US GEOTRACES cruise in the Southern Ocean successfully completed

The RVIB Nathaniel B. Palmer arrived in Lyttelton, New Zealand on the evening of January 28, 2024, marking the completion of GEOTRACES cruise GP17-ANT, almost two months after departing from Punta Arenas, Chile. The cruise sampled 21 stations over the Amundsen Sea continental shelf, 3 stations over the continental slope, and 3 off-shelf stations, including one deep-ocean station that provides a crossover with the preceding companion cruise, GP17-OCE. All GP17-ANT stations included the collection of samples with a near-surface towfish, a conventional CTD-rosette, a trace-metal clean CTD-rosette, and McLane in-situ pumps. Additional sampling activities included collection of aerosols, precipitation, sea ice and snow, as well as sediment cores for pore-fluid extraction, and high-volume pumped seawater samples for radium isotopes and beryllium-7. Although most of the GP17-ANT science goals were achieved, 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. With support from the U.S. National Science Foundation, samples were collected for 23 separate science projects, which together will encompass measurements of nearly all of the GEOTRACES key trace elements and isotopes.