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Jack Denur
Jack Denur
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There is a balance between precipitation on the one hand, and sublimation and outflow on the other. Ice evaporates directly to water vapor, especially during the summers. The thicker the ice, the greater the pressure at the bottom of the ice owing to the weight of the overlying ice, and hence the faster the outflow. The thicker the ice, the less the precipitation, because the less the atmosphere above the ice sheet. The pressure at the bottom of an ice sheet 250 km thick, or even 125 km thick, would be so great that outflow would be very much faster than at present, and very much exceed even current average precipitation of perhaps 1 inch per year. Indeed precipitation would be ZERO for such a thick ice sheet because its height would be above any appreciable atmosphere. Even neglecting sublimation and outflow, an ice sheet could never attain a thickness of 125 km, much less 250 km, because precipitation over the ice sheet would vanish well before such a thickness was attained.

There is a balance between precipitation on the one hand, and sublimation and outflow on the other. Ice evaporates directly to water vapor, especially during the summers. The thicker the ice, the greater the pressure at the bottom of the ice owing to the weight of the overlying ice, and hence the faster the outflow. The thicker the ice, the less the precipitation, because the less the atmosphere above the ice sheet. The pressure at the bottom of an ice sheet 250 km thick, or even 125 km thick, would be so great that outflow would be very much faster than at present, and very much exceed even current average precipitation of perhaps 1 inch per year. Indeed precipitation would be ZERO for such a thick ice sheet because its height would be above any appreciable atmosphere.

There is a balance between precipitation on the one hand, and sublimation and outflow on the other. Ice evaporates directly to water vapor, especially during the summers. The thicker the ice, the greater the pressure at the bottom of the ice owing to the weight of the overlying ice, and hence the faster the outflow. The thicker the ice, the less the precipitation, because the less the atmosphere above the ice sheet. The pressure at the bottom of an ice sheet 250 km thick, or even 125 km thick, would be so great that outflow would be very much faster than at present, and very much exceed even current average precipitation of perhaps 1 inch per year. Indeed precipitation would be ZERO for such a thick ice sheet because its height would be above any appreciable atmosphere. Even neglecting sublimation and outflow, an ice sheet could never attain a thickness of 125 km, much less 250 km, because precipitation over the ice sheet would vanish well before such a thickness was attained.

Source Link
Jack Denur
Jack Denur
  • 758
  • 5
  • 7

There is a balance between precipitation on the one hand, and sublimation and outflow on the other. Ice evaporates directly to water vapor, especially during the summers. The thicker the ice, the greater the pressure at the bottom of the ice owing to the weight of the overlying ice, and hence the faster the outflow. The thicker the ice, the less the precipitation, because the less the atmosphere above the ice sheet. The pressure at the bottom of an ice sheet 250 km thick, or even 125 km thick, would be so great that outflow would be very much faster than at present, and very much exceed even current average precipitation of perhaps 1 inch per year. Indeed precipitation would be ZERO for such a thick ice sheet because its height would be above any appreciable atmosphere.