ALBERT

Description: We report on the EPICA Dronning Maud Land (East Antarctica) deep drilling operation. Starting with the scientific questions that led to the outline of the EPICA project, we introduce the setting of sister drillings at NorthGRIP and EPICA Dome C within the European ice-coring community. The progress of the drilling operation is described within the context of three parallel, deep-drilling operations, the problems that occurred and the solutions we developed. Modified procedures are described, such as the monitoring of penetration rate via cable weight rather than motor torque, and modifications to the system (e.g. closing the openings at the lower end of the outer barrel to reduce the risk of immersing the drill in highly concentrated chip suspension). Parameters of the drilling (e.g. core-break force, cutter pitch, chips balance, liquid level, core production rate and piece number) are discussed. We also review the operational mode, particularly in the context of achieved core length and piece length, which have to be optimized for drilling efficiency and core quality respectively. We conclude with recommendations addressing the design of the chip-collection openings and strictly limiting the cable-load drop with respect to the load at the start of the run.

Description: ECM data of the DYE-3 cores obtained with the technique described by Hammer (1980). People involved in the measurements include Henrik B. Clausen, Dorthe Dahl-Jensen, Niels Gundestrup and Steffen B. Hansen, Jakob Schwander, and J.P. Steffensen. Data were originally recorded on paper in high resolution but was digitized by hand in 1 cm resolution by laboratory assistant Anita Boas. The data set includes data from the DYE-3 main core and from two shallow cores, known as 4B and 18C, drilled upstream of the main drilling site. Main core: Drilled to bedrock 1979-1981 during the GISP program. Position: 65.18N, 43.83W, 2480 m a.s.l.. Core 4B: Drilled to 174 m 8 km upstream from DYE-3. Exact position not available. Core 18C: Drilled to 110 m 36 km upstream from DYE-3. Position 65.03N 44.39W. The data are given as H^+ ion concentration versus depth (measured from the undisturbed surface at the year where drilling started), but the absolute calibration must be considered tentative. For more information on the measurements and calibration, see Hammer 1980. Please cite the Hammer (1980), Neftel et al. (1985), and Rasmussen et al. (2023) when using this data file.

Description: ECM data from the GRIP core obtained with the technique described by Hammer (1980). People involved in the measurements include Henrik B. Clausen, Dorthe Dahl-Jensen, Christine Hvidberg, Niels Gundestrup, Steffen B. Hansen, P. M. Kristinsdottir, Jakob Schwander, and J.P. Steffensen. Data were recorded in parallel on paper in high resolution and digitally in 1 cm resolution. The main core was drilled during the GRIP project in 1989-1992 at the Summit of the Greenland ice sheet. The length is 3025 m. Present-day accumulation 0.23 m ice/yr. Data from the top 101.3 m comes from the S3 shallow core, but the two data sets have been fully integrated on a common depth scale. The data are given as H+ ion concentration versus depth (measured from the undisturbed surface in 1989), but the absolute calibration (H+ = 0.045 I^1.73) must be considered tentative. For more information on the measurements and calibration, see Hammer 1980 and Clausen et al. (1995). Please cite the Hammer (1980), Clausen et al. (1995), and Rasmussen et al. (2023) when using this data file.

Description: ECM data of the DYE-3 cores obtained with the technique described by Hammer (1980). People involved in the measurements include Henrik B. Clausen, Dorthe Dahl-Jensen, Niels Gundestrup and Steffen B. Hansen, Jakob Schwander, and J.P. Steffensen. Data were originally recorded on paper in high resolution but was digitized by hand in 1 cm resolution by laboratory assistant Anita Boas. The data set includes data from the DYE-3 main core and from two shallow cores, known as 4B and 18C, drilled upstream of the main drilling site. Main core: Drilled to bedrock 1979-1981 during the GISP program. Position: 65.18N, 43.83W, 2480 m a.s.l.. Core 4B: Drilled to 174 m 8 km upstream from DYE-3. Exact position not available. Core 18C: Drilled to 110 m 36 km upstream from DYE-3. Position 65.03N 44.39W. The data are given as H^+ ion concentration versus depth (measured from the undisturbed surface at the year where drilling started), but the absolute calibration must be considered tentative. For more information on the measurements and calibration, see Hammer 1980. Please cite the Hammer (1980), Neftel et al. (1985), and Rasmussen et al. (2023) when using this data file.

Description: ECM data of the DYE-3 cores obtained with the technique described by Hammer (1980). People involved in the measurements include Henrik B. Clausen, Dorthe Dahl-Jensen, Niels Gundestrup and Steffen B. Hansen, Jakob Schwander, and J.P. Steffensen. Data were originally recorded on paper in high resolution but was digitized by hand in 1 cm resolution by laboratory assistant Anita Boas. Main core: Drilled to bedrock 1979-1981 during the GISP program. Position: 65.18N, 43.83W, 2480 m a.s.l.. Core 4B: Drilled to 174 m 8 km upstream from DYE-3. Exact position not available. Core 18C: Drilled to 110 m 36 km upstream from DYE-3. Position 65.03N 44.39W. The data are given as H^+ ion concentration versus depth (measured from the undisturbed surface at the year where drilling started), but the absolute calibration must be considered tentative. For more information on the measurements and calibration, see Hammer 1980. Please cite the Hammer (1980), Neftel et al. (1985), and Rasmussen et al. (2023) when using this data file.

Description: ECM data of the DYE-3 cores obtained with the technique described by Hammer (1980). People involved in the measurements include Henrik B. Clausen, Dorthe Dahl-Jensen, Niels Gundestrup and Steffen B. Hansen, Jakob Schwander, and J.P. Steffensen. Data were originally recorded on paper in high resolution but was digitized by hand in 1 cm resolution by laboratory assistant Anita Boas. The data set includes data from the DYE-3 main core and from two shallow cores, known as 4B and 18C, drilled upstream of the main drilling site. Main core: Drilled to bedrock 1979-1981 during the GISP program. Position: 65.18N, 43.83W, 2480 m a.s.l.. Core 4B: Drilled to 174 m 8 km upstream from DYE-3. Exact position not available. Core 18C: Drilled to 110 m 36 km upstream from DYE-3. Position 65.03N 44.39W. The data are given as H^+ ion concentration versus depth (measured from the undisturbed surface at the year where drilling started), but the absolute calibration must be considered tentative. For more information on the measurements and calibration, see Hammer 1980. Please cite the Hammer (1980), Neftel et al. (1985), and Rasmussen et al. (2023) when using this data file.

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

Description: We report on the EPICA Dronning Maud Land (East Antarctica) deep drilling operation. Starting with the scientific questions that led to the outline of the EPICA project, we introduce the setting of sister drillings at NorthGRIP and EPICA Dome C within the European ice-coring community. The progress of the drilling operation is described within the context of three parallel, deep-drilling operations, the problems that occurred and the solutions we developed. Modified procedures are described, such as the monitoring of penetration rate via cable weight rather than motor torque, and modifications to the system (e.g. closing the openings at the lower end of the outer barrel to reduce the risk of immersing the drill in highly concentrated chip suspension). Parameters of the drilling (e.g. corebreak force, cutter pitch, chips balance, liquid level, core production rate and piece number) are discussed. We also review the operational mode, particularly in the context of achieved core length and piece length, which have to be optimized for drilling efficiency and core quality respectively. We conclude with recommendations addressing the design of the chip-collection openings and strictly limiting the cable-load drop with respect to the load at the start of the run.