As the Arctic warms, sea ice is decreasing rapidly. In the Antarctic, sea ice has slowly increased, driven by local changes in wind patterns and freshening sea water. However, in recent years Antarctic sea ice has stopped growing. Over the past few decades the ice sheets (the great masses of land ice at the poles) in Greenland and the Antarctic have shrunk, as have most glaciers around the world. More damaging extreme weather events are being seen around the world. Heat waves have become more frequent and are lasting longer. The height of extreme sea levels caused by storms has increased.