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.

Description: Abstract ID: 11526 PosterID: A0020 We are focused on determining the total concentrations of the anthropogenic radionuclides 239Pu, 240Pu, 237Np, and 137Cs in depth profiles from 2010 Atlantic GEOTRACES sections. Data from the equatorial region (A11) compared to GEOSECS data indicate water column inventories of 137Cs have increased over the last 40 years, while those of Pu are variable. By comparison, Pu and 237Np water column inventories are similar to regional soil core inventories, whereas 137Cs inventories are significantly higher, further suggesting continued supply of 137Cs to the open ocean. Water column 240Pu/239Pu inventory ratios are indicative of global fallout (~0.18). Deviations of the water column 237Np/239Pu inventory ratio from the average global fallout value (~0.48) can be used to estimate Pu-particulate fluxes, which are comparable to sediment trap data and may be used to assess scavenging at different locations along the cruise track. Data from mid and high latitude regions (A02) will be compare them to GEOSECS data; inventories and ratios will be used to identify additional contaminant sources, as water mass tracers, and to elucidate important processes such as scavenging and remineralization.