Discovery of relict subglacial lakes and their geometry and mechanism of drainage.
Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow.
Department of Geography, Sheffield University, Winter Street, Sheffield S10 2TN, UK.
Stephen J
SJ
Livingstone
Alberta Geological Survey, Edmonton, Alberta T6B 2X3, Canada.
Daniel J
DJ
Utting
School of Geography, Archaeology and Palaeoecology, Queen's University Belfast, Northern Ireland BT9 6AY, UK.
Alastair
A
Ruffell
Department of Geography, Sheffield University, Winter Street, Sheffield S10 2TN, UK.
Chris D
CD
Clark
Alberta Geological Survey, Edmonton, Alberta T6B 2X3, Canada.
Steven
S
Pawley
Alberta Geological Survey, Edmonton, Alberta T6B 2X3, Canada.
Nigel
N
Atkinson
Mathematics Applications Consortium for Science and Industry (MACSI), University of Limerick, Limerick, Ireland.|Mathematical Institute, University of Oxford, Oxford OX2 6GG, UK.
Andrew C
AC
Fowler