The various types of Arctic observation systems (satellite, aircraft, and in situ) and scales of operation
Change in the cryosphere takes place on different timescales, from seasonal changes in snow cover or river and lake ice, to change over centuries, such as the diminishing Greenland Ice Sheet, or thawing permafrost. Some observed changes affect a large area all at once, such as changes in Arctic sea ice. Others are smaller scale, like changes to ice cover over lakes and rivers. These different scales of change mean that a range of different techniques is required to observe, monitor and project cryospheric change for the whole Arctic.