GEO-01 Present and past ocean-atmosphere-climate interactions
A high-resolution reconstruction of SST and paleoproductivity from the Banda Sea, Indonesia across the mid-Brunhes event (last 820 kyr)
Ziye Li, MARUM–Center for Marine Environmental Sciences, University of Bremen, Germany College of Marine Geosciences, Ocean University of China, Qingdao, China
Mahyar Mohtadi* , MARUM–Center for Marine Environmental Sciences, University of Bremen, Germany
Hung-Lin Tsai, Institute of Earth Sciences, College of Ocean Science and Resource, National Taiwan Ocean University, Keelung, Taiwan
Yuan-Pin Chang, Institute of Marine Geology and Chemistry,National Sun Yatsen University, Kaohsiung, Taiwan
Markus Kienast, Dalhousie University, Department of Oceanography, Halifax, Canada
Shih-Yu Lee, Academia Sinica, Research Center for Environmental Changes, Taipei, Taiwan
Jeroen Groeneveld, Institute of Oceanography,National Taiwan University,Taipei, Taiwan
Axel Timmermann, Pusan National University
Min-Te Chen, Institute of Earth Sciences, College of Ocean Science and Resource, National Taiwan Ocean University, Keelung, Taiwan

Our understanding of the paleoclimate dynamics and their underlying mechanisms of the Indo- Pacific Warm Pool (IPWP) at long time scales are still limited by the low temporal coverage of paleoclimate records. High resolution and long duration paleo-records covering several glacial-interglacial cycles in the central IPWP would advance our understanding of IPWP dynamics. Here we present high-resolution data sets (alkenone SST, alkenone mass accumulation rate, opal wt%) from a piston core (MD01-2380) retrieved from the Banda Sea, eastern Indonesia, to track the changes in sea surface temperature, paleoproductivity and upwelling variability over the last 820,000 years.

Our results show that the amplitude of variations in alkenone SST was small before the Mid-Brunhes Event (MBE) and became larger after the MBE, emphasizing glacialinterglacial changes. The paleoproductivity reconstruction shows no significant variation on glacialinterglacial timescales, but rather shows an overall increase after the MBE suggesting enhanced upwelling activity.
In addition, the mean temperature of each Marine Isotope Stage (MIS) and the peak events show that the the interglacials did not change, but that the glacials became significantly colder after the MBE. It is interesting to see a too warm MIS 6 and a surprisingly cold MIS 8.
Our study shows how the mid-Brunhes event is expressed in the Banda Sea, Indonesia by changing the character of the seasonal upwelling with regard to both productivity and SSTs. We hypothesize that the increase in upwelling across the MBE may have occurred global-wide. This would have released extra carbon dioxide from the deeper ocean into the atmospheric explaining the increase in atmospheric CO2 as shown by ice core records. The reason why global upwelling did intensify, however, remains elusive.