GP17 - ANT

Overview

The U.S. GEOTRACES GP17-ANT expedition departed Punta Arenas, Chile on November 29th,  2023 and arrived in Lyttelton, New Zealand on January 29th, 2024. The cruise took place in the Amundsen Sea aboard the R/V Nathaniel B. Palmer with a team of 35 scientists lead by Peter Sedwick (Old Dominion University), Phoebe Lam (University of California, Santa Cruz) and Robert Sherrell (Rutgers University). GP17 was planned as a two-leg expedition, with its first leg (GP17-OCE) as a southward extension of the 2018 GP15 Alaska-Tahiti expedition and this second leg (GP17-ANT) into coastal and shelf waters of Antarctica's Amundsen Sea.

The almost two months cruise was largely successful in achieving its science goals, with 21 stations over the Amundsen Sea continental shelf, 3 stations over the continental slope and 3 off-shelf stations, including one deep-ocean station as a crossover with the preceding GP17-OCE cruise. All stations included collections 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 the collection of aerosols, precipitation, sea ice an snow as well as sediment cores for pore-fluid extraction and high-volume pumped seawater samples for radium isotopes and beryllium-7. The heavy sea ice cover prevented access to a number of planned stations including the Thwaites Ice Shelf, Pine Island Bay and the eastern portion of the outer Amundsen Sea shelf. Nonetheless, samples were collected 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 from 23 separate science projects, which together encompass measurements of nearly all of the GEOTRACES key trace elements and isotopes.