Perspectives of transient tracer applications and limiting cases.

Stöven, Tim , Tanhua, Toste , Hoppema, M. and Bullister, J. L. (2015) Perspectives of transient tracer applications and limiting cases. Open Access Ocean Science, 11 . pp. 699-718. DOI 10.5194/os-11-699-2015.

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Abstract

Currently available transient tracers have different application ranges that are defined by their temporal input (chronological transient tracers) or their decay rate (radioactive transient tracers). Transient tracers range from tracers for highly ventilated water masses such as sulfur hexafluoride (SF6) through tritium (3H) and chlorofluorocarbons (CFCs) up to tracers for less ventilated deep ocean basins such as argon-39 (39Ar) and radiocarbon (14C). In this context, highly ventilated water masses are defined as water masses that have been in contact with the atmosphere during the last decade. Transient tracers can be used to empirically constrain the transit time distribution (TTD), which can often be approximated with an inverse Gaussian (IG) distribution. The IG-TTD provides information about ventilation and the advective/diffusive characteristics of a water parcel.

Here we provide an overview of commonly used transient tracer couples and the corresponding application range of the IG-TTD by using the new concept of validity areas. CFC-12, CFC-11 and SF6 data from three different cruises in the South Atlantic Ocean and Southern Ocean as well as 39Ar data from the 1980s and early 1990s in the eastern Atlantic Ocean and the Weddell Sea are used to demonstrate this method. We found that the IG-TTD can be constrained along the Greenwich Meridian south to 46° S, which corresponds to the Subantarctic Front (SAF) denoting the application limit. The Antarctic Intermediate Water (AAIW) describes the limiting water layer in the vertical. Conspicuous high or lower ratios between the advective and diffusive components describe the transition between the validity area and the application limit of the IG-TTD model rather than describing the physical properties of the water parcel. The combination of 39Ar and CFC data places constraints on the IG-TTD in the deep water north of the SAF, but not beyond this limit.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/264879
Additional Information: WOS:000361971200003
Keywords: POLARSTERN; ANT-XXVIII/3; CLIVAR A13.5
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
HGF-AWI
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography > Water column biogeochemistry
Refereed: Yes
Open Access Journal?: Yes
Publisher: Copernicus Publications (EGU)
Projects: CARBOCHANGE, Eddy Pump, CLIVAR
Expeditions/Models/Experiments:
Date Deposited: 16 Oct 2014 10:25
Last Modified: 21 Apr 2021 12:12
URI: https://oceanrep.geomar.de/id/eprint/25821

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