The temporal evolution of the mass balance of different ice categories was 
monitored at 10 sites that were carefully selected to represent the widest 
possible range of ice types and conditions.  These sites typically consisted 
of a thermistor string and several thickness gauges. At two sites 
(Quebec 2, Seattle) there was an above ice acoustic sounder that every 
hour measured surface position to within 5 mm. A water level recorder was 
used at Quebec 2  and the Doghouse to measure the hydrostatic equilibrium 
of the floe during the melt season. These readings are valuable since changes 
in hydrostatic equilibrium represent integrated changes in the mass of the entire 
floe. To reduce error, the water level reading can be adjusted for changes in the 
density of the underlying water.We also made measurements of individual melt ponds 
and pressure ridges. 

There were over 120 mass balance points where an ablation stake measured mass loss 
at the surface and a hot-wire thickness gauge measured bottom accretion or ablation. 
Data was manually collected every 1-2 weeks during winter and every other day during 
the summer melt season. Thickness gauge results showed a general decrease in ice 
thickness during the SHEBA year.  

Mass balance sites:
Pittsburgh - SHEBA column site, undeformed multiyear, thermistors, gauges
The Ridge - thick second year ridge, gauges, thermistors
Quebec 1 - thinner, multiyear, gauges, thermistors
Quebec 2 - thick multiyear, gauges, thermistors, water level recorder, acoustic
Seattle - ponded area, hummocks nearby, thermistors, gauges, acoustic sensor
Tuk - mature multiyear ridge, thermistors, gauges
Baltimore - first-year ice, thermistors, gauges
Mainline - multiyear ice adjacent to snow Mainline, gauges only
Atlanta - multiyear ice, gauges only
Doghouse - thick multiyear ice, gauges, water level recorder
Sarah's Lake - first year ice near a lead, thickness gauges.