DOI: 10.5281/zenodo.4068349
title: SnowMicroPen Measurements on Sea Ice 2016-2017

description: Local-scale variations in snow density and layering on Arctic sea ice were characterized using a combination of traditional snow pit and SnowMicroPen (SMP) penetrometer measurements. The SMP profiles provide detailed information about the snow microstructure and stratigraphy and were collected to evaluate coincident airborne and satellite measurements aimed at improving the understanding of inter-annual variability of Arctic snow and sea ice properties. The measurements were acquired during two April field campaigns conducted near the time of maximum snow thickness, coinciding with NASA Operation IceBridge (17 April 2016) and ESA CryoVEx (26 April 2017). In total, 8 survey sites were evaluated within the Canadian Arctic Archipelago near Eureka (80.0°N 85.9°W) and 6 survey sites on the Arctic Ocean (spanning 83.4°N and 86.3°N), on both first (FYI) and multi-year (MYI) sea ice. The SMP measurements were recorded using a SnowMicroPen® 4 penetrometer.
description: In total 613 SMP profiles were recorded on Arctic sea ice. Coincident SMP profiles were made at 26 snow pit locations (20 near Eureka between April 8th-17th 2016, and 6 on the Arctic Ocean between April 11th-13th 2017), to evaluate derived estimates of snow density. Maintaining a horizontal separation of 10 cm, profiles were located behind the snow pit wall in proximity to the manual density cutter measurements. In addition to collecting SMP profiles at snow pit locations to derive density estimates, SMP transect were established to characterize spatial variability in snow microstructure. For Eureka, multi-scale sampling was applied where unidirectional sets of 10 profiles were separated at distances of 0.1, 1, and 10m, in sequence. Where time permitted, additional profiles were completed with 1 m spacing adjacent to the primary transect. An average of 69 SMP profiles were collected per survey site near Eureka (total n=550). It was not possible to execute an identical sampling strategy for the Arctic Ocean sites due to time constraints. Instead, a single set of 10 profiles were spaced 1 m apart, parallel to the snow pit wall. An average of 11 profiles were made per site for the Arctic Ocean campaign (total n=63). The location of each SMP profile was recorded with the onboard GPS (±5 m accuracy). Further details on the SMP sampling and data processing methods can be found in King et al., (2020). The SMP acquires high vertical resolution (~250 measurements per mm) profiles of the force measured in Newtons (N), required to drive a motorized probe into the snow at a constant measurement speed of 20 mm/s. Typical force measurements range from 0.01 N for soft snow up to 40 N for very hard snow, to a maximum depth of 1.2 m. SMP Instrument details are provided in Schneebeli and Johnson (1998), Johnson and Schneebeli (1999), and Proksch et al. (2015). From these force measurements, snow microstructure parameters such as density, layering and snow grain type, and snow grain specific surface area (SSA) can be derived, but only the raw force profiles are provided in this data set. Users will need to apply algorithms for identifying the air/snow and snow/ground interfaces, vertically smoothing the raw data, and converting the force measurements to snow microstructure parameters (see https://github.com/kingjml/SMP-Sea-Ice). Errors and Limitations In very limited cases, negative force measurements were obtained for a small proportion of measurements within a profile. Other potential sources of uncertainty include the probe not entering the snowpack orthogonally to the surface (due to imprecise placement of the instrument base) and shifting of the probe during measurement due to snowpack settling. REFERENCES: Johnson, J.B., Schneebeli, M. 1999. Characterizing the microstructural and micromechanical properties of snow. Cold Regions Science and Technology 30(1-3), 91-100. King, J., Howell, S., Brady, M., Toose, P., Derksen, C., Haas, C., and Beckers, J.: Local-scale variability of snow density on Arctic sea ice, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-305, in review, 2020. Proksch, M., Löwe, H. and Schneebeli, M.: Density, specific surface area, and correlation length of snow measured by high‐ resolution penetrometry, J Geophys Res-Earth, 120, 346-362, doi:10.1002/2014JF003266, 2015. Schneebeli, M., and J. Johnson, J.: A constant-speed penetrometer for high-resolution snow stratigraphy, Ann. Glaciol., 26, 107–111, doi: 10.3189/1998AoG26-1-107-111, 1998.