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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., METEOR-Berichte

Within a process study in the framework of the international GEOTRACES program and led by the Institute of Oceanology of the Polish Academy of Sciences (IOPAN) a two-week cruise on the R/V Oceania sailed in November 2011 to investigate the distribution of trace elements and their isotopes in the Baltic Sea. The scientific goals were particularly focused on compiling trace element budgets for the Baltic Sea including in- and outflow, as well as to investigate elemental behavior and isotopic fractionation associated with the redox gradients of the Baltic Sea water column and the permanently anoxic conditions within its deep basins (i.e. Gotland Deep, Landsort Deep). The Baltic Sea is a shallow, brackish inland sea with an average salinity of ~7 psu in the mixed layer. It is fed by the Bothnian Sea in the north, by the Finland Sea in the east, as well as by numerous rivers from Scandinavia and the Baltic states, and it is drained through the Danish Strait into the North Sea. In the opposite direction, a denser bottom water mass enters the Baltic Sea through deeper channels from the Danish Strait successively filling the deep basins northward. Below 130 m water depth, the water column is permanently anoxic. Here we present the first combined data set of Nd and Hf concentrations and isotopic compositions for the Baltic Sea. A total of 21 water samples (60L volume per sample) including two water column profiles from the deeper basins were filtered (0.45 μm) and Nd and Hf were extracted and analysed following the accepted GEOTRACES protocols. The distribution patterns of the two elements and their isotopic compositions are compared to hydrographic data and oxygen measurements and provide information on sources and mixing of water masses, as well as on exchange processes with the underlying sediments, which are influenced by the prevailing redox gradients.

The radiogenic isotope systems of neodymium (Nd), strontium (Sr) and lead (Pb) have been used in numerous studies throughout the last decades to investigate water mass circulations of the past and present oceans, and to trace changing contributions of detrital material from different source areas. Clay mineral assemblages and clay mineral ratios from the fine fraction of marine sediments have also been used to characterize endmember sources. This thesis focuses on a reconstruction of the late Quaternary hydrographic variability of the flow path of the Mediterranean Outflow Water (MOW) and the changing weathering contributions of the detrital clay‐size fraction to the SW Iberian shelf. Mediterranean Outflow Water is characterized by higher temperatures and salinities than other ambient water masses. MOW spreads at water depths between 500 and 1500 m from the Strait of Gibraltar into the eastern North Atlantic and has been a source of salinity for the Atlantic Meridional Overturning Circulation in the North Atlantic. In order to evaluate the hydrographic changes of MOW since the Last Glacial Maximum (LGM) high‐resolution Nd and Pb isotope records of past ambient seawater obtained from authigenic ferromanganese oxyhydroxide coatings of bulk marine sediments from three gravity cores in the Gulf of Cadiz (577 m water depth) and along the Portuguese margin (1 745 m and 1 974 m water depth) were produced. The surface and downcore Nd isotope data from all water depths exhibit only a very small variability close to the present day composition of MOW but do not reflect the present day Nd isotopic stratification of the water column as determined from a nearby open ocean hydrographic station. In contrast, the Pb isotope records show significant and systematic variations, which provide evidence for a significantly different pattern of the MOW pathways between 20 000 and 12 000 years ago compared with the subsequent period of time. The assemblages of marine sediments on the SW Iberian shelf consist of the various regional particulate sources that comprise North African dust, river transported particles from the Iberian Peninsula and suspended particulate matter (SPM) carried by Mediterranean Outflow Water. It is noted that the relatively rapid, decadal scale Mediterranean overturning circulation permits mixing of suspended particles from the entire Mediterranean Sea. In order to reconstruct climate and circulation driven changes in the supply of sediments from these sources over the past ~23 000 years, radiogenic Nd, Sr and Pb isotope records from the clay‐size sediment fraction of the three core locations in the Gulf of Cadiz and along the Portuguese margin were produced. These records were supplemented by time series analyses of clay mineral abundances and clay mineral ratios from the same set of samples. Contrary to expectations, the transition from the LGM to the Holocene was not marked by very strong environmental changes but Heinrich stadial 1 and the African Humid Period (AHP; ~5500‐12000 B.P.) are reflected by significantly different isotopic records. Interestingly, the mineralogical time series vary significantly out‐of‐phase to the isotope records. This suggests that due to the sensitivity of clay formation to climate conditions, the clay mineral assemblages allow insights to the prevailing chemical weathering regime through time in addition to information about detrital source areas.

The radiogenic isotope systems of neodymium (Nd), strontium (Sr) and lead (Pb) have been used in numerous studies throughout the last decades to investigate water mass circulations of the past and present oceans, and to trace changing contributions of detrital material from different source areas. Clay mineral assemblages and clay mineral ratios from the fine fraction of marine sediments have also been used to characterize endmember sources. This thesis focuses on a reconstruction of the late Quaternary hydrographic variability of the flow path of the Mediterranean Outflow Water (MOW) and the changing weathering contributions of the detrital clay‐size fraction to the SW Iberian shelf. Mediterranean Outflow Water is characterized by higher temperatures and salinities than other ambient water masses. MOW spreads at water depths between 500 and 1500 m from the Strait of Gibraltar into the eastern North Atlantic and has been a source of salinity for the Atlantic Meridional Overturning Circulation in the North Atlantic. In order to evaluate the hydrographic changes of MOW since the Last Glacial Maximum (LGM) high‐resolution Nd and Pb isotope records of past ambient seawater obtained from authigenic ferromanganese oxyhydroxide coatings of bulk marine sediments from three gravity cores in the Gulf of Cadiz (577 m water depth) and along the Portuguese margin (1 745 m and 1 974 m water depth) were produced. The surface and downcore Nd isotope data from all water depths exhibit only a very small variability close to the present day composition of MOW but do not reflect the present day Nd isotopic stratification of the water column as determined from a nearby open ocean hydrographic station. In contrast, the Pb isotope records show significant and systematic variations, which provide evidence for a significantly different pattern of the MOW pathways between 20 000 and 12 000 years ago compared with the subsequent period of time. The assemblages of marine sediments on the SW Iberian shelf consist of the various regional particulate sources that comprise North African dust, river transported particles from the Iberian Peninsula and suspended particulate matter (SPM) carried by Mediterranean Outflow Water. It is noted that the relatively rapid, decadal scale Mediterranean overturning circulation permits mixing of suspended particles from the entire Mediterranean Sea. In order to reconstruct climate and circulation driven changes in the supply of sediments from these sources over the past ~23 000 years, radiogenic Nd, Sr and Pb isotope records from the clay‐size sediment fraction of the three core locations in the Gulf of Cadiz and along the Portuguese margin were produced. These records were supplemented by time series analyses of clay mineral abundances and clay mineral ratios from the same set of samples. Contrary to expectations, the transition from the LGM to the Holocene was not marked by very strong environmental changes but Heinrich stadial 1 and the African Humid Period (AHP; ~5500‐12000 B.P.) are reflected by significantly different isotopic records. Interestingly, the mineralogical time series vary significantly out‐of‐phase to the isotope records. This suggests that due to the sensitivity of clay formation to climate conditions, the clay mineral assemblages allow insights to the prevailing chemical weathering regime through time in addition to information about detrital source areas.

Mediterranean Outflow Water (MOW) is characterised by higher temperatures and salinities than other ambient water masses. MOW spreads at water depths between 500 and 1500 m into the eastern North Atlantic and has been a source of salinity for the Atlantic Meridional Overturning Circulation. We used high-resolution Nd and Pb isotope records of past ambient seawater obtained from authigenic ferromanganese coatings of sediments in three gravity cores at 577, 1745 and 1974 m water depths in the Gulf of Cadiz and along the Portuguese margin complemented by a selection of surface sediments to reconstruct the extent and pathways of MOW over the past 23 000 years. In addition, radiogenic Nd, Pb and Sr isotope ratios obtained from total digestion of the residual clay fraction of the leached samples were used to evaluate any changes in the endmember compositions. The surface and downcore seawater Nd isotope data from all water depths exhibit only a very small variability close to the present day composition of MOW but do not reflect the present day Nd isotopic stratification of the water column as determined from a nearby open ocean hydrographic station, which is most likely the consequence of downslope sediment transport in the nepheloid boundary layer as well as the small variations in the Nd endmember compositions. In contrast, the seawater Pb isotope records show significant and systematic variations, which provide evidence for a significantly different pattern of the MOW pathways between 20 000 and 12 000 years ago compared with the subsequent period of time. A deeper situated MOW during the Last Glacial Maximum (LGM) raised during the early deglaciation with its shallowest position around Heinrich event H1, followed by a moderate deepening and the establishment of present-day MOW hydrography. The radiogenic isotope signatures of the residual clay fractions document a pulse of sediment input from the north during Heinrich event H1 around 14.8 ka, but other than that exhibit little varibility over time suggesting surprisingly constant sedimentary endmember compositions and mixing ratios since the LGM.