Ocean & Sea Ice Satellite Application Facility (OSI SAF)

The OSI SAF provides comprehensive information derived from meteorological satellites at the ocean-atmosphere interface.

You can access current and historical data via their website.

In relation to polar ice, one very useful metric is the Sea Ice Index, which you can find out more about here.

This chart is an example of the visualisation tools available via the website. Given the obvious differences between ice behaviour at the two poles due to the different seasons in the two hemispheres, most charts come in "pairs" for the Northern and Southern Hemispheres.

Sea Ice Extent Monthly Time Series

Another useful visualisation of changes in sea ice extent is provided by charts like this one.

This shows how sea ice extent for a specific month of the year has changed over many years.

However, as you can see if you review the many analyses and charts on the OSI SAF site, it is easy to pick one or two such charts and be misled into thinking extent is generally increasing based on a small number of exceptions, such as the one shown here that shows that if we look only at the month of September in the Southern Hemisphere there has been a slight upward trend over many years.

Northern Hemisphere Time Series

Given the seasonal nature of ice extent in both hemispheres many of these charts do not help if you want to detect an overall trend.

So, rather than look at charts for a specific month over time, let's look at extent over time for all months.

This chart for the Northern Hemisphere was drawn using the OSI SAF data visualisation tool. Click on the chart to enlarge it.

The downward trend is clear.

Southern Hemisphere Time Series

The equivalent chart for the Southern Hemisphere is shown here. Click on the chart to enlarge it.

The trend is not clear, and a "line of best fit" for the data covering the last 40 years or so does not show a significant trend.

For a discussion of Antarctic sea ice extent see this article.

The National Snow and Ice Data Center (NSIDC)

The NSIDC at the University of Colorado Boulder (CU Boulder) conducts innovative research and provides open data to understand how the frozen parts of Earth affect the rest of the planet and impact society.

Their website provides both historical and current information on ice around the world, including data on

• Ice sheets;
• Glaciers;
• Sea Ice;
• Snow.

NSIDC is "the authoritative data management and science center for cryospheric data and research", and it is a good place to research the history and status of polar ice.

The Ice Sheets are Losing Mass

So far I've mainly concentrated on area. What about mass?

Antarctica is losing ice mass - i.e. melting - at an average rate of about 150 billion tons per year. The chart shows satellite data from 2002 to the present.

Greenland is losing about 270 billion tons per year. You can see the corresponding chart for Greenland here. On that page you can also get access to NASA ice sheet data.

Between them the Greenland and Antarctic ice sheets store about 2/3 of all the fresh water on Earth. Warming of these ice sheets is therefore making a major contribution to sea level rise.