Nathan Steiger and Jason Smerdon gave a presentation for the PAGES2k Network Seminar Series titled Annual Reconstructions of Global Hydroclimate Fields over the Common Era using Data Assimilation. The description of the presentation and its recording are below.
The Paleo Hydrodynamics Data Assimilation (PHYDA) product was the first global reconstruction of hydroclimate and associated dynamical variables over the past 2000 years. The reconstruction was derived using a data assimilation framework that optimally combined 2978 paleoclimate proxytime series, including the complete PAGES 2k database, with the physical constraints of the NCAR CESM climate model.
In the first half of our presentation, the details of the PHYDA reconstruction will be presented. We will discuss the specific data assimilation methodology that was employed, how the proxy database was curated and incorporated, and the skill assessments that were used to validate the PHYDA reconstruction. We will give an overview of the reconstructed variables that are available from PHYDA and conclude by describing our plans to develop an improved and updated version of the PHYDA.
In the second half of our presentation, we will describe the use of the PHYDA to improve our understanding of several important hydroclimatic problems. The first investigation will explore the causes and coupling of simultaneous multi-decadal droughts in southwestern North America and central Chile. The second investigation will describe our work to characterize global hydroclimatic responses to large tropical volcanic eruptions. These two examples demonstrate the power of the PHYDA to provide new insights into our understanding of past hydroclimatic variability and change, with relevance for our assessment of future hydroclimatic risks.