The temporal evolution of the mass balance was monitored at five sites. The instrumentation at these sites typically consisted of a Campbell scientific datalogger, thermistor string, snow stakes, thickness gauges, an air temperature sensor, and an above-ice acoustic sounder measuring the position of the surface every hour to within 5 mm. The thickness gauges consisted of an ablation stake measuring mass loss at the surface and a hot-wire gauge measuring bottom accretion or ablation. Data was manually collected every 1-2 weeks during winter and every 2-4 days during the melt season.

Thermistor strings were PVC rod with YSI thermistors spaced every 10 cm. These rods could easily be connected to assemble strings that extended from the air through the snow and ice into the upper ocean. The thermistor accuracy was better than 0.1 C. The default spacing was 10 cm, though occassionally strings were overlapped to provide 5 cm spacing. Temperatures were automatically logged every hour. 

We used a combination of ablation stakes and hot-wire thickness gauges to measure ice growth and decay at the Elson Lagoon, Chukchi Sea, Beaufort Sea, and Imikpuk Lake sites. Four stake and gauge combinations were installed at each site. The ablation stakes were a 2.4-m-long wooden stake, painted white with metric tape. The stakes were typically installed with 1.2 m frozen in the ice and the other 1.2 m in the air. A hot-wire thickness gauge was installed adjacent to the ablation stake. This gauge consisted of stainless steel wire with a steel rod attached on the bottom end for ballast and a wooden handle on the top end. 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 about 0.5 cm. Since Imikpuk Lake is fresh water the gauges only worked in the summer after the stainless steel wire melted free. An upward-looking acoustic sensor was placed under the ice at the Beaufort Sea site. This sensor automatically measured the position of the ice bottom hourly. At the Tundra site there was a thermistor string measuring air, snow, and tundra temperatures, as well as a downward looking acoustic sensor measuring snow depth. Hobo temperature sensors were installed at many of the thickness gauges.

Ablation stake / thickness gauge combination.