Thepressure melting point of ice is the temperature at which ice melts at a given pressure. The pressure melting point is nearly a constant 0 °C at pressures above thetriple point at 611.7 Pa—where ice, water, and water vapour coexist in equilibrium—through atmospheric pressure (100 kPa) until about 10 MPa. With increasing pressure above 10 MPa, the pressure melting point decreases to a minimum of −21.9 °C at 209.9 MPa. Thereafter, the pressure melting point rises rapidly with pressure, passing back through 0 °C at 632.4 MPa.[1]
Glaciers are subject to geothermal heat flux from below and atmospheric warming or cooling from above. As the pressure increases with depth in a glacier from the weight of the ice above, the pressure melting point of ice decreases within bounds, as shown in the diagram. The level where ice can start melting is where the pressure melting point equals the actual temperature.[2] In static equilibrium conditions, this would be the highest level where water can exist in aglacier. It would also be the level of the base of anice shelf, or the ice-water interface of asubglacial lake.[3]
 | Thisglaciology article is astub. You can help Wikipedia byadding missing information. |