Description: The data are from samples of core HLYHLY0503-11MC8, which was collected onboard the American research vessel Healy on the Mendeleev Ridge during the Healy-Oden Trans Arctic Expedition (HOTRAX) in summer 2005 (Darby et al., 2005). The core site is located at 83°07.7300N, 174°41.5700W (water depth = 2570 m). The data include dolomite and total carbonate, stable isotope data in planktic foraminifers and bulk (18O and 13C), sand and clay content, in addition to 230Thxs and 231Paxs. Data are reported vs. depth (cm). Methods : The multicore was sampled at half-centimeter intervals. The sediment was dried and ground in an agate mortar. Particle-size analyses were performed from wet sieved sediment in the 〈 2 mm fraction after disaggregating in an ultrasonic bath for 90 seconds. The disaggregated sediment was analyzed with a laser-diffraction particle-size analyzer (LS13320, Beckman-Coulter™). Laser calibration was verified before and after analyses using three standards Latran 300-0.3 mm, G15-15 mm, and GB500-500 mm). The particle-size data and granulometric statistics were processed with the Gradistat program of Blott and Pye (2001). Percentages of sand and clay data are reported here. The foraminifer samples used for isotopic investigation consist of sieved then hand-picked ~ 80 mg sub-assemblages of Neogloboquadrina pachyderma, i.e., about 10 to 12 shells. Samples were analyzed with a Micromass Isoprime™ isotope ratio mass spectrometer in dual inlet mode coupled to a MultiCarb™ preparation system. CO2 was extracted at 90°C by acidification with 100% concentration H3P04. Measurements were made with an internal reference carbonate material calibrated against the VPDB scale. The analytical reproducibility determined by replicate measurements of the internal carbonate material (UQ6a; dl3C= 2.25‰; d18O = -1.4‰) was routinely better than 0.05 ‰ for both isotopes. Mineralogical assemblages were determined by X-ray diffraction using a Siemens D5000 with CoKa2 radiation and Si detector. Aliquots of dry bulk sediment were dispersed in distilled water and then sieved on a 63 mm mesh. Following this sieving, the samples were then sieved on a 10 mm mesh. Each sample was placed on an X-ray diffractometer three times, one with no specific treatment, one heated, and one with an ethylene-glycol treatment. Semi¬ quantitative estimations N (s ~ 5%) of the main mineral species were based on the area of the diffraction peak for each mineral corrected for quartz. The carbonate fraction reported here is defined as the sum of calcite and dolomite contents. The methods for 230Th measurements, 230Th excess, and 231Pa excess calculations are described in Not and Hillaire-Marcel (2010). The 230Th excess data are already archived in PANGAEA (https://doi.org/10.1594/PANGAEA.914619). Blott, S.J., Pye, K., (2001) Gradistat: a grain size distribution and statistics package for the analysis of unconsolidated sediments. Earth Surface Processes and Landforms 26, 1237-1248. Darby, D.A., Jakobsson, M., Polyak, L. (2005). Ice breaker expedition collects key Arctic seafloor and ice data. EOS Transactions American Geophysical Union 86, 549-552. Not, C., Hillaire-Marcel, C. (2010) Time constraints from 230Th and 231Pa data in late Quaternary, low sedimentation rate sequences from the Arctic Ocean: an example from the northern Mendeleev Ridge. Quat. Sci. Rev. 29, 3665–3675.

Description: In this dataset we present a global compilation of over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the Late Holocene (0-5000 years ago, or 0-5 ka) and the Last Glacial Maximum (18.5-23.5 ka). Data have been screened for age control, errors, and lithogenic corrections. Overall quality levels were computed by summing each record's scores on the individual criteria. A record is optimal if it is based on a chronology that is constrained by δ18O or 14C and it provides both the raw nuclide concentrations and the associated errors. About one quarter of the records in the database achieved this highest quality level. The large majority of the records in the database are good, passing two of the three criteria, while the remaining quarter are of fair or poor quality.

Description: PP43B-1476 Mg to Ca ratios of the benthic foraminifer species Cibicidoides wuellerstorfi provide a great potential for reconstructing bottom water temperatures, especially from the lower end of the temperature range between 0 and 6°C (Tisserand et al., 2013). A set of core top samples from the Fram Strait and the Norwegian margin have been studied for Mg/Ca ratios in C. wuellerstorfi in order to establish a calibration relationship to the environmental conditions. In this part of the northern North Atlantic the bottom water temperature range between -0.5 and -1°C. For the calibration to modern water mass conditions, modern oceanographic data from both existing conductivity-temperature-depth (CTD) casts and the World Ocean Data Base 2013 (Boyer et al., 2013) have been used. Benthic Mg/Ca ratios are relatively high suggesting a preference of C. wuellerstorfi to incorporate Mg below 0°C. Although no correlation has been found to existing temperature calibrations, the data are in line with earlier Mg/Ca data from C. wuellerstorfi in the area (Martin et al., 2002; Elderfield et al., 2006). The carbonate ion effect is most likely a main cause for the relatively high Mg/Ca ratios found in core top samples from the Fram Strait and the Nordic Seas, however, other factors may influence the values as well. Holocene records of benthic trace metal/Ca ratios from the eastern Fram Strait display trends similar to those found in other proxy indicators, despite the difficulties to constrain a temperature calibration for this low temperature range. In particular, the benthic B/Ca and Li/Ca records resemble trends in Holocene planktic foraminifer assemblages, suggesting to be influenced by environmental factors such as the carbonate ion effect consistent for the entire water column.

Description: Mg to Ca ratios of the epibenthic foraminifer species Cibicidoides wuellerstorfi have been identified to be strongly controlled by temperature and thus to have great potential for reconstructing bottom water temperatures, especially from the lower end of the temperature range (0-6°C; Tisserand et al., 2013). In the Fram Strait, where main water mass exchanges between the Arctic Ocean and the world’s oceans occur, new temperature estimation tools independent from faunal assemblages can help to better understand the complex interaction of different water masses with possible implications to changes in the meridional overturning circulation and the heat flux to the Arctic Ocean. Furthermore, Mg/Ca temperatures can help unravelling the local impact (e.g., of brine-enriched waters) from general trends in bottom water circulation. In order to apply Mg/Ca-derived temperatures to paleo-records from the Fram Strait, a calibration relationship between modern Mg/Ca ratios to bottom water temperatures which fits the environmental conditions of the Fram Strait needs to be developed. We therefore studied Mg/Ca ratios of C. wuellerstorfi in a set of coretop samples from the Fram Strait and the Norwegian margin where bottom temperatures range between -0.5 and -1°C. For the calibration to modern temperatures, we used modern oceanographic data from both existing conductivity-temperature-depth (CTD) casts and the World Ocean Data Base 2013 (Boyer et. al., 2013). Benthic Mg/Ca ratios are relatively high suggesting a preference of C. wuellerstorfi to incorporate Mg at temperatures below 0°C. Although no correlation has been found to existing temperature calibrations using higher temperature ranges (0-6°C), the data are in line with existing Mg/Ca data from C. wuellerstorfi from the Norwegian Sea and the Fram Strait (Martin et al., 2002; Elderfield et al., 2006).While correlation between Mg/Ca ratios to either temperature or salinity is difficult to constrain, better correlation exists to water depth. We therefore consider the carbonate ion effect as one possible explanation for the relatively high Mg/Ca ratios found in coretop samples from the Fram Strait and the Nordic Seas. Despite the difficulties to constrain a temperature calibration for this low temperature range down to -1°C, variations in benthic Mg/Ca ratios investigated in Holocene records from the eastern Fram Strait display trends similar to those found in other benthic proxy indicators. A short-lived decrease in benthic carbon isotopes and sortable silt mean grain size thus seems to correlate to lower Mg/Ca ratios during the 8.2 ka event. Also, a Late Holocene trend towards significantly higher benthic oxygen isotopes may be related to decreasing Mg/Ca ratios. Essential bibliography Boyer, T.P., Antonov, J.I., Baranova, O.K., Coleman, C., Garcia, H.E., Grodsky, A., Johnson, D.R., Locarnini, R.A., Mishonov, A.V., O'Brien, T.D., Paver, C.R., Reagan, J.R., Seidov, D., Smolyar, I.V., Zweng, M.M. 2013. World Ocean Database 2013. Sydney Levitus, Ed., Alexey Mishonov, Technical Ed., NOAA Atlas NESDIS 72. 209 pp. Elderfield, H., Yu, J., Anand, P., Kiefer, T., Nyland, B. 2006. Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis. Earth and Planetary Science Letters 250, 633-649. Martin, P.A., Lea, D.W., Rosenthal, Y., Shackleton, N., Sarnthein, M., Papenfuss, T. 2002. Quaternary deep sea temperature histories derived from benthic foraminiferal Mg/Ca. Earth and Planetary Science Letters 198, 193-209. Tisserand, A.A., Dokken, T.M., Waelbroeck, C., Gherardi, J.-M., Scao, V., Fontanier, C., Jorissen, F. 2013. Refining benthic foraminiferal Mg/Ca-temperature calibrations using core-tops from the western tropical Atlantic: Implication for paleotemperature estimation. Geochemistry, Geophysics, Geosystems, 14(4), 929-946.