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 This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017.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: The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this Special Issue, results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among seventeen articles. Here, the scientific context, project objectives and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue.

Description: Highlights: • GEOTRACES releases its first integrated and quality controlled Intermediate Data Product 2014 (IDP2014). • The IDP2014 digital data are available at http://www.bodc.ac.uk/geotraces/data/idp2014/ in 4 different formats. • The eGEOTRACES Electronic Atlas at http://egeotraces.org/ provides 329 section plots and 90 animated 3D tracer scenes. • The new 3D scenes provide geographical and bathymetric context crucial for tracer assessment and interpretation. 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-σ 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.

Description: Since the discovery of oil in early 1900, the Arabian Gulf has experienced a continuous and fast coastal development leading to increase the human pressures on the marine environment and its enrichment with various pollutants. The present study attempts to describe the historical changes of trace elements in the sediments of vegetated coastal habitats in the western Arabian Gulf. 210Pb–dated sediment cores collected from seagrass, mangrove and saltmarsh habitats were analyzed to evaluate historical variations in concentrations and burial rates of 20 trace elements (Al, As, Ba, Ca, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, S, Sr, V and Zn). The highest correlations (Spearman correlation coefficients ≥0.51) were found between crustal elements (Al, Fe, Co, Cr, K, Na, Mg, Mn, Ni, V, and P), suggesting a common crustal source in the Gulf. The increased concentrations of these crustal elements in modern marine sediments of the Arabian Gulf seem to be linked to increased mineral dust deposition in the area. Over the last century, both elemental concentrations and burial rates increased by factors of 1–9 and 1–15, respectively, with a remarkably fast increase occurring in the past six decades (~1960 – early 2000). The considerable enrichment of trace elements in the Arabian Gulf during the last decades is most likely due to an increase in anthropogenic pressures, including industrial, urban and agricultural development. Our study demonstrates that sediments in vegetated coastal habitats provide long-term archives of trace elements concentrations and burial rates reflecting human activities in the Arabian Gulf.

Description: The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the 234Th/238U and 210Po/210Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The 234Th/238U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C/m**2/d) in late summer. Relationships obtained between the 234Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to the downward fluxes, likely via incorporation into sea-ice algal aggregates and zooplankton-derived material. The magnitude of the depletion of 210Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. 210Po fluxes and 210Po-derived POC fluxes correlated positively with sea-ice concentration, showing that particle sinking was greater under heavy sea-ice conditions than under partially ice-covered regions. Although the POC fluxes were low, a large fraction of primary production (〉30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic. This article is protected by copyright. All rights reserved.

Description: The dataset content the 14C and 210Pb geochronologies of mangroves, seagrass and saltmarshes of the Central eastern red sea coast and western Arabian Gulf. It also content depth profiles of CaCO3 content in the sediments of these ecosystems as well as the calculated burial rates in those sediments. A total of 52 cores were sampled along 80 km coastline of the Kingdom of Saudi Arabia in the central Red Sea (2015) and the Arabian Gulf (2016) (29 in mangroves forests and 23 in seagrass meadows, table 1). Seagrass soil cores were sampled in 1 to 4 m deep seagrass meadows, dominated by Halophila sp., Thalassia hemprichii, Enhalus acoroides, Thalassodendrum ciliatum and Cymodeacea sp., and mangrove soil cores were sampled in intertidal mono-specific A. marina forests. The sites sampled in the Red Sea include the coastal island of Al Taweelah (22°16'N, 39°05'E; 8 mangrove and 3 seagrass coring locations) and 3 coastal lagoons: Khor Almesena'a (22°22'N, 39°07'E; 8 mangroves and 10 seagrass coring locations), Khor Al-Baqila (22°44'N, 39°00'E; 6 coring locations in mangroves) and Khor Al-Kharrar (22°57'N, 38°51'E; 7 coring locations in mangroves and 10 in seagrasses) (Fig 1). Khor Al-Baqila underwent a major alteration with the conversion of the entire southern side of the embayment into a petrochemical terminal starting in 1981. Similarly, an important development of hard engineering structures occurred in the shoreline in front of Al Taweelah Island in the early 2010's . We also sampled 25 cores in the Saudi Arabian coast of the Arabian Gulf at 4 sites, Ras Safaniya (27°58'N, 48°46'E), Abu Ali Island (27°17' N, 49°33' E), Ras Tanura - Safwa (26°41' N, 50°00' E) and Uqair (25°43' N, 50°13' E) (Fig. 1). Three seagrass cores were sampled at each location in Halodule uninervis and Halophila stipulacea meadows (total of 12 cores). Additionally, 3 mangrove and 3 sabkha cores were sampled in the south of Abu Ali Island and 4 mangrove cores and 3 sabkha cores were sampled in the area of Ras Tanura - Safwa (Fig 1). All sites except Uqair have underwent alterations associated with the prevalent industrial and urban development in the region since the 1950s, including land reclamation, dredging, construction of bridges and pipelines, and oil spills. Soil cores were sampled using manual percussion and rotation (PVC pipe with an inner diameter of 70 mm). The length of core barrel inserted into the soil and the length of retrieved soil was recorded in order to correct for compression effects following the guidelines of Howard et al. (2014). All variables studied here are referenced to the corrected, uncompressed depths. The cores were sealed at both ends, transported vertically and stored at 4 °C before processing in the laboratory. 2.3 Biogeochemical analysis The soil cores were segmented into 1-cm-thick slices, which were oven-dried at 60 °C until constant weight to determine the dry bulk density (g cm-3). The slices were then grounded in an agate mortar and subdivided for analysis. All depths were corrected for compression considering a uniform distribution of the compaction throughout the total length of the cores as described by Serrano et al. (2016b). The mean ± SE compression factors (depth ratio between compressed and uncompressed soil) were 1.05 ± 0.18, 1.04 ± 0.03 and 1.16 ± 0.11 in the cores from sabkha, mangrove and seagrass sites of the Arabian Gulf respectively, and 1.19 ± 0.14 and 1.23 ± 0.17 in the seagrass and mangrove cores of the Red Sea. Short-term (last decades - century) and long-term (millennia) soil chronologies were established using 210Pb and 14C analyses, respectively. Forty-five cores were analyzed to retrieve chronologies using the 210Pb technique, 20 cores from the Red Sea (9 in seagrass and 11 in mangroves) and 25 cores from the Arabian Gulf (7 in mangroves, 12 in seagrass and 6 in sabkhas). The activity concentrations of 210Pb in the upper 20 to 30 cm (compressed) were determined in the soil fraction 〈0.125 mm by alpha spectrometry through the measurement of its granddaughter 210Po, assuming radioactive equilibrium between both radionuclides (Sanchez-Cabeza et al., 1998). The activity concentrations of excess 210Pb used to obtain the age models were determined as the difference between total 210Pb and 226Ra (supported 210Pb). Concentrations of 226Ra were determined for selected samples along each core by low-background liquid scintillation counting method (Wallac 1220 Quantulus) adapted from Masqué et al. (2002). These activity concentrations were found to be comparable with the concentrations of total 210Pb at depth below the excess 210Pb horizons. Analyses of reagent blanks, replicates and a reference material (IAEA-315, marine soils) were carried out for both 210Pb and 226Ra to assess for any contamination and to ensure reproducibility of the results. Average soil mass accumulation rates (MAR, expressed in g DW cm?2 yr?1) for the last decades/century were estimated using the Constant Flux: Constant Sedimentation model (CF:CS, Krishnaswamy et al., 1971). MAR were transformed into SAR (cm yr-1) using the dry bulk density (DBD) of each core. A total of 179 radiocarbon analyses were conducted in 77 cores (25 cores from the Arabian Gulf and 52 from the Red Sea) by Accelerator Mass Spectrometry. Analyses were done at 2 soil depths per core in the Red Sea cores and 3 depths in the Arabian Gulf cores, following standard procedures (ISO 17025 and ISO 9001) at the AMS Direct Laboratory, USA. Samples consisted of either pooled shells or bulk soils. The raw radiocarbon dates reported by the laboratory were calibrated using the R routine "Bacon" for Bayesian chronology building (Blaauw & Christen, 2011), assuming marine reservoir corrections of 110 ± 38 and 180 ± 53 years for the Red Sea and the Arabian Gulf, respectively (Southon et al., 2002). From the Bacon routine output, the mean age was used to produce an age-depth weighted regression model forced through 0 (0 cm is 1950 BP), using as weight the sum of the Euclidean distances of the minimum and maximum ages. We report the slope ± SE of the regression as the corresponding long-term SAR. 2.4 Carbonate content and Cinorg burial rates Calcium carbonate (CaCO3) content was determined in every fourth to fifth cm from surface to 20 cm depth. CaCO3 measurements were done with a calcimeter (Pressure Gauge Model 432, Fann, Houston, TX, USA; ASTM D 4373-84 Standard) by reacting the CaCO3 present in the sample with 10% HCl in a sealed reaction cell. The pressure build up due to the CO2 was measured with a bourdon tube pressure gauge that was pre-calibrated with reagent grade CaCO3.