Age determination of mixed water masses using CFC and oxygen data.

Karstensen, Johannes and Tomczak, M. (1998) Age determination of mixed water masses using CFC and oxygen data. Open Access Journal of Geophysical Research: Oceans, 103 (C9). pp. 18599-18610. DOI 10.1029/98JC00889.

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Abstract

We present a new method based on a combination of optimum multiparameter analysis and CFC/oxygen mixing analysis to determine the ages of water masses in regions of mixing. It enables us to follow water mass movements in greater detail than with other methods, which give only the combined pseudoage of a water mass mixture. We define the age of a water mass as the time a water parcel needs to spread from its source region, where it received its individual tracer characteristics, to the point of observation. The age distribution allows us to determine pathways of water masses, which differ from simple advection trajectories because the age is determined by a combination of advective and diffusive processes. We apply the method to hydrographic data along World Ocean Circulation Experiment section I5 in the south east Indian Ocean. In the thermocline, Indian Central Water (ICW) and Subantarctic Mode Water (SAMW) meet and mix. These distinct water masses have different formation mechanisms but similar temperature/salinity characteristics. It is shown that the convective formation of SAMW is a major ventilation mechanism for the lower Indian thermocline. In the eastern part of the south Indian Ocean, SAMW dominates the oceanic thermocline and is found to be about 5 years old. Pure ICW is present only in the thermocline of the region 48 degrees-55 degrees E, with increasing age with depth, confirming the subduction theory. While most SAMW joins the equatorward gyre movement of the southeastern Indian Ocean, some of it propagates westward through turbulent diffusive mixing, reaching 55 degrees E after 15-20 years. It takes ICW some 25-30 years to reach 110 degrees E.

Document Type: Article
Keywords: OPTIMUM MULTIPARAMETER ANALYSIS; ANTARCTIC INTERMEDIATE WATER; SOUTH INDIAN-OCEAN; NORTH-ATLANTIC; VENTILATION; THERMOCLINE; CIRCULATION; SEAWATER; SECTION
Refereed: Yes
Open Access Journal?: No
Publisher: AGU (American Geophysical Union)
Date Deposited: 03 Mar 2008 11:15
Last Modified: 17 Apr 2018 08:20
URI: https://oceanrep.geomar.de/id/eprint/3589

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