Beschreibung: The GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 22 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017.

Beschreibung: This study investigates the oceanic behavior of the lithogenic trace elements Al and Ti in the upper 200 m of the Atlantic Ocean. The distribution of both metals in the dissolved and particulate phases was assessed along an E-W transect in the eastern tropical North Atlantic (December 2009) and along a meridional Atlantic transect (April-May 2010). The surface water concentrations of particulate and dissolved Al and Ti reflected the previously observed pattern of atmospheric inputs into the Atlantic Ocean. Subsurface minima at stations with pronounced fluorescence maxima were observed, suggesting a link between biological productivity and the removal of both dissolved and particulate Al and Ti. This may include uptake mechanisms, adsorption and aggregation processes on biogenic particle surfaces and the formation of large, fast sinking biogenic particles, e.g., fecal pellets. Residence times in the upper water column (100 m) of the tropical and subtropical North Atlantic were estimated to range in the order of days to weeks in the particulate phases (Al: 3-22 days, Ti: 4-37 days) and were 0.9-3.8 years for Al and 10-31 years for Ti in the dissolved phases. Longer residence times in both phases in the South Atlantic are consistent with lower biological productivity and decreased removal rates. In the upper water column, Al was predominantly present in the dissolved form, whereas Ti mostly occurred in the particulate form. Largest deviations in the partition coefficients between the particulate and dissolved phases were found in the surface waters, together with excess dissolved Al over Ti compared to the crustal source. This likely reflects elevated dissolution of Al compared to Ti from atmospheric mineral particles

Beschreibung: The distribution and speciation of dissolved copper (Cu) was investigated in the Atlantic sector of the Southern Ocean in austral autumn of 2008 as part of the IPY GEOTRACES expedition ZERO & DRAKE. Distribution measurements focused on two transects across the major frontal systems along the Zero Meridian and across the Drake Passage whereas speciation work was investigated in the Drake Passage and the ice covered Weddell Sea. Along the two transects the dissolved Cu concentration exhibited a gradient in the surface with Cu values increasing poleward. Vertical profiles of Cu showed in general monotonic increases with depth, which correlated slightly with silicate but poorly with phosphate. Benthic sources of Cu were observed along the Zero Meridian transect and close to the Antarctic Peninsula for the Drake Passage. Dissolved Cu (DCu) appears to be removed from surface waters through adsorption/complexation by particulate matter. Speciation measurements on DCu indicated a relatively uniform distribution of 25-50nM of L2 (log K ~11.8) class ligands. No L1 class ligands (log K 〉13) were detected in any of the samples examined. Estimates of free Cu (pCu=13.5 to 12.5) showed only small variations in the upper water column and was generally uniform in deep waters. These findings indicate that there is insufficient free copper to account for the rapid reactivity of superoxide (O2 -) with Cu in these waters (Heller and Croot, 2010c) suggesting that the organic Cu complexes present in seawater can undergo rapid redox reactions.

Beschreibung: The first large-scale international intercomparison of analytical methods for the determination of dissolved iron in seawater was carried out between October 2000 and December 2002. The exercise was conducted as a rigorously "blind" comparison of 7 analytical techniques by 24 international laboratories. The comparison was based on a large volume (700 L), filtered surface seawater sample collected from the South Atlantic Ocean (the "IRONAGES" sample), which was acidified, mixed and bottled at sea. Two 1-L sample bottles were sent to each participant. Integrity and blindness were achieved by having the experiment designed and carried out by a small team, and overseen by an independent data manager. Storage, homogeneity and time-series stability experiments conducted over 2.5 years showed that inter-bottle variability of the IRONAGES sample was good (〈 7), although there was a decrease in iron concentration in the bottles over time (0.8-0.5 nM) before a stable value was observed. This raises questions over the suitability of sample acidification and storage. For the complete dataset of 45 results (after excluding 3 outliers not passing the screening criteria), the mean concentration of dissolved iron in the IRONAGES sample was 0.59 ± 0.21 nM, representing a coefficient of variation (CV) for analytical comparability ("community precision") of 36 (1s), a significant improvement over earlier exercises. Within-run precision (5-10), inter-run precision (15) and inter-bottle homogeneity (〈 7) were much better than overall analytical comparability, implying the presence of: (1) random variability (inherent to all intercomparison exercises); (2) errors in quantification of the analytical blank; and (3) systematic inter-method variability, perhaps related to secondary sample treatment (e.g. measurement of different physicochemical fractions of iron present in seawater) in the community dataset. By grouping all results for the same method, analyses performed using flow injection-luminol chemiluminescence (with FeII detection after sample reduction) Bowie, A.R., Achterberg, E.P., Mantoura, R.F.C., Worsfold, P.J., 1998. Determination of sub-nanomolar levels of iron in seawater using flow injection with chemiluminescence detection. Anal. Chim. Acta 361, 189-200 and flow injection-catalytic spectrophotometry (using the reagent DPD) Measures, C.I., Yuan, J., Resing, J.A., 1995. Determination of iron in seawater by flow injection analysis using in-line preconcentration and spectrophotometric detection. Mar. Chem. 50, 3-12 gave significantly (P = 0.05) higher dissolved iron concentrations than analyses performed using isotope dilution ICPMS Wu, J.F., Boyle, E.A., 1998. Determination of iron in seawater by high-resolution isotope dilution inductively coupled plasma mass spectrometry after Mg(OH) 2 co-precipitation. Anal. Chim. Acta 367, 183-191. There was, however, evidence of scatter within each method group (CV up to 59%), implying that better uniformity in procedures may be required. This paper does not identify individual data and should not be viewed as an evaluation of single laboratories. Rather it summarises the status of dissolved iron analysis in seawater by the international community at the start of the 21st century, and can be used to inform future exercises including the SAFE iron intercomparison study in the North Pacific in October 2004. © 2005 Elsevier B.V. All rights reserved.

Beschreibung: The first Southern Ocean Iron RElease Experiment (SOIREE) was performed during February 1999 in Antarctic waters south of Australia (61°S, 140°E), in order to verify whether iron supply controls the magnitude of phytoplankton production in this high nutrient low chlorophyll (HNLC) region. This paper describes iron distributions in the upper ocean during our 13-day site occupation, and presents a pelagic iron budget to account for the observed losses of dissolved and total iron from waters of the fertilised patch. Iron concentrations were measured underway during daily transects through the patch and in vertical profiles of the 65-m mixed layer. High internal consistency was noted between data obtained using contrasting sampling and analytical techniques. A pre-infusion survey confirmed the extremely low ambient dissolved (0.1 nM) and total (0.4 nM) iron concentrations. The initial enrichment elevated the dissolved iron concentration to 2.7 nM. Thereafter, dissolved iron was rapidly depleted inside the patch to 0.2-0.3 nM, necessitating three re-infusions. A distinct biological response was observed in iron-fertilised waters, relative to outside the patch, unequivocally confirming that iron limits phytoplankton growth rates and biomass at this site in summer. Our budget describing the fate of the added iron demonstrates that horizontal dispersion of fertilised waters (resulting in a quadrupling of the areal extent of the patch) and abiotic particle scavenging accounted for most of the decreases in iron concentrations inside the patch (31-58 and 12-49 of added iron, respectively). The magnitude of these loss processes altered towards the end of SOIREE, and on days 12-13 dissolved (1.1 nM) and total (2.3 nM) iron concentrations remained elevated compared to surrounding waters. At this time, the biogenic iron pool (0.1 nM) accounted for only 1-2 of the total added iron. Large pennate diatoms (〉 20 μm) and autotrophic flagellates (2-20 μm) were the dominant algal groups in the patch, taking up the added iron and representing 13 and 39 of the biogenic iron pool, respectively. Iron regeneration by grazers was tightly coupled to uptake by phytoplankton and bacteria, indicating that biological Fe cycling within the bloom was self-sustaining. A concurrent increase in the concentration of iron-binding ligands on days 11-12 probably retained dissolved iron within the mixed layer. Ocean colour satellite images in late March suggest that the bloom was still actively growing 42 days after the onset of SOIREE, and hence by inference that sufficient iron was maintained in the patch for this period to meet algal requirements. This raises fundamental questions regarding the biogeochemical cycling of iron in the Southern Ocean and, in particular, how bioavailable iron was retained in surface waters and/or within the biota to sustain algal growth. © 2001 Elsevier Science Ltd.

Beschreibung: Atmospheric iron and underway sea-surface dissolved (〈0.2 μm) iron (DFe) concentrations were investigated along a north-south transect in the eastern Atlantic Ocean (27°N/16°W-19°S/5°E). Fe concentrations in aerosols and dry deposition fluxes of soluble Fe were at least two orders of magnitude higher in the Saharan dust plume than at the equator or at the extreme south of the transect. A weaker source of atmospheric Fe was also observed in the South Atlantic, possibly originating in southern Africa via the north-easterly outflow of the Angolan plume. Estimations of total atmospheric deposition fluxes (dry plus wet) of soluble Fe suggested that wet deposition dominated in the intertropical convergence zone, due to the very high amount of precipitation and to the fact that a substantial part of Fe was delivered in dissolved form. On the other hand, dry deposition dominated in the other regions of the transect (73-97), where rainfall rates were much lower. Underway sea-surface DFe concentrations ranged 0.02-1.1 nM. Such low values (0.02 nM) are reported for the first time in the Atlantic Ocean and may be (co)-limiting for primary production. A significant correlation (Spearman's rho = 0.862, p〈0.01) was observed between mean DFe concentrations and total atmospheric deposition fluxes, confirming the importance of atmospheric deposition on the iron cycle in the Atlantic. Residence time of DFe in the surface waters relative to atmospheric inputs were estimated in the northern part of our study area (17 ± 8 to 28 ± 16 d). These values confirmed the rapid removal of Fe from the surface waters, possibly by colloidal aggregation. © 2003 Elsevier Ltd. All rights reserved.

Beschreibung: Vertical distributions of iron (Fe) concentrations and isotopes were determined in the total dissolvable and dissolved pools in the water column at three coastal stations located along the Peruvian margin, in the core of the Oxygen Minimum Zone (OMZ). The shallowest station 121 (161 m total water depth) was characterized by lithogenic input from the continental plateau, yielding concentrations as high as 456 nM in the total dissolvable pool. At the 2 other stations (stations 122 and 123), Fe concentrations of dissolved and total dissolvable pools exhibited maxima in both surface and deep layers. Fe isotopic composition (δ56Fe) showed a fractionation toward lighter values for both physical pools throughout the water column for all stations with minimum values observed for the surface layer (between −0.64 and −0.97‰ at 10–20 m depth) and deep layer (between −0.03 and −1.25‰ at 160–300 m depth). An Fe isotope budget was established to determine the isotopic composition of the particulate pool. We observed a range of δ56Fe values for particulate Fe from +0.02 to −0.87‰, with lightest values obtained at water depth above 50 m. Such light values in the both particulate and dissolved pools suggest sources other than atmospheric dust deposition in the surface ocean, including lateral transport of isotopically light Fe. Samples collected at station 122 closest to the sediment show the lightest isotope composition in the dissolved and the particulate pools (−1.25 and −0.53‰ respectively) and high Fe(II) concentrations (14.2 ± 2.1 nM) consistent with a major reductive benthic Fe sources that is transferred to the ocean water column. A simple isotopic model is proposed to link the extent of Fe(II) oxidation and the Fe isotope composition of both particulate and dissolved Fe pools. This study demonstrates that Fe isotopic composition in OMZ regions is not only affected by the relative contribution of reductive and non-reductive shelf sediment input but also by seawater-column processes during the transport and oxidation of Fe from the source region to open seawater.

Beschreibung: Dangerous climate change is best avoided by drastically and rapidly reducing greenhouse gas emissions. Nevertheless, geoengineering options are receiving attention on the basis that additional approaches may also be necessary. Here we review the state of knowledge on large-scale ocean fertilization by adding iron or other nutrients, either from external sources or via enhanced ocean mixing. On the basis of small-scale field experiments carried out to date and associated modelling, the maximum benefits of ocean fertilization as a negative emissions technique are likely to be modest in relation to anthropogenic climate forcing. Furthermore, it would be extremely challenging to quantify with acceptable accuracy the carbon removed from circulation on a long term basis, and to adequately monitor unintended impacts over large space and time-scales. These and other technical issues are particularly problematic for the region with greatest theoretical potential for the application of ocean fertilization, the Southern Ocean. Arrangements for the international governance of further field-based research on ocean fertilization are currently being developed, primarily under the London Convention/London Protocol. Highlights: ► Fertilization using iron can increase the uptake of CO2 across the sea surface. ► But most of this uptake is transient; long-term sequestration is difficult to assess. ► Unintended impacts of ocean fertilization may be far removed in space and time. ► For climate benefits, the Southern Ocean has most potential – also most problems. ► A regulatory framework for ocean fertilization research has been developed.

Beschreibung: A sensitive method using Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) has been developed to determine for the first time iron (Fe) organic speciation in rainwater over the typical natural range of pH. We have adapted techniques previously developed in other natural waters to rainwater samples, using the competing ligand 1-nitroso-2-naphthol (NN). The blank was equal to 0.17 +/- 0.05 nM (n = 14) and the detection limit (DL) for labile Fe was 0.15 nM which is 10-70 times lower than that of previously published methods. The conditional stability constant for NN under rainwater conditions was calibrated over the pH range 5.52-6.20 through competition with ethylenediaminetetraacetic acid (EDTA). The calculated value of the logarithm of beta'(FE3+(NN)3) increased linearly with increasing pH according to log beta'(FE3+(NN)3) = 2.4 +/- 0.6 x pH + 11.9 +/- 3.5 (salinity =2.9, T= 20 degrees C). The validation of the method was carried out using desferrioxamine mesylate B (DFOB) as a natural model ligand for Fe. Adequate detection windows were defined to detect this class of ligands in rainwater with 40 mu M of NN from pH 5.52 to 6.20. The concentration of Fe-complexing natural ligands was determined for the first time in three unfiltered and one filtered rainwater samples. Organic Fe-complexing ligand concentrations varied from 104.2 +/- 4.1 nM equivalent of Fe(III) to 336.2 +/- 19.0 nM equivalent of Fe(III) and the logarithm of the conditional stability constants, with respect to Fe3+, varied from 21.1 +/- 0.2 to 22.8 +/- 0.3. This method will provide important data for improving our understanding of the role of wet deposition in the biogeochemical cycling of iron.

Beschreibung: A shipboard analytical intercomparison of dissolved (〈0.2 μm) iron in the surface waters of the Atlantic Ocean was undertaken during October 2000. A single underway surface (1-2 m) seawater sampling and filtration protocol was used, in order to minimise differences from possible sample contamination. Over 200 samples (1/h) were collected over 12 days and analysed immediately using four different analytical methods, based on three variants of flow injection with luminol chemiluminescence (FI-CL) and cathodic stripping voltammetry (CSV). Dissolved iron concentrations varied between 0.02 and 1.61 nM during the intercomparison. On average, CSV Electroanalysis 12 (2000) 565 measured 0.08 nM higher iron concentrations than one FI-CL method Anal. Chim. Acta 361 (1998) 189, which measured 0.13 nM higher iron values than the other two Anal. Chem. 65 (1993) 1524; Anal. Chim. Acta 377 (1998) 113, Statistical analyses (paired two-tailed t-test) showed that each analytical method gave significantly different dissolved iron concentrations at the 95% confidence interval. These data however, represent a significant improvement over earlier intercomparison exercises for iron. The data have been evaluated with respect to accuracy and overall inter-laboratory replicate precision, which was generally better than the 95% confidence intervals reported for the NASS Certified Reference Materials. Systematic differences between analytical methods were probably due to the extraction of different physico-chemical forms of iron during preconcentration, either on the micro-column resin (in the FI methods) or with competing ligand equilibration (in the CSV method). Small systematic concentration differences may also have resulted from protocols used for quantification of the analytical blank and instrument calibration. © 2003 Elsevier B.V All rights reserved.