Spatio-Temporal Patterns of Jet Stream Influence on Phenology

Abstract

Atmospheric circulation patterns are the primary mechanism by which energy is distributed in the midlatitudes across terrestrial ecosystems. Plant and animal phenology integrate the influence of seasonal atmospheric circulation patterns on surface weather events. As these drivers of climate variability change, and are projected to change, it is important to quantify the observed response of ecosystem growth and processes to drivers of climate variability across scales. In this dissertation, I merge phenology, climatology, and dendrochronology disciplines, novel data availability, and research computing, to quantify and visualize the influence of jet stream variability on phenology across scales: from the individual species to the hemisphere, and from seasons to centuries. First, I examined the influence of multiple seasonal atmospheric circulation indices on a network of trees growing in semi-arid conditions at high altitudes in the Bighorn Mountains, WY (Hudson et al. 2019, Dendrochronologia; Appendix A). While all 11 sites shared a majority of common variance- suggesting a common climate driver- I found that winter and spring circulation pattern signals in annual rings were possibly modulated by microclimate conditions dictating snowpack and water availability into the growing season. I then expanded from one region to the Northern Hemisphere and contracted to the satellite period to determine for which regional ecosystems the spring and fall Northern Hemisphere Jet stream (NHJ) Indices (Belmecheri et al., 2017 Earth Interactions) influenced the length of the growing season (Hudson et al., in prep; Appendix B). Spring and/or fall NHJ influenced length of season for 30% of our domain, although similar NHJ shifts in the spring and fall resulted in very different LOS response- possibly linked to the seasonal limiting factor of temperature and its modulation on water availability for specific land cover and climate types. The final portion of this dissertation focused on North America, where I examined the influence of monthly jet stream position on cross-continental monarch migration, as estimated by annual overwintering acreage in Mexico (Hudson et al., in prep; Appendix C). Remarkably, multiple months of jet stream position across the continent corresponded with monarch migration due to the influence on monarch physiology, flight conditions, and resource availability. Overall, spatio-temporal patterns of NHJ influence on growth varied by season and were very much system dependent. These patterns can be used for model benchmarking and to prioritize land management and conservation efforts in a warming world. A macrosystem ecology framework of phenology that includes seasonal atmospheric circulation patterns allows us to ultimately increase our predictive power of ecosystem response to a changing climate by 1) moving beyond trends in mean states to consider the variability and extreme events ecosystems are exposed to, and 2) emphasizing the connectivity of the landscape- particularly important for migrating organisms and when aggregating land surface response to climate change.