|Fernanda Hoefel and Rob. L. Evans, Impact of Low Salinity Porewater on Seafloor
Electromagnetic Data: A Means of Detecting
Submarine Groundwater Discharge?, Estuarine, Coastal and Shelf Science, 2001|
Submarine groundwater discharge has been recognized as an important process in coastal and shelf environments, but,
due to the diffuse nature of the process, methods to identify and map zones of discharge still need development. Vertical
profiles of subseafloor salinity from two locations off the east coast of the U.S. and from a coastal embayment in Cape
Cod, MA, have been used to model seafloor electromagnetic (EM) responses to changes in porewater salinity. Ordinarily,
porewaters of salinity close to that of seawater will be electrically conductive. Replacement of this conductive porewater
by a body of fresh groundwater will reduce the electrical conductivity of the porewater and, hence, that of the seafloor.
Based on in situ measurements of porewater salinity and reasonable estimates of sediment porosity, our modelling
quantifies the changes in EM apparent porosity measurements that might be expected over coastal and nearshore regions
of fresh water discharge. Given the results obtained, we demonstrate that existing EM technology might be used to map
zones of fresh water in conjunction with other methods.
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