Placing constraints on submarine permafrost extent along the U.S. Beaufort Shelf using thermodynamic modeling

Abstract. This study constrains submarine permafrost extent along the U.S. Beaufort Shelf through eighteen thermodynamic simulations conducted along an offshore transect from Oliktok Point, Alaska, to improve characterization of the nearshore Arctic Ocean. The results demonstrate that lithology, pore water salinity, and geothermal heat flux are key controls on submarine permafrost distribution and offshore continuity. Comparison with existing geophysical observations suggests pore water salinity is near seawater levels, while geothermal heat flux could be elevated above the regional average. Synthetic resistivity logs reveal that ignoring subsurface lithologic heterogeneity can lead to misclassification of ice saturation, underscoring the need to incorporate geological context in geophysical interpretations. Moreover, comparison with prior resistivity-based interpretations suggests that some deep high-resistivity signals may reflect hydrocarbons trapped beneath the permafrost wedge rather than additional ice-bearing permafrost. Temperature profiles extracted at 2 m sediment depth provide additional constraints on subsurface thermal regimes and support calibration of Distributed Temperature Sensing (DTS) data in the absence of direct absolute temperature observations. The close agreement among modeled profiles indicates that localized DTS anomalies may represent true thermal perturbations, potentially linked to methane seepage. Collectively, these findings place meaningful limits on submarine permafrost extent along the U.S. Beaufort Shelf and provide a framework for integrating thermodynamic modeling, resistivity analysis, and DTS monitoring into future investigations of Arctic permafrost dynamics and their broader climatic implications, while also suggesting that submarine permafrost in this region may extend farther than previously recognized.