Ask a Scientist

These articles provide answers to frequently asked questions related to Earth's frozen realms. Questions range from general background information and detailed science processes to the data gathered and archived at the National Snow and Ice Data Center (NSIDC) and its data management programs including NOAA@NSIDC, the NASA NSIDC Distributed Active Archive Center (DAAC), and the Exchange for Local Observations and Knowledge of the Arctic (ELOKA). If you have a question that is not answered here, please contact NSIDC User Services.


Filter by:
2-up showing sea ice concentration and extent of the same region
Although area and extent may sound synonymous, they are different measurements, rendering different numbers, even from the same satellite observations. Sea ice area is the total region covered by ice. Extent is the total region with at least 15 percent sea ice cover. NSIDC usually reports extent, which gives higher values than area.
About 70 percent of the planet’s freshwater is locked up in ice sheets: massive ice bodies spanning more than 50,000 square kilometers (20,000 square miles). Our planet has two ice sheets, one covering roughly 80 percent of Greenland and the other
Dig Tsho glacial lake in Nepal
A glacial lake is a body of water that originates from a glacier. It typically forms at the foot of a glacier, but may form on, in, or under it. As Earth’s climate warms, the world’s glaciers are shrinking, increasing freshwater outputs to all kinds
On the landmasses surrounding the Arctic Ocean, tundra typically thrives. Tundra landscapes consist of low-profile, cold-adapted plants that eke out their tiny lives in short, cool summers. Since the early 1980s, though, satellites and ground-based
Sample image of Antarctic sea ice extent
Besides occurring on the opposite side of the globe, Antarctic sea ice differs from Arctic sea ice in a couple of respects. First, the Arctic is an ocean basin largely surrounded by land whereas the Antarctic is a continent surrounded by ocean, and
A tipping point is a critical threshold where an incremental change could push a system over the edge to a new state. Two types of tipping points exist. One involves a rapid transition, like what happens when a canoe rocks back and forth. Eventually