ИСТИНА

The stability of Antarctic ice sheet is very important. The rapid melting and collapse of ice sheets can provide a significant sea level rise. The future of the Antarctic ice sheet represents the largest uncertainty in sea level projections for future centuries. Satellite observations and high-resolution modelling have recently suggested the onset of ice sheet instability in the Amundsen Sea sector of West Antarctica, driven by increased melting of the basal ice shelf. It is unclear the degree of future degradation of ice shelves for West Antarctica. High subglacial heat flow and volcanic activity in West Antarctica also contribute to instability and accelerated ice flows into the ocean of the West Antarctic ice sheet. Beyond the slow melting of ice, there is also a more apocalyptic scenario. А catastrophic rise in sea level (tens centimeters the first meters) can occur in a very short geological time (years-decades) due to the rapid sliding of large masses of ice in West Antarctica into the ocean. If the Pine Island (50 cm sea level rise) or Doomsday (65 cm sea level rise) glaciers slide into the ocean, the West Antarctic Ice Sheet can lose support from these glaciers and may begin to collapse. In this case, the sea level will rise by a few meters. The trigger for the beginning of such rapid sliding can be a strong subglacial volcanic eruption or additional stresses in the glacier due to arrival of tectonic waves from the strongest earthquakes in subduction zones. We use PISM 3D model to investigate the stability of Antarctic ice sheet. The calculated velocities of ice sheets varies from about ~20 m/year for conditions of adhesion to the bed to ~2000 m/year for conditions of sliding along the bedrock when the lower edge of the glacier melts due to increased heat flow. The calculated velocities are in good agreement with the observed velocities for the Pine, Doomsday (Thwaites), Amery and other glaciers. The rapid movement of some outlet glaciers in East Antarctica is also likely caused by melting of their bases, suggesting increased subglacial heat flow in these areas of East Antarctica.