The ability to accurately quantify differences in the timing of change in different aspects of the earth system (deep ocean, surface ocean, and atmosphere) is one of the key means by which scientists are able to decipher the physics underlying climate change in response to variability in global ice volume, greenhouse gasses, and solar insolation. To accurately quantify the differences in this timing of change requires accurate ages for climate data developed from deep-sea cores. This project seeks to improve the accuracy of ages for marine climate records developed from deep-sea cores by comparing these records to well-established, highly-accurate land-based records of mineral deposits (speloethems) in the Hulu-Sanbao cave in China. The results of this research will make ages for marine climate records more accurate, thus providing better data for climate models that enhance our ability to understand climate change, past and future.
This proposed work has two main objectives: 1) Understanding the mechanisms underlying the strong sensitivity of East Asia to monsoonal climate change 2) Significantly increasing the accuracy of the global benthic delta 18-O chronology over the past 350,000 years. The first objective is part of a longer-term international collaborative effort associated with Integrated Ocean Drilling Program (IODP) Expedition 346, located in the region between Japan and Korea. The collaborative research will last beyond the two-year term of this grant proposal, whereas the second objective is the primary focus of this proposal and will be completed in the proposed project duration. Planktonic foraminifer (Globigerinoides ruber) delta 18-O and delta 13-C will be measured on 3800 samples spanning the 180 m length of the IODP Site U1429 in the northern East China Sea. This data will result in a ~425,000 year long time series with ~100 year temporal resolution, capable of resolving centennial through orbital-scale variability in the East Asian monsoon system. Collaborators from the University of Kiel, Germany, will analyze the same 3800 samples for benthic foraminifer (Cibicidoides wuellerstorfi) delta 18-O and delta 13-C. The plantonic delta 18-O will be mapped onto the radiometrically dated Hulu-Sanbao speleothem delta 18-O record using dynamic programming methods, thus transferring this highly accurate age scale into the paired benthic marine record. This is possible because both the cave and planktonic delta 18-O records are driven by the same large-scale monsoonal forcings (temperature and precipitation); the location, length, and sedimentation rates at Site U1428 are uniquely suited to this effort
