Design, construction and laboratory testing (prior to testing in Madison) of a melt
probe with cabling to enable deployment of Raman DTS, as well as injection of ethanol
at 0 C above the descending probe, in collaboration with Collaborative Research
partners at the University of Nevada - Reno (Scott Tyler, PI) and Oregon State
University (J. Selker, PI). The University of Nevada/OSU focus is on the integration of
the DTS system into the melt probe design to provide both real time feedback on the
thermal condition of the probe, and most importantly, the entire borehole from the ice
surface to the probe. This aspect is critical as the system design relies upon a small
diameter unfroze portion of the borehole to remain open throughout the descent
phase.

Deployment in February 2019 to Madison, WI Ice Drilling Program testing facility,
equipment testing, and return to Seattle (see Supporting Files 1 and 2 for
photographs). The new trials tested our approaches to melt-hole control and probe
recovery in the taller column, as well as cable and cable-tension-management methods
more nearly approximating those needed to work on ice sheets. Following the Madison
field trial, we conducted extensive discussion and review of data and lessons
learned. Post audit analysis of the test indicated weaknesses in the heater designs as
well as the cable feed system, weaknesses that the testing was designed to probe. We
then carried out modifications to the melt probe, changing the heater mountings and
control system and redesigning the DTS fiber termination system to allow for a more
seamless integration of other telemetry and ethanol.

Numerical modeling of melt-hole refreezing with and without injection of anti-freeze,
to understand quantitatively conditions where slush formation in a melt-hole filled with
ethanol/water solution and thus to guide equipment design and experimental
procedures (see Supporting Files 3 and 4 for explanatory figures). This work resulted in
a publication currently under review for a special issue of the Annals of Glaciology.

RAW DTS data can be found here: https://nevada.app.box.com/folder/118092693469