Mapping the fresh-water-salt-water interface in the terminal moraine of the Bering Glacier

• Main Authors: Andrus, Austin B., Endsley, K. A., Espino, Silvia, Gierke, John S.
• Format: Text
• Language: unknown
• Published: Digital Commons @ Michigan Tech 2010
• Subjects: Physical Sciences and Mathematics; glacier; Alaska
• Online Access: https://digitalcommons.mtu.edu/mtri_p/66; https://doi.org/10.1130/2010.2462(19; http://specialpapers.gsapubs.org/content/462/341.full.pdf

The principal objective of this investigation was to delineate the geometry of the subterranean discharge of fresh melt water from Vitus Lake (VL) at the terminus of the Bering Glacier into the Gulf of Alaska (GoA). It was hypothesized that during the seasons where the glacier was exhibiting melting, increases in VL elevation would push freshwater through the moraine toward the GoA. Because of the proximity to the GoA, intruded seawater would lie below the freshwater. The fresh and salt waters were delineated by measuring variations in apparent resistivity—as a proxy for salinity—with depth using two-dimensional electrical resistivity tomography at a variety of locations between the GoA and VL. The surveys were conducted using Schlumberger and pole-dipole arrays, along with temporal surveys to examine tidal effects. The results of field surveys conducted in August 2007 and 2008 showed that an interface between the fresh and salt water exists within the moraine at depth and that the interface is deeper progressing from the GoA toward VL. Although the fresh/salt water interface was readily apparent proximal to the GoA, a distinct interface was not apparent closer to VL. The inability to measure a distinct interface could be due to depth limitations (~68 m) for the maximum array length (330 m) and/or mixing of fresh and seawater due to the seasonal effects on melting, which would likely result in seasonal changes in the interface.