Figure 4 from  Geophysical Investigations conducted by the U. S. Geological Survey on Fletcher's Ice Island (T-3) during the International Geophysical Year.

From Page 11: "Drilling a hole through sea ice. Most of the work involved in setting up the geophysical program consisted of drilling holes through sea ice. The hole being dug in this photograph was intended as a seismic shot hole. A pilot hole was drilled a short distance into the ice, a small charge detonated and the rubble removed. This process was repeated until sea water was reached. About three dozen holes were drilled or shot through the sea ice around Fletcher's Ice Island. Ice thickness ranged from 12 to 20 feet, considerably thicker than normal sea ice."