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AN ANALOG APPROACH FOR UNDERSTANDING FUTURE PACIFIC NORTHWEST CLIMATE CHANGE USING RECENT RECORD CLIMATE EVENTS
Dissertation   Open access

AN ANALOG APPROACH FOR UNDERSTANDING FUTURE PACIFIC NORTHWEST CLIMATE CHANGE USING RECENT RECORD CLIMATE EVENTS

Luke Reyes
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2024
DOI:
https://doi.org/10.7273/000007197
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Open Access CC BY-SA V4.0

Abstract

amplification extreme events nonlinear snow threshold Hydrologic sciences Precipitation
Successful adaptation to climate change requires an accurate understanding of future conditions. Observations made during today’s extreme periods, particularly those characterized by sustained anomalous warmth that are analogous to future projections, can complement more traditional tools for predicting the future (trends, models) to provide insight into aspects of the earth system which remain highly uncertain. These include 2nd- and 3rd-order impacts and hydrological factors. This dissertation covers three chapters of distinct record periods in the Pacific Northwest where this analog approach was applied: (1) a record warm, wet fall (2016); (2) the June 2021 heat dome; and (3) the warm winters with accompanying snow droughts of 2005 and 2015. In Chapter One, isotope measurements of precipitation coupled with satellite data, historical records, and terrestrial observations, uncovered multiple novel fall climate change dynamics, including a long term (1970-2018) trend of increasing monthly rainfall (+17% decade–1 in October), more southerly storm origins, and the decoupling of leaf-fall from low temperatures. In Chapter Two, daily snowmelt in cooler, higher-elevation zones revealed multiple spring heatwaves, concluding with the 2021 heat dome itself, rapidly and dramatically accelerated snowmelt in previously resilient areas, and the heat load of these spring heatwaves has doubled since the mid-1990s. Lastly in Chapter Three, we found that warming in 2005 and 2015, which are analogous to projected mid-century warming under RCP8.5, advances the spring transition to net snowmelt by ~80 days in up to 72% of Oregon and Washington’s typically resilient higher-elevation snowpack, driven by both extreme warming (up to +2.5°C above normal) and solid-liquid precipitation phase shifts (~60% decline in solid precipitation). These findings demonstrate the value of a granular evaluation of record periods to improve model accuracy and better understand ecosystems under the warming conditions expected in the coming decades.

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