Heat Flow on the U.S. Beaufort Margin, Arctic Ocean: Implications for Ocean Warming, Methane Hydrate Stability, and Regional Tectonics.

Results from the first focused heat flow study on the U.S. Beaufort Margin provide insight into decadal-scale Arctic Ocean temperature change and raise new questions regarding Beaufort Margin evolution. This study measured heat flow using a 3.5-m Lister probe at 103 sites oriented along four north-south transects perpendicular to the similar to 700-km long U.S. Beaufort Margin. The new heat flow measurements, corrected both for seasonal ocean temperature fluctuations and bathymetric effects, reveal low average heat flow values (similar to 35 mW/m(2)) at seafloor depths of 300-900 m below sea level (mbsl) and anomalously high (similar to 80 mW/m(2)) values at seafloor depths of >1,000 mbsl, near the predicted continent-ocean transition. Anomalously low heat flow values measured on the upper margin are consistent with previous studies suggesting decadal-scale ocean temperature warming to similar to 500 mbsl. Our results, however, indicate this ocean warming likely extends to depths as great at 900 mbsl-400 m deeper than previous studies suggest-implying widespread, ongoing, methane hydrate destabilization across much of the U.S. Beaufort Margin. The cause of the anomalously high heat flow values observed at seafloor depths >1,000 at the continent-ocean transition is unclear. We suggest three candidate processes: (1) higher heat production and lower thermal conductivity on the margin edge due to the thickest sedimentary cover at the ocean-continent transition, (2) seaward migrating subsurface advection, and (3) possible fault-reactivation at the northern boundary of the Alaskan Microplate.