reservoiralter der Oberflächenwässer und die durch sie belegten Änderungen der Ozeanzirkulation wurden mit publizierten Ergebnissen aus Ozeanzirkulations-Modellen (OZM) verglichen. So konnte die Qualität der Modelldaten im Vergleich mit empirischen Daten direkt überprüft werden.

During RV Sonne-217 "MAJA" Cruise from Makassar (Indonesia) to Singapore from 25th July to 16th August 2011, we acquired Multibeam/Parasound-transects and deployed the shipboard CTD (with water sampler) as well as a multicorer and piston corer in three main working areas: 1) northern part of Makassar Strait, north of the Labani Channel including the Mahakam Delta and southernmost Celebes Sea; 2) central part of the Makassar Strait, south of the Labani Channel; and 3) southernmost part of the Makassar Strait including the Flores Sea and eastern Java Sea. The prime objective of the SO-217 MAJA cruise was to recover high resolution sediment archives to decipher the variability of the Indonesian Throughflow and to reconstruct regional climate history on decadal to millennial timescales over the past 150 000 years. To achieve this primary objective, 32 sediment and water stations were sampled along the Makassar Strait between the southern Celebes Sea, eastern Java Sea and eastern Flores Sea. The shipboard CTD including water sampler was deployed at 17 stations to obtain hydrographic profiles and sample the water column. The multicorer was deployed at 29 stations to obtain high quality sediment surface samples for core top calibrations. A total of 23 long piston cores with overall recovery of more than 350 m core length (26 m maximum core length, average core length over 15 m) provided high resolution sediment archives over the Holocene and the last two glacial cycles. All piston cores were measured for magnetic susceptibility in 2 cm intervals before being split into working and archive halves, the latter of which were described and measured for color reflectance in 1 cm ��� intervals. An initial shipboard stratigraphy was obtained by matching the magnetic susceptibility and lightness (L*) records with the stacked isotope record of Lisiecki and Raymo (2005). Prominent ash layers corresponding to the Tambora 1815 eruption and to earlier eruptions additionally provided invaluable stratigraphic marker beds for cross-correlation of piston cores recovered south of 5��S.