Sea ice
Going to the sea ice is difficult and sometimes dangerous. This makes it impossible to keep track of all the sea ice at once and see how its changing. To solve this, scientists often look at sea ice from space using satellites. There are many ways to do this. Some satellites use cameras that work similarly to common consumer ones. Others make pictures of the sea ice using microwave energy that can go through clouds. Some don't just look at the ice, but send down energy from laser and radar machines and then record how it bounces off the ice.