Denudation rates in the Arctic estimated from lake sediments on Spitsbergen, Svalbard

Abstract

A mean Holocene denudation rate of 15 mm/1000 yr is calculated for the high arctic valley Linnédalen, western Svalbard, based on estimates of the total volume of lacustrine sediments deposited in Lake Linnévatnet. Thirty-six sub-bottom sediment profiles and 16 sediment cores have been used to map the postglacial sediments stored in the lake. These reveal a lower marine unit overlain by lacustrine sediments. The base and top of the marine sediments were radiocarbon dated to around 12,300 and 9600 yr B.P. respectively. From isopach maps of the lacustrine unit and the total sediment thickness we calculated 0.9 × 10 −2 km 3 of Holocene lacustrine sediments and 20.1 × 10 −2 km 3 of marine sediments. A denudation rate of 15 mm/1000 yr is calculated from the volume of the lacustrine sediments; this demonstrates that fluvial erosion does not contribute significantly to the lowering of the landscape in the present climate. In contrast, glacial erosion rates in nearby areas on Svalbard are much higher, indicating that glacial erosion by warm-based valley glaciers is the most important geomorphic process in the present climate. Three km of Tertiary sediments are postulated to have been removed from central parts of Svalbard. Our denudation rates suggest that this could not have occurred in the present interglacial type of climate. We suggest that most of that was removed either in a warmer climate or by glaciers.