Iron, manganese and nutrient data from four cruises in the eastern tropical North Pacific, 2012 to 2018 (NCEI Accession 0278409)

This dataset contains chemical and physical data collected on NOAA Ship Ronald H. Brown, R/V Roger Revelle, R/V Sikuliaq, and R/V Thomas G. Thompson during cruises RB1603, RR1805, SKQ201617S, and TN278 in the North Pacific Ocean from 2012-03-26 to 2018-04-17. These data include Iron, Manganese, Nitrate, Nitrite, depth, dissolved Oxygen, salinity calculated from CTD primary sensors, and water temperature. The instruments used to collect these data include CTD Sea-Bird SBE 911plus, Inductively Coupled Plasma Mass Spectrometer, Nutrient Autoanalyzer, Sea-Bird SBE 43 Dissolved Oxygen Sensor, and Trace Metal Bottle. These data were collected by James W. Moffett of University of Southern California as part of the "Development and Intercomparison of Methodologies to Measure Dissolved Ferrous Iron in Seawater (Ferrous iron in seawater)" project. The Biological and Chemical Oceanography Data Management Office (BCO-DMO) submitted these data to NCEI on 2020-11-04.

The following is the text of the dataset description provided by BCO-DMO:

Iron and manganese in the ETNP

Acquisition Description:
Samples were collected and analyzed as described in Bolster et al. Briefly, samples were collected from a trace-metal clean rosette, sampled under filtered nitrogen pressure through acid-washed 0.2 μm polyethersulfone filters into acid-washed low-density polyethylene bottles. Iron(II) was measured using luminol chemiluminescence, using diethylenetriaminepentaacetic acid as a masking ligand to correct for interferents (Bolster et al., 2018). Total dissolved metal samples were acidified with Optima grade hydrochloric acid (final concentration 20 mM) and stored at room temperature for several months. Dissolved iron and manganese were determined using inductively coupled plasma mass spectrometry with an offline preconcentration system.

Additional hydrographic and nutrient data is provided for some samples. Temperature, salinity, and oxygen were measured using a CTD, and measurements of phosphate, nitrate, and nitrite were performed using a nutrient auto-analyzer onboard, as described in Selden et al.

Trace metal samples were collected in 5 L Teflon-coated external spring “Niskin-type” bottles (Ocean Test Equipment) mounted on a powder-coated trace metal clean rosette (SeaBird Electronics). Samples were preconcentrated using a seaFAST system (ESI), and quantified using isotope dilution for iron and standard additions for manganese. Analyses were performed on an inductively coupled mass spectrometer in medium resolution mode (Thermo Element 2), using indium as an internal standard. Trace metal quantification was performed using Microsoft Excel 2016.

Temperature, salinity, and oxygen were determined from a SeaBird SBE 11plus CTD and a model 43 dissolved oxygen sensor, attached to a sampling rosette for dissolved nutrient concentrations. Nutrients were measured using an Astoria-Pacific nutrient autoanalyzer.

A number of samples have no measured values for total dissolved iron and manganese, either because sample collection was not logistically possible, or because some of the samples were lost in transit.