Thick sediments beneath Greenland’s ablation zone and their potential role in future ice sheet dynamics

Abstract

Research Article| June 01, 2014 Thick sediments beneath Greenland's ablation zone and their potential role in future ice sheet dynamics Fabian Walter; Fabian Walter 1Institut des Sciences de la Terre, Université de Grenoble I, CNRS, BP 53, 38041 Grenoble Cedex 9, France Search for other works by this author on: GSW Google Scholar Julien Chaput; Julien Chaput 1Institut des Sciences de la Terre, Université de Grenoble I, CNRS, BP 53, 38041 Grenoble Cedex 9, France Search for other works by this author on: GSW Google Scholar Martin P. Lüthi Martin P. Lüthi * 2Laboratory of Hydraulics, Hydrology and Glaciology, ETH Zürich, HIT E 42.1, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland *Current address: Department of Geography, 3G, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. Search for other works by this author on: GSW Google Scholar Author and Article Information Fabian Walter 1Institut des Sciences de la Terre, Université de Grenoble I, CNRS, BP 53, 38041 Grenoble Cedex 9, France Julien Chaput 1Institut des Sciences de la Terre, Université de Grenoble I, CNRS, BP 53, 38041 Grenoble Cedex 9, France Martin P. Lüthi * 2Laboratory of Hydraulics, Hydrology and Glaciology, ETH Zürich, HIT E 42.1, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland *Current address: Department of Geography, 3G, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. Publisher: Geological Society of America Received: 22 Jan 2014 Revision Received: 06 Mar 2014 Accepted: 09 Mar 2014 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2014 Geological Society of America Geology (2014) 42 (6): 487–490. https://doi.org/10.1130/G35492.1 Article history Received: 22 Jan 2014 Revision Received: 06 Mar 2014 Accepted: 09 Mar 2014 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Fabian Walter, Julien Chaput, Martin P. Lüthi; Thick sediments beneath Greenland's ablation zone and their potential role in future ice sheet dynamics. Geology 2014;; 42 (6): 487–490. doi: https://doi.org/10.1130/G35492.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The geological nature of glacier beds plays a key role in ice sheet dynamics. Whereas little is known about Greenland's subglacial geology, the presence of basal sediments is a necessary condition for fast-flowing Antarctic ice streams. Such sediments sustain subglacial till layers, which if water saturated and under high pore-water pressure provide little resistance to ice flow. Using receiver function modeling of teleseismic P-waves, we report a thick (at least tens of meters) sediment layer beneath a site in Greenland's ablation zone, ∼15 km away from the western ice sheet margin. Although we do not discuss the origin or detailed nature of these subglacial sediments, we suggest that they are capable of sustaining a till layer. Due to the prevalence of an inefficient, pressurized subglacial drainage system, this till layer would typically be under high pore pressures and fail at the shear stresses transmitted from the overlaying ice. Ice flow resistance is thus focused on regions where till is consolidated or absent, or where form drag over obstacles takes place. In contrast to Antarctica, Greenland's surface melt now affects practically all latitudes, and efficient hydraulic connections between ice sheet surface and bed are pervasive throughout the ablation zone. This implies that rapid, melt-induced changes in subglacial water pressure are possible. The time required for basal till strength to react to these changes depends on the till's properties. We estimate that formation and destruction of flow resistance can occur on time scales of less than a few years. This could lead to changes in ice flow that are currently difficult to predict. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.