Mechanisms and variability of salt transport in partially-stratified estuaries

The variability of salt transport determines the variation of the length of the salinity intrusion and the large-scale density gradient in an estuary. This thesis contains three studies that address salt transport and the salt balance. The variation of salt transport with the depth, the along-channel salinity gradient, and the amplitude of the tidal velocity is investigated with analytic and numerical models. The results indicate that salt transport increases dramatically during stratified periods when vertical mixing is weak. Analysis of salt transport from observations in the Hudson Estuary show that stratified periods with elevated estuarine salt transport occur in five-day intervals once a month during apogean neap tides. Oscillatory salt transport, which is hypothesized to be primarily caused by lateral exchange and mixing of salt, appears to play a more minor role in the salt balance of the estuary. The salt balance of the estuary adjusts very little to the spring-neap modulation of salt transport but adjusts rapidly to pulses of freshwater flow. A simple model is used to investigate the process and time scales of adjustment of the salt balance by connecting variations of salt transport to the variations of freshwater flow and vertical mixing. The results show the length of the salinity intrusion adjust via advection to rapid and large increases in freshwater flow. The salinity intrusion adjusts more rapidly to the spring-neap cycle of tidal mixing the higher the freshwater flow.

Department dc:contributor.department

Joint Program in Physical Oceanography

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2000

Author dc:creator

• Bowen, Melissa Marie

Advisor dc:contributor.advisor

• W. Rockwell Geyer and Steven J. Lentz.

• Joint Program in Physical Oceanography.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://hdl.handle.net/1912/2130
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://hdl.handle.net/1721.1/58542

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/58542