Ice and Sea-Ice
The cryosphere plays an important role in moderating the global climate, and as such, the consequences of receding ice cover due to global warming are far-reaching and complex. While evidence suggests that ice sheets are relatively stable, there are indications that rapid changes are occurring around their margins, where the ice reaches the sea: changes that could weaken the ice sheet.
Altimetry is one of the most powerful tools for observing sea ice and ice sheets. For sea ice, altimetry provides a unique way of measuring its thickness. For ice sheets, their topography can be measured by altimeters, at least by those that can reach high latitudes such as Sentinel-3 or CryoSat. Moreover, altimeters also provide other parameters such as backscatter coefficient and waveform shape that give information on surface roughness and snow pack characteristics such as stratification or ice grain size. These parameters are related to relevant unknown quantities affecting the climate, such as snow accumulation rate or snow drift caused by wind.
The SENTINEL-3 improved along track resolution (approximately 300 m) in SAR mode facilitates measurement over sea-ice and land-ice. The SRAL instrument is in SAR Open Loop mode over the ice sheet margins, in SAR Closed Loop mode over sea-ice areas and in SAR mode over interior ice sheets. The Level-2 SRAL/MWR products have three dedicated outputs for ice sheets, ice and sea-ice.
New disseminated Level-1 products (Level-1A, Level-1B-s and Level-1B) allow improved measurements over the ice-sheets and sea-ice through improved and customised retracking techniques for these surfaces. The SENTINEL-3 SRAL instrument does not support SAR-In operating mode.
The Sentinel-3 mission provides continuity with the ERS, Envisat and CryoSat missions deriving with high resolution sea-ice thickness and ice sheet topography.
Figure 1: CryoSat's exceptionally detailed data have been used to generate the map of sea-ice thickness in the Arctic shown in Figure 1. The sea-ice thickness map is based on data from January and February 2011 and shows thicker, rough, multi-year ice north of Canada and Greenland, stretching to the North Pole and slightly beyond. (Credit: CPOM/UCL/ESA)
Figure 2: Data from ESA's CryoSat mission have been used to map the height of the ice sheet that blankets Antarctica as shown in Figure 2. The data used here are from February and March 2011. CryoSat's ability to map the edges of the ice sheet is demonstrated by the detail that can be seen of the flow from east Antarctica onto the Ronne-Filchner ice shelf in the west. (Credit: CPOM/ESA/Planetary Visions)
For further information about applications related to ice see: Center for Polar Observation and Modelling (CPOM), Ice Sheet Climate Change Initiative , SPICE project and Sea Ice Climate Change Initiative.
For further information about ice and sea-ice applications and services available, see: Copernicus website.