MORPHOLOGY AND FIELD OBSERVATIONS OF TUNNEL VALLEYS IN DEVON ISLAND, ARCTIC ARCHIPELAGO: EXPLORING THE FINGERPRINTS OF SUBGLACIAL DRAINAGE

Tunnel valleys are bedrock incised channels attributed to erosion by highly pressurized channelized subglacial meltwater. They exert a key control on meltwater accumulation at the base of ice sheets, serving as meltwater drainage conduits and retarding ice flow rates. However, the inaccessibility of active subglacial channels makes in situ studies challenging, whereas precipitation and weathering limit the preservation of tunnel valleys to polar deserts in the high Arctic and Antarctica. Here we present results and observations from a field campaign in Devon Island, situated in the Canadian high Arctic, where we studied the morphology of a number of tunnel valleys recently exposed by the retreating Devon Island ice cap. We first identified the tunnel valleys according to well stablished guidelines, including their undulating longitudinal profiles, recurrent directionality consistent with ice paleoflow lines, and with direct observations of valleys emerging under the ice cap. We report tunnel valley lengths between 1 and 2 Km and characteristic shallow, U-shaped cross sections 5-10m wide. Valleys occur in groups of 5-10 systems, which incise the ground forming a straight line and run parallel to each other. Consistent with models of esker emplacement, we observe first order channels to be periodically spaced an average of 150m throughout the island. This close spacing suggest that tunnel valleys formed through the emergence of highly pressurized groundwater from a subglacial aquifer. Our work aims to build understanding of the formation of channelized subglacial drainage and to discuss the morphologies that these systems present.