Award: ANT-2023214

Project Outcomes

Collaborative Research: Management and Implementation of U.S. GEOTRACES GP17 Section: Amundsen Sea Sector of the Antarctic Continental Margin (GP17-ANT)

Intellectual Merit

Planning a major oceanographic expedition requires a great deal of advance planning, sometimes years in advance.  This has been the case with the US GEOTRACES GP17-ANT research cruise to the Amundsen Sea sector of the West Antarctic continental shelf and proximal deep ocean water.  The management team comprising four experienced scientists started the detailed organization and planning in 2021 and the efforts continued through 2024 and beyond.  This grant funded those planning efforts, hiring of technical staff, and preparation of shared equipment.

Stimulated by recent preliminary research on the trace element biogeochemistry of this region, the overarching goal of this expedition was to thoroughly explore the trace element and isotope distributions on a sector of the Antarctic shelf where warming over the last few decades has greatly increased the rate at which continental glaciers are melting into the sea.  This cruise provided a sampling platform in support of 23 individual NSF-funded science projects, following the successful model of previous U.S. GEOTRACES cruises that have been conducted in the Atlantic, Pacific and Arctic ocean basins. 

In addition to essential sampling and sample processing operations, the management team provided critical ancillary measurements (hydrography, nutrients, algal pigments).  The GP17-ANT cruise aimed to sample the ocean region between 100°W and 135°W, with stations ranging from 67°S in the Antarctic Circumpolar Current southward to the Amundsen Sea continental shelf, including stations adjacent to several rapidly melting ice shelves and in highly-productive regions not covered in sea ice, called polynyas.  Seawater samples from all depths were collected using two different CTD-rosette systems, in-situ high-volume submersible pumps, and an underway “towed fish” surface water sampler.  We also collected seafloor sediments, snow and sea ice, and atmospheric aerosol (particle) samples from the marine boundary layer.  The common theme of these sample collections was the necessity to avoid contamination of the samples with material from the steel ship, the clothes of the participants, and even the normal laboratory air.

The GP17-ANT expedition was originally proposed as a 60-day cruise in January-March 2022, to follow immediately after a complementary open-ocean US GEOTRACES cruise, GP17-OCE.  Due to ship scheduling constraints and the impacts of the COVID-19 pandemic on Antarctic fieldwork and logistics, GP17-ANT was delayed until late 2023.  The expedition finally departed Punta Arenas, Chile, aboard the research icebreaker Nathaniel B. Palmer (cruise NBP24-01) on 29 November 2023, and arrived in Lyttleton, New Zealand, on 28 January 2024.  Led by chief scientists Peter Sedwick, Phoebe Lam and Robert Sherrell, and assisted by Antarctic Support Contract personnel, the 35 cruise participants collected samples and observations, working around the clock.

The key outcome of the GP17-ANT expedition was the safe and successful collection of samples and observations from 21 stations over the Amundsen Sea continental shelf, 3 stations over the continental slope, and 3 off-shelf stations, largely according to plan.  Most of the GP17-ANT science goals were achieved, although large expanses of heavy sea ice surrounding the Amundsen Sea Polynya prevented access to several planned sampling locations, including the Thwaites Ice Shelf, Pine Island Bay, and the eastern portion of the outer Amundsen Sea shelf.  Nevertheless, the cruise provided exciting opportunities to collect samples from stations adjacent to the Dotson and Getz Ice Shelves, as well as on- and off-shelf stations impacted by melting sea ice, polynya stations where phytoplankton biomass was extraordinarily high, and a station adjacent to fast ice with near-zero chlorophyll fluorescence. 

Broader Impacts

There was also significant progress in outreach activities over the course of the project.  The cruise included participation by a freelance science journalist selected by the Council for the Advancement of Science Writing, Sofia Moutinho, who was included in co-PI Lam's portion of the cruise management proposal.  Ms. Moutinho published a feature article in the American Geophysical Union magazine Eos, and presented four Scientific American online podcasts devoted to the expedition. Through these media, and through additional outreach activities to come from the expedition PIs, the public will be able to learn about how critical trace elements move around this environment, through biological and chemical processes, overlain by dynamic currents and large inputs of glacial meltwater.

Last Modified: 05/26/2025
Modified by: Robert M Sherrell