title: Inner gorges cut by subglacial meltwater during Fennoscandian ice sheet decay.
abstract: The century-long debate over the origins of inner gorges that were repeatedly covered by Quaternary glaciers hinges upon whether the gorges are fluvial forms eroded by subaerial rivers, or subglacial forms cut beneath ice. Here we apply cosmogenic nuclide exposure dating to seven inner gorges along ~500 km of the former Fennoscandian ice sheet margin in combination with a new deglaciation map. We show that the timing of exposure matches the advent of ice-free conditions, strongly suggesting that gorges were cut by channelized subglacial meltwater while simultaneously being shielded from cosmic rays by overlying ice. Given the exceptional hydraulic efficiency required for meltwater channels to erode bedrock and evacuate debris, we deduce that inner gorges are the product of ice sheets undergoing intense surface melting. The lack of postglacial river erosion in our seven gorges implicates subglacial meltwater as a key driver of valley deepening on the Baltic Shield over multiple glacial cycles.
authors.affiliation: 1] Bolin Centre for Climate Research, Department of Physical Geography & Quaternary Geology, Stockholm University, S-10691 Stockholm, Sweden [2] School of Earth & Environmental Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia.
authors.forename: J D
authors.initials: JD
authors.lastname: Jansen
authors.affiliation: 1] School of Earth & Environmental Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia [2] Institute of Earth & Environmental Sciences, University of Potsdam, D-14776 Potsdam, Germany.
authors.forename: A T
authors.initials: AT
authors.lastname: Codilean
authors.affiliation: Bolin Centre for Climate Research, Department of Physical Geography & Quaternary Geology, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: A P
authors.initials: AP
authors.lastname: Stroeven
authors.affiliation: School of Geographical & Earth Sciences, University of Glasgow, Glasgow 412 8QQ, UK.
authors.forename: D
authors.initials: D
authors.lastname: Fabel
authors.affiliation: Bolin Centre for Climate Research, Department of Physical Geography & Quaternary Geology, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Hättestrand
authors.affiliation: Bolin Centre for Climate Research, Department of Physical Geography & Quaternary Geology, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Kleman
authors.affiliation: 1] Bolin Centre for Climate Research, Department of Physical Geography & Quaternary Geology, Stockholm University, S-10691 Stockholm, Sweden [2] Department of Earth, Atmospheric, & Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Harbor
authors.affiliation: Bolin Centre for Climate Research, Department of Physical Geography & Quaternary Geology, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Heyman
authors.affiliation: Laboratory of Ion Beam Physics, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: P W
authors.initials: PW
authors.lastname: Kubik
authors.affiliation: AMS Laboratory, Scottish Universities Environmental Research Centre, East Kilbride 475 0QF, UK.
authors.forename: S
authors.initials: S
authors.lastname: Xu