Richard Fiorella Presents Work at CESM Paleoclimate Working Group Meeting 2024

Richard Fiorella Presents Work at CESM Paleoclimate Working Group Meeting 2024

Richard Fiorella Presents Work at CESM Paleoclimate Working Group Meeting 2024

Richard Fiorella, a scientist at Los Alamos National Laboratory and the New Mexico Consortium, recently attended the Community Earth System Model (CESM) Paleoclimate Working Group Meeting 2024 which place at the NSF NCAR Mesa Lab, Boulder CO and online on Monday, February 26th, 2024. The primary goal of the CESM project is to develop a state-of-the-art climate model and to use it to perform the best possible science to understand climate variability and global change, and this meeting was for scientists to present their research on paleoclimate modeling, proxy data development, and synthesis of model-data information.

Fiorella presented on Understanding variations in precipitation isotope ratios using process-oriented water tracers.

The hydrologic cycle couples the Earth’s energy and carbon budgets through evaporation, moisture transport, and precipitation. Even though we have many years of observations and models, there are still some major limitations in our understanding of even the most basic properties of the hydrological cycle, including the spatial pattern of the residence time (RT) of water in the atmosphere and the mean distance traveled from evaporation sources to precipitation sinks. Geochemical tracers such as stable water isotope ratios provide a tool to probe hydrological processes, and are a popular tool for trying to reconstruct past environments as they are preserved in many materials such as ice cores and tree rings, but the interpretation of these tracers remains uncertain despite several decades of use.

As a result, there is a need for new mechanistic tools that link variations in water isotope ratios to underlying hydrological processes. Water tracers have been used to link different locations in the water cycle, but in this talk Fiorella discussed “process-oriented tags” (Fiorella et al. 2021), which scientists use to explicitly trace hydrological processes within the Community Atmosphere Model. Using these tags, they test the hypotheses that precipitation isotope ratios respond to parcel rainout, variations in atmospheric RT, and preserve information regarding meteorological conditions during evaporation.

Fiorella presented results for a historical simulation from 1980 to 2004, forced with winds from the ERA5 reanalysis. He found strong evidence that precipitation isotope ratios record information about atmospheric rainout and meteorological conditions during evaporation, but little evidence that precipitation isotope ratios vary with water vapor RT. These new tracer methods will enable more robust linkages between observations of isotope ratios in the modern hydrologic cycle or proxies of past terrestrial environments and the environmental processes underlying these observations. He also discussed how these new “process-oriented” tracers can be useful for improving understanding of paleoclimate simulations using CESM.

This project supported by the National Science Foundation under Grant No. 2309269. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.