Award: ANT-2023178

The international research program GEOTRACES aims to improve understanding of the distribution and behavior of trace elements and their isotopes (TEIs) in the world's oceans. Trace elements are chemical elements that are present in seawater at very low concentrations, typically less than one part per billion. Many trace elements have two or more isotopes, which exhibit similar chemical behavior but have slightly different atomic masses, and may be radioactive in some cases (for example, the element radium has four isotopes that are radioactive: radium-223, radium-224, radium-226 and radium-228). In the ocean, TEIs are important because they can serve as essential "micronutrients" that regulate marine biological production (e.g., iron and manganese), or can be toxic to living organisms (e.g., lead and copper), or can provide chemical tracers of past and present oceanic processes such as circulation and particle transport (e.g., neodymium and thorium).

A major activity of the GEOTRACES program has been oceanographic expeditions (research cruises) that have collected water-column samples and related observations from the all of the major ocean basins for measurements of a suite of key TEIs. With funding support from the U.S. National Science Foundation (NSF), The U.S. GEOTRACES program has completed research cruises in the Atlantic, Arctic, Pacific and Southern Oceans. One such NSF-supported research cruises was the U.S. GEOTRACES GP17-ANT expedition, which collected samples and data from the Amundsen Sea, over the continental shelf and slope of West Antarctica. The GP17-ANT cruise management and implementation project supported the planning and execution of this two-month oceanographic research expedition, including the collection and processing of samples for analyses of a broad suite of TEIs as well as "core" ancillary measurements (hydrography, nutrients, phytoplankton pigments, optical parameters) and field observations, and the post-cruise compilation, distribution and interpretation of the core ancillary data collected during the field program.

The GP17-ANT expedition departed Punta Arenas, Chile, aboard the research icebreaker Nathaniel B. Palmer on 29 November 2023, and arrived in Lyttleton, New Zealand, on 28 January 2024. The cruise occupied 21 sampling stations over the Amundsen Sea continental shelf, 3 stations over the adjacent continental slope, and 3 off-shelf stations, including one deep-ocean station that provided a crossover comparison with a preceding U.S. GEOTRACES cruise GP17-OCE (Figure 1). All sampling stations included the collection of water-column samples using a near-surface towed sampler, samplers mounted on carousels that included conductivity-temperature-depth sensors, and in-situ pumps to collect particles. Additional sampling activities included collection of aerosols, precipitation, sea ice and snow, as well as seafloor sediments and interstitial fluids. These samples were collected in support of 23 individual NSF-funded science projects, which examine a variety of TEIs to address a range of questions concerning topics that include the sources and fate of micronutrients in this highly productive ocean region, and the chemical changes that occur as warm Circumpolar Deep Water intrudes onto the continental shelf and drives the melting of glacial ice shelves along the Antarctic coastline.

Following the field expedition, the GP17-ANT cruise management team have analyzed the core ancillary cruise data to provide an essential contextual framework for the individual science projects, such as information on regional circulation, and the progression of seasonal sea ice retreat and primary production in the study region during the cruise period. In addition, during fall 2025 and spring 2026, the cruise management team convened fortnightly virtual presentations of emerging results by individual investigators, to facilitate collaboration and synthesis of the scientific results from the GP17-ANT expedition. These activities were furthered by an in-person data synthesis workshop that was convened at Old Dominion University in June 2026, with the aim of fostering the preparation of collaborative scientific journal publications that present and synthesize the key findings from the GP17-ANT expedition – a process that is ongoing at this writing. Finally, the GP17-ANT cruise management team has overseen the submission and archiving of the core ancillary cruise data with the NSF Biological and Chemical Oceanography Data Management Office (BCO-DMO), a publicly accessible data repository.

In summary, this project has provided essential samples, data and contextual framework for 23 NSF-funded science projects, the results of which will significantly advance our understanding of the distributions of TEIs in the Antarctic marine environment, the processes that shape these distributions, and the processes that are impacted by these TEIs. The project study region in the Amundsen Sea is experiencing rapid environmental changes, with anticipated impacts on oceanic circulation, biology and chemical cycling, and the data resulting from the GP17-ANT expedition are crucial to testing and refining the conceptual and numerical models that are required to understand the future trajectory of the Earth system. Finally, this project provided training, field experience, samples and data for graduate students and early-career scientists, who participated in the field program or are making use of project data in their research.

Last Modified: 08/06/2026
Modified by: Peter N Sedwick