Combined Geophysical Measurements Provide Evidence for Unfrozen Water in Permafrost in the Adventdalen Valley in Svalbard

Quantifying the unfrozen water content of permafrost is critical for assessing impacts of surface warming on the reactivation of groundwater flow and release of greenhouse gasses from degrading permafrost. Unfrozen water content was determined along an ~12-km transect in the Adventdalen valley in Svalbard, an area with continuous permafrost, using surface nuclear magnetic resonance and controlled source audio-magnetotelluric data. This combination of measurements allowed for differentiation of saline from fresh pore water, and frozen from unfrozen pore water. Above the limit of Holocene marine transgression, no unfrozen water was detected, associated with high electrical resistivity. Below the marine limit, within several kilometers of the coast, up to ~10% unfrozen water content was detected, associated with low resistivity values indicating saline pore water. These results provide evidence for unfrozen water within continuous, thick permafrost in coastal settings, which has implications for groundwater flow and greenhouse gas release in similar Arctic environments