CryoRad : An innovative Radiometric Mission for the study of the polar oceans and of the cryosphere

Observations from space are essential for more accurate description of the processes that dominate polar regions, but existing or planned space-borne sensors do not provide all the necessary geophysical parameters at the required spatial coverage and resolution, revisit time, and accuracy. Processes that need particular attention are: the freshening of the Arctic Ocean (impacted by effects such as melting sea ice, increased continental runoff, and ocean circulation changes); variations in sea surface salinity in the Southern Ocean associated with the changes of Antarctic sea ice extent and thickness and their implications for oceanic circulation and for the ocean’s capability to absorb atmospheric heat and carbon; the progressive reduction in sea ice extent and thickness and its effects on Earth’s climate including environmental, economic and societal impacts; the acceleration of ice sheet mass loss and its effect on sea level rise; the collapse of Antarctic ice shelves, which affect the ocean stratification and bottom water formation.

The CryoRad satellite mission, a European Space Agency Earth Explorer 12 candidate mission, aims to address all these limitations by developing an innovative sensor able to investigate physical properties of the cryosphere and its cold oceans, and to better understand their interconnections.

CryoRad consists of a wideband, low-frequency microwave radiometer that explores a new spectral range from 0.4 to 2 GHz with continuous frequency sampling. This new technology will enable breakthroughs in key climate variable measurements such as :

• the sea surface salinity (SSS) : it will eliminate the high uncertainties in cold waters of current L-band spaceborne radiometers;
• the sea ice thickness by improving current estimations in the range 0.5-1 m

It will also provide measurements of the sea ice salinity, that has never previously been obtained from space, to improve estimates of sea ice freshwater fluxes, and of the ice sheet and shelf temperature profile of Antarctica and Greenland from the top to the bottom, never previously measured from space with sufficient accuracy and available only from sparse borehole sites.

The CryoRad swath will be 120 km, with a spatial resolution on the ground that varies from 47 km at 0.4 GHz to 14 km at 2 GHz. The average revisit time will be around 3 days at latitudes higher than 55° and about 10 days at the equator. CryoRad will open a new era in microwave radiometry and will provide a better understanding of polar processes in a warming climate from the ice sheet interior to the open ocean.