Resolving records of climate extremes in western North America climate at the end of the Little Ice Age using tree-ring, reanalysis, and historical data

Keywords: tree rings, western United States, Little Ice Age, historical data, climate, precipitation, dendrochronology, reanalysis, extreme events, drought, flood, North America
Session Type: Virtual Poster Abstract
Day: Sunday
Session Start / End Time: 2/27/2022 03:40 PM (Eastern Time (US & Canada)) - 2/27/2022 05:00 PM (Eastern Time (US & Canada))
Room: Virtual 27

Abstract

Rapidly fluctuating climate extremes have been recorded in western North American climate in the mid-1800s, including extreme cold and snow, droughts, and “unprecedented” flood events. Paleoclimate and paleoecology evidence suggest a complex change in climate dynamics occurred during this period at the end of the Little Ice Age. A gridded climate data product, NOAA-CIRES-DOE Twentieth Century Reanalysis V3, extends to 1836, but caution is needed with 19th century data due to the lack of comparable data to test against. In this study, we investigate cool-season climate on an annual basis during this key climate transition period (1840-1869) using a combination of reanalysis, historical, and tree-ring data. Focusing on atmospheric pressure and precipitation patterns, we "ground-truth" discrepancies between reanalysis output and tree-ring reconstructions using the historical climate record. We find that reanalysis data capture some known extremes, particularly the wet extremes of the 1860s, but most years in this period repeat a similar pattern that is not supported by other data types. The patterns produced using tree-ring data are strongly supported by historical records, with the exception of 1848-1849, possibly due to that year's extreme weather characteristics. This research supports the strength of the tree-ring record and suggests that available reanalysis data may not yet be sufficient for studying climate in the 1800s. Continuing to strengthen reanalysis data is important, as the information on moisture transport and synoptic patterns provided by this valuable product will help delineate driving mechanisms of climate extremes.