South Pacific GEOTRACES cruise GP21 Completed!

Cruise GP21 (SO289)
RV Sonne
Valparaiso (Chile) – Noumea (New Caledonia)
February 18 – April 8 2022

Report by Eric Achterberg and Martin Frank:

“Cruise GP21(SO289) started 5 days delayed in Talcahuano (Chile). The delay was due to severe congestion in the commercial ports of Chile, and therefore we were transferred from Valparaiso to Talcahuano to load our containers at a shipyard. Covid also stopped two of our cruise participants to sail with us.”

Figure 1: Cruise track (white line) for GP21 with standard stations as white dots and superstations as orange dots. Brown dots are volcanoes and black triangle hydrothermal vent fields. Bottom: stations positioned on bathymetry map. Figure by Chris Galley.

“We sampled the narrow shelf off Chile, the East Pacific Rise, and deep stations until 141°W (Figure 1). We then needed to divert to Tahiti for a medical evacuation. We continued along a more northerly transect as initially planned (Figure 1). This saved us steaming time to Noumea, and also allowed us to sample in the international waters between the Exclusive Economic Zones (EEZs) of Tonga and New Zealand. Dealings with New Zealand authorities to navigate their complex permission system to work in their EEZ were not fruitful. Sampling the Kermadec trench and a shallow volcanic system (Monowai) on the adjacent arc was very exciting (Figure 2).”

Figure 2: Multibeam bathymetry data of cruise track over Monowai volcano cone, with the vertical profile of turbidity in the water column at station 40. Graph produced by Chris Galley. Global inset by N Augustine (GEOMAR), coarse bathymetry from GEBCO.

“We also managed to sample 4 stations in the South Fiji Basin before sailing to Noumea. We needed to arrive in Noumea earlier as planned, as New Caledonia was threatened to be hit by a severe tropical cyclone. So, the start, middle and end of the cruise were challenging. Nevertheless, the cruise was a success. We had a great team on board. We sailed nearly 7500 nautic miles, sampled 44 stations (full depth) of which 14 were superstations, and collected many thousands of samples. We now look forward to getting our containers back to GEOMAR, distributing the samples and starting the sample analyses!”

Scientists and crew of GP21/SO289. Photo by Nico Fröhberg.