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| Southeast Pacific High | |
|---|---|
| Name | Southeast Pacific High |
| Type | subtropical anticyclone |
| Location | Southeast Pacific Ocean |
| Coordinates | approximate 30°S, 90–120°W |
| Typical season | austral winter–spring |
| Influencing factors | Humboldt Current, South Pacific Convergence Zone, Andes |
Southeast Pacific High The Southeast Pacific High is a persistent subtropical anticyclonic circulation located over the southeastern Pacific Ocean that influences atmospheric pressure, surface winds, and oceanic upwelling off the coasts of Chile, Peru, and the broader South American west coast. It interacts with the Humboldt Current, the South Pacific Convergence Zone, and teleconnection patterns such as the El Niño–Southern Oscillation, modulating regional climate, marine ecosystems, and fisheries. Variability of the feature is documented in observational records from the NOAA era, reconstructions using paleoclimate proxies, and coupled climate model simulations from CMIP projects.
The feature is a subtropical high-pressure cell associated with the southern branch of the Hadley Cell, positioned adjacent to the eastern limb of the South Pacific Ocean gyre and linked to the midlatitude Southern Hemisphere circulation. Its presence establishes a gradient between the anticyclonic center and the low-pressure regions of the Intertropical Convergence Zone, the Bolivian Winter, and the midlatitude westerlies emanating from the Roaring Forties. The anticyclone modulates the alongshore wind stress that drives coastal upwelling in the Peru Current system, influencing sea-surface temperature patterns recorded by AVHRR and ARGO floats.
Formation of the anticyclone results from the subsidence limb of the Hadley Cell, radiative cooling over subtropical oceans, and wave-mean flow interactions with the Pacific Walker Circulation and transient eddies from the Southern Ocean. Rossby wave propagation linked to perturbations in the Tropical Pacific and energy dispersion from the Antarctic Circumpolar Current contribute to its dynamical maintenance. Baroclinic adjustments interact with the eastern boundary upwelling system along the Peruvian and Chilean shelves, while orographic influences of the Andes modify the spatial imprint of the anticyclone on coastal atmospheric pressure fields.
Seasonal migration follows austral winter maxima and summer contraction, modulated by the seasonal cycle of solar insolation and cross-equatorial pressure gradients. Interannual variability is tied to phases of El Niño and La Niña, changes in the Pacific Decadal Oscillation, and remote teleconnections such as the Southern Annular Mode and Madden–Julian Oscillation, producing anomalies in wind stress, sea level pressure, and coastal SST. Extreme configurations during strong El Niño of 1997–98 and paleoevents like the Paleocene–Eocene Thermal Maximum analogs in reconstructions have been inferred from isotopic and sedimentary proxies.
By enforcing persistent southeasterly trade and upwelling-favorable winds, the anticyclone maintains the cold Humboldt Current tongue and coastal cold-filaments that shape regional precipitation and cloud regimes over Atacama Desert and central Chile. Its modulation affects moisture transport into the Altiplano and the occurrence of coastal marine stratus affecting solar insolation and agricultural zones associated with Santiago and Lima. Oceanographically, wind stress curl associated with the cell drives Ekman pumping, influences thermocline depth, and alters the distribution of oxygen minimum zones and nutrient fluxes critical to primary productivity documented in time series from Station Papa analogs and Time Series programs.
The anticyclone-driven upwelling sustains high primary productivity that supports major fisheries targeting species such as anchoveta, jack mackerel, and sardine, underpinning national economies of Peru and Chile and feeding into international markets regulated by organizations like the FAO. Variability influences recruitment, biogeographic shifts, and events such as hypoxic episodes and harmful algal blooms recorded in ecosystem assessments and stock surveys by institutions including IMARPE and IFOP. Impacts cascade through trophic webs affecting seabirds linked to Guanay cormorant and marine mammals documented in studies by Charles Darwin-era and modern naturalists.
Observational characterization uses satellite remote sensing from NOAA and NASA platforms, in situ measurements from ARGO profilers, coastal tide gauges, and reanalysis datasets such as ERA-Interim and JRA-55. Modeling studies employ regional ocean–atmosphere coupled models, high-resolution configurations in CMIP5 and CMIP6, and idealized atmospheric general circulation experiments to isolate forcing from the ENSO cycle, atmospheric rivers, and anthropogenic greenhouse forcing. Data assimilation and machine-learning approaches in studies by WMO and academic groups refine forecasts for fisheries management and climate adaptation planning.
Historical meteorological records from 19th century ship logs, hydrographic expeditions by explorers like James Cook, and instrumental archives reveal century-scale trends in the anticyclone's intensity and position. Paleoclimate reconstructions using marine sediment cores, foraminiferal assemblages, diatom records, and isotopic analyses link shifts in the anticyclone to Holocene climate variability, ~centennial modes such as the Medieval Climate Anomaly, and Younger Dryas–scale perturbations documented in Southern Hemisphere syntheses. Understanding past behavior informs projections under scenarios considered by IPCC assessments and regional adaptation by national agencies.
Category:Climate of South America Category:Oceanic gyres