Departure of the German cruise in the Equatorial Pacific Ocean

The German cruise SO298 (GP11) on RV Sonne in the Equatorial Pacific Ocean will soon leave port for an expedition of nearly 9000 nautical miles. The cruise will commence in Guayaquil (Ecuador) on 14 April 2023 and arrive port in Townsville, Australia on 2 June 2023. The cruise is led by Eric Achterberg (GEOMAR Helmholtz Centre for Ocean Research Kiel). GEOTRACES principal investigators are Eric Achterberg, Andrea Koschinski, Martin Frank, Walter Geibert, Tim Conway, Stephan Galer and Wafa Abouchami. The team plans to undertake 42 full depth stations to collect GEOTRACES key trace element and isotope parameters and also investigate surface ocean biogeochemical processes related to (micro-) nutrient limitation and co-limitation, and nitrogen fixation.

Figure: Cruise SO298 (GP11) cruise track.

The main scientific aim of cruise SO298 (GP11) are to establish the distributions of trace elements and their isotopes (TEIs), quantify their sources from the four major ocean boundaries, and determine their biogeochemical cycling and relationships to large scale ocean circulation along a cruise track in the Equatorial Pacific Ocean (EPO). Specific objectives are to:

• Obj 1. Determine the distribution, as well as the physical and chemical speciation of TEIs, including micronutrients (such as Cd, Co, Cu, Fe, Mn, Mo, Ni, V, Zn, Cr), non biologically essential elements (such as Al, Pb, Hg, Ti, Zr, Hf, Nb, U, W and REEs (Rare Earth Elements)) and a range of isotope systems (including Ra, Nd, Ba, Si, Pb, Fe, Cd) in high resolution full-depth profiles and along a continuous surface water section sampled by a towed fish.

• Obj 2. Quantify the fluxes of these TEIs and micronutrients to the ocean from the four ocean boundaries: atmosphere, continent, ocean crust and sediments and assess the role of physical and chemical speciation of TEIs for their fluxes from the different sources.

• Obj 3. Assess, using chemical tracers and physical oceanography, the mixing and advection of these TEIs away from their sources into the ocean interior, and upwards into the surface ocean.

• Obj 4. Explore the relationship between macro- and micro-nutrient concentrations and fluxes, ocean productivity, particle and zooplankton distribution, metagenomic markers of particle export, nutrient utilization and limitation, diazotrophy, and the nitrogen and carbon cycles.

Learn more about this cruise by following the cruise blog here: