NOAA/WDS Paleoclimatology - Great Plains Low-Level Jet 300 Year Wind and Moisture Transport Reconstructions

The Great Plains Low-Level Jet (GPLLJ) plays a critical role in transporting moisture into the central United States and has been linked to floods and droughts. Here, we use tree-ring records to separately reconstruct both the wind and moisture transport components of May-July GPLLJ to examine long-term changes and compare variability in the wind and moisture components over time. We then integrate proxy- and data-assimilation-based reconstructions of Atlantic and Pacific teleconnection indices to determine the consistency of those influences on the GPLLJ over multiple centuries. The resulting long-term records of GPLLJ wind and moisture transport (based on meridional wind and integrated water vapor transport), which span 1690-1989 CE, demonstrate periods of synchrony and asynchrony through time, with a notable lack of coherence in the mid-to-late 1800s. In recent decades, high extremes in GPLLJ moisture transport (but not wind) appear to be moving outside the bounds of the pre-instrumental past. The wind component shows spectral power in the decadal (10-15 year) and subdecadal (7-8 year) bands, while moisture transport varies at bidecadal (19-27 year) and lower frequencies. Changes in GPLLJ wind and moisture are driven by a complex mix of both Atlantic and Pacific variability. GPLLJ wind is most consistently linked to Pacific conditions, while GPLLJ moisture transport has a stronger Atlantic influence. Warm-season oceanic conditions more strongly impact GPLLJ wind and moisture than conditions in the preceding cool season. The complex set of influences on GPLLJ and their impact during the concurrent season underline the challenges in modeling and predicting warm-season hydroclimate in this region.