ENSO teleconnections over North America are non-stationary during the Common Era: Insights from data assimilation and reconstructions
Abstract
The El Niño-Southern Oscillation (ENSO) plays a critical role in modulating temperature and rainfall over North America via its remote impacts, or 'teleconnections.' However, observations show that teleconnections differ widely between individual ENSO events. Understanding future changes in ENSO teleconnections is important for seasonal climate prediction. However, short instrumental records (spanning only ~50 ENSO events) limit our ability to examine the long-term stationarity of ENSO teleconnections, and thus precludes our ability to characterize their response to future anthropogenic climate change. Here, we use a paleoclimate proxy network spanning core ENSO-teleconnection regions, composed of high resolution coral, ice core, and tree ring width data, in combination with paleoclimate data assimilation (DA) products (LMR, PHYDA) spanning the Last Millennium (LM). We focus on two key regions: the Southwest U.S. and the Mississippi River Basin. The Common Era reconstructions augment the number of ENSO events available for analysis and help us answer the key question: How stationary are teleconnections? We compute the 50-year moving correlations between the NINO 3.4 index (or coral records in NINO 3.4 region) and regional mean Palmer Drought Severity Index (PDSI). Regional ENSO teleconnections are non-stationary over the LM, and exhibit large decadal-to-centennial variability in terms of rainfall intensity. We further differentiate El Niño events into Central Pacific (CP) and Eastern Pacific (EP) types to investigate the impacts of ENSO diversity on teleconnection stability. The results show that the signs of hydroclimate conditions (dry/wet) during CP/EP El Niño are relatively consistent over the Southwest U.S. and Mississippi River Basin. We assert that nonstationarity in ENSO teleconnections (measured via correlation coefficients) are partially driven by the competing impacts of CP and EP event frequencies during different periods of the LM. While our results are sensitive to proxy locations and DA products, the combination of the new multi-proxy network and DA techniques provide novel insight into the non-stationarity and multi-decadal variability of ENSO teleconnections. Implications for seasonal forecasting are discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMPP45D1178L