Dataset: Concentrations of dissolved thorium and protactinium isotopes (Th-232, Th-230, Pa-231) in seawater, sea ice, and melt ponds collected during the U.S. GEOTRACES Arctic cruise (HLY1502, GN01) on USCGC Healy from August to October 2015

This dataset contains concentrations of dissolved thorium and protactinium isotopes (Th-232, Th-230, Pa-231) in seawater, sea ice, and melt ponds collected during the U.S. GEOTRACES Arctic cruise (HLY1502, GN01) on USCGC Healy from August to October 2015. This is compiled data produced by two laboratories with the following associations: Lamont-Doherty Earth Observatory of Columbia University (LDEO) and the University of Minnesota (UMN). All data have been deemed intercalibrated by the International GEOTRACES Standards and Intercalibration (S&I) Committee.

Naming Conventions:
Parameter names in the form such as "Th_232_D_CONC_BOTTLE" are adopted based on a recommendation from the GEOTRACES community (https://www.geotraces.org/parameter-naming-conventions/).

A GEOTRACES sample number (Sample_ID) appended with an "A" denotes the archive sample collected during the same cast and at the same depth as the sample that was originally analyzed.

"Dissolved" (D) here refers to that which passed through stacked 0.8/0.45 µm Acropak™ 500 filter capsules sampled from conventional Niskin bottles on a CTD rosette (BOTTLE; NIS and GSNIS). This is true for all dissolved samples except for a select number that were collected using GO-FLO bottles on a CTD rosette (BOTTLE; GF), a pump from a small boat (BOAT_PUMP; SMBT), a pump through sea ice into seawater (SUBICE_PUMP), a trace metal clean ice corer (CORER), and a pump into a melt pond (MELTPOND_PUMP). Sampling system is indicated by the parameter name, and in some cases by Bottle_ID. For Bottle_ID, NIS represents Niskin bottles sampled from the 12-place 30 liter ODF rosette, GSNIS represents Niskin bottles sampled from the 36-place 10 liter GO-SHIP rosette, GF represents GO-FLO bottles sampled from the 24-place 12 liter GTC clean carousel, and SMBT represents surface (1 m) seawater samples collected from a small boat upstream of the ship using a battery-powered pump and Teflon-lined PVC tubing. SUBICE_PUMP represents seawater samples collected from under the ice (at approximately 1, 5, and 20 m) with the same pumping system used for BOAT_PUMP, MELTPOND_PUMP represents melt pond water samples that were collected using a battery-powered peristaltic pump and silicone tubing, and CORER represents sea ice samples that were collected using a trace metal clean ice corer. Bulk sea ice (CORER) samples were collected as ice cores about 1 m in length and melted overnight in LDPE melting chambers before they were subsampled into 5 liter cubitainers. BOAT_PUMP, SUBICE_PUMP, and MELTPOND_PUMP samples were each stored in 25 liter carboys during sample collection and then subsampled into 5 liter cubitainers aboard the ship. GF (BOTTLE), BOAT_PUMP, MELTPOND_PUMP, and CORER samples were passed through a 0.2 µm Acropak™ 200 filter capsule, unlike NIS (BOTTLE), GSNIS (BOTTLE), and SUBICE_PUMP samples, which were passed through stacked 0.8/0.45 µm Acropak™ 500 filter capsules. All seawater, sea ice, and melt pond samples were weighed directly in the on-shore laboratory to determine sample size, taking into account acid added at sea.

Units of Measurement:
Radionuclide concentrations are given as micro-Becquerel (10e-6 Bq, µBq or micro-Bq) per kilogram water for Th-230 and Pa-231, and picomole (10e-12 mol, pmol) per kilogram water for Th-232. A Becquerel is the SI unit for radioactivity and is defined as 1 disintegration per second. These units are recommended by the GEOTRACES community.

Results Publications:
These data have been published in the following:
Charette et al., 2020 – Dissolved Th-232 concentrations in upper ocean waters (Th_232_D_CONC_BOTTLE_dan73c)