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The dynamics of a subglacial salt wedge

Wilson, Earle A. and Wells, Andrew J. and Hewitt, Ian J. and Cenedese, Claudia (2020) The dynamics of a subglacial salt wedge. Journal of Fluid Mechanics, 895 . Art. No. A20. ISSN 0022-1120. https://resolver.caltech.edu/CaltechAUTHORS:20200604-132612460

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Abstract

Marine-terminating glaciers, such as those along the coastline of Greenland, often release meltwater into the ocean in the form of subglacial discharge plumes. Though these plumes can dramatically alter the mass loss along the front of a glacier, the conditions surrounding their genesis remain poorly constrained. In particular, little is known about the geometry of subglacial outlets and the extent to which seawater may intrude into them. Here, the latter is addressed by exploring the dynamics of an arrested salt wedge – a steady-state, two-layer flow system where salty water partially intrudes a channel carrying fresh water. Building on existing theory, we formulate a model that predicts the length of a non-entraining salt wedge as a function of the Froude number, the slope of the channel and coefficients for interfacial and wall drag. In conjunction, a series of laboratory experiments were conducted to observe a salt wedge within a rectangular channel. For experiments conducted with laminar flow (Reynolds number Re < 800), good agreement with theoretical predictions are obtained when the drag coefficients are modelled as being inversely proportional to Re. However, for fully turbulent flows on geophysical scales, these drag coefficients are expected to asymptote toward finite values. Adopting reasonable drag coefficient estimates for this flow regime, our theoretical model suggests that typical subglacial channels may permit seawater intrusions of the order of several kilometres. While crude, these results indicate that the ocean has a strong tendency to penetrate subglacial channels and potentially undercut the face of marine-terminating glaciers.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1017/jfm.2020.308DOIArticle
ORCID:
AuthorORCID
Wilson, Earle A.0000-0003-2329-5115
Wells, Andrew J.0000-0001-7929-6227
Hewitt, Ian J.0000-0002-9167-6481
Additional Information:© 2020 The Author(s). Published by Cambridge University Press. Received 23 October 2019; revised 6 February 2020; accepted 13 April 2020. Published online by Cambridge University Press: 20 May 2020. We thank two anonymous reviewers who provided constructive feedback, which led to substantial improvement of the manuscript. The laboratory experiments described herein were conducted at the Woods Hole Oceanographic Institution (WHOI), with financial support from the WHOI Geophysical Fluid Dynamics summer program. We thank A. Jensen for his assistance in assembling our tank experiments. E.W. gratefully acknowledges financial support from the National Science Foundation under NSF award PLR-1425989 to the University of Washington. A.J.W. acknowledges support through the research program of the European Union FP7 award PCIG13-GA-2013-618610 SEA-ICE-CFD. I.J.H. was supported by a Marie Curie FP7 Career Integration Grant PCIG13-GA-2013-618007. C.C. was supported by NSF OCE-1658079. The authors declare no conflicts of interest.
Funders:
Funding AgencyGrant Number
NSFPLR-1425989
Marie Curie FellowshipPCIG13-GA-2013-618610 SEA-ICE-CFD
Marie Curie FellowshipPCIG13-GA-2013-618007
NSFOCE-1658079
Subject Keywords:stratified flows, ocean processes
Record Number:CaltechAUTHORS:20200604-132612460
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200604-132612460
Official Citation:Wilson, E., Wells, A., Hewitt, I., & Cenedese, C. (2020). The dynamics of a subglacial salt wedge. Journal of Fluid Mechanics, 895, A20. doi:10.1017/jfm.2020.308
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103695
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Jun 2020 21:37
Last Modified:04 Jun 2020 21:37

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