Spatiotemporally continuous temperature monitoring using optical fibers (Loop1) in the internal forest areas in Alaska for the period from 2017 to 2019

A fiber-optic DTS (distributed temperature sensing) system using Raman-scattering optical time domain reflectometry was implemented at a research site in the interior of Alaska (Poker Flat Research Range) to delineate the spatiotemporal characteristics of the variations in air, surface, and ground temperatures associated with the boreal forest heterogeneity in terms of surface and canopy conditions. This is the last portion of the Loop1 measurements, which started in 2012, continued with occasional partial and total interruptions due to several factors, and terminated because of the malfunction of the DTS equipment. In the Loop1 measurement, a fiber-optic cable sensor (multi-mode, GI50/125, dual-core; 3.4 mm) was deployed across the landscape to measure temperatures at high spatiotemporal resolution (0.5 m intervals, every 30 minutes) horizontally across the different land surface cover types (i.e., relict thermokarst lake, open moss, shrub, deciduous forest, sparse spruce, and dense spruce). It also had four sub-sections where the cable sensor was set in coil configurations (1.2 m high), installed vertically half below and half above the ground to capture high-resolution vertical temperature profiles from the subsurface up to snowpack height at approximately 5 mm intervals. The total cable ran 1.9 km, within which about a 1.4 km section covered horizontal surface paths. Measurements were made from September 23, 2017, to September 6, 2019 (372 observation days).