Award: OCE-2023080

This project advanced understanding of the processes that regulate the production, transformation, and sequestration of biologically fixed carbon in the North Atlantic Ocean, with broader implications for quantifying the global ocean carbon cycle. The central objective was to improve estimates of the magnitude, timing, and efficiency of the ocean’s biological carbon pump by integrating complementary observations from biogeochemical (BGC) profiling floats and satellite ocean color data. Particular emphasis was placed on the timing and magnitude of the subpolar spring bloom and on mechanisms controlling carbon export efficiency in subtropical regions.

A major scientific outcome of the project was the development and application of new methods to quantify carbon export transfer efficiency across ocean biomes, resolved by season and particle size class. Using data from the global BGC Argo array, carbon fluxes associated with both small and large particles were evaluated across depth and biogeographic regions defined by the Fay and McKinley biome classification. Results demonstrate that both small and large particles contribute significantly to carbon export, while large particles increasingly dominate flux at greater depths. These findings reveal predictable, regionally and seasonally varying patterns in export transfer efficiency that can inform improved parameterizations of the biological pump in Earth system models.

The project produced multiple peer-reviewed manuscripts currently under review, including a lead paper titled Global patterns of biological carbon pump transfer efficiency by particle size (Park and Nicholson, Global Biogeochemical Cycles) and a collaborative study led by University of Washington researchers examining discrepancies between float- and satellite-based estimates of net primary production in the North Atlantic. Together, these studies highlight the value of combining chemical, optical, and remote sensing perspectives to better constrain carbon production and export processes. Project results were also disseminated through invited and contributed presentations at major international meetings, including the 2025 Chemical Oceanography Gordon Research Conference and the Ocean Sciences Meeting.

Beyond scientific advances, the project made a substantial contribution to workforce development and training. Graduate student Ellen Park completed her Ph.D. dissertation in September 2025, with this project forming a core component of her research. Her dissertation focused on quantifying ocean carbon and oxygen cycles using BGC Argo observations. Following graduation, she was awarded a postdoctoral fellowship with the Canadian Ocean Frontier Institute at Dalhousie University. The project supported regular collaboration among investigators, postdoctoral researchers, graduate students, and undergraduates at Woods Hole Oceanographic Institution, the University of Washington, the University of Maine, MBARI, and NOAA PMEL, fostering mentorship, professional development, and interdisciplinary exchange. Park also served as a lead organizer for the upcoming GO-BGC workshop, supporting community engagement and training for early-career BGC Argo users.

This collaborative effort strengthened international partnerships with the broader Argo community, including groups in Canada and the United Kingdom. These collaborations contributed to a review paper on ocean productivity estimates from BGC Argo and contributed to the development of shared data quality control and analysis tools. These tools and methods are publicly available, lowering barriers for other researchers and students to work with large volumes of BGC float and satellite data.

Overall, the project delivered new insights into the efficiency and variability of the ocean’s biological carbon pump, reduced uncertainties in estimates of carbon export, and demonstrated the power of sustained, distributed observations for studying climate-relevant ocean processes. The outcomes of this work provide an important foundation for improving predictions of how ocean carbon sequestration may respond to ongoing and future climate change.

Last Modified: 01/07/2026
Modified by: David Nicholson