Along with a gradual warming of the oceans, melting of the Greenland and Antarctic ice sheets are main contributors to the sea level rise of our oceans. Satellite altimetry can help to quantify these two contributions and improve predictions of future changes in sea level.

Sea ice

For three decades satellites have been documenting the decline of Arctic summer sea ice. This shows that the ice-covered area during the summer minimum (September) has been shrinking much faster than expected from climate models.

The loss of Arctic summer ice is important for several reasons:

• Open water absorbs far more of the incoming solar energy than an ice covered ocean, so the loss of ice contributes to increase global warming

• The ice is a critical part of polar ecosystems, so the loss of ice will have profound impacts on Arctic life and humans who depend on Arctic living resources for their livelihoods

• An opening up of the Arctic will increase ship traffic and exploration for oil and other resources in the Arctic, with its own potential problems

SAR altimeters from CryoSat and Sentinel-3 satellites can measure sea ice thickness, although only during the winter months. Melt-water on the ice surface prevents reliable measurements during the polar summer.

Land ice

While melting sea ice does not contribute to sea level rise, melting land ice in Greenland and Antarctica has a direct effect on sea level by adding water to the oceans. Recent satellite observations from Greenland and Antarctica indicate that this rate of ice loss in these areas may be increasing.

Altimeters can measure changes to the topography of ice sheets. The spatial resolution of early altimeters prevented accurate measurements from being made over the ice sheet margins, where most of the changes take place. Modern SAR altimetry (CryoSat and Sentinel-3) can measure changes also over the ice sheet margins. This has led to more accurate estimates of ice loss and the contribution this makes to global sea level rise.

Changes to the volume of ice sheets can also be calculated from satellite gravimetry (GRACE and GOCE).

Optional mini task:

Visit the US National Snow and Ice Data Centre’s interactive sea ice graph You can use the legend on the side to view the current sea ice extent for the Arctic or Antarctic, as well as each year from 1979. How does this year compare to other years?

Featured Educators:

• Dr Val Byfield

Explore the data

EUMETSAT Oceans MOOC Data Viewer

View featured satellites on the satellite tracking app

• CryoSat-2

• GRACE-1

Don’t forget you can download the video and transcript with the links on the right.