Lt. Cmdr. Rob Tucker, expedition team leader for the U.S. Coast Guard, attaches shoe chains over the soles of his boots for better traction while trekking on the glacier's icy surface near Koge Bay, Greenland, Aug. 9, 2013. The fast-melting snow covering the ice made the surface difficult to walk on while working at the dig site. (U.S. Coast Guard photo by Petty Officer 2nd Class Jetta H. Disco)