Deglacial dynamics of the Vestfjorden - Trænadjupet palaeo-ice stream, northern Norway

Abstract

Few well‐dated records of the deglacial dynamics of the large palaeo‐ice streams of the major Northern Hemisphere ice sheets are presently available, a prerequisite for an improved understanding of the ice‐sheet response to the climate warming of this period. Here we present a transect of gravity‐core samples through Trænadjupet and Vestfjorden, northern Norway, the location of the Trænadjupet – Vestfjorden palaeo‐ice stream of the NW sector of the Fennoscandian Ice Sheet. Initial ice recession from the shelf break to the coastal area (~400 km) occurred at an average rate of about 195 m a⁻¹, followed by two ice re‐advances, at 16.6–16.4 ka BP (the Røst re‐advance) and at 15.8–15.6 ka BP (the Værøy re‐advance), the former at an estimated ice‐advance rate of 216 m a⁻¹. The Røst re‐advance has been interpreted to be part of a climatically induced regional cold spell while the Værøy re‐advance was restricted to the Vestfjorden area and possibly formed as a consequence of internal ice‐sheet dynamics. Younger increases in IRD content have been correlated to the Skarpnes (Bølling – Older Dryas) and Tromsø – Lyngen (Younger Dryas) Events. Overall, the decaying Vestfjorden palaeo‐ice stream responded to the climatic fluctuations of this period but ice response due to internal reorganization is also suggested. Separating the two is important when evaluating the climatic response of the ice stream. As demonstrated here, the latter may be identified using a regional approach involving the study of several palaeo‐ice streams. The retreat rates reported here are of the same order of magnitude as rates reported for ice streams of the southern part of the Fennoscandian Ice Sheet, implying no latitudinal differences in ice response and retreat rate for this ~1000 km² sector of the Fennoscandian Ice Sheet (~60–68°N) during the climate warming of this period.