Transient electromagnetic soundings were taken at several sites along a line from the North Prudhoe Bay State (NPBS) 1 well to Reindeer Island in the Beaufort Sea during the spring of 1984. The purpose of these soundings was to delineate the depth to, and the thickness of, the ice-bonded permafrost layer known to exist below the seabed.

Offshore, about 1.5-2 m of sea ice covers shallow (< 7-m or 22-ft) sea water underlain by saline, saturated sediments. Data reductions, appropriate for such high electrical conductivity, and subsequent interpretations suggest an unfrozen (or partially unfrozen) layer overlying a more resistive ice-bonded permafrost layer. Beneath the ice-bonded layer, the sediments are unfrozen and more conductive.

A permafrost profile along the line, showing the depths and thicknesses of ice-bonded permafrost, was inferred from the interpretations. The unfrozen sediments appear to increase in depth from zero onshore to a maximum of about 175 m at 6 km from shore. The thickness of ice-bonded permafrost steadily decreases with increasing distance offshore, from about 560 m onshore to 300 m at 6 km from shore; it displays an increasing complexity from 9 to 14 km.

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