Discover real natural events happening around our amazing planet right now!
Real-time Arctic and Antarctic ice monitoring from NASA NSIDC and EONET satellites
View on Globe →In very cold places, the surface of oceans and lakes can freeze solid. This ice is a home for animals like polar bears, seals, and penguins. Scientists watch sea ice very carefully because changes in how much ice there is tell us a lot about how our planet's climate is changing.
NASA satellites track sea ice continuously — even during the polar night when there is no sunlight — using microwave sensors that can see through clouds. This data gives scientists the longest and most complete record of how polar ice is responding to a warming world.
NASA's National Snow and Ice Data Center (NSIDC) monitors global sea ice extent using passive microwave sensors aboard satellites including SSMIS and AMSR2. These instruments detect the microwave radiation naturally emitted by ice, water, and snow — allowing scientists to map sea ice extent even through clouds and during the months-long polar night when optical cameras are useless.
The ICESat-2 satellite uses a laser altimeter to measure ice surface height with centimetre-level precision. By comparing measurements over time, scientists can calculate how thick the ice is and how fast it is thinning. Thinner ice is more vulnerable to melting in summer, making ice thickness as important as extent for understanding the health of polar ice.
NASA's Operation IceBridge conducted thousands of airborne survey flights over the Arctic and Antarctic between 2009 and 2020, carrying a suite of instruments to measure ice thickness, surface elevation, and gravity in areas not covered by satellites, creating a vital bridge in the long-term record of polar change.
Earth Explorer displays sea ice and lake ice events tracked by NASA's EONET monitoring network. Significant ice formation, extreme ice loss events, and notable changes in polar ice extent appear on the interactive globe as they are reported.
View Live Ice Events →Sea ice is frozen ocean water that forms at the poles when surface temperatures drop below −1.8°C (the freezing point of seawater). Unlike icebergs — which are chunks of freshwater glacier ice that have broken off land — sea ice is part of the ocean itself. It grows in winter and shrinks in summer, and its seasonal cycle drives many important ocean and climate processes.
Sea ice reflects about 80% of incoming sunlight back into space, acting like a giant mirror that keeps the poles cool. When it melts, dark ocean water absorbs 94% of sunlight — warming the water and air. This creates a feedback: less ice → more warming → even less ice. Sea ice also regulates ocean circulation, affects weather patterns far beyond the poles, and provides habitat for the entire Arctic and sub-Antarctic food web.
Sea ice forms when the ocean surface freezes — it is saltwater ice, part of the sea itself, and relatively thin (1–5 metres). An iceberg is a massive chunk of freshwater glacier ice that has calved off a land-based ice sheet or glacier and is now floating. About 90% of an iceberg sits below the surface. When sea ice melts, sea level barely changes; when land ice melts into the ocean, sea level rises.
Arctic sea ice extent has declined by about 13% per decade since 1979. September minimum ice — the lowest point of the year — has dropped dramatically, opening shipping routes through the Arctic that were previously impassable. Antarctic sea ice hit a record low in 2023. Scientists link these changes to human-caused climate change, which is warming the Arctic about four times faster than the global average.
Polar bears hunt seals from sea ice platforms — without ice, they cannot catch enough food to survive. Ringed seals give birth in snow dens on sea ice. Walruses use ice as resting platforms. Beneath the ice, algae grow on the underside, forming the base of the entire Arctic food web that feeds krill, Arctic cod, seals, beluga whales, narwhals, and polar bears. Loss of sea ice threatens this entire ecosystem.
NASA's NSIDC uses SSMIS and AMSR2 microwave sensors to map sea ice extent daily — through clouds and in polar darkness. ICESat-2's laser altimeter measures ice thickness to centimetre precision. Operation IceBridge airborne surveys filled gaps in the satellite record. Together these tools give scientists the world's most complete long-term record of polar ice change, feeding into EONET and the Earth Explorer globe display.