Description: 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 This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017.

Description: A major surface circulation feature of the Arctic Ocean is the Transpolar Drift (TPD), a current that transports river‐influenced shelf water from the Laptev and East Siberian Seas toward the center of the basin and Fram Strait. In 2015, the international GEOTRACES program included a high‐resolution pan‐Arctic survey of carbon, nutrients, and a suite of trace elements and isotopes (TEIs). The cruises bisected the TPD at two locations in the central basin, which were defined by maxima in meteoric water and dissolved organic carbon concentrations that spanned 600 km horizontally and ~25‐50 m vertically. Dissolved TEIs such as Fe, Co, Ni, Cu, Hg, Nd, and Th, which are generally particle‐reactive but can be complexed by organic matter, were observed at concentrations much higher than expected for the open ocean setting. Other trace element concentrations such as Al, V, Ga, and Pb were lower than expected due to scavenging over the productive East Siberian and Laptev shelf seas. Using a combination of radionuclide tracers and ice drift modeling, the transport rate for the core of the TPD was estimated at 0.9 ± 0.4 Sv (106 m3 s‐1). This rate was used to derive the mass flux for TEIs that were enriched in the TPD, revealing the importance of lateral transport in supplying materials beneath the ice to the central Arctic Ocean and potentially to the North Atlantic Ocean via Fram Strait. Continued intensification of the Arctic hydrologic cycle and permafrost degradation will likely lead to an increase in the flux of TEIs into the Arctic Ocean.

Description: Highlights • Fe-binding ligands associated with primary productivity together with ligands from the Arctic Ocean are the main sources of Fe-binding ligands in surface waters of Fram Strait. • Fe-binding ligands are present in a high concentrations in front of the glacier terminus, but the ligands have a relatively low binding capacity, thus less reactive. • Low binding strength coupled with low competing strength of ligands result in a higher inorganic Fe concentration, causing Fe to precipitate or scavenged. Abstract There is a paucity of data on Fe-binding ligands in the Arctic Ocean. Here we investigate the distribution and chemical properties of natural Fe-binding ligands in Fram Strait and over the northeast Greenland shelf, shedding light on their potential sources and transport. Our results indicate that the main sources of organic ligands to surface waters of Fram Strait included primary productivity and supply from the Arctic Ocean. We calculated the mean total Fe-binding ligand concentration, [Lt], in Polar Surface Water from the western Fram Strait to be 1.65 ± 0.4 nM eq. Fe. This value is in between reported values for the Arctic and North Atlantic Oceans, confirming reports of north to south decreases in [Lt] from the Arctic Ocean. The differences between ligand sources in different biogeochemical provinces, resulted in distinctive ligand properties and distributions that are reflected in [Lt], binding strength (log KFe'L′) and competing strength (log αFe'L) of ligands. Higher [Lt] was present near the Nioghalvfjerdsfjorden (79 N) Glacier terminus and in the Westwind Trough (median of [Lt] = 2.17 nM eq. Fe; log KFe'L′ = 12.3; log αFe'L = 3.4) than in the Norske Trough (median of [Lt] = 1.89 nM eq. Fe; log KFe'L′= 12.8; log αFe'L = 3.8) and in Fram Strait (median of [Lt] = 1.38 nM eq. Fe; log KFe'L′ = 13; log αFe'L= 3.9). However, organic ligands near the 79 N Glacier terminus and in the Westwind Trough were weaker, and therefore less reactive than organic ligands in the Norske Trough and in Fram Strait. Our findings reveal the fundamental mechanism that underpin transport of dissolved-Fe (DFe) from the 79 N Glacier to Fram Strait, less reactive ligands will reduce Fe solubility. Accordingly, a portion of the glacial DFe will not be transported over the shelf into the ocean. The lower ligand binding strength in the outflow results in a higher inorganic Fe concentration, [Fe´], which is more prone to precipitation and/or scavenging than Fe complexed with stronger ligands. Ongoing changes in the Arctic and sub-Arctic Oceans will influence both terrestrially derived and in-situ produced Fe-binding ligands, and therefore will have consequences for Fe solubility and availability to microbial populations and Fe cycling in Fram Strait.

Description: The Arctic Ocean is considered a source of micronutrients to the Nordic Seas and the North Atlantic Ocean through the gateway of Fram Strait. However, there is a paucity of trace element data from across the Arctic Ocean gateways, and so it remains unclear how Arctic and North Atlantic exchange shapes micronutrient availability in the two ocean basins. In 2015 and 2016, GEOTRACES cruises sampled the Barents Sea Opening (GN04, 2015) and Fram Strait (GN05, 2016) for dissolved iron (dFe), manganese (dMn), cobalt (dCo), nickel (dNi), copper (dCu) and zinc (dZn). Together with the most recent synopsis of Arctic-Atlantic volume fluxes, the observed trace element distributions suggest that Fram Strait is the most important gateway for Arctic-Atlantic dissolved micronutrient exchange as a consequence of Intermediate and Deep Water transport. Combining fluxes from Fram Strait and the Barents Sea Opening with estimates for Davis Strait (GN02, 2015) suggests an annual net southward flux of 2.7 ± 2.4 Gg·a-1 dFe, 0.3 ± 0.3 Gg·a-1 dCo, 15.0 ± 12.5 Gg·a-1 dNi and 14.2 ± 6.9 Gg·a-1 dCu from the Arctic towards the North Atlantic Ocean. Arctic-Atlantic exchange of dMn and dZn were more balanced, with a net southbound flux of 2.8 ± 4.7 Gg·a-1 dMn and a net northbound flux of 3.0 ± 7.3 Gg·a-1 dZn. Our results suggest that ongoing changes to shelf inputs and sea ice dynamics in the Arctic, especially in Siberian shelf regions, affect micronutrient availability in Fram Strait and the high latitude North Atlantic Ocean.

Description: This study traces dissolved organic matter (DOM) in different water masses of the Arctic Ocean and its effect on the distributions of trace elements (TEs; Fe, Cu, Mn, Ni, Zn, Cd) using fluorescent properties of DOM and the terrigenous biomarker lignin. The Nansen, Amundsen, and Makarov Basins were characterized by the influence of Atlantic water and the fluvial discharge of the Siberian rivers with high concentrations of terrigenous DOM (tDOM). The Canada Basin and the Chukchi Sea were characterized by Pacific water, modified through contact with productive shelf sediments with elevated levels of marine DOM. Within the surface layer of the Beaufort Gyre, meteoric water (river water and precipitation) was characterized by low concentrations of lignin and terrigenous DOM fluorescence proxies as DOM is removed during freezing. High-resolution in situ fluorescence profiles revealed that DOM distribution closely followed isopycnals, indicating the strong influence of sea-ice formation and melt, which was also reflected in strong correlations between DOM fluorescence and brine contributions. The relationship of DOM and hydrography to TEs showed that terrigenous and marine DOM were likely carriers of dissolved Fe, Ni, Cu from the Eurasian shelves into the central Arctic Ocean. Chukchi shelf sediments were important sources of dCd, dZn, and dNi, as well as marine ligands that bind and carry these TEs offshore within the upper halocline (UHC) in the Canada Basin. Our data suggest that tDOM components represent stronger ligands relative to marine DOM components, potentially facilitating the long-range transport of TE to the North Atlantic. Key Points Dissolved Organic Matter (DOM) distribution in the Arctic Ocean is largely controlled by sea ice formation and melt processes DOM distribution in the Arctic Ocean reveals its potential as a tracer for halocline formation and freshwater source assignments Terrigenous and marine DOM are carriers of trace elements from shelves to the open Arctic Ocean, but terrigenous DOM represent stronger ligands

Description: 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 25 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. This article is part of a special issue entitled: Conway GEOTRACES - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.

Description: Abstract The {GEOTRACES} Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international {GEOTRACES} programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The {IDP2014} covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The {TEI} data in the {IDP2014} are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including {ASCII} spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the {IDP2014} also contains data quality flags and 1-� data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the {IDP2014} data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes.