TY - JOUR
T1 - General Hydrography of the Beagle Channel, a Subantarctic Interoceanic Passage at the Southern Tip of South America
AU - Giesecke, Ricardo
AU - Martín, Jacobo
AU - Piñones, Andrea
AU - Höfer, Juan
AU - Garcés-Vargas, Jose
AU - Flores-Melo, Ximena
AU - Alarcón, Emilio
AU - Durrieu de Madron, Xavier
AU - Bourrin, François
AU - González, Humberto E.
N1 - Funding Information:
We would like to thank the Chilean and Argentinean Navy for providing bathymetry charts, as well as the captain and crew of the Forrest vessel for their professional assistance and help during sampling procedures. We acknowledge the support of Prefectura Naval Argentina, MINCYT and thank Gustavo Ferreyra for making possible the cruise onboard M/O Bernardo Houssay and two reviewers for valuable comments on the manuscript. We would like to express our gratitude and our respects to Nelson Silva who passed away in August 2020. His pioneer work and passion for chemical oceanography research in Patagonia ecosystems opened new avenues for those of us who came after him.
Publisher Copyright:
© Copyright © 2021 Giesecke, Martín, Piñones, Höfer, Garcés-Vargas, Flores-Melo, Alarcón, Durrieu de Madron, Bourrin and González.
PY - 2021/10/1
Y1 - 2021/10/1
N2 - 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.
AB - 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.
KW - Beagle Channel
KW - hydrography and bathymetry
KW - interoceanic channel
KW - micro-basins
KW - southern Patagonia
UR - http://www.scopus.com/inward/record.url?scp=85117140529&partnerID=8YFLogxK
U2 - 10.3389/fmars.2021.621822
DO - 10.3389/fmars.2021.621822
M3 - Article
AN - SCOPUS:85117140529
VL - 8
JO - Frontiers in Marine Science
JF - Frontiers in Marine Science
SN - 2296-7745
M1 - 621822
ER -