Vertical and horizontal extension of the oxygen minimum zone in the eastern South Pacific Ocean |
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| Institution: | 1. Programa de Postgrado en Oceanografía, Departamento de Oceanografía, Universidad de Concepción, Casilla 160-C, Concepción, Chile;2. Departamento de Ciencias del Mar, Universidad Arturo Prat, Avenida Arturo Prat 2120, Casilla 121, Iquique, Chile;3. Centro de Investigación Oceanográfica en el Pacífico Sur-Oriental (FONDAP-COPAS), Universidad de Concepción, Casilla 160-C, Concepción, Chile;4. Facultad de Ciencias Naturales y Oceanográficas, Departamento de Oceanografía, Universidad de Concepción, Casilla 160-C, Concepción, Chile;5. Instituto de Biología Marina “Dr. Jürgen Winter”, Universidad Austral de Chile, Casilla 567, Valdivia, Chile;1. Department of Oceanography & Center for Oceanographic Research in the eastern South Pacific University of Concepcion PO Box 160-C, Concepcion, Chile;2. Department of Oceanography & Center for Oceanographic Research in the eastern South Pacific University of Concepcion PO Box 160-C, Concepcion, Chile;1. College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA;2. Bodega Marine Laboratory, University of California, Davis, Bodega Bay, CA, USA;3. CESAM, Physics Department, University of Aveiro, Aveiro, Portugal;4. Centro i-mar, Universidad de Los Lagos, Puerto Montt, Chile;5. Laboratorio de Funcionamiento de Ecosistemas Acuáticos, Centro de Ciencias Ambientales EULA-Chile, Universidad de Concepción, Concepción, Chile;6. Departamento de Oceanografía and Interdisciplinary Center for Aquaculture Research (INCAR), Universidad de Concepción, Concepción, Chile;1. Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, PO Box 1020, Valparaíso, Chile;2. Aquatic Ecosystem Functioning Lab (LAFE), Department of Aquatic System, Faculty of Environmental Sciences & Environmental Sciences Center EULA Chile, Universidad de Concepción, Concepción, Chile;1. Laboratoire d''Océanographie et de Climatologie: Expérimentation et Analyse Numérique (LOCEAN), Institut Pierre-Simon Laplace (IPSL), UPMC/CNRS/IRD/MNHN, 4 Place Jussieu, Case 100, 75252 Paris cedex 05, France;2. Instituto del MAR del PEru (IMARPE), Esquina general Gamarra y Valle, Callao, Peru;3. Laboratoire de Physique des Océans (LPO), UBO/CNRS/IRD/Ifremer, Ifremer – Centre de Brest, 29280 Plouzané, France;4. Helmolz Center for Ocean Research, Kiel, Germany;5. Mercator Océan, Parc Technologique du Canal, 8-10 rue Hermès, 31520 Ramonville St-Agne, France;1. GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148, Kiel, Germany;2. Institute for Geosciences, Christian-Albrechts-Universität zu Kiel, Otto-Hahn-Platz 1, 24118 Kiel, Germany |
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| Abstract: | Recent hydrographic measurements within the eastern South Pacific (1999–2001) were combined with vertically high-resolution data from the World Ocean Circulation Experiment, high-resolution profiles and bottle casts from the World Ocean Database 2001, and the World Ocean Atlas 2001 in order to evaluate the vertical and horizontal extension of the oxygen minimum zone (<20 μmol kg?1). These new calculations estimate the total area and volume of the oxygen minimum zone to be 9.82±3.60×106 km2 and 2.18±0.66×106 km3, respectively. The oxygen minimum zone is thickest (>600 m) off Peru between 5 and 13°S and to about 1000 km offshore. Its upper boundary is shallowest (<150 m) off Peru, shoaling towards the coast and extending well into the euphotic zone in some places. Offshore, the thickness and meridional extent of the oxygen minimum zone decrease until it finally vanishes at 140°W between 2° and 8°S. Moving southward along the coast of South America, the zonal extension of the oxygen minimum zone gradually diminishes from 3000 km (15°S) to 1200 km (20°S) and then to 25 km (30°S); only a thin band is detected at ～37°S off Concepción, Chile. Simultaneously, the oxygen minimum zone's maximum thickness decreases from 300 m (20°S) to less than 50 m (south of 30°S). The spatial distribution of Ekman suction velocity and oxygen minimum zone thickness correlate well, especially in the core. Off Chile, the eastern South Pacific Intermediate Water mass introduces increased vertical stability into the upper water column, complicating ventilation of the oxygen minimum zone from above. In addition, oxygen-enriched Antarctic Intermediate Water clashes with the oxygen minimum zone at around 30°S, causing a pronounced sub-surface oxygen front. The new estimates of vertical and horizontal oxygen minimum zone distribution in the eastern South Pacific complement the global quantification of naturally hypoxic continental margins by Helly and Levin 2004. Global distribution of naturally occurring marine hypoxia on continental margins. Deep-Sea Research I 51, 1159–1168] and provide new baseline data useful for studies on the role of oxygen in the degradation of organic matter in the water column and the related implications for biogeochemical cycles. Coastal upwelling zones along the eastern Pacific combine with general circulation to provide a mechanism that allows renewal of upper Pacific Deep Water, the most oxygen-poor and oldest water mass of the world oceans. |
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