Thickness gauges and ablation stakes

Instrument: Ablation stake, thickness gauge
Uncertainty: Variable from stake to stake. Typically +/- 1-2 cm.
File format: Files are in a directory GAUGES. Each stake has its own 
file with a filename of the form GXXXYYY, where XXX is the gauge number 
and YYY is the site code. The data in the file are date, snow depth, ice 
surface position, ice bottom position, and pond depth


Measuring ice growth and decay was decidedly a low-tech operation. We used 
a combination of an ablation stake and a hot-wire thickness gauge. The 
ablation stake was a 3 m long wooden stake painted white with metric tape. 
The stakes were typically installed with 1.5 m frozen in the ice and the other 
1.5 m in the air. Adjacent to the ablation stake was a hot-wire thickness gauge. 
This gauge consisted of stainless steel wire with a steel rod attached on one 
end for ballast and a wooden handle on the other. The stainless steel wire was 
hooked to a generator that was also connected to a copper wire grounded in the 
ocean. The current would melt the wire free and the handle was pulled upward 
until the steel rod hit the bottom of the ice. The handle position was read off 
the ablation stake giving the position of the ice bottom. Accuracies of stake and 
gauge readings were typically 1 cm. In some cases gauges gave erratic reading, 
due to ice blocks on the ice bottom. A few gauges were crushed in pressure ridges 
and in some cases the rod was frozen into the ice. During summer several of the 
ablation stakes in ponds melted through the ice. The thickness gauge results 
are beta data - refinement is underway.

We installed 135 thickness gauge/ ablation stake combinations. They were 
clustered at 10 sites:

Pittsburgh - SHEBA column site, undeformed multiyear
The Ridge - thick second year ridge
Quebec 1 - thinner, multiyear
Quebec 2 - thick multiyear
Seattle - ponded area, hummocks nearby
Tuk - mature multiyear ridge, thermistors
Baltimore - first-year ice, thermistors
Mainline - multiyear ice adjacent to snow Mainline
Atlanta - multiyear ice
Doghouse - thick multiyear ice
Sarah's Lake - first year ice near a lead