*Please note: in-person attendance is limited to LDEO affiliates. If you would like to participate via zoom, please contact the Seminar organizer for a link*
Title: How do we get subannual climate reconstructions from annual tree rings?
Abstract:How do we get subannual climate reconstruction from annual tree rings? And if we can do that, how do we ensure that the reconstructions "make sense", e.g., that the sum of the monthly flows matches the annual flow closely (mass balance preservation)? In this talk, I will present a new reconstruction framework that can solve these two problems in one go. The two key ideas are: (1) we combine, in an optimal way, multiple proxies with different seasonal sensitivities; and (2) to preserve mass balance, we minimize the differences between the annual flow and the total monthly flows in the regression equation. This mass balance criterion is necessary to avoid misguiding water management decisions, such as the allocation of water rights or dam release decisions. Using the framework, and leveraging a multi-species network of ring width and cellulose δ18O in Southeast Asia, we reconstruct monthly streamflow to all four major tributaries of the Chao Phraya River, Thailand's largest and most important watershed. The reconstructions are statistically skillful. Furthermore, they preserve the mass balance well: the differences are mostly within 10% of the mean annual flow. As a result, the reconstructions provide more reliable estimates of surface water availability. This work is one step closer toward operational usability of streamflow reconstruction in water resources management.