Freshened water exists in continental shelf aquifers worldwide. One remarkable example is the US Atlantic shelf, where groundwater in shallow sand aquifers >100 km offshore has salinity that is 10 % of seawater salinity. Expedition 501 will drill sites off Massachusetts, US, to estimate how much freshened water there is, processes that emplace the water, and rates of emplacement. The expedition will also assess whether salinity patterns have important implications for microbial processes.

Unexpected shallow and large slip on the plate boundary fault during the 2011 Tōhoku-oki earthquake contributed to a large tsunami. However, our knowledge on the past history of such slips is limited due to the long recurrence interval of the events. IODP³ Expedition 503 recovers the whole trench-fill sequence in the central Japan Trench to understand the nature and recurrence of hadal trench tsunamigenic slips and their earthquake-related carbon accumulation and element cycles.

IODP³ Expedition 502 will drill the outer-rise area of the Japan Trench, where the sediments above the acoustic basement are thin. The thin sediments are hypothesized to be caused by basalt intrusions or lava flows related to petit-spot magmatism, a type of volcanic activity caused by the bending of the incoming plate near the trench. Our goal is to determine whether petit-spot magmatism is more widespread than previously thought and to understand its role in the Earth's systems.

Ontong Java Plateau, the largest oceanic plateau, has played a key role in the tectonics of the Ring of Fire. Volcanic ash that fell on the plateau has the potential to test competing ideas about how plates change their motion and to record ancient wind systems. Previous scientific ocean drilling drilled cores on the plateau, but the ashes have not been analysed. Expedition 504S will sample archived cores, analyse the ash, and compare it with volcanic rocks from the nearby Solomon Islands.

IODP³ Expedition 506S will integrate sediment core data from key North Atlantic drill sites, aligning records to build a regional climate history. The team will develop advanced computational tools for signal alignment and image analysis, improving correlations of past climatic shifts. The expedition will also create user-friendly resources to train new paleoclimate researchers, and all data and methods will be shared openly.