How cold is the bottom of a glacier?

The bottom of a glacier is extremely cold, but its exact temperature depends on the type of glacier, location, and whether it is a cold-based or warm-based glacier. Glaciers are divided into cold-based glaciers where the entire ice mass is below freezing, and warm-based or temperate glaciers where the bottom is at the melting point. In Antarctica, where air temperatures can be minus 60 degrees Fahrenheit, the bottom of the Antarctic Ice Sheet, which is up to 15,000 feet thick, can be minus 40 to minus 20 degrees Fahrenheit, well below freezing, and the ice is frozen solid to the bedrock. In Alaska, including Glacier Bay, most tidewater glaciers are temperate glaciers, meaning the bottom of the glacier is actually at 32 degrees Fahrenheit, the melting point of ice, even though the surface is colder. This is because pressure from the weight of ice lowers the melting point and geothermal heat from the Earth warms the base, creating a thin film of water that allows the glacier to slide. So the bottom is at the pressure-melting point, around 32 degrees Fahrenheit or slightly below, about 28 to 32 degrees due to pressure. This basal water is why glaciers move and carve valleys. So the bottom can be minus 40 degrees in Antarctica or 32 degrees in Alaska. In either case, it is far too cold for human survival without specialized equipment.