T250 Coastal Hydrogeology in An Age of Rising Seas

Wednesday, 25 September 2019
8:00 AM - 12:00 PM
Room 102AB, West Building

SUBSURFACE SALTWATER INTRUSION DYNAMICS AND FRESHWATER POND AREA DECLINE ON A REMOTE ISLAND (SABLE ISLAND, NOVA SCOTIA)

Paper number: T250-5
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

Small-island, freshwater resources support unique ecosystems and often dense human populations, and are highly vulnerable to shifts in ocean, land, and climate conditions. For instance, low-lying islands are susceptible to seawater overwash during large storm events and concomitant salinization of freshwater resources. Sable Island, a Canadian National Park Reserve, is a small low-lying barrier island located in the Northwest Atlantic Ocean with a unique ecosystem of wild horses, endangered seabirds, and the world’s largest grey seal population. This relatively pristine site has been established as an island groundwater observatory as it has a strong record of environmental data, and the freshwater resources are highly influenced by ocean processes and the changing climate.

Freshwater ponds on Sable Island, which are the only surface source of freshwater, have declined dramatically in size in recent decades, raising concern for the island’s ecosystem. Surface water and sediment temperature monitoring in the ponds is used to assess pond-aquifer connectivity and provide insight into the observed long-term decline in pond volumes. Multiple 2D transects of subsurface resistivity inferred using a WalkTEM are compared to geophysical surveys from the 1970s to assess trends in the subsurface freshwater lens volume. Data collected from near-shore wave loggers and pressure transducers in groundwater wells are analyzed to characterize the effect of oceanic forcings on the island’s groundwater dynamics. Finally, to investigate episodic salinization of freshwater resources, a time-lapse camera and a transect of piezometer nests are installed and monitored in a low-lying area on Sable Island. Data from this newly established observatory will provide insight into episodic and gradual salinization of freshwater resources on Sable Island. These insights are critical to enhance our understanding of the future vulnerability of freshwater resources on small islands.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-340231

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