Samples were filtered, acidified, and split at sea.\u00a0Samples were collected by Niskin bottle. Refer to the\u00a0cruise report for more information on cruise operations (http://dmoserv3.whoi.edu/data_docs/GEOTRACES/Arctic/ARC01-report.pdf).\u00a0
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For REE concentrations we removed an aliquot before pH-adjustment of each sample. Sample methodology is modified from the Lab #3 methods in Behrens et al. (2006) using a technique pioneered by Tachikawa et al. (1999). Samples were spiked with a mixed 142Ce, 148Nd, and 176Yb enriched isotope spike blend, and 10 ml of this spiked sample was preconcentrated offline using a SeaFast PICO system (ESI). Resulting solutions were analysed at Oregon State University (Corvallis, OR) using a Thermo X-Series II ICP-MS.
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We prepared our 5L split for neodymium isotopic analysis following Shabani et al. (1992). Samples were pH-adjusted to pH ~3.5, then pumped through 300 \u00b5l of HDEHP in a C18 cartridge to capture REEs. Rare earth elements were eluted from the cartridge using 6M HCl, then Nd was isolated using sequential chromatographic columns: AG50-X8 (BioRad) and Ln-Spec (Eichrom). Neodymium isotopic measurements were made at Oregon State University using a Nu Plasma 3 multicollector ICP-MS (Nu Instruments).
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Problem report: Gaps in Nd isotope data are due to errors made during column chromatography. Where the 2-sigma error of epsilon-Nd is \u22650.7, data is flagged with QV:IODE code 3, questionable/suspect quality.
Neodymium isotope ratios were corrected using JNdi-1 standard for reference (Tanaka et al., 2000). Dissolved concentrations were determined by a combination of isotope dilution and external calibration following methods developed by Tachikawa et al. (1999) and used by Lacan and Jeandel (2001) and Jeandel et al. (2013). Calibration standards were diluted and spiked with a mixed 142Ce, 148Nd, and 176Yb enriched isotope spike blend and were pre-concentrated using the same method as the samples. For Ce the concentration was determined by isotope dilution using 142Ce. For the other REEs we determined the concentrations of Nd and Yb in the samples both by isotope dilution and by external calibration, then used these two results to generate a ratio (spiked value / external calibration value) that we applied to the other REEs. Precision was determined by repeated measurements of two in-house seawater samples, one from Bransfeld Strait (~1100m depth) and one from nearshore California (~surface depth). Reported values here of Ce, Nd, and Yb are calculated by isotope dilution, and for other REEs by external calibration modified by the ratio described above.