SO228 (EISPAC / WESTWIND / SIODP)
Kaohsiung (TWN)- Townsville (AUS)
04.05.2013 - 23.06.2013
The RV SONNE expedition SO-228 combined three research proposals for the Western Pacific
1. Glacial sequestration of atmospheric CO2 in the deep Pacific (EISPAC)
Compared to interglacial periods, the atmospheric CO2 content was significantly reduced
during glacial periods, which has been related to a temporal sequestration of CO2 in the deep ocean. To date, no clear evidence exists for a postulated glacial abyssal reservoir of the atmospheric CO2 in the Pacific and its deglacial release through the Southern Ocean. We aim to verify the hypothesis of the glacial sequestration of atmospheric CO2 in the deep Pacific. We sampled sediments and the water column on the continental margin off Mindanao (Philippines) and Papua New Guinea. The samples/data will allow us to test whether and how atmospheric CO2 was sequestered into abyssal Pacific during glacials for thousands of years and then ventilated rapidly through intermediate waters that circulated through the Southern Ocean during glacial terminations.
2. Hydroclimate of the Western Pacific Warm Pool (WPWP) and its influence on the Indonesian Throughflow (WESTWIND)
The hydrological cycle of the Western Pacific Warm Pool (WPWP) is presently influenced by
variations in El Niño-Southern Oscillation (ENSO) as well as by high latitude climate. Despite
the significance of this cycle for the regional climate and its active role in global circulation, its
long-term variation and its influence on the Indonesian Throughflow (ITF) are largely unknown. Aiming to better understand the processes in order to improve the simulation of the dynamics of the WPWP in the models, we cored rapidly accumulating sediments off Philippines and Papua New Guinea, a critical region for understanding the response of the tropical hydrological cycle to different forcings, but where very few high-quality paleoclimate reconstructions are available. These records will enable the reconstruction of zonal and meridional gradients in temperature, salinity, and precipitation, and isolate the relative influence of different potential forcing mechanisms under different boundary conditions. Results of this research project will advance knowledge on the climate sensitivity of the WPWP.
3. Seismic Survey to support the IODP-full proposal 799 (SIODP)
We conducted seismic survey (multi-channel seismic, MSC) at two sites in the Davao Bay and south of Manus Island that had been proposed as drill sites in the IODP-full proposal 799 (Paleoceanographic records of the Western Pacific Warm Pool variability by Rosenthal, Mountain, Mohtadi et al.). The expedition took place in 2016 (IODP expedition #363) and while the Davao Bay site was abandoned due to safety concerns, the site south of Manus Island could be successfully drilled (see http://publications.iodp.org/preliminary_report/363/).
- Moffa-Sanchez P., Rosenthal Y., Babila T.L., Mohtadi M., Zhang X., accepted. Temperature evolution of the Indo-Pacific Warm Pool over the Holocene and the last deglaciation. Paleoceanography and Paleoclimatology, doi:10.1029/2018PA003455.
- Groeneveld J., Ho S.L., Mackensen A., Mohtadi M., Laepple T., 2019. Deciphering the variability in Mg/Ca and stable oxygen isotopes of individual foraminifera. Paleoceanography and paleoclimatology, doi:10.1029/2018PA003533.
- Hollstein M., Mohtadi M., Rosenthal Y., Prange M., Oppo D.W., Martinez-Mendez G., Tachikawa K., Moffa Sanchez P., Steinke S., Hebbeln D., 2018. Variations in Western Pacific Warm Pool surface and thermocline conditions over the past 110,000 years: Forcing mechanisms and implications for the glacial Walker circulation. Quaternary Science Reviews 201, 429-445.
- Lehmann N., Granger J., Kienast M., Brown K.S., Rafter P.A., Martínez-Méndez G., Mohtadi M., 2018. Isotopic Evidence for the Evolution of Subsurface Nitrate in the Western Equatorial Pacific. Journal of Geophysical Research Oceans 123, doi:10.1002/2017JC013527.
- Hollstein M., Mohtadi M., Rosenthal Y., Moffa Sanchez P., Oppo D., Martínez Méndez G., Steinke S., Hebbeln D., 2017. Stable oxygen isotopes and Mg/Ca in planktic foraminifera from modern surface sediments of the Western Pacific Warm Pool: Implications for thermocline reconstructions. Paleoceanography 32, doi:10.1002/2017PA003122.
- Mohtadi, M. and cruise participants, 2013. Report and preliminary results of RV SONNE cruise SO-228, Kaohsiung-Townsville, 04.05.2013-23.06.2013, EISPAC-WESTWIND-SIODP. Berichte, MARUM – Zentrum für Marine Umweltwissenschaften, Fachbereich Geowissenschaften, Universität Bremen, No. 295, 110 pages. ISSN 2195-9633.