Snow Pit Mass Balance Protocols
(Adapted from the International Trans-Antarctic Scientific Expedition protocols, which can be
found at http://www2.umaine.edu/itase/content/Science/appb.html.)
Site Selection
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at least several km from exposed mountains, scientific stations and transportation
corridors in order to minimize inputs of locally derived crustal debris or anthropogenic
emissions;
at least 400-500 m upwind from local camp; and
local snow surface should be relatively flat and have minimal sastrugi with a nonrecently eroded surface.
Sampling Equipment
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Plastic (Poly) or Metal Shovel
Snow Saw
Tape Measure (folding 2-m is best)
Snow Density Kit
Notebook
Snow Pit Sampling
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Snow pit Excavation
After selecting the site for a snow pit, determine the direction of the wind and using a shovel
define an edge perpendicular to the wind direction about 1.5-2 meters long. This will be the
sampling wall. Nothing should be placed on the upwind part of this line (see below for
exception, building wind block) at any time. Also it is imperative that while digging nothing
touches the sampling wall except the shovel or saw (hands, body, etc.). The upper 10-50 cm will
probably be most easily removed using the shovel. Once the loose snow is removed from the
upper 10-50 cm the snow saw can be usually be used to cut blocks and using the shovel break
the blocks free. All excavated snow from the pit should be thrown downwind, away from the
sampling wall. If there is blowing snow a snow wall may be built on the upwind side of the pit.
This should be done using the blocks cut out of the pit. The wall should be at least 1 meter from
the sampling wall and the person building the wall must not step between the snow wall and
sampling wall. Once the wall is built no one should be upwind of the pit.
Ideally the sampling wall of the snow pit will not be in direct sunlight. It may be necessary to
plan the snow pit excavation and sampling according to wind and sun direction. It is possible to
shift the sampling wall angle to the wind up to 45 degrees to keep the direct sun off the
sampling wall. Obviously this planning must be done before excavation is started. Final depth of
the snow pit should be ~ 2 meters. To help facilitate the sampling of the pit, a large firn block
can be left in the bottom of the pit to stand on while sampling the top of the pit.
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Snowpit Sampling
Upon completion of the excavation of the snow pit, a measuring tape can be hung down the
wall to allow for good sample depth registration. The ideal sample interval is 8-10
samples/year. Record notes about the snow pit which include description of snow, general
weather and sampling conditions and miscellaneous notes related to sampling (eg. stratigraphy,
grain size, etc.). Parameters such as layer thickness, hardness, colour, crystal size and shape,
location and thickness of ice or debris bands should be recorded. Photographs of the pit wall
should be taken to record the visible structure and layering, if possible. Using the Snow Density
Kit tools, sample the wall for snow densities and record the density scoop used and the weight
measured on the balance (so densities can be later calculated).