| Abstrakt: |
Modes of climate variability, such as the El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multi‐decadal Oscillation (AMO), have been shown to have large impacts on North American hydroclimate through their atmospheric teleconnections. However, short instrumental records limit our ability to examine the long‐term stability (or stationarity) of hydroclimate teleconnections. Here, we use two last millennium (LM) paleoclimate data assimilation (DA) products to assess the stationarity of hydroclimate teleconnections over two key regions: the southwestern U.S. and Lower Mississippi River basin. Moving correlations between climate indices and regional hydroclimate expose highly nonstationary regional hydroclimate teleconnections with significant periodic variations on multi‐decadal and multi‐centennial timescales. Although limitations of the DA products prohibit a robust analysis of climate mode intensity, consistent sea surface temperature (SST) patterns between DA products during strong and weak teleconnection periods suggest that changing teleconnection strength is driven by the changing relationships between climate modes over the LM. Although our results are sensitive to proxy availability, the DA techniques provide novel insight into the nonstationarity and long‐term variability of North American hydroclimate teleconnections. This work provides a baseline for teleconnection behavior from DA products, which is potentially valuable for decadal prediction. Plain Language Summary: Changing sea‐surface temperature (SST) patterns in the tropical Pacific, the North Pacific, and the North Atlantic have been shown to affect North American rainfall and modulate hazards such as drought and flooding. However, the relatively short time period of observations during the 20th century limits our ability to assess the reliability and predictability of the relationship between these SST patterns and regional rainfall amounts. This work uses a technique that combines records of past climate, such as corals, ice cores, and trees, with climate models to investigate SST‐rainfall relationships over North America during the last millennium with a focus on two key regions: the southwestern U.S. and the Lower Mississippi River basin. We find that, in the context of the past 1000 years, rainfall variability driven by SST patterns changes on decadal to centennial timescales. The strength of SST‐rainfall relationships is modulated by SST patterns in different ocean basins. Our results quantify the natural range of North American rainfall variability in the time before the industrial period of strong human influence, such as fossil fuel pollution on climate, which harbors implications for long‐term water management and hydroclimate risk assessment in the 21st century. Key Points: ENSO, PDO, and AMO‐driven rainfall anomalies over North America are evaluated in paleoclimate data assimilation productsHydroclimate teleconnections are variable over the last millennium but are driven in part by predictable SST patternsAssessing teleconnection stationarity offers a robust estimate of the range of North American hydroclimate without anthropogenic forcing [ABSTRACT FROM AUTHOR] |
Plný text