Description: Seawater-derived neodymium (Nd) isotope ratios of sediment coatings have increasingly been used in paleoceanographic reconstructions to derive information on the past variability of deepwater sources and mixing. Dissolved Nd in seawater originates from weathering processes of the continental crust. It is delivered to the oceans either through boundary exchange processes or in dissolved or particulate form through riverine input (Frank, 2002). The use of radiogenic Nd isotopes as oceanic tracers is enabled by the average ocean residence time of Nd, which is similar to the global mixing time of oceans (ca 400 – 2,000 years) and by their independence of stable isotope fractionation by biological or physical processes (van de Flierdt et al., 2006). In this study, we investigate Nd isotope ratios of both core-top and Holocene sediment samples (leachates and detritus) and compare them to modern seawater Nd isotope signatures in the eastern Fram Strait, as well as to a multitude of proxy indicators for the climatic and oceanographic variability in the eastern Fram Strait during the past 8,500 years. The West Spitsbergen Current (WSC) represents the major means of northward heat transport to the Arctic Ocean via eastern Fram Strait. While the upper layers of the WSC are fed by warm and saline Atlantic Water derived from the North Atlantic Current, deepwater inflow through eastern Fram Strait is still subject of debate. Our study is primarily intended to reconstruct Holocene variability of bottom water sources in the Arctic Gateway. However, relatively radiogenic Nd isotope ratios of the leached fraction since the late Holocene suggest a contribution of fine lithic grains transported by sediment-laden sea ice from the East Siberian shelves to the Fram Strait (Dethleff and Kuhlmann, 2009). This is in contrast to the less radiogenic Nd isotope ratios of present-day intermediate and deep water in the area documenting an Atlantic source. We therefore suggest an alternative explanation, which is input and transport of sediment material with preformed sediment coatings from source areas on the Siberian shelf to the Central Arctic and the eastern Fram Strait. The eastern Fram Strait has been the bottleneck of Arctic sea ice export and main ablation area for ice-transported (fine-grained) material since approximately 5 cal ka BP. References Dethleff, D. and Kuhlmann, G., 2009. Entrainment and export of fine-grained surface deposits into new ice in the southwestern Kara Sea, Siberian Arctic. Continental Shelf Research, 29, 691-701. Frank, M., 2002. Radiogenic Isotopes: Tracers of Past Ocean Circulation and Erosional Input. Reviews of Geophysics, 40, 1001, 10.1029/2000RG000094. Van de Flierdt, T., Robinson, L.F., Adkins, J.F. and Hemming, S.R., 2006. Temporal stability of the neodymium isotope signature of the Holocene to glacial North Atlantic. Paleoceanography, 21, PA4102

Description: The scientific objectives of METEOR cruise M84/5 focused on the measurement and analysis of the environmental controls of modern and fossil cold-water coral growth along a transect in the Bay of Biscay. In four working areas we successfully deployed lander systems and CTD/Ro’s to document the physical and hydrochemical characteristics of bottom water masses and the water column in general. These are used to shed light on potential linkages to modern cold-water coral growth and distribution. These investigations were flanked by plankton tows in surface waters. The base for all investigations was a thorough hydroacoustic survey to characterize potential cold-water coral bearing areas with living colonies. Based on these maps we deployed all video-guided gear such as the OFOS-video sled, the TV grab, and the lander systems. Benthic assemblages and sedimentary structures have been documented and sampled with the OFOS and a box corer. Simultaneously, genetic samples of the living coral material were taken for additional studies. Furthermore, we have taken gravity cores to investigate the paleoceanographic conditions as well as the timing of cold-water coral colonization in the Bay of Biscay. Along with the coring efforts, a detailed sampling and study of porewater properties was performed. An additional aim of this cruise was to investigate the influence of boundary exchange processes on the Neodymium isotopy in bottom waters along the pathway of the Mediterranean Outflow water (MOW) by taking multiple samples with the CTD/Ro. The new data and samples of this METEOR cruise will provide the framework to investigate the timing of cold-water coral colonization in the Bay of Biscay, as well as its interplay with the ambient hydrography and geochemistry. This successful cruise has provided the basis to investigate the scientific aims of this expedition in great detail.

Description: Summary Meteor Cruise M81/1 was dedicated to the investigation of the distribution of dissolved and particulate trace metals and their isotopic compositions (TEIs) in the full water column of the tropical Atlantic Ocean and their driving factors including main external inputs and internal cycling and ocean circulation. The research program is embedded in the international GEOTRACES program (e.g. Henderson et al., 2007), which this cruise was an official part of and thus corresponds to GEOTRACES cruise GA11. This cruise was completely dedicated to the trace metal clean and contamination-free sampling of waters and particulates for subsequent analyses of the TEIs in the home laboratories of the national and international participants. Besides a standard rosette for the less contaminant prone metals, trace metal clean sampling was realized by using a dedicated and coated trace metal clean rosette equipped with Teflon-coated GO-FLO bottles operated via a polyester coated cable from a mobile winch that was thankfully made available by the U.S. partners of the GEOTRACES program for this cruise. The particulate samples were also collected under trace metal clean conditions using established in-situ pump systems. The cruise track led the cruise southward from the Canary Islands to 11°S and then continued northwestward along the northern margin of South America until it reached Port of Spain, Trinidad & Tobago. The track crossed areas of major external inputs including exchange with the volcanic Canary Islands, the Saharan dust plume, as well as the plume of the Amazon outflow. In terms of internal cycling the equatorial high biological productivity band, as well as increased productivity associated with the Amazon Plume were covered. All major water masses contributing the Atlantic Meridional Overturning Circulation, as well as the distinct narrow equatorial surface and subsurface east-west current bands were sampled. A total of 17 deep stations were sampled for the different dissolved TEIs, which were in most cases accompanied by particulate sampling. In addition, surface waters were continuously sampled under trace metal clean conditions using a towed fish.