The GEOTRACES Intermediate Data Product 2017 ☆

data of the and measured and controlled before the of 2016. The data from the Atlantic, Paci c, Southern and Indian with about twice the data volume of the previous IDP2014. For the ﬁ rst time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and iso- tope (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 ﬂ ags and 1- σ data error values where available. Quality ﬂ ags and error values are useful for data ﬁ ltering 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 e ﬀ ort 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 This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017.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.

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.

Introduction
In 2014, the international GEOTRACES programme (Anderson et al., 2014a(Anderson et al., , 2014bSCOR Working Group, 2007;GEOTRACES, 2006;Anderson and Henderson, 2005;Frank et al., 2003; http://www. geotraces.org/) released its first Intermediate Data Product 2014 (IDP2014, Mawji et al., 2015). The main motivation was to not wait until the end of the programme to issue a final data product. Instead, GEOTRACES wants to create and release a series of intermediate data products at times when the programme is still very active and expanding, both in terms of observational activities as well as the scientific analysis and synthesis of the data produced so far. By releasing and sharing data at early stages, GEOTRACES intends to strengthen and intensify collaboration within the geochemical community itself, but also to attract and invite colleagues from other communities, such as physical, biological and paleo-oceanography, as well as modelling, to apply their unique knowledge and skills to marine biogeochemical research questions.
The release of the IDP2014 was a big success and was widely covered by international news media as well as a broad range of scientific journals (e.g., Morrison, 2014). The data product resulted from a significant effort to combine data from 15 cruises conducted by seven countries. The IDP2014 data cover the Atlantic, Arctic, Southern and Indian oceans and span the 2007 to 2012 period. There are data for 237 hydrographic parameters as well as trace elements and isotopes (TEIs) contributed by 133 scientists from 16 countries. Having such a large group of researchers collaborate on the project and submit high-quality data, sometimes unpublished, was a remarkable achievement.
The IDP2014 is being used widely and has stimulated collaborative research that would not have been possible without such a large, aggregated dataset. Since its release, users worldwide have downloaded the IDP2014 dataset 1410 times. Users of the data product are encouraged to cite the original papers written by the data originators, but the IDP contains significant unpublished data. The publications describing the IDPs thus provide the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP. The publication describing the IDP2014 (Mawji et al., 2015) has been cited 43 times, indicating that there is a significant number of scientific studies, such as large-scale modelling and basinscale to global TEI evaluations, that make use of large portions of the IDP2014 data and could not have been performed otherwise (e.g., Abadie et al., 2017;Chien et al., 2016;Frants et al., 2016;Lerner et al., 2016;Schlitzer, 2016). In particular, the aggregated dissolved iron datasets from IDP2014 facilitated the first rigorous intercomparison of dissolved iron cycling from 13 global ocean models (Tagliabue et al., 2016).
Building on the success of the IDP2014 and following the long-term data product release plan, GEOTRACES released its second intermediate data product (IDP2017) at the Goldschmidt Conference 2017 in Paris. As with the previous product, IDP2017 consists of two parts: (1) the digital data compilation of TEIs as well as standard hydrographic parameters; and (2) the eGEOTRACES Electronic Atlas providing section plots and animated 3D scenes of the data. As described in detail below, the IDP2017 contains twice as much data compared to the previous IDP2014. For the first time, the IDP2017 contains significant amounts of biogeochemistry data as well as data for aerosols and rain. All data in the IDP2017 have passed the GEOTRACES standardisation and intercalibration protocols.

Intercalibration of data for IDP2017
The direct comparability of GEOTRACES TEI data from any cruise is a prerequisite for assessing global-scale distributions of TEIs, for identifying and quantifying sources and sinks as well as rates of internal cycling, and for providing a baseline against which future changes can be measured. This is also essential for our ability to model natural processes affected by TEIs in the ocean. Therefore, the standardisation and quality control of data sets has always been a cornerstone of the GEOTRACES programme. The importance of intercalibration was illustrated by the U.S. National Science Foundation (NSF)-funded 2003 SAFe iron intercomparison cruise (Johnson et al., 2007), which resulted in widely used consensus material for dissolved trace metals and rare earth elements. Through the GEOTRACES programme, two additional intercalibration cruises were conducted for all the main TEIs and documented in a special issue of Limnology and Oceanography Methods in 2012 (Vol. 10 issue 6). Moreover, a cookbook detailing recommended sample collection methods was produced to support intercalibration (http://www.geotraces.org/images/Cookbook.pdf). This document was updated prior to IDP2017 with new intercalibration procedures for TEIs not included in the IDP2014.
While the IDP2014 contained some data that were not quality controlled (identified as tier 2 data), IDP2017 is the first GEOTRACES intermediate data product in which all TEI data have passed the intercalibration procedures and been approved by the Standards and Intercalibration Committee (S&I Committee). This committee is currently a group of eight members approved by the GEOTRACES Scientific Steering Committee. Its members cover a broad range of analytical expertise for the TEIs in IDP2017. In addition, there are element co-ordinators for each group of TEIs who can guide new investigators in developing sample collection and analytical methods (http://www.geotraces.org/sic/s-i-committee/elemental-coordinators).
The intercalibration assessment of the TEI parameters for IDP2017 differed depending on several criteria. For example, the committee had to consider the maturity of the available analytical techniques for a given TEI, the type of TEI in GEOTRACES, the possibly transient nature of the signal, the nature of the data acquisition (e.g., sensor vs. bottle), and the participation in other programmes (such as CLIVAR) that have their own intercalibration procedures.
Irrespective of the quality criteria for individual TEIs, all data were expected to follow certain minimum standards, as shown in Fig. 1. First, written documentation of sampling, measurement and intercalibration procedures was required, provided directly to the S&I Committee as an intercalibration report. This report included details on how samples were collected, how they were processed on board, and how they were stored prior to analyses. This assessment must be carried out for each individual cruise leg, not just for a given laboratory, since the sampling equipment, analytical techniques and analysts may change between cruise legs. The actual assessment was based on the information in these reports and took place during meetings of the S&I Committee.
Second, the methods were assessed for suitability, which included (for example) a check if the procedures were following the cookbook or equivalent, if there were sufficient blank assessments, if detection limits were adequate for the target, and if the laboratory had systems for checking the internal consistency of data, for example replicate analyses, analyses of certified reference materials, or analyses of consensus materials produced from GEOTRACES intercalibration cruises.
Third, the external comparability of the data was assessed. This crucial step comprised an assessment of the crossover stations for key TEIs, that is, those TEIs considered to be of such widespread interest that they should be measured on every GEOTRACES section, and for other TEIs whenever possible. If no crossover stations were possible (e.g., only one cruise had taken place in this region), external comparability had to be demonstrated by participation in a laboratory intercalibration exercise (if such an exercise was available), by the analysis of replicate samples (e.g., where samples were exchanged with another laboratory), and by analyses of certified reference materials or consensus materials. For some TEIs it could also include a comparison to other data in the region of interest. External validation for certain parameters with a core user group outside the GEOTRACES community (e.g., DIC & Alkalinity data, CFCs, sensor data) could also be demonstrated via some other programme (e.g., GO-SHIP, CLIVAR). The assessment of external comparability had to consider the state of the art for any given TEI, with the recognition that the state of the art is changing rapidly, in large part due to GEOTRACES intercalibration activities.
Finally, the S&I Committee assessed jointly if the information provided had demonstrated that the analytical methods reflected the state of the art, and if the data provided had satisfied the quality requirements. If information was missing, the committee contacted the analysts to see if additional information could be provided that would satisfy the need for documentation and quality assurance.
Several parameters have been intercalibrated through new intercalibration exercises (e.g., Si isotopes: Grasse et al., 2017, REE: Behrens et al., 20167 Be, particulate TEIs and leachable particulate trace metals; Hg speciation), and new consensus materials have become available for the use of the GEOTRACES community (e.g., Arizona Test Dust for aerosols; Morton et al., 2013). More recently, a sea-ice intercalibration has begun. Results from these on-going intercalibration exercises will be publicised by GEOTRACES as they become available.

IDP2017 digital data
Creation of the IDP2017 was coordinated and overseen by the GEOTRACES Data Management Committee (DMC). Collation of the cruise data and linkage with extensive metadata was carried out at the GEOTRACES Data Assembly Centre (GDAC) located at the British Oceanographic Data Centre. GDAC received data submissions from four national data centres (Biological & Chemical Oceanography Data Management Office (BCO-DMO; https://www.bco-dmo.org/), Japan Oceanographic Data Centre (JODC; http://www.jodc.go.jp/jodcweb/), LEFE CYBER France (http://www.obs-vlfr.fr/proof/index2.php), NIOZ -Netherlands Data Centre (https://www.nioz.nl/en/research/researchdata)) or from GEOTRACES data originators directly. The lead author of this publication carried out the integration of the cruise data into global datasets.
The IDP2017 digital data package consists of three datasets: (1) discrete water sample data; (2) CTD sensor data; and, as a new dataset, (3) aerosol and rain data. The discrete sample and aerosol/rain datasets contain the GEOTRACES TEI data as well as data for a large suite of standard hydrographic data (discrete sample dataset only). The CTD sensor dataset contains high-resolution data from a variety of electronic sensors that are useful for TEI data interpretation and evaluation.
The discrete sample datasets include data from 39 cruises conducted by 11 countries during the 7-year period from 2007 to 2014 (Table 1). Twenty-four of the 39 cruises are new in the IDP2017. The dataset covers the Arctic, Atlantic, Southern, Indian oceans and, the Pacific Ocean (Fig. 2). The best coverage and highest station density is found in the Atlantic, but the new data from the Pacific have already allowed accurate mapping of TEI distributions in parts of the South and North Pacific. In addition to twelve GEOTRACES sections (GA01, GA02, GA03, GA04, GA06, GA10, GA11, GI04, GP02, GP13, GP16, and GP18), which eventually will produce measurements of the large set of GEO-TRACES key TEIs (Table 2 in GEOTRACES, 2006), the IDP2017 also includes data from six cruises conducted as part of the International Polar Year (GIPY2, GIPY4, GIPY5, GIPY6, GIPY11, and GIPY13; for an overview of IPY activities see: https://www.icsu.org/publications/ understanding-earths-polar-challenges-international-polar- year-2007-2008). For the first time, the IDP2017 also includes GEOTRACES Compliant Data from four cruises (GAc02, GPc01, GPc02, and GPc03) and six GEOTRACES Process Studies (GPpr01, GPpr02, GPpr04, GPpr05, GPpr07, and GPpr10). Typically, these activities produce smaller sets of TEI measurements and sometimes have limited geographical coverage. Nevertheless, compliant data and process studies fill gaps in the overall sampling scheme and provide invaluable data for the quantification of TEI sources and sinks as well as the study of the internal cycling of TEIs. Links to the cruise reports of all cruises in the IDP2017 are provided in Table 2.
In total, the IDP2017 discrete sample dataset contains data for 1810 stations. Of these stations, 817 provide full-depth coverage of the water column. There are data for a total of 458 parameters, including (1) classical hydrographic parameters and tracers such as temperature, salinity, oxygen, nutrients, CFCs, SF 6 , Tritium, and He-3, (2) dissolved Table 1 List of cruises included in the GEOTRACES Intermediate Data Product 2017. Section suffixes denote individual parts of a section. A lower case "c" in the section name (as in GAc01) indicates compliant data while a lower case "pr" (as in GPpr01) indicates a process study. A y in the New column indicates new sections in the IDP2017. Many of the already existing sections had new data added since IDP2014. Cruise locations are illustrated in Fig. 2 (4) radioactive isotopes such as Pb-210, Po-210, Th-230, Pa-231, and Th-234. The IDP2017 discrete sample dataset also contains data for a wide range of biogeochemistry parameters, such as HPLC pigments,  A total of 46,794 discrete samples were analysed from the 1810 stations. The average number of depths sampled at each station was 33 but reached up to 182 depths at heavily sampled "super" stations. Table 3 summarises the number of observations for selected parameters, including micronutrients essential to life in the ocean (e.g., Fe, Zn, Cd, Cu), tracers of modern processes in the ocean (e.g., Al, Mn, N-15), tracers significantly perturbed by human activities (e.g., Hg, Pb), and tracers used as proxies to reconstruct the past (e.g., Th-230, Pa-231, Nd isotopes). Data for the micronutrients are most abundant, with the total number of Fe measurements totalling 12,050; of these, 7690 are for dissolved Fe alone. There are 3768 data values for the radioactive isotope Th-234 and around 1800 values for Th-230 and Pa-231.
The CTD sensor dataset contains temperature, salinity, oxygen, fluorescence, transmissometer, turbidity, and photosynthetically active radiation (PAR) data at 1827 stations at 1 m vertical resolution. The fluorescence and transmissometer data provide information on phytoplankton abundance and suspended particle concentrations and are thus important for the interpretation of TEI data. Where calibrated data were not available, raw values are provided. These uncalibrated data are still useful as they reveal the horizontal and vertical extent of phytoplankton patches and suspended particle layers.
For the first time, the IDP2017 contains TEI aerosol and rain data sampled from GEOTRACES cruises. Such data were collected at 243 locations in the Atlantic, Pacific, Mediterranean, and Black Sea (Fig. 3). Data are provided for 99 aerosol parameters, including total TEI concentrations as well as soluble TEI after strong or mild leaching. Also included are size-fractionated TEI concentrations on fine and coarse aerosols. The rain data consist of 68 parameters, including dissolved and total dissolvable TEI concentrations.
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 statistical data analysis. Quality flags are single character codes reflecting the quality of the respective data value. The IDP2017 uses the IODE quality flag set that is a standard flagging scheme for the exchange of oceanographic and marine meteorological data (www.iode.org/mg54_3). The IODE flagging scheme is generic and simple, only containing the five flags listed in Table 4.
The IDP2017 is an "intermediate" product, and there is clearly a significant amount of further data to come from GEOTRACES cruises, Table 3 Number of measurements of selected GEOTRACES parameters in the discrete sample dataset of the IDP2017. Numbers in parentheses indicate the percentage of discrete samples that contain data for that parameter. The "All forms" values include dissolved as well as particulate measurements. For Fe this also includes data for Fe_II and soluble Fe.  both those represented in the IDP2017, and those sections more recently completed or planned. The IDP2017 contains only those data that were completed and submitted before a cut-off date of December 2016. Further data will be included in subsequent intermediate products (as detailed below) and will significantly augment the data coverage represented in IDP2017.

Parameter naming conventions
The overall structure of the databases combined in IDP2017, including a single convention for naming all parameters (variables), was organised by a six-person Parameter Naming Committee (PNC) whose members interacted regularly with the Data Management Committee and with the Standards and Intercalibration Committee. With well over 400 parameters in IDP2017, and with the expectation that the number of parameters could eventually exceed 1000, a structure was sought that would allow users to search intuitively for data, using either tools incorporated into IDP2017 (see "Obtaining IDP2017 Data") or other search engines, utilising a common set of keywords or commands. The structure was designed to accommodate hydrographic and biogeochemical variables as well as TEIs, and to span a range of sampling environments, including seawater, aerosols and rain, while also anticipating the future addition of data from sea ice and sediments. With this in mind, the PNC devised a six-token parameter naming scheme, described in the next two paragraphs, that would encompass all of these characteristics as well as information about operationally defined chemical speciation and physical form of the substance of interest. It is hoped that incorporating all of this information into each parameter name will facilitate searches for highly specific types of data. The IDP2017 employs the following parameter naming scheme. Standard hydrographic parameters, such as temperature, salinity and oxygen use names as defined in the WOCE/CLIVAR naming convention (CTDTMP, CTDSAL and CTDOXY for temperature, salinity and oxygen Missing data Used as place holder when data are missing  Roy et al., 2011) or names that intuitively define the parameters (e.g., nifH_UCYN-A_DNA_P_CONC_BOTTLE; concentration of nifH genes from uncultured unicellular cyanobacteria (UCYN-A) particles (P) in a bottle sample). All other trace elements and isotope names are composed of up to six separate tokens, as follows: Tokens 2 and 3 are optional, while all other tokens are mandatory. The meaning and possible values for all the six tokens are described in Table 5. Example parameter names can be found in Table 6.
The PNC sought to verify that parameter names supplied by contributing investigators complied with the convention described above. In cases where reported data did not comply with a master list of parameters, the PNC would examine the metadata accompanying the original data submission and rename the parameter if appropriate. If there were any question about the correct parameter name, then the PNC would contact the data originator to verify that the parameter had been renamed correctly.

Metadata and publication references
The IDP2017 digital datasets include the cruise reports of all the cruises (Table 2). These cruise reports provide detailed documentation of the ship operations, including descriptions of sampling procedures and gear as well as information on the laboratories and principal investigators involved. Access to the cruise reports is very easy. When using the ODV collection version of the IDP2017, a simple mouse click on the Cruise Report meta-variable opens the given cruise report and allows viewing in the web browser.
In addition, the IDP2017 also contains, for every parameter and every cruise, a data info file containing information about data originators, sample preparation and analytical methods as well as links to original publications related to the data. These info files are delivered with all IDP2017 output formats and can be viewed easily in the web browser. Access is particularly easy in ODV, where only one mouse click on the info symbol ⓘ is required to open the respective info file in the web browser and obtain detailed information about the data originator and the analytical methods for the clicked parameter and cruise. One more mouse click shows the references of the original publications associated with the given parameter and cruise. Fig. 4 shows an example publication list for parameter Fe_D_CONC_BOTTLE along GP16. Proper linkage of the originator and publication information with the actual data is an important feature of the IDP2017 that makes it easy for users to identify, contact, and acknowledge originators.
The publication links in the IDP2017 info files refer to the reference database of original publications maintained at the GEOTRACES International Programme Office (IPO). This reference database is dynamic and updated whenever new papers are published. Clicking on a reference link in the IDP2017 will always show the up-to-date publication list at the time of the click. Future requests of the publication list related to, for instance, Fe_D_CONC_BOTTLE along GP16 will, in addition to what is shown in Fig. 4, also include new papers published since the Fig. 4 creation date of December 2017. This dynamic inclusion of papers published after the release of the data product was a required feature for the IDP2017, because many datasets were unpublished at the time of data submission.
As a novelty for the IDP2017, the GEOTRACES IPO has made the publication database into a searchable on-line database available on the following GEOTRACES web page: http://www.geotraces.org/library-88/scientific-publications/peer-reviewed-papers. This database is not limited to the IDP2017 as it also includes other publications that are relevant for GEOTRACES research along with Master and PhD dissertations. Three types of search functionalities are available: (1) Simple search: users can search publications by "author", "title" or "journal" entering the desired term into a search box, (2) Advanced search: by means of dropdown menus, users can select publications by "author", "title", "GEOTRACES cruise", "year" or "type of document", and. Atom ratio of given isotopes for dissolved Nd Nd_143_144_D_EPSILON_BOTTLE Atom ratio of dissolved Nd isotopes expressed in conventional EPSILON notation Cd_114_110_D_DELTA_BOTTLE Atom ratio of dissolved Cd isotopes expressed in conventional DELTA notation Cu_Cu'_D_CONC_BOTTLE Concentration of dissolved inorganic Cu Pb_206_204_D_RATIO_BOTTLE Atom ratio of given isotopes for dissolved Pb DIC_13_12_D_DELTA_BOTTLE Atom ratio of given isotopes for dissolved C as DIC in delta notation DIC_14_12_D_DELTA_BOTTLE Atom ratio of radiocarbon as dissolved C in DIC in DELTA notation NITRATE_15_14_D_DELTA_BOTTLE Atom ratio of given isotopes for dissolved N as nitrate in delta notation L1_Fe_D_CONC_BOTTLE Concentration of dissolved L1 Fe-binding ligand L1_Fe_D_LogK_BOTTLE Log (3) Parameter search: allows users to access a list of publications by specific TEI. In addition users can also retrieve publications by group of parameters (e.g., Aerosols, Dissolved TEIs, etc.) or by predefined subgroups (e.g., dissolved trace elements, etc.).
In each case, search queries for "parameter" or "GEOTRACES cruise" will only list those publications linked to data included in the IDP2017.

Obtaining IDP2017 data
The IDP2017 digital data are available in two forms: (1) as full package downloads, or, (2) as customised data subsets using a new online data extraction service. Both methods require users to register (or login if already registered) and agree to IDP2017 usage rules before being able to access and download IDP2017 digital data. The usage rules ask for proper citation of the relevant original papers associated with the particular data used, as well as citation of the IDP2017 data product itself (this paper). Users are also asked to describe the purpose of the IDP2017 data download.
Full packages of the three IDP2017 datasets are available for download at https://www.bodc.ac.uk/geotraces/data/idp2017/. The data are provided in four formats: (1) ASCII text files suitable for usage in standard software, (2) Excel spreadsheet files for Microsoft Excel or similar software, (3) netCDF files suitable for access by models and netCDF readers, and (4) as ODV collections for use with the popular Ocean Data View software (https://odv.awi.de).
Users who only need data for a smaller subset of parameters and/or smaller geographical domain can use the new data subsetting and extraction service provided at https://webodv.awi.de/geotraces. After registration and login the user is guided through a three-step procedure.
Step 1 allows for subsetting the set of stations to be downloaded by selecting one or more entries from the cruise list, zooming into a specific map domain and/or specifying one or more required parameters (variables). Only stations containing data for all the selected required parameters are included in the output dataset.
Step 2 lets users customise the set of parameters (variables) to be included in the download file. This is done using a hierarchical tree of parameter groups and individual parameters. Users open/close parameter groups by clicking the +/− symbols. All parameters of a given group are selected/unselected by clicking the specific group box; individual parameters are selected/unselected by clicking the box of the individual parameter. A Selection status box always shows the currently selected numbers of stations and parameters (variables) to be included in the download file.
Step 3 lets users choose among four data output formats (ASCII, ODV collection, netCDF, or WOCE WHP exchange) and initiate the actual data download. Selection settings are remembered when a user exits the session and are restored when logging in again later.

eGEOTRACES electronic atlas
The eGEOTRACES Electronic Atlas is the visual component of the IDP2017 and provides 593 section plots (Fig. 5) and 132 animated 3D scenes (Fig. 6) for many (but not all) of the parameters in the IDP2017. All plots are based on the digital data in the IDP2017, but data values flagged as Questionable/suspect or Bad (see Table 4) were filtered out and not used for the plots. The eGEOTRACES website http://egeotraces.org/ provides a dynamic map, where users start by selecting a data group and a tracer of interest. Sections containing a plot for the selected tracer are highlighted in red in the map, and basins containing a 3D animation for the selected tracer are highlighted in blue. Clicking on a red section label or a blue basin label will show the respective section plot or play the respective 3D scene. All section plots and 3D scenes show the names of scientists who produced or are responsible for the data. This makes it easy for users to identify and acknowledge data producers. Further clicking on a section plot loads a high-resolution version of the image, which can be saved for use in publications and presentations. The browser's Back button is used to return to the original section page. When viewing a rotating 3D scene clicking the Larger-size Video link produces a blown-up version of the animation. Clicking the Normalsize Video link at the bottom of the blown-up animation returns to the original size. An options bar appears when the mouse is over the 3D animation. Elements on the options bar can be used to stop the animation at arbitrary angles and quickly choose other viewing angles. Some browsers also allow download of the 3D movie file.
All section and 3D animation pages contain groups of links near the bottom of the page. These include (a) links to other tracers along this section or in this scene, (b) other 3D scenes with this tracer, and (c) other sections with this tracer. These links greatly facilitate switching between and comparing of different tracers, sections, and 3D scenes. All section plots use the same window layout, and the different section plots perfectly match when switching between tracers. The links under category (c) allow easy transitions between section plots and 3D animations.
Section and 3D scene pages also contain links to the original publications associated with the given tracer and section. Clicking on these links shows the current list of publications from the dynamically updated reference database maintained at the GEOTRACES IPO (see above).
eGEOTRACES provides quick overviews of the distributions of many geochemically relevant tracers. The 3D scenes provide geographical and bathymetric context crucial for correctly assessing the extent and origin of tracer plumes as well as for inferring processes acting on the tracers and shaping their distribution. The numerous links to other tracers, sections, and basins found on section plots and 3D animations allow quick switching between tracers and domains, and facilitate comparisons between tracers. In addition to the benefit for scientific research, eGEOTRACES and its visual material can also help in teaching and outreach activities. The eGEOTRACES visuals can also help convey societally relevant scientific results to interested non-scientists and policy makers.
Images or 3D movies from the eGEOTRACES Atlas can be used free of charge for non-commercial purposes, such as in scientific publications, posters, presentations and teaching activities, as long as the source is cited as follows: Schlitzer, R., eGEOTRACES -Electronic Atlas of GEOTRACES Sections and Animated 3D Scenes, http://egeotraces.org, 2017. Users must not remove the names of data producers and graphics creator. High-resolution images of the 3D scenes are available on request.

Summary
The new IDP2017 is a significant improvement over the earlier IDP2014 and roughly doubles the number of included cruises, stations, samples and parameters. The IDP2017 is a truly international product containing data from 326 researchers from 25 countries. The IDP2017 provides data for the Pacific Ocean, and the Mediterranean and Black seas, in addition to Atlantic, Arctic and Indian Oceans that were already represented in the previous data product. For the first time, the IDP2017 contains significant amounts of biogeochemistry data as well as TEI data for aerosols and rain. As before, users can obtain complete IDP2017 data sets as bulk downloads. Alternatively, there is now a customisable online data extraction service that allows data selections by domain, GEOTRACES sections, as well as parameters of interest. The extractor delivers smaller, more manageable data packages.
GEOTRACES invites and promotes use of the IDP2017 in the widest possible sense and envisages intensified collaboration within the marine geochemical community and beyond. Availability of large integrated and quality-controlled datasets, such as the IDP2017, enables a much wider range of studies than would be possible with individual single-cruise data alone.
The new, updated eGEOTRACES electronic atlas now contains more than 590 section plots (compared to 330 in IDP2014) and more than 130 animated 3D scenes (95 in IDP2014). Section and 3D scene pages are interlinked, and switching between different GEOTRACES sections, ocean basins and parameters is achieved with simple mouse clicks. eGEOTRACES section and 3D scene pages are now connected to the GEOTRACES publication database, easily providing with a simple mouse click up-to-date reference lists to the original publications related to the displayed data. This feature makes identification of data originators easy and encourages proper citation or initiation of collaborative research.
The animated 3D scenes in the eGEOTRACES Atlas show large amounts of data in an intuitive way and with geographic and bathymetric context, thereby providing quick large-scale overviews of TEI distributions and helping the scientific interpretation of TEI data. In addition, these animations are also appealing to a wider target community, including scientists from other disciplines or policy makers, as well as interested members of the general public. GEOTRACES encourages wide usage of eGEOTRACES visuals for all purposes, including teaching and outreach.
The IDP2017 is the second in a series of planned intermediate data products, with the next scheduled for release in 2021. Future data products will extend the geographical coverage by including data from new GEOTRACES cruises, as well as providing additional data from existing cruises for parameters that take longer to measure and complete. GEOTRACES invites user feedback (ipo@geotraces.org) on the IDP2017 to help make the next IDP an even more useful product.