title: Clean subglacial access: prospects for future deep hot-water drilling.
abstract: Accessing and sampling subglacial environments deep beneath the Antarctic Ice Sheet presents several challenges to existing drilling technologies. With over half of the ice sheet believed to be resting on a wet bed, drilling down to this environment must conform to international agreements on environmental stewardship and protection, making clean hot-water drilling the most viable option. Such a drill, and its water recovery system, must be capable of accessing significantly greater ice depths than previous hot-water drills, and remain fully operational after connecting with the basal hydrological system. The Subglacial Lake Ellsworth (SLE) project developed a comprehensive plan for deep (greater than 3000 m) subglacial lake research, involving the design and development of a clean deep-ice hot-water drill. However, during fieldwork in December 2012 drilling was halted after a succession of equipment issues culminated in a failure to link with a subsurface cavity and abandonment of the access holes. The lessons learned from this experience are presented here. Combining knowledge gained from these lessons with experience from other hot-water drilling programmes, and recent field testing, we describe the most viable technical options and operational procedures for future clean entry into SLE and other deep subglacial access targets.
authors.affiliation: British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK kmak@bas.ac.uk.
authors.forename: Keith
authors.identifier: http://orcid.org/0000-0002-5791-1767
authors.initials: K
authors.lastname: Makinson
authors.affiliation: Faculty of Health and Life Sciences, University of Northumbria, Ellison Building, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: David
authors.initials: D
authors.lastname: Pearce
authors.affiliation: British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
authors.forename: Dominic A
authors.initials: DA
authors.lastname: Hodgson
authors.affiliation: Department of Geography, Durham University, Lower Mountjoy, South Road, Durham DH1 3LE, UK.
authors.forename: Michael J
authors.identifier: http://orcid.org/0000-0002-2048-0019
authors.initials: MJ
authors.lastname: Bentley
authors.affiliation: British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Smith
authors.affiliation: School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK.
authors.forename: Martyn
authors.identifier: http://orcid.org/0000-0003-2071-3094
authors.initials: M
authors.lastname: Tranter
authors.affiliation: British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
authors.forename: Mike
authors.initials: M
authors.lastname: Rose
authors.affiliation: School of Geography, Politics and Sociology, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Ross
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK.
authors.forename: Matt
authors.initials: M
authors.lastname: Mowlem
authors.affiliation: School of Geosciences, University of Aberdeen, King's College, Aberdeen AB24 3UE, UK.
authors.forename: John
authors.initials: J
authors.lastname: Parnell
authors.affiliation: Grantham Institute and Department of Earth Science and Engineering, Imperial College London, South Kensington SW7 2AZ, UK.
authors.forename: Martin J
authors.identifier: http://orcid.org/0000-0002-0090-4806
authors.initials: MJ
authors.lastname: Siegert
keywords: clean access; deep hot-water drilling; environmental stewardship; subglacial environment