CO 2 outgassing off central Chile (31-30°S) and northern Chile (24-23°S) during austral summer 1997: The effect of wind intensity on the upwelling and ventilation of CO 2-rich waters

Torres R.; Turner D.; Rutllant, J.; Sobarzo, M; Antezana, T.; González H.E.

Keywords: marine, gas, biology, ocean, pacific, biomass, wind, ph, dioxide, interaction, carbon, upwelling, coastal, measurement, zones, exchange, salinity, effects, alkalinity, air-sea

Abstract

The distribution of pH and alkalinity has been used to calculate the distribution of total inorganic carbon (TC) and fugacity of carbon dioxide (fCO 2) in the upper 200 m of the water column in coastal upwelling areas off northern Chile (23-24°S, near Antofagasta) and central Chile (30-31°S, near Coquimbo) during austral summer 1997. In these upwelling areas, colder surface waters were oxygen poor and strongly CO 2 supersaturated (100% near Antofagasta and 200% near Coquimbo), although below the pycnocline the CO 2 supersaturation invariably exceeded 200% in both areas. The larger surface CO 2 supersaturation and outgassing at 30°S were associated with stronger winds that promoted the upwelling of denser water (richer in CO 2) as well as a higher air-sea CO 2 transfer velocity. The consistent decrease in intensity of the southerly winds (as derived from NSCAT scatterometer data) from 30-31°S to 23-24°S suggests a corresponding decline in the intensity of the CO 2 outgassing due to upwelling. Additionally, we suggest here that the intensity of the local upwelling forcing (i.e. alongshore-equatorward winds) plays a role in determining the water mass composition and phytoplankton biomass of the coastal waters. Thus, while deep upwelling of salty and cold water resulted in high fCO 2 (up to 1000 ?atm) and very low phytoplankton biomass (chlorophyll a concentration lower than 0.5 mg m -3), the shallow upwelling of less salty (e.g. salinity <34.5) and less CO 2-supersaturated water resulted in a higher phytoplankton biomass, which further reduced surface water fCO 2 by photosynthesis. © 2002 Elsevier Science Ltd. All rights reserved.

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Título de la Revista: DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
Volumen: 49
Número: 8
Editorial: PERGAMON-ELSEVIER SCIENCE LTD
Fecha de publicación: 2002
Página de inicio: 1413
Página final: 1429
URL: http://www.scopus.com/inward/record.url?eid=2-s2.0-0036691106&partnerID=q2rCbXpz