Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Seawater was sampled from Niskin bottles on GO-SHIP P16N, P18, and IO7N cruises using acid-cleaned silicone tubing (soaked in 10% HCl). Seawater from depths shallower than 200m was filtered using pre-combusted Whatman GF/F 0.7 micrometer (µm) filters. Solid-phase extracted dissolved organic carbon (SPE-DOC) was extracted using Bond Elut PPL 1 gram resins and established protocols (Dittmar et al., 2008). On P18 and IO7N, SPE-DOC was extracted on the vessel. Seawater from P16N was stored frozen until processing at the laboratory at University of California, Irvine (UCI).

SPE-DOC elutions in methanol follow established protocols (Dittmar et al., 2008), that have been slightly adapted to increase carbon yields (Lewis et al., 2020). After elution, SPE-DOC was dried using a centrifugal evaporator, sealed on a vacuum line, and combusted at 850C for 2 hours. SPE-DOC concentrations were measured manometrically on a vacuum line, and radiocarbon measurements were performed at the Keck Carbon Cycle Accelerator Mass Spectrometry Lab at the University of California, Irvine.

Refer to "Related Datasets" for the related Niskin bottle data from these GO-SHIP cruises. Seawater from multiple Niskin bottles was integrated for solid-phase extraction. The stations and depth ranges listed (between the minimum and maximum depths) refer to the Niskin bottles from the GO-SHIP bottle file in related datasets.

Data were processed using Microsoft Excel spreadsheets. SPE-DOC PPL recovery was calculated by dividing [SPE-DOC] by total [DOC]. Total [DOC] measurements can be found at https://doi.org/10.7289/v5cv4g1w or in (Druffel et al., 2021) currently in press at Geophysical Research Letters.

BCO-DMO Processing Description:
- Adjusted field/parameter names to comply with BCO-DMO naming conventions
- Missing data identifier ‘-999’ replaced with 'nd' 
- Added a conventional header with dataset name, PI names, version date

NSF Award Abstract:
Controls on the Aging of Marine Dissolved Organic Carbon

Most of the organic carbon in ocean water is in the dissolved form. Surprisingly, the age of this dissolved organic carbon is thousands of years old, even though it is thought to form during photosynthesis in the surface ocean. One explanation for the age of this carbon is the amount of time that it takes for carbon to circulate through the ocean. Investigators at the University of California Irvine (UCI) will investigate the aging of dissolved organic carbon in the Pacific, Southern and Indian oceans using C-14 isotopes. This work is important for knowing how carbon produced from human activities will be distributed on Earth in the future. This project will support the work of two graduate and two undergraduate students, providing hands-on experience that will prepare them for careers as scientists and educators. Both graduate students will be involved in a variety of educational activities. They will also help teach a short course on applications of C-14 in Ecology and Earth System Science for graduate students, technicians, postdocs and researchers during summer. UCI is a Hispanic-serving institution (27% of undergraduates identify as Hispanic), and 60% of students who attend UCI are first generation family representatives.

This study will examine the concentration, isotopic (14C, 13C) and molecular composition of dissolved organic carbon (DOC) in depth profiles from the Pacific, Southern and Indian Oceans. This information will help to determine the main controls on DOC cycling in the world’s oceans. The project will test the hypothesis that circulation is the primary control on DOC cycling in the deepest water (>3500 meters). The research will also investigate two alternative processes that could influence the age of DOC in deep water (2000-3000 meters): (1) dissolution of surface-derived particles and (2) input of ancient carbon from hydrothermal vents and flanks. Spectroscopic and spectrometric measurements designed to characterize a portion of the DOC will be performed on surface and deep water. Results will be incorporated into an inverse model of DOC cycling to determine the main processes controlling the DOC cycle in the ocean. DOC may serve as a sink for excess carbon dioxide produced from human activities and the size of the refractory DOC pool in the ocean could increase as circulation slows. Measuring the 14C age of DOC in the surface and deep ocean is important for understanding how the global carbon cycle will change as the Earth's climate shifts.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.