Temperature profiles in the Barnes Ice Cap, Baffin Island, Canada, and heat flux from the subglacial terrane

Abstract

Temperature measurements were made in seven boreholes, ranging in depth from 50–276 m, in the Barnes Ice Cap. Holes B4, D4, and T0975 are approximately 1 km from the margin and an average of 8 km apart. Holes T091, T081, T061, and T020 lie along a 10.2 km flow line passing through T0975. Temperature profiles are convex upward in all holes except T020, reflecting the combined effects of longitudinal and upward vertical advection, and frictional heating. The profile in T020 is concave near the bottom of the hole, as a result of downward vertical advection, but convex above mid-depth, owing to a 2.5 °C cooling of the near-surface ice in the early 1940's.Modeling, using a finite difference scheme, suggests that the profiles are in equilibrium with slightly lower vertical velocities and longitudinal advection rates than exist at present, and that temperatures at the glacier surface have increased 0.1–0.5 °C over the last few decades. The modeling further suggests that the heat flux from the subglacial terrane beneath most holes is 0.5–0.8 heat-flow units (HFU), which is somewhat lower than the average geothermal flux on the Canadian Shield. The heat flux seems to decrease down-glacier along the flow line through T0975, apparently reflecting climatic warming of about 2 °at the end of the Little Ice Age. In contrast, the heat flux appears to increase southeastward from the flow line, reaching an anomalously high value of about 1.9 HFU at B4. This trend is unexplained.Measurements of U, Th, and K in rock samples collected near the margin suggest heat production rates of about 5 heat-generation units (HGU), which is slightly higher than previous measurements on Baffin Island.