Global Climate Change The Exploratorium
home atmosphere hydrosphere cryosphere biosphere global effects

 Southern Ice Concentration

Sea ice is frozen water floating on top of the ocean. The extent of sea ice expands and shrinks seasonally, responding relatively swiftly to rising or falling air temperatures (unlike glaciers, which may take years to begin retreating or advancing in response to climate trends). Time series data on annual sea ice concentration can provide some indication of general changes in climate.

Using microwave sensors on satellites, scientists can monitor sea ice changes on a daily basis. Accurate monitoring of global snow and ice cover is a key component in the study of climate as well as daily weather forecasting. Sea ice plays an important role in regulating the amount of heat, moisture, and salinity in the polar oceans. With an insulating cover of ice, less heat is lost from the ocean to the cold polar air. In places where sea ice is cracked, there is a greater loss of heat and water vapor to the atmosphere. This in turn can affect local cloud cover and precipitation.

When sea water freezes, its salt content drops. So freezing sea water increases the salt content of the water locally, making it denser. This increase in density helps to drive some of the ocean currents.

In late winter, sea ice typically covers 17 to 20 million square kilometers in the Antarctic's Southern Ocean. At the end of the summer, typically only 3 to 4 million square kilometers of ice remain.

 glossary glossary terms  

Click for definitions of words used on this page:

climate model
ice core

View the full, printable version of the glossary.

Global Glacier Mass Balance

Southern Ice Concentration - This satellite image shows the extent of sea ice around the Antarctic continent (light brown area). The colors represent the amount of ice coverage from 100% (light violet) to 0% light blue). Source:Fleet Numerical Meteorology and Oceanography Center.

 questions about the data  

question With so much variation in sea ice every year, how do scientists know if recent changes can be blamed on global warming?

email Email your own questions about this data set. 

 research connection  

When considering the effects of a warming climate on sea level rise, scientists don’t worry about melting sea ice. Because sea ice is already floating on top of the ocean, sea levels don’t rise when it melts (for the same reason your glass of iced tea doesn’t overflow when the ice in it melts). However, the presence or absence of sea ice does affect heat and moisture conditions on the surrounding land, greatly altering the coastal climate as well as the habitats of ocean ecosystems.

 related sites  

Arctic and Southern Ocean Sea Ice Concentrations - Provides data on sea ice concentrations and links to other sources of data.

home | atmosphere | hydrosphere | cryosphere | biosphere | global effects

about this site - © 2002 The Exploratorium