Southeast Pacific subtropical anticyclone

Southeast Pacific subtropical anticyclone
Name	Southeast Pacific subtropical anticyclone
Type	subtropical anticyclone
Location	Southeast Pacific Ocean
Coordinates	approx. 30°S, 90–110°W
Related	Humboldt Current, Peru, Chile

Southeast Pacific subtropical anticyclone The Southeast Pacific subtropical anticyclone is a persistent high-pressure circulation over the southeastern Pacific Ocean influencing coastal Peru, Chile, the Humboldt Current, and the eastern subtropical Pacific climate. It sits poleward of the Equator and interacts with tropical systems such as the El Niño–Southern Oscillation, the Intertropical Convergence Zone, and the South Pacific Convergence Zone, modulating marine stratocumulus decks, coastal upwelling, and regional precipitation regimes.

Overview

The anticyclone is a quasi-permanent feature in the southern hemisphere subtropics that anchors the eastern subtropical Pacific circulation, lying west of the South American coast near the Atacama Desert, the port city of Valparaíso, and the marine zones exploited by fleets from Peru and Chile. It shapes the position of the Humboldt Current and the associated upwelling system that influences fisheries such as those managed by the National Fisheries Service (Sernapesca) in Chile and the Ministry of Production in Peru, while modulating maritime routes used by vessels bound for Panama, Valparaíso, and Callao.

Formation and Dynamics

The anticyclone results from large-scale atmospheric angular momentum and Rossby wave dynamics linked to the subtropical ridge of the southern hemisphere and the Hadley circulation, with influences from the South Pacific Anticyclone and remote teleconnections like Pacific Decadal Oscillation, Southern Annular Mode, and Madden–Julian Oscillation. Baroclinic and barotropic processes involving sea surface temperature gradients associated with the Humboldt Current and the eastern Pacific cold tongue establish a shallow, stratified inversion that supports persistent subsidence and clockwise flow, interacting with synoptic systems such as extratropical cyclones tracked by meteorological services like Servicio Meteorológico Nacional (Argentina) and NOAA.

Climate and Oceanic Impacts

By enforcing subsidence and stabilizing the marine boundary layer, the anticyclone maintains extensive stratocumulus decks that affect radiative budgets documented in campaigns by NASA, NOAA, and the European Space Agency. Its presence intensifies coastal upwelling of nutrient-rich waters in the Peru Current system, supporting productive fisheries exploited by fleets associated with organizations like the Food and Agriculture Organization and influencing biogeochemical cycles studied by institutions such as the Scripps Institution of Oceanography and the Institute of Marine Research. The anticyclonic circulation also shifts the climatological precipitation patterns over Atacama Desert, Arica, and central Chile, affecting water resources managed by regional authorities including the Comisión Nacional del Medio Ambiente (CONAMA) and hydrological services in Peru.

Variability and Trends

Interannual and decadal variability arises from interactions with El Niño, La Niña, the Pacific Decadal Oscillation, and anthropogenic climate change signals reported by the Intergovernmental Panel on Climate Change and regional assessments by the IPCC. Observational analyses from satellites operated by NOAA, NASA, and EUMETSAT and reanalyses from centers like the European Centre for Medium-Range Weather Forecasts illustrate trends in the anticyclone’s position, strength, and central pressure tied to changing sea surface temperatures influenced by greenhouse gas emissions reported by the United Nations Framework Convention on Climate Change. Paleoclimate reconstructions using proxies collected by teams at the Lamont–Doherty Earth Observatory and the British Antarctic Survey further document variability over centennial timescales.

Interactions with Weather Systems

The anticyclone modulates the tracks and intensities of midlatitude cyclones that traverse the South Pacific toward the Southern Cone, influencing frontal passages that affect cities such as Santiago and Buenos Aires via downstream Rossby wave propagation studied by researchers at NIWA and the Met Office. It exerts steering on tropical sources of moisture linked to the South Pacific Convergence Zone and can suppress or enhance convective outbreaks tied to the Madden–Julian Oscillation and remote forcing from Tropical Cyclone activity near the subtropical South Pacific islands including Easter Island and Pitcairn Islands.

Ecological and Socioeconomic Effects

Ecologically, the anticyclone’s control of upwelling sustains planktonic productivity that underpins fisheries targeted by fleets from Peru and Chile and processed by companies registered with agencies such as the Food and Agriculture Organization and national ministries. Socioeconomically, variations influence fishery yields, aquaculture operations tied to firms in Antofagasta and Pisco, coastal fog incidence impacting agriculture in Norte Chico managed by local water authorities, and urban water supplies for conurbations like Lima and Santiago whose governance involves institutions such as municipal water utilities and national ministries. Hazard modulation includes effects on hypoxia and harmful algal blooms monitored by research centers like the Copernicus Marine Service and regional universities.

Observations and Modeling Methods

Monitoring employs satellite remote sensing from platforms by NASA, NOAA, and JAXA measuring sea surface temperature, sea level pressure, and cloud properties, complemented by in situ observations from research vessels operated by institutions such as the Scripps Institution of Oceanography and the French Research Institute for Exploitation of the Sea (IFREMER), and moored arrays linked to programs like the TAO/TRITON and regional observing networks coordinated with the Global Ocean Observing System. Numerical modeling uses coupled atmosphere–ocean general circulation models developed at centers such as the National Center for Atmospheric Research, the European Centre for Medium-Range Weather Forecasts, and national meteorological agencies, with downscaling experiments employing frameworks from universities including University of California, San Diego and University of Chile to assess impacts under scenarios from the Intergovernmental Panel on Climate Change.

Category:Climate of South America