Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP)
Drilling an ice core through an ice sheet (typically 2000 to 3000 m thick) is a technical challenge that nonetheless generates valuable and unique information on palaeo-climate and ice dynamics. As technically the drilling cannot be done in one run, the core has to be fractured approximately every 3...
Main Authors: | , , , , , , , , |
---|---|
Format: | Conference Object |
Language: | unknown |
Published: |
2020
|
Subjects: | |
Online Access: | https://epic.awi.de/id/eprint/52078/ https://epic.awi.de/id/eprint/52078/1/EGU2020-21768_presentation.pdf https://meetingorganizer.copernicus.org/EGU2020/EGU2020-21768.html https://hdl.handle.net/10013/epic.704fe3cc-c192-4696-90b3-dbfdeb2b5d47 https://hdl.handle.net/ |
id |
ftawi:oai:epic.awi.de:52078 |
---|---|
record_format |
openpolar |
institution |
Open Polar |
collection |
Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
op_collection_id |
ftawi |
language |
unknown |
description |
Drilling an ice core through an ice sheet (typically 2000 to 3000 m thick) is a technical challenge that nonetheless generates valuable and unique information on palaeo-climate and ice dynamics. As technically the drilling cannot be done in one run, the core has to be fractured approximately every 3 m to retrieve core sections from the bore hole. This fracture process is initiated by breaking the core with core-catchers which also clamp the engaged core in the drill head while the whole drill is then pulled up with the winch motor. This standard procedure is known to become difficult and requires extremely high pulling forces (Wilhelms et al. 2007), in the very deep part of the drill procedure, close to the bedrock of the ice sheet, especially when the ice material becomes warm (approximately -2°C) due to the geothermal heat released from the bedrock. Recently, during the EastGRIP (East Greenland Ice coring Project) drilling we observed a similar issue with breaking off cored sections only with extremely high pulling forces, but started from approximately 1800 m of depth, where the temperature is still very cold (approximately -20°C). This has not been observed at other ice drilling sites. As dependencies of fracture behaviour on crystal orientation and grain size are known (Schulson & Duval 2009) for ice, we thus examined the microstructure in the ice samples close to and at the core breaks. First preliminary results suggest that these so far unexperienced difficulties are due to the profoundly different c-axes orientation distribution (CPO) in the EastGRIP ice core. In contrast to other deep ice cores which have been drilled on ice domes or ice divides, EastGRIP is located in an ice stream. This location means that the deformation geometry (kinematics) is completely different, resulting in a different CPO (girdle pattern instead of single maximum pattern). Evidence regarding additional grain-size dependence will hopefully help to refine the fracturing procedure, which is possible due to a rather strong grain size layering observed in natural ice formed by snow precipitation. --- Wilhelms, F.; Sheldon, S. G.; Hamann, I. & Kipfstuhl, S. Implications for and findings from deep ice core drillings - An example: The ultimate tensile strength of ice at high strain rates. Physics and Chemistry of Ice (The proceedings of the International Conference on the Physics and Chemistry of Ice held at Bremerhaven, Germany on 23-28 July 2006), 2007, 635-639 Schulson, E. M. & Duval, P. Creep and Fracture of Ice. Cambridge University Press, 2009, 401 |
format |
Conference Object |
author |
Weikusat, Ilka Wallis, David Franke, Steven Stoll, Nicolas Westhoff, Julien Hansen, Steffen Bo Popp, Trevor James Wilhelms, Frank Dahl-Jensen, Dorthe |
spellingShingle |
Weikusat, Ilka Wallis, David Franke, Steven Stoll, Nicolas Westhoff, Julien Hansen, Steffen Bo Popp, Trevor James Wilhelms, Frank Dahl-Jensen, Dorthe Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) |
author_facet |
Weikusat, Ilka Wallis, David Franke, Steven Stoll, Nicolas Westhoff, Julien Hansen, Steffen Bo Popp, Trevor James Wilhelms, Frank Dahl-Jensen, Dorthe |
author_sort |
Weikusat, Ilka |
title |
Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) |
title_short |
Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) |
title_full |
Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) |
title_fullStr |
Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) |
title_full_unstemmed |
Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) |
title_sort |
issues with fracturing ice during an ice drilling project in greenland (eastgrip) |
publishDate |
2020 |
url |
https://epic.awi.de/id/eprint/52078/ https://epic.awi.de/id/eprint/52078/1/EGU2020-21768_presentation.pdf https://meetingorganizer.copernicus.org/EGU2020/EGU2020-21768.html https://hdl.handle.net/10013/epic.704fe3cc-c192-4696-90b3-dbfdeb2b5d47 https://hdl.handle.net/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
East Greenland Greenland ice core Ice Sheet |
genre_facet |
East Greenland Greenland ice core Ice Sheet |
op_source |
EPIC3EGU General Assembly 2020, 2020-05-04-2020-05-08 |
op_relation |
https://epic.awi.de/id/eprint/52078/1/EGU2020-21768_presentation.pdf https://hdl.handle.net/ Weikusat, I. orcid:0000-0002-3023-6036 , Wallis, D. , Franke, S. orcid:0000-0001-8462-4379 , Stoll, N. orcid:0000-0002-3219-8395 , Westhoff, J. , Hansen, S. B. , Popp, T. J. , Wilhelms, F. orcid:0000-0001-7688-3135 and Dahl-Jensen, D. (2020) Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) , EGU General Assembly 2020, 4 May 2020 - 8 May 2020 . doi:10.5194/egusphere-egu2020-21768 <https://doi.org/10.5194/egusphere-egu2020-21768> , hdl:10013/epic.704fe3cc-c192-4696-90b3-dbfdeb2b5d47 |
op_doi |
https://doi.org/10.5194/egusphere-egu2020-21768 |
_version_ |
1766399651473260544 |
spelling |
ftawi:oai:epic.awi.de:52078 2023-05-15T16:03:57+02:00 Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) Weikusat, Ilka Wallis, David Franke, Steven Stoll, Nicolas Westhoff, Julien Hansen, Steffen Bo Popp, Trevor James Wilhelms, Frank Dahl-Jensen, Dorthe 2020-05 application/pdf https://epic.awi.de/id/eprint/52078/ https://epic.awi.de/id/eprint/52078/1/EGU2020-21768_presentation.pdf https://meetingorganizer.copernicus.org/EGU2020/EGU2020-21768.html https://hdl.handle.net/10013/epic.704fe3cc-c192-4696-90b3-dbfdeb2b5d47 https://hdl.handle.net/ unknown https://epic.awi.de/id/eprint/52078/1/EGU2020-21768_presentation.pdf https://hdl.handle.net/ Weikusat, I. orcid:0000-0002-3023-6036 , Wallis, D. , Franke, S. orcid:0000-0001-8462-4379 , Stoll, N. orcid:0000-0002-3219-8395 , Westhoff, J. , Hansen, S. B. , Popp, T. J. , Wilhelms, F. orcid:0000-0001-7688-3135 and Dahl-Jensen, D. (2020) Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP) , EGU General Assembly 2020, 4 May 2020 - 8 May 2020 . doi:10.5194/egusphere-egu2020-21768 <https://doi.org/10.5194/egusphere-egu2020-21768> , hdl:10013/epic.704fe3cc-c192-4696-90b3-dbfdeb2b5d47 EPIC3EGU General Assembly 2020, 2020-05-04-2020-05-08 Conference notRev 2020 ftawi https://doi.org/10.5194/egusphere-egu2020-21768 2021-12-24T15:45:36Z Drilling an ice core through an ice sheet (typically 2000 to 3000 m thick) is a technical challenge that nonetheless generates valuable and unique information on palaeo-climate and ice dynamics. As technically the drilling cannot be done in one run, the core has to be fractured approximately every 3 m to retrieve core sections from the bore hole. This fracture process is initiated by breaking the core with core-catchers which also clamp the engaged core in the drill head while the whole drill is then pulled up with the winch motor. This standard procedure is known to become difficult and requires extremely high pulling forces (Wilhelms et al. 2007), in the very deep part of the drill procedure, close to the bedrock of the ice sheet, especially when the ice material becomes warm (approximately -2°C) due to the geothermal heat released from the bedrock. Recently, during the EastGRIP (East Greenland Ice coring Project) drilling we observed a similar issue with breaking off cored sections only with extremely high pulling forces, but started from approximately 1800 m of depth, where the temperature is still very cold (approximately -20°C). This has not been observed at other ice drilling sites. As dependencies of fracture behaviour on crystal orientation and grain size are known (Schulson & Duval 2009) for ice, we thus examined the microstructure in the ice samples close to and at the core breaks. First preliminary results suggest that these so far unexperienced difficulties are due to the profoundly different c-axes orientation distribution (CPO) in the EastGRIP ice core. In contrast to other deep ice cores which have been drilled on ice domes or ice divides, EastGRIP is located in an ice stream. This location means that the deformation geometry (kinematics) is completely different, resulting in a different CPO (girdle pattern instead of single maximum pattern). Evidence regarding additional grain-size dependence will hopefully help to refine the fracturing procedure, which is possible due to a rather strong grain size layering observed in natural ice formed by snow precipitation. --- Wilhelms, F.; Sheldon, S. G.; Hamann, I. & Kipfstuhl, S. Implications for and findings from deep ice core drillings - An example: The ultimate tensile strength of ice at high strain rates. Physics and Chemistry of Ice (The proceedings of the International Conference on the Physics and Chemistry of Ice held at Bremerhaven, Germany on 23-28 July 2006), 2007, 635-639 Schulson, E. M. & Duval, P. Creep and Fracture of Ice. Cambridge University Press, 2009, 401 Conference Object East Greenland Greenland ice core Ice Sheet Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Greenland |