Groundwater Flow Under a Paleo-Ice Stream of the Scandinavian Ice Sheet and Its Implications for the Formation of Stargard Drumlin Field, NW Poland

• Published in: Journal of Geophysical Research: Earth Surface
• Main Authors: Hermanowski, Piotr, Piotrowski, Jan A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: drumlins; glaciation; groundwater modeling; ice/bed interface; paleo-ice streams; subglacial groundwater; Ice Sheet
• Online Access: https://pure.au.dk/portal/en/publications/660d1f39-f089-47ff-b638-a3aa19c4eaba; https://doi.org/10.1029/2018JF004939; https://pure.au.dk/ws/files/196903062/Groundwater_flow_under_a_paleo_ice_stream_of_the_Scandinavian_Ice_Sheet_and_its_implications_for_the_formation_of_Stargard_drumlin_field_NW_Poland.pdf; http://www.scopus.com/inward/record.url?scp=85068517593&partnerID=8YFLogxK

Subglacial groundwater flow was an integral part of glaciological systems of past ice sheets, but its impact on the origin of active-ice landforms remains unexplored. Using numerical experiments, we attempt to constrain groundwater flow dynamics under a major paleo-ice stream of the southern Scandinavian Ice Sheet and its impact on the formation of the Stargard drumlin field. Flow models show a total reorganization of groundwater dynamics under the advancing ice stream to a depth of up to ~200 m. A mosaic of intervening groundwater recharge and discharge areas originates, whereby the same areas may experience multiple shifts in flow directions. A prominent time- and space-transgressive pressure pump recharges groundwater in a subglacial zone up to about 20 km within the ice margin and discharges it in front of the ice sheet. The simulated groundwater flow pattern suggests that drumlins occupying a portion of the ice stream area occur preferentially where groundwater upwells and discharges at the ice/bed interface. Consistent with the geological composition, a possible drumlin-forming mechanism involves an excess of pressurized water under the ice reducing the strength of the subglacial deposits and facilitating glacial erosion, erosion by turbulent meltwater flows or both, streamlining antecedent deposits into drumlin shapes. This study emphasizes the importance of causal feedback between subglacial groundwater flow and the ice sheet dynamics and suggests an impact of the former on the formation of streamlined subglacial landforms in general.