France: ESA’s ice mission is now giving scientists a closer look at oceans, coastal areas, inland water bodies and even land, reaching above and beyond its original objectives.
Launched in 2010, the polar-orbiting CryoSat was developed to measure the changes in the thickness of polar sea ice, the elevation of the ice sheets that blanket Greenland and Antarctica, and mountain glaciers.
The satellite’s radar altimetre not only detects tiny variations in the height of the ice, it also measures sea level and the sea ice’s height above water to derive sea-ice thickness with an unprecedented accuracy.
At a higher precision than previous altimetres, CryoSat’s measurements of sea level are improving the quality of the model forecasts. Small, local phenomena in the ocean surface like eddies can be detected and analysed.
Taking CryoSat a step further, scientists have now discovered that the altimetry readings have the potential to map sea level closer to the coast, and even greater capabilities to profile land surfaces and inland water targets such as small lakes, rivers and their intricate tributaries.
Radar altimetres have more difficulty doing this because, compared to open ocean measurements, the landscape surrounding inland water bodies is a lot more complex.
These had not been previously monitored with satisfying accuracy by conventional altimetres because the sensor footprints – about 5×5 km – were too large to detect subtle differences in the topography around small landforms.
CryoSat, however, has a resolution along its ground track of about 300 m.
In order to thoroughly investigate the possibilities offered by CryoSat over water, ESA recently began scientific exploitation projects coined ‘CryoSat+’.
Scientists are reprocessing large, raw and uncompressed sets of data coming directly from CryoSat to obtain new information on oceans, inland water bodies and land.
CryoSat’s altimetre made readings over central Cuba, extending north and south into the surrounding water.
“Thanks to CryoSat being operated over some inland water targets in high resolution mode, we were able to distinctly chart the contours of a flood that occurred last March at Rio Negro in the Amazon,” said Salvatore Dinardo, working for ESA on CryoSat+.
Jérôme Benveniste, the ESA scientist who initiated the project, continued, “We were able to emphasise the unique capability to see the floodwater extent under the forest canopy, where optical sensors or even imaging radars are blocked by the trees.”