Dataset: Combined bottle data for nutrients and hydrographic parameters collected on the US GEOTRACES GP17-ANT cruise in the Amundsen Sea on RVIB Nathaniel B. Palmer (NBP2401) from November 2023 to January 2024

Water column samples were collected using seven different sampling systems, each of which is detailed below. Wherever feasible, methods adhered to protocols described in the GEOTRACES Cookbook (Aguilar-Islas et al., 2024)

(1) Conventional CTD rosette ("ODF rosette") system deployments. The ODF rosette casts were performed with a package consisting of a 36-bottle rosette frame, a 36-place carousel and 36 x 10.6 liter (L) Bullister-style Niskin sampler bottles. The carousel was provided by the NOAA PMEL, with primary underwater electronic components consisting of a SeaBird Electronics housing unit with a pressure sensor, temperature sensors, conductivity sensors, and a membrane oxygen sensor, as well as a transmissometer, chlorophyll-a fluorometer, altimeter, and turbidity sensor. The package was deployed on a conducting steel hydrowire using the winch in the Baltic Room of RVIB Nathaniel B. Palmer. Further details are provided in the Instruments section and the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

(2) Trace-metal clean CTD rosette ("GTC rosette") system deployments. The GTC rosette casts were performed using the U.S. GEOTRACES trace-element rosette sampling system with a SeaBird custom-built frame and carousel (newly purchased) and 24 x 12 L GoFlo sampler bottles. The system included a SeaBird Electronics CTD unit with a pressure sensor, temperature sensors, conductivity sensors, and a membrane oxygen sensor, as well as a transmissometer, chlorophyll-a fluorometer, altimeter, and turbidity sensor. The package was deployed on sheathed conducting cable with Vectran strength member using a Dynacon winch mounted on the 02 deck of RVIB Nathaniel B. Palmer. Further details are provided in the Instruments section and the GP17-ANT cruise report (Sedwick et al., 2024).

(3) McLane in-situ pump deployments. During deep casts of the McLane in-situ pumps, which were deployed on Hytrel-coated, non-conducting Vectran line using a MASH4k winch mounted on the 02 deck of RVIB Nathaniel B. Palmer, 30 L Niskin samplers were attached to the Vectran line ~1-2 meters above each McLane pump, and were closed using Teflon-coated messengers. Sample depths are estimated using data collected by a SeaBird Electronics 19-plus v2 Seacat self-recording CTD that was shackled to the end of the Vectran wire for each pump cast. Further details are provided in the GP17-ANT cruise report (Sedwick et al., 2024).

(4) Multicorer deployments. During sediment collections using a Bowers and Connelly Mega Corer ("multicorer"), an external-closure Niskin-type sampler modified and cleaned for trace metal use was attached to the multicorer frame in a position ~1 meter above the seafloor, and was closed by means of a cable released upon initial descent of the multicorer tubes and associated weights. Sample depths are estimated from seafloor depths as indicated by the shipboard multibeam sonar system. The Niskin sampler closed successfully and returned samples for 8 of the 9 multicorer deployments, at Stations 7, 10, 14, 15, 17, 21, 25, and 27. Further details are provided in the GP17-ANT cruise report (Sedwick et al., 2024).

(5) Towfish deployments. Near-surface (~2 meters depth) seawater was collected while underway on approach to or departure from each station using an overboard towed-fish ("towfish") sampling system deployed outside of the ship's wake. Using a deckboard pneumatic Teflon diaphragm pump, seawater from the towfish was pumped into a shipboard clean-air laboratory van. Further details are provided in the GP17-ANT cruise report (Sedwick et al., 2024).

(6) Radium surface pump deployments. Near-surface (~3 meters depth) seawater samples for analysis of radium isotopes were collected using a surface pump deployed by hand over the starboard quarter of RVIB Nathaniel B. Palmer.

(7) Beryllium-7 pump deployments. Upper water-column (<200 meters depth) seawater samples for analysis of beryllium-7 were collected using a deckboard pump system and overboard weighted inlet tube. Sample depths are estimated from an in-situ logging pressure sensor.

Dissolved nutrients (nitrate+nitrite, nitrite, phosphate and silicate) were determined shipboard in unfiltered seawater samples using a Seal Analytical continuous-flow AutoAnalyzer 3 following methods described in the nutrient section of the updated GO-SHIP repeat hydrography manual (Becker et al., 2019; 2020). Accuracy and precision were assessed from the analysis of Reference Materials for Nutrients in Seawater (RMNS) batch CM at every station, which yielded concentrations ± one standard deviation of 33.12 ± 0.18 micromoles per kilogram (µmol/kg) nitrate, 2.39 ± 0.02 µmol/kg phosphate, 100.8 ± 1.0 µmol/kg silicate, and 0.025 ± 0.005 µmol/kg nitrite, versus RMNS assigned concentrations of 33.2 µmol/kg, 2.28 µmol/kg, 100.5 µmol/kg and 0.02 µmol/kg, respectively. Further methodological details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

Salinity was measured in discrete samples using the Guildline 8410A "Portasal" salinometer aboard RVIB Nathaniel B. Palmer. The salinometer was standardized for each group of samples analyzed (normally 2 to 6 casts, up to ~95 samples) using two bottles of standard seawater: one at the beginning and one at the end of each set of measurements. IAPSO Standard Seawater Batch P-167 was used for all calibrations: K15 = 0.99988, salinity 34.994, expiration 2026-02-21. PSS-78 salinity was calculated for each sample from the measured conductivity ratios. The offset between the initial standard seawater value and its reference value was applied to each sample. Then the difference (if any) between the initial and final vials of standard seawater was applied to each sample as a function of elapsed run time. Further methodological details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

Dissolved oxygen was measured in discrete samples using an SIO/ODF-designed automated oxygen titrator using photometric end-point detection based on the absorption of 365-nanometer (nm) wavelength ultraviolet light using a whole-bottle modified-Winkler titration following the technique of Carpenter (1965) with modifications by Culberson (1991), but with higher concentrations of potassium iodate standard (~0.012 N), and thiosulfate solution (~55 grams per liter (g/L)). Further methodological details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

Instrumentation Details:
ODF CTD rosette system and sensors: ODF rosette casts were performed with a package consisting of a 36-bottle rosette frame and carousel, and 36 (plus spares) x 10.6 L Bullister-style Niskin bottles. Underwater electronic components primarily consisted of an SBE-9plus housing unit with Digiquartz pressure sensor with dual plumbed lines where each line has a pump, SBE-3plus temperature sensor, SBE-4C conductivity sensor, and exhaust line. An SBE-43 membrane oxygen sensor was mounted on the "primary" line. An SBE-35 reference thermometer, JFE-Advantech RINKO oxygen optode, WetLabs C-Star transmissometer and ECO-FL-RTD chlorophyll-a fluorometer, Valeport VA500 altimeter, and SeaPoint turbidity sensor were also mounted on the rosette. The CTD pressure, temperature, conductivity, and oxygen sensors were calibrated prior to the cruise, whereas the transmissometer was calibrated before the start and after the end of science operations. The CTD data acquisition system consisted of an SBE-11plus (V1) deck unit and a networked generic PC workstation running Windows 10. SBE SeaSave7 v.7.26.7.121 software was used for data acquisition and to close bottles on the rosette. Further details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

GTC CTD rosette system and sensors: GTC rosette casts were performed with a package consisting of the 24-bottle U.S. GEOTRACES SBE trace-element rosette frame and carousel, and 24 (plus spares) x 12 L GoFlo sampler bottles. Underwater electronic components primarily consisted of an SBE 9plus housing unit with a Digiquartz pressure sensor, dual SeaBird SBE-3 temperature sensors and SBE-4C conductivity sensors, an SBE-43 membrane dissolved oxygen sensor, and a WetLabs C-Star transmissometer and ECO-FL-RTD chlorophyll-a fluorometer. Sensors were calibrated during summer 2023, immediately prior to the GP17-ANT cruise, and the transmissometer was calibrated before the start and after the end of science operations. The GTC rosette also included a Benthos altimeter, which ceased functioning during the latter part of the cruise and was replaced with a Valeport altimeter borrowed from the shipboard USAP equipment, and a Seapoint turbidity sensor. The CTD data acquisition system consisted of an SBE-11plus deck unit and a networked generic PC workstation running Windows 10. SBE SeaSave7 v.7.26.7.121 software was used for data acquisition and to close bottles on the rosette. Further details are provided in the GP17-ANT cruise report (Sedwick et al., 2024).

CTD used with McLane in-situ pump deployments: Niskin sampling depths were estimated from data recorded by an SBE 19-plus v2 Seacat self-recording CTD. Further details are provided in the GP17-ANT cruise report (Sedwick et al., 2024).

Dissolved nutrient analysis: Seal Analytical continuous-flow AutoAnalyzer 3. Further details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

Salinity measurements: Guildline 8410A Portasal salinometer. Further details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).

Dissolved oxygen analyses: SIO-ODF-designed automated oxygen titrator using photometric end-point detection based on the absorption of 365 nm wavelength ultra-violet light. Sample titration and data logging were controlled by PC LabView software. Thiosulfate was dispensed by a Dosimat 665 buret driver fitted with a 1.0 ml burette. Further details are provided in the ODF cruise report (Scripps Institution of Oceanography Ocean Data Facility team, 2024).