The International Ocean Discovery Program (IODP) is now accepting applications for scientific participants on Expeditions 390/393 South Atlantic Transect aboard the JOIDES Resolution.

South Atlantic Transect Expeditions 390 and 393 (based on IODP Proposals 853-Full2 and 853-Add) are a multidisciplinary and joint scientific ocean drilling project that aims to recover complete sedimentary sections and ~200 m of oceanic crust along a crustal age transect at ~31°S across the South Atlantic Ocean to (1) investigate the history of low-temperature hydrothermal interactions between the aging ocean crust and the evolving South Atlantic Ocean; (2) quantify past hydrothermal contributions to global geochemical cycles; (3) investigate sediment and basement-hosted microbial community variation with substrate composition and age in the low energy South Atlantic Gyre subseafloor biosphere; and (4) investigate the responses of Atlantic Ocean circulation patterns and the Earth’s climate system to rapid climate change, including elevated CO₂ during the Cenozoic.

The South Atlantic Transect expeditions will target six primary sites on 7, 15, 31, 48, and 63 Ma ocean crust. The proposed transect, which follows a Mid-Atlantic Ridge crustal flow-line, will fill critical gaps in our sampling of intact in-situ ocean crust with regards to crustal age, spreading rate, and sediment thickness. The transect traverses the previously unexplored sediment- and basalt-hosted deep biosphere beneath the South Atlantic gyre, samples of which are essential to refine global biomass estimates and investigate microbial ecosystems’ responses to variable conditions in a low energy gyre and aging ocean crust. The transect is located near World Ocean Circulation Experiment (WOCE) line A10, providing access to records of carbonate chemistry and deep-water mass properties across the western South Atlantic through key Cenozoic intervals of elevated atmospheric CO₂ and rapid climate change. Reconstruction of the history of the deep western boundary current and deep-water formation in the Atlantic basins will yield crucial data to test hypotheses regarding the role of evolving thermohaline circulation patterns in climate change, and the effects of tectonic gateways and climate on ocean acidification.

Original proposals: 853-Full2 & 853-Add PDF