Atmospheric blocking events are persistent quasi‐stationary geopotential height anomalies that divert the jet stream from its climatological path in the mid‐ to high‐latitudes. Previous studies have found that different phases of the El Niño–Southern Oscillation (ENSO) influence the characteristics of blocking, but none have considered the spatial diversity of El Niño. In this study, we examine Northern Hemisphere blocking events with respect to the “Central Pacific” (CP) and “Eastern Pacific” (EP) flavors of El Niño in 83 years of ERA5 reanalysis. The two El Niño flavors have dissimilar patterns of forcing on atmospheric circulation that impact the strength and placement of the upper‐level jet stream, thus affecting blocking event frequency and duration. Significant contrasts in blocking characteristics between CP and EP years are disregarded when a single ENSO index is used, and we emphasize that El Niño flavors should be considered in future investigations of blocking and ENSO‐related variability.
Sediment records from Lake Pallcacocha, Ecuador, have been interpreted as proxies of El Niño–Southern Oscillation (ENSO) variability, owing to increased precipitation in the area during El Niño events. However, the lake's watershed receives precipitation from processes arising from both the eastern and western Andes, where ENSO has different impacts; this has led to ambiguity in observed regional ENSO signals and has consequently challenged the suitability of the lake's records as ENSO proxies. Here, a mesoscale weather prediction model is used to investigate the regional circulation dynamics and precipitation response during different ENSO events, namely, Eastern Pacific (EP), Central Pacific (CP), coastal El Niño (COA), and La Niña (LN). The region receives more accumulated precipitation during COA and LN compared to EP and CP events. However, during EP and COA events, the region is prone to extreme precipitation associated with convective bursts originating from the Pacific. During CP and LN, moisture originates from the Atlantic and may reach the area as broader‐scale less‐intense precipitation. Statistical analysis of modeled precipitation reveals consistency between the number of threshold‐exceeding precipitation events in the high Andean elevations and the number of events identified in the late Holocene Pallcacocha record. These results illustrate the importance of considering ENSO flavors when interpreting paleoclimate proxies, highlight the role of COA events in understanding eastern Pacific proxy records, and support the hypothesis that Holocene changes in the number of events recorded in the lake sediment may indicate a change in the relative frequency of ENSO flavors.
more » « less- NSF-PAR ID:
- 10459303
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Paleoceanography and Paleoclimatology
- Volume:
- 34
- Issue:
- 2
- ISSN:
- 2572-4517
- Page Range / eLocation ID:
- p. 217-236
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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