MARQUETTE, Mich. (AP) Lake Superior changes mystify scientists - Deep enough to hold the combined water in all the other Great Lakes and with a surface area as large as South Carolina, Lake Superior's size has lent it an aura of invulnerability. But the mighty Superior is losing water and getting warmer, worrying those who live near its shores, along with scientists and companies that rely on the lake for business. The changes to the lake could be signs of climate change, although scientists aren't sure. Superior's level is at its LOWEST POINT IN EIGHT DECADES and will set a record this fall if, as expected, it dips three more inches. Meanwhile, the average water temperature has surged 4.5 degrees since 1979, significantly above the 2.7-degree rise in the region's air temperature during the same period. That's no small deal for a freshwater sea that was created from glacial melt as the Ice Age ended and remains chilly in all seasons. A weather buoy on the western side recently recorded an "amazing" 75 degrees, "AS WARM A SURFACE TEMPERATURE AS WE'VE EVER SEEN IN THIS LAKE." Water levels also have receded on the other Great Lakes since the late 1990s. But the suddenness and severity of Superior's changes worry many in the region. As the bay heats up, the perch, walleye and smallmouth bass that have lured anglers to campgrounds and tackle shops are migrating to cooler waters in the open lake. Low water has cost the shipping industry millions of dollars, with vessels forced to carry lighter loads. Precipitation has tapered off across the upper Great Lakes since the 1970s and is nearly 6 inches below normal in the Superior watershed the past year. Water evaporation rates are up sharply because mild winters have shrunk the winter ice cap - just as climate change computer models predict for the next half-century. Yet those models also envision more precipitation as global warming sets in - instead, there's drought, suggesting other factors. "It's just not clear what the ultimate result will be as we turn the knob up. It could be great for fisheries or fisheries could crash."