The datasets are basal probe sensor time series measuring suspended sediment concentration, water pressure, electrical conductivity and temperature. Each sensor was located at a discrete depth within one of six boreholes into Khumbu Glacier, Nepal. Boreholes were drilled in May 2017 and 2018 to investigate the internal properties of Khumbu Glacier, specifically ice thickness, temperature, deformation and structure, as part of the NERC-funded 'EverDrill' research project. Supporting borehole information is provided as a related dataset.
Funding was provided by the NERC grant NE/P00265X/1 and NE/P002021/1.
***** PLEASE BE ADVISED TO USE VERSION 2.0 DATA *****
The VERSION 2.0 data set (see 'Related Data Set Metadata' link below) which contains an additional 10 months of measurements.
Ice boreholes, Ice temperature, Khumbu Glacier, Nepal, Water pressure
|ISO Topic Categories:||
|Role(s)||Investigator, Technical Contact|
|Organisation||University of Leeds|
|Organisation||University of Leeds|
|Reference:||Orwin, J.F. & Smart, C.C. (2005), An inexpensive turbidimeter for monitoring suspended sediment, Geomorphology, 68, pp. 3-15
Miles, K.E., Hubbard, B., Quincey, D.J., Miles, E.S., Sherpa, T.C., Rowan, A.V. and Doyle, S.H. (2018), Polythermal structure of a Himalayan debris-covered glacier revealed by borehole thermometry, Scientific Reports, 8, 16825, doi.org/10.1038/s41598-018-34327-5
Doyle, S.H., Hubbard, B., Christoffersen, P., Young, T.J., Hofsteded, C., Bougamont, M., Box, J.E., and 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, doi.org/10.1002/2017JF004529
|Quality:||Detailed methodology of suspended sediment concentration, water pressure and electrical conductivity measurements is given in Doyle et al. (2018). Detailed methodology of thermistor measurements, including accuracy estimation, is presented by Miles et al. (2018).|
|Lineage:||The datasets are time series of various sensors (suspended sediment content, water pressure, electrical conductivity and temperature) mounted onto a basal probe string, installed in three boreholes drilled into Khumbu Glacier, Nepal. The data are presented in whole or in part in Miles et al. (2018). For borehole information, see Instrumented Borehole Info.|
|Data Set Creator||Hubbard, Bryn; Miles, Katie; Doyle, Samuel; Quincey, Duncan; Miles, Evan|
|Data Set Title||Data time-series from sensors installed at the base of boreholes drilled into Khumbu Glacier, Nepal, in 2017 and 2018 as part of EverDrill research project|
|Data Set Release Date||2019|
|Data Set Publisher||Polar Data Centre,Natural Environment Research Council,UK Research & Innovation|
|Other Citation Details||shortdoi:10/c4bc|
|Detailed Location||Khumbu Glacier, Himalaya|
|Data Collection:||Suspended sediment concentration was measured using turbidity sensors based on Orwin & Smart (2004). They use a photo diode to measure the backscatter of infrared light emitted by an infrared light-emitting diode.
Water pressure was measured using Omega pressure transducers (model PX209-300GI). They are 4-20 mA current loop transducers that were measured using a 100 Ohm shunt resistor.
Electrical conductivity was determined by inverting the resistance measured across two brass-rod electrodes (5 mm diameter, ~11 mm long, 11 mm separation). To cancel polarisation effects, the polarity of the excitation voltage was reversed.
Temperatures were acquired by using Honeywell UNI-curve 192-502-LET-AOI negative temperature coefficient thermistors.
All sensors were controlled by Campbell Scientific CR1000 data loggers from the glacier surface. Further details are provided in Miles et al. (2018) and Doyle et al. (2018).
The turbidity (suspended sediment concentration) sensors were calibrated in the laboratory using non-local, fine (grain size < 63 um) glacial sediment, using SSCs ranging from 0 (distilled water) to 6 g l-1. Calibration limitations are detailed in Doyle et al. (2018), but regardless, we expect SSCs between 3 - 20 g l-1 to fall within the full scale range of the sensors.
The water pressure transducers are calibrated by the manufacturer, who report the sensors to be accurate to +/- 0.75 psi (+/- 0.53 m head) between 0 - 300 psi.
The electrical conductivity sensors were calibrated in sodium chloride solutions against a laboratory EC probe between 0 - 200 uS cm-1. More details are given in Doyle et al. (2018).
The thermistors have an interchangeability of 0.4 degrees Celsius. After an ice bath calibration, previous studies have suggested that an accuracy of +/- 0.05 degrees can be achieved around 0 degrees. This is therefore the expected accuracy at 0 degrees, but represents an indication of uncertainty rather than a maximum limit (particularly as temperatures diverge away from 0 degrees). See Doyle et al. (2018) and Miles et al. (2018) for more information.
|Data Storage:||The data are structured in three comma-separated ASCII files (*.csv format), one for each borehole basal probe. Each file is ~2 MB in size. Each file holds the data for a single borehole, with each column presenting a different sensor of the basal probe: 'SSC' refers to suspended sediment content (grams per litre); ''Pw_m' to the water pressure head (in metres); 'EC' to the electrical conductivity (μS per cm); and 'T_m' the temperature (degrees Celsius). For borehole information, see Instrumented Borehole Info under related datasets.|
|Access Constraints:||No restrictions apply.|
|Use Constraints:||This data is governed by the NERC data policy http://www.nerc.ac.uk/research/sites/data/policy/ and supplied under Open Government Licence v3.0 http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/.|