The research project Manihiki II intends on reconstructing the dynamics and development of the Western Pacific Warmpool (WPWP) during the Pleistocene, in particular changes of the thermocline due to the influence of high-latitude intermediate water masses.

The WPWP is a key area for ocean-atmosphere heat transport and hence, global climate. The temperature gradient between the eastern and western tropical pacific is crucial for the El Niño Southern Oscillation (ENSO) climate phenomena. But whether the thermal development and dynamic of tropical regions are controlled by extra-tropical climate mechanisms either via atmospheric teleconnections or by “oceanic tunnels” is not resolved by paleoceanographic studies yet.

Water mass exchange between the Southern Ocean and the equatorial regions via “ocean tunnels” are the key mechanism to cool the tropics from below as cool nutrient-rich surface waters (SAMW) are subducted in the south (“thermocline ventilation”) and transported northward on defined pathways (“ocean tunnels”) into the tropical regions. Further they affect the biological pump of the equatorial divergence and interact with the global carbon cycle by connecting the Southern Ocean, a sink for atmospheric CO₂, with the equatorial Pacific as a source for atmospheric CO₂.

During expedition RV Sonne SO225 in 2012/2013 several sediment cores, in-situ measurements with CTD-Rosette and a mulitnet catchment were obtained. In a close cooperation with the GEOMAR Helmholtz Centre for Ocean Research Kiel these material will be used to reconstruct the dynamic and influencing factors on the WPWP and thus, global climate.

Nadine Rippert

Ralf Tiedemann