Mindanao Eddy, Halmahera Eddy: Variability of West Pacific Warm Pool and Indonesian Throughflow (inflow passages and main gateway)
Final Report Abstract
Paleoproductivity, SST and thermocline temperature reconstructions within the main inflow path of the ITF in the equatorial West Pacific Ocean reveal considerable glacialinterglacial as well as sub-orbital variability over the last 160 kyr. Enhanced surface productivity, unusually low SST, low thermal gradient within the upper water column in Core MD06-3067 (6°31 N, 126°30 E, 1575 m water depth) provide evidence for periodic upwelling during MIS 2 and MIS 3. Increased glacial upwelling of the Mindanao Dome promoted inflow of cooler, nutrient-enriched waters with reduced vertical stratification. Thus during glacials, the ITF acted as a more direct conduit of Pacific surface and thermocline waters and provided a major channel for nutrient export from the Pacific to Indian Ocean, especially because the South China Sea was disconnected from the ITF. During Heinrich events, sea surface warming mark periodic collapses of the Mindanao Dome upwelling. We attribute rapid SST changes during MIS 2 and MIS 3 to changes in the ENSO state and associated latitudinal shifts in the ITCZ position that affected boreal winter monsoonal winds and upper ocean circulation patterns. Our results indicate that La Niña conditions prevailed during the LGM, whereas an El Niño mode dominated during Heinrich events. XRF-scanning derived Fe, Ti, K and Al concentrations and the sedimentary concentration of magnetic particles, interpreted to reflect past changes in runoff from Mindanao, indicate weakened summer monsoon precipitation in the equatorial West Pacific during northern hemisphere insolation maxima. Benthic stable isotope data from Cores MD06-3067 and MD06-3075 indicate long-term influence of mid-depth water originating from the Southern Ocean, interrupted by abrupt incursions of 13C-depleted water masses originating from the North Pacific during Terminations I and II. These sudden shifts in intermediate and deep circulation close to Mindanao indicate major reorganization in the penetration of mid-depth water masses within the entire West Pacific during glacial-interglacial climatic transitions.
Publications
- (2006), IMAGES XIV, MD155- Marco Polo 2 cruise report OCE/2006/06, in Les rapports de campagne à la mer, 55 pp., Inst. Polaire Fr., Plouzané, France
Laj, C., Balut, Y., Wang, P., Kissel, C., Holbourn, A., Kienast, M., Chen, M.-T. and Catane, S.
- (2007) Investigating the inflow path of the Indonesian troughflow: a palaeontological and geochemical multiproxy reconstruction for the last 140 kyrs. EGU General Assembly 2007. EGU2007-A-04970. BG5.05 Environmental Micropaleontology: microfossils as proxies of recent and past environmental change
Bolliet, T.; Kuhnt, W.; Holbourn, A.; Beaufort, L.; Kissel, C.; Laj, C.; Andersen, N.
- (2007). Investigating the inflow path of the Indonesian Throughflow: A palaeontological and geochemical multiproxy reconstruction for the last 150 kyr, IX International Conference in Paleoceanography, Shanghai, Sept. 2007
Bolliet, T., A. Holbourn, W. Kuhnt, C. Laj, C. Kissel, L. Beaufort, M. Kienast, N. Andersen
- (2007). Temporal variability of the sedimentary magnetic properties off southeastern Mindanao, IX International Conference in Paleoceanography, Shanghai, Sept. 2007
Kissel, C., C. Laj, T. Bolliet, A. Holbourn, A., M.Kienast, W. Kuhnt, C. Wandres
- (2008). Indonesian Throughflow variability over the last 140 kyr: Temperature and precipitation proxy records from the Timor Sea. AGU Fall Meeting San Francisco
Kuhnt, W., Holbourn, A., Xu, J., Bolliet, T., Duerkop, A., Nuernberg, D., Zuraida, R., Andersen, N.
- (2008): A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline? Geophysical Research Letters, 35(L23610)
Kienast, M., M. F. Lehmann, A. Timmermann, E. Galbraith, T. Bolliet, A. Holbourn, C. Normandeau, and C. Laj
(See online at https://doi.org/10.1029/2008GL035464) - (2010). West Pacific climate and circulation over the last 160 kyr: A palaeontological and geochemical multiproxy reconstruction within the inflow path of the Indonesian Throufghflow. Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Christian-Albrechts-Universität zu Kiel. 163 pp.
Bolliet, T.
- (2010): Mindanao Dome variability over the last 160 kyr: Episodic glacial cooling of the West Pacific Warm Pool. Paleoceanography
Bolliet, T., A. Holbourn, W. Kuhnt, C. Laj, C. Kissel, L. Beaufort, M. Kienast, N. Andersen, and D. Garbe-Schönberg
(See online at https://doi.org/10.1029/2010PA001966) - (2010): Monsoon variability and deep oceanic circulation in the western equatorial Pacific over the last climatic cycle: insights from sedimentary magnetic properties and sortable silt. Paleoceanography, 25, PA3215
Kissel, C. Laj, M. Kienast, T. Bolliet, A. Holbourn, P. Hill, W. Kuhnt, and P. Braconnot
(See online at https://doi.org/10.1029/2010PA001980)
