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Constraints on mantle ^3He fluxes and deep-sea circulation from an oceanic general circulation model

Farley, K. A. and Maier-Reimer, E. and Schlosser, P. and Broecker, W. S. (1995) Constraints on mantle ^3He fluxes and deep-sea circulation from an oceanic general circulation model. Journal of Geophysical Research B, 100 (B3). pp. 3829-3839. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20121121-111551304

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Abstract

We have simulated the steady-state distribution of helium in the deep sea to investigate the magnitude and spatial and temporal variability of mantle degassing and to characterize deep-sea circulation and ventilation. The simulation was produced by linking a simple source function for helium injected at mid-ocean ridges with an oceanic general circulation model (GCM). By assuming that the flux of mantle helium is linearly proportional to the seafloor spreading rate and by using previous estimates for the total flux of mantle helium into the oceans, the GCM yields an oceanic ^3He distribution which is in qualitative agreement with observations both in overall magnitude and in general distribution. This provides new evidence that the flux of mantle ^3He into the oceans is about 1000 mol/yr and that mid-ocean ridges are the dominant source of mantle helium. Although the match with observations is good in the Pacific and Indian Oceans, the simulated ^3He anomalies throughout the Atlantic Ocean are much higher than has been measured. Because the GCM is thought to reproduce Atlantic circulation reasonably well, this discrepancy suggests an error in the helium source function. Either helium injection is not a linear function of seafloor emplacement rate, or eruption and concomitant degassing are highly episodic at the slow spreading rates characteristic of the Mid-Atlantic Ridge (MAR). The latter explanation would imply minimal volcanic activity along the entire length of the MAR over the last few centuries. In addition to constraints on the degassing flux, our work provides information on the transport and ventilation of deep ocean waters and constrains the degree to which current GCMs can reproduce deep-water circulation patterns. While the results generally support the GCM's abyssal circulation, our simulation reveals regions of overly-intense lateral diffusion and upwelling in the model, particularly in the equatorial Pacific. Similarly, there appears to be insufficient production of He-ventilated bottom waters in the model Antarctic. These observations suggest that further refinement of the GCM abyssal circulation is required.


Item Type:Article
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http://dx.doi.org/10.1029/94JB02913DOIUNSPECIFIED
http://www.agu.org/pubs/crossref/1995/94JB02913.shtmlPublisherUNSPECIFIED
Additional Information:© 1995 American Geophysical Union. Received April 7, 1994; revised October 24, 1994; accepted November 2, 1994. We thank Keith Dixon for a thorough and constructive review of this manuscript. This work was supported by NSF Grant OCE-9111404 (P.S.). This is LDEO contribution number 5293.
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NSFOCE-9111404
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LDEO5293
Record Number:CaltechAUTHORS:20121121-111551304
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20121121-111551304
Official Citation:Farley, K. A., E. Maier-Reimer, P. Schlosser, and W. S. Broecker (1995), Constraints on mantle 3He fluxes and deep-sea circulation from an oceanic general circulation model, J. Geophys. Res., 100(B3), 3829–3839, doi:10.1029/94JB02913.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35606
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:21 Nov 2012 20:31
Last Modified:27 Dec 2012 03:02

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