General Hydrography of the Beagle Channel, a Subantarctic Interoceanic Passage at the Southern Tip of South America
Year: 2021
Type: article
Abstract: The Beagle Channel (BC) is a long and narrow interoceanic passage (∼270 km long and 1–12 km wide) with west-east orientation and complex bathymetry connecting the Pacific and Atlantic oceans at latitude 55°S. This study is the first integrated assessment of the main oceanographic features of the BC, using recent oceanographic observations from cruises, moored instruments and historical observations. The waters transported into the BC are supplied mainly by the Cape Horn Current, which carries Subantarctic Water (SAAW) at depth (100 m below surface) along the Pacific Patagonian continental shelf break. SAAW enters the continental shelf via a submarine canyon at the western entrance of the BC. The SAAW is diluted by fresh, nutrient depleted (nitrate, phosphate and silicic acid) Estuarine Water (EW) from Cordillera Darwin Ice Field (CDIF) forming modified SAAW (mSAAW). Freshwater inputs from the CDIF generate a two-layer system with a sharp pycnocline which delimits the vertical distribution of phytoplankton fluorescence (PF). Two shallow sills (<70 m) along the BC contribute to EW and mSAAW mixing and the homogenization of the entire water column east of the sills, coherent with Bernoulli aspiration. The central section of the BC, extending ∼100 km toward the east, is filled by a salty (31–32) variety of EW. In winter, this central section is nearly vertically homogeneous with low nutrient concentrations (0.9–1.1 μM PO4 and 7.5–10 μM NO3) and PF. The temporal variability of seawater temperature from 50 to 195 m in the central section of the BC was found to be mostly dominated by the annual and semiannual cycles and influenced by tidal forcing. The middle section of the BC was less influenced by oceanic inputs and its basin-like structure most likely favors retention, which was observed from the weakly stratified water column at the mooring site. Toward the east, the central section bathymetry is disrupted at Mackinlay Strait where another shallow sill separates the middle channel from the shallow eastern entrance that connects to the Atlantic Ocean. In this section, a weakly stratified two-layer system is formed when the eastward surface outflow (salty-EW) flows over a deeper, denser tongue of oceanic mSAAW.
Source: Frontiers in Marine Science
Institutions: Austral University of Chile, Center for Dynamic Research on High Latitude Marine Ecosystems, Consejo Nacional de Investigaciones Científicas y Técnicas, National University of Tierra del Fuego, Centro Austral de Investigaciones Científicas, University of Concepción, Pontificia Universidad Católica de Valparaíso, Fundación San Ignacio del Huinay, Patagonian Ecosystems Investigation Research Center, Centre National de la Recherche Scientifique, Université de Perpignan, Centre de Formation et de Recherche sur les Environnements Méditerranéens
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life below water
Open Access status: gold
Estimated APC paid: $2,801
Funders: Aix-Marseille Université, Bundesministerium für Bildung und Forschung, Consejo Nacional de Investigaciones Científicas y Técnicas, Ministerio de Ciencia, Tecnología e Innovación Productiva, Agencia Nacional de Investigación y Desarrollo, Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias
Awards: G1035980808, G1077226843, G1217376423, G3569058204, Sinergias y conflictos entre las actividades económicas y los socio-ecosistemas de Tierra del Fuego: Mantenimiento de la productividad y los servicios ecosistémicos en el largo plazo, CENTRO DE INVESTIGACION DINAMICA DE ECOSISTEMAS MARINOS DE ALTAS LATITUDES (IDEAL)
OpenAlex ID: W3203786359