Characteristics of changing permafrost temperatures in the Alaskan Arctic, USA

Temperatures in permafrost were measured annually from 1983 through 1993 in drill holes (nominally 60 m in depth) at three sites in Northern Alaska; West Dock, Deadhorse, and Franklin Bluffs. Active layer and near-surface permafrost temperatures (to 1 m) were measured every 4 h from 1986 through 1993. This paper combines two previously published data sets with numerical simulations to fill the data gap in daily permafrost temperatures from Im to the depth of penetration of the annual temperature wave (about 20 m). These daily values were used to calculate mean temperature profiles for the annual period, a 10- to Il-yr cycle and for other periods. Calculated profiles were used to revise estimates of the surface amplitude of the 10- to Il-yr cycle at Franklin Bluffs from 0.6 K to about 1 K. The data show that, for the 10- to Il-yr cycle, cooling of the permafrost began prior to 1983 with the warming part of the cycle beginning in the late 1980s. This is consistent with the U.S. Geological Survey data suggesting that their reported cooling may have been part of a natural cycle and not an effect of the disturbance at the ground surface associated with drilling. The means of the measured temperature profiles below the 20 m depth show curvatures toward warmer temperatures. These curvatures may be associated with climatic fluctuations, a cycle or a longer-term warming trend. While these time series of permafrost temperatures are too short to distinguish between these alternatives, it is important to do so because of their possible relationship with the predicted climatic warming.