Measuring Snow Cover Thickness by Miniature Data Loggers

Ole Humlum, The University Courses on Svalbard (UNIS), Norway.

General

The thickness of the winter snow cover represents an important control on ground surface temperatures (see diagram below), and by this on ground temperatures below. In the late winter picture above, the ground below the scooter is covered by 5-10 cm snow only, while about 180 cm snow covers the ground below the person to the left. For this reason, the average winter ground surface temperature is 6-7 ^oC lower at the scooter than at the person. 

One way of monitoring the snow cover thickness is by manual measurements throughout the winter; another is by means of automated digital photography. The first method requires manpower at hand at the study site throughout the winter, and the second method does not work satisfactory during periods of complete winter darkness. To circumvent this difficulty, a simple setup with miniature data loggers may be applied as described below.

Ground surface temperature at monitoring site in Adventdalen, Svalbard, showing the isolating effect of snow. The dampening effect is significant for even a shallow snow cover (3-5 cm).

Installation of Temperature Loggers

A number of temperature data loggers with external thermistor are mounted at intervals on a vertical structure, as shown in the photo below. Depending upon the vertical distance between individual thermistors, the temperature recordings will enable an estimate of the position of the snow cover surface, and from this, the snow cover thickness. In addition, information on the internal temperature in the snow pack is obtained by this setup. 

The vertical structure should be able to withstand high winds during the winter, before burial by snow. The data loggers and thermistors should be mounted securely, in order no to be displaced during compaction and metamorphosis of the snow pack. During spring, considerable internal water pressure may be build up in the snow pack near the ground surface or above internal horizons with reduced permeability. For this reason data loggers and thermistors should preferentially be of watertight type. 

In areas of complete winter darkness, the setup should be equipped with reflecting material (see photo below), in order to warn scooters and skiers. If possible, supporting wires should be avoided, in order not to represent a danger for animals, such as, e.g., reindeers. Stability without support wires may be obtained by burial of the lower part of the structure, if unconsolidated sediments are at hand. Later freezing will then provide the stability required. For this reason, the optimal time for installation is late autumn.

Setup for registering thickness and vertical temperature profile in snow pack, Adventdalen, Svalbard.

Latest update: 11. November 2002.