Dataset: GN01 Ice Pond NO3 H2O

Sea ice was collected using a trace metal clean Kovacs T-handle corer to collect 1 m long cores at 6 sea ice stations along the Canada Basin transect. Snow was collected into precleaned HDPE bottles, while seawater was pumped from beneath the sampled sea ice hole into a carboy and filtered into pre-cleaned bottles aboard the Healy. All samples were stored frozen until analyses or further sample prep could take place. Ice cores were bagged and stored at -20 degrees celsius onboard until cores could be cut and sub-sectioned in a cold room at University of Washington in Seattle prior to shipment back to Brown University.

Concentration analysis of samples was completed using an automated colorimetric system (WestCo SmartChem 200); the pooled standard deviation of control standards run within each sample set run was 0.3 micromoles per Liter (6.2 ppb nitrate); detection limit was 0.09 micromoles per Liter. Based upon nitrate concentration, 20 nmol of N were injected into vials containing denitrifying bacteria to convert nitrate to nitrous oxide for isotopic analysis on a ThermoFisher Delta V isotope ratio mass spectrometer. Analysis for d15N and d18O of nitrate are described in Sigman et al. (Analytical Chemistry; 2001), Casciotti et al. (Analytical Chemistry; 2002), McIlvin and Casciotti (Analytical Chemistry; 2011). Kaiser et al. (Analytical Chemistry; 2007) describes similar methodology for the determination of D17O of nitrate.  D17O analyses require 50 nmol of N for complete analysis.