RV SONNE cruise TransGeoBiOc

09.09.2012 – 08.10.2012 (Pusan – Suva)

Possible alternative sources of CO2 in the ocean contributing to the glacial/interglacial variations in atmospheric CO2 in addition to CO2 dissolved in deep water reservoirs

To date, the causes of the glacial/interglacial variations in atmospheric CO2 are still poorly understood. It has been proposed for example, that atmospheric CO2 was sequestered into an abyssal water mass located in the Pacific during glacials for thousands of years and then ventilated rapidly through intermediate waters that circulated through the Southern Ocean during the last glacial termination. In the case of the so-called deep-water reservoir hypothesis however, there is no clear evidence that an isolated deep-water reservoir rich in CO2 was released during the last glacial termination.

During the past decade submarine surveys conducted along the active volcanic arcs in the Pacific and at hydrothermal vents in the NE and tropical E Pacific have discovered CO2-rich fluids venting at intermediate water depths. Estimates of the CO2 flux at these sites are sparse and the spatial extent of active vents from which there is a separate CO2 gas or liquid phase venting has only recently come to light. The initial results from these surveys indicate that there are CO2 fluxes from submarine arc volcanoes along the Pacific trench system in the western Pacific that far exceed that of Mid Ocean Ridge systems and hence, constitute a greater source of carbon to the global carbon budget than was previously thought. Most notably, liquid CO2 is not only venting from these sites, liquid CO2 is accumulating within the sediments on the margins of active volcanoes, kept in place by a hydrate caps that regulate the steady-state flux of neutrally buoyant liquid CO2 from the sediments beneath. To date, liquid CO2 accumulations have only been observed at sites in the western Pacific. The distribution of sites where liquid CO2 is documented includes the Okinawa Trough, the volcanoes along the Mariana and the Tonga-Kermadec Arcs.

We are drawn to these recent observations as a means of explaining the enigmatic nature of the glacial/interglacial CO2 changes. If indeed there is an additional source of CO2 that contributes to the glacial/interglacial variability in addition to CO2 dissolved in deep water reservoirs, a strategically important place to test this idea is near the source of that carbon. The back arc of the Mariana system near the Island of Rota is an ideal location to investigate the deglacial signature from intermediate water depths near one of the active volcanic systems. This expedition aims to obtain a suite of cores from sites near the Island of Rota that can yield biogenic carbonate through the last glacial termination to investigate whether there were sources of CO2 released from the North Pacific volcanic systems that contributed to the distinctive glacial/interglacial CO2 cycles.

The RV SONNE cruise TransGeoBiOc is a joint research cruise of the MARUM (Dr. Mahyar Mohtadi, Marine Sedimentology group), the University of Cologne (Prof. Dr. Hartmut Arndt, Zoological Institute, General Ecology group) and the University of Oldenburg (Dr. Katharina Pahnke, Institute for Chemistry and Biology of the Marine Environment, Marine Isotope Geochemistry group).

Chief scientist / contact person:
Dr. Mahyar Mohtadi
Room: MARUM II / 3170
Phone: +49 421 218 – 65660
E-mail:

Rota Island working area