TITLE: Distributed temperature sensing data from a borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland, in July 2019 ASSOCIATED PUBLICATION: Thermodynamics of a fast-moving Greenlandic outlet glacier revealed by fiber-optic distributed temperature sensing ASSOCIATED PUBLICATION TEASER: Highly resolved observations from a 1,043 m deep borehole show highly variable ice properties and heterogeneous deformation. ABSTRACT: This is distributed temperature sensing (DTS) data from a 1,043 m borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland, 28 km inland from the glacier terminus. The DTS system was installed on 5 July 2019, with recordings continuing until cable failure on 13 August 2019. The record resolution is ~0.65 m. KEYWORDS: Greenland, distributed temperature sensing (DTS), ice boreholes, Store Glacier, marine-terminating glacier, ice temperature PERSONNEL: NAME: Robert Law ROLE: ContactPerson, DataCollector, DataCurator, ProjectMember ORGANISATION: Scott Polar Research Institute, University of Cambridge ORCID: orcid.org/0000-0003-0067-5537 NAME: Poul Christoffersen ROLE: ProjectLeader, ProjectManager ORGANISATION: Scott Polar Research Institute, University of Cambridge ORCID: orcid.org/0000-0003-2643-8724 NAME: Bryn Hubbard ROLE: ProjectManager ORGANISATION: Centre for Glaciology, Aberystwyth University ORCID: orcid.org/0000-0002-3565-3875 NAME: Samuel Doyle ROLE: DataCollector, ProjectMember ORGANISATION: Centre for Glaciology, Aberystwyth University ORCID: orcid.org/0000-0002-0853-431X LINEAGE/METHODOLOGY: The data was gathered from Store Glacier, Greenland, in 2019 using a borehole drilling system as described in Doyle et al. (2018) with an additional heater unit. Drilling occured from 4-5 July 2019. The vertical spatial resolution is ~0.65 m, with a sampling resolution of 0.25 m. The measurement averaging time was originally set at 2 minutes with near continuous operation from 5 July to 21 July whereupon it was set to 10 minutes with a rest time of 40 minutes, with the rest time increased to 4 hours on 23rd July to reduce power consumption for unattended operation. This raw instrument-produced data was then processed using the DTS processing package 'dtsalibration' written in Python (des Tombe et al., 2020) with the sampling time increased dependent on usage/figure output (8 hours for image plot of entire record, 96 hours for final plot before failure). INSTRUMENTATION: The data was collected with a Silixa XT-DTS. The cable was a BRUsens DTS steel-armored cable with 2 single-mode (OS2) fibres and 4 multi-mode (OM3) fibres in a dublex arrangement using a basal turnaround assemblage. The single-mode fibres were used in a seperate distributed acoustic sensing study (Booth et al., 2020). The dtscalibration Python package (v0.9.2) was used to process the data (https://python-dts-calibration.readthedocs.io/ https://pypi.org/project/dtscalibration/ https://github.com/dtscalibration/python-dts-calibration). Data sheets are provided where possible in the data_sheets directory. QUALITY: The data was calibrated using thermistor data and temperate ice at the phase-transition temperature. 95% confidence intervals are reported in Law et al. (2021) and are provided in this data set, derived from a Monte Carlo simulation. The data was fitted to thermistors, subjectivity in this fitting, and thermistor uncertainty from factors such as ice-bath calibration may further increase unertainty - see Law et al. (2021) for a full discussion. RELATED URLS: https://www.spri.cam.ac.uk/people/law/ https://www.spri.cam.ac.uk/people/christoffersen/ https://www.erc-responder.eu/ TEMPORAL COVERAGE: 07:45 5 July 2019 - 21:30 13 August 2019. SPATIAL COVERAGE: 70.57 N, 50.09 W RESOLUTION: ~0.65 m spatial resolution. LOCATION: Sermeq Kujalleq (Store Glacier), Uummannaq Fjord, Greenland. Drill site at 70.57 N, 50.09 W. REFERENCES: Booth, A. D., Christoffersen, P., Schoonman, C., Clarke, A., Hubbard, B., Law, R., Doyle, S. H., Chudley, T. R., & Chalari, A. (2020). Distributed Acoustic Sensing of Seismic Properties in a Borehole Drilled on a Fast‐Flowing Greenlandic Outlet Glacier. Geophysical Research Letters, 47(13), e2020GL088148. https://doi.org/10.1029/2020GL088148 des Tombe, B., Schilperoort, B., Perkó, Z., Bakker, M., Van De Giesen, N., & Selker, J. (2019). Distributed Temperature Sensing (DTS) calibration with confidence intervals. European Geophysical Union, Geophysical Research Abstracts, 21, 2019–16681. https://doi.org/10.3390/s20082235 Doyle, S. H., Hubbard, B., Christoffersen, P., Young, T. J., Hofstede, C., Bougamont, M., Box, J. E., & Hubbard, A. (2018). Physical Conditions of Fast Glacier Flow: 1. Measurements From Boreholes Drilled to the Bed of Store Glacier, West Greenland. Journal of Geophysical Research: Earth Surface, 123(2), 324–348. https://doi.org/10.1002/2017JF004529 Law, R., Christoffersen, P., Hubbard, B., Doyle, S. H., Chudley, T. R., Schoonman, C., Bougamont, M., des Tombe, B., Schilperoort, B., Kechavarzi, C., Booth, A., & Young, T. J. (2021). Thermodynamics of a fast-moving Greenlandic outlet glacier revealed by fiber-optic distributed temperature sensing. Minor revisions in Science Advances.
DATA STRUCTURE AND DATA FORMAT: The data is stored in a few different ways: raw data is provided as (DTS) machine outputted .xmls found in the directories: /channel_1 (5.4 GB) raw data spanning the entire measurement period from channel one of the DTS machine, subdivided into .xmls with equal number of samples* and averaging period. /channel_3 (4.6 GB) raw data spanning the entire measurement period from channel one of the DTS machine, subdivided into .xmls with equal number of samples* and averaging period. /channel_1_civil_eng (43 MB) raw data from experiments at Cambridge Univeristy Civil Engineering Building to determine integrated differential attenuation-strain relationship. /channel_1_SPRI_basement (944 KB) measurements used in laboratory calibration of the cable zeta parameter. /processed_data (4.7 GB) the processed raw data for figure plotting with Python consisting of: DataSet_ST_data_ch1.nc (2.5 GB) and DataSet_ST_data_ch3.nc (2.4 GB)(NetCDF) uncalibrated (anti-)Stokes data from the DTS used in calculating integrated differential attenuation for DTS channels 1 and 3 respectively. ch1_full_processed.nc (42 MB)(NetCDF) fully processed temperature data for full measurement period for channel 1 for figure plotting use. ch1_end_processed.nc (0.3 MB) (NetCDF) fully processed temperature data for final 96 hours of measurement period for channel 1. /Doyle_data/analog_blue.csv (csv) csv data for thermistors from Samuel Doyle. The processed data can be viewed using the Python files in the root directory. The packages used in the creation of these scripts are found within Python_env_packages.txt . dtscalibration is dependent on specific versions of some packages, so if you are having trouble getting things going I recommend checking your package versions. If you are just wish to visualise the data, then use 3_plotting.py which will produce the figures used in the publication unless ch1_full_processed.nc or ch1_end_processed.nc have been overwritten. If you're doing this there is no need to download the raw DTS data contained in /channel_1 and /channel_3 Running 1_full_process.py and 2_end_profile will overwrite ch1_full_processed.nc and ch1_end_processed.nc respectively. As supplied, if you do generate new files they should be identical to the ones already present. These files are probably most helpful if you wanted to process a new DTS dataset and needed an example, though better guidance on the dtscalibration package is avaiable at: https://github.com/dtscalibration/python-dts-calibration/tree/master/examples . A full processing run through takes about 30 mins on a 2018 i7 processor. *sample number varies from 11078 to 11079, probably a result of a minor change in fibre refractive index with temperature. The dtscalibration package is not yet adapted to account for these variations automatically.
Greenland, Distributed temperature sensing, DTS, Store Glacier, Glacier borehole, Ice temperature, Marine-terminating glacier