Disentangling Drivers of Heat and Freshwater Transport through the Indonesian Seas Across Timescales: Insights from Marine Sediments and Model Simulations

The Indo-Pacific Warm Pool (IPWP) covers a large area of the tropical western Pacific and eastern Indian Oceans. Recent observations indicate that the IPWP is undergoing profound changes. The Indonesian Throughflow (ITF) is also changing. The ITF moves relatively warm and fresh upper ocean waters from the western Pacific and Indonesian Seas to the Indian Ocean. This movement plays a critical role in the climate of the region. However, limited oceanographic data from the region make separating natural variability from anthropogenic trends challenging. Given the significance of the IPWP, separating multidecadal variability and anthropogenic trends is critical. This study will combine data collected from sediment cores with model simulations to investigate 1100 year of changes in the ITF. As part of this work, K-12 educational material will be created for schools in the Indo-Pacific region. The project will support a graduate student, and a post-doctoral researcher. The team will conduct a modeling – data collection effort to gain insights into the controls of the ITF and how they might differ across time scales and background climate states over the last millennium, including the Industrial Era. New, well-dated, highly-resolved, records of thermocline structure, reconstructed using geochemical and faunal measurements, will extend instrumental records from the ITF region to span the last millennium. Dynamical interpretations of the data will be provided by a hierarchy of ocean and climate models, which will be used to evaluate the dominance of wind and buoyancy forcing on different time scales, and link reconstructed variability to multidecadal variations in tropical Pacific mean state (e.g., the Walker circulation) and the monsoons. Models will also be used to assess if and why modern warming has altered the relationship between global temperature and the Walker circulation, as well as to evaluate the climate impacts of ITF variability and how they are transmitted (atmospheric or oceanic teleconnections) in simulations of the past, and in future projections. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.