<jats:p>Abstract. A fibre-optic DTS (distributed temperature sensing) system
using Raman-scattering optical time domain reflectometry was deployed to
monitor a boreal forest research site in the interior of Alaska. Surface
temperatures range between −40 ∘C in winter and 30 ∘C in
summer at this site. In parallel experiments, a fibre-optic cable sensor
system (multi-mode, GI50/125, dual core; 3.4 mm), monitored at
high resolution, (0.5 m intervals at every 30 min) ground surface
temperatures across the landscape. In addition, a high-resolution vertical
profile was acquired at one-metre height above the upper subsurface. The total
cable ran 2.7 km with about 2.0 km monitoring a horizontal surface path.
Sections of the cable sensor were deployed in vertical coil configurations
(1.2 m high) to measure temperature profiles from the ground up at 5 mm
intervals. Measurements were made continuously over a 2-year interval from
October 2012 to October 2014. Vegetation at the site (Poker Flat Research
Range) consists primarily of black spruce underlain by permafrost. Land cover
types within the study area were classified into six descriptive categories:
relict thermokarst lake, open moss, shrub, deciduous forest, sparse conifer
forest, and dense conifer forest. The horizontal temperature data exhibited
spatial and temporal changes within the observed diurnal and seasonal
variations. Differences in snow pack evolution and insulation effects
co-varied with the land cover types. The apparatus used to monitor vertical
temperature profiles generated high-resolution (ca. 5 mm) data for air
column, snow cover, and ground surface. This research also identified several
technical challenges in deploying and maintaining a DTS system under
subarctic environments.
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