Arctic freeboard and snow depth from near-coincident CryoSat-2 and ICESat-2 (CRYO2ICE) observations: A first examination during winter 2020-2021

In the summer of 2020, ESA changed the orbit of CryoSat-2 to align periodically with NASA’s ICESat-2 mission, a campaign known as CRYO2ICE, which allows for near-coincident CryoSat-2 and ICESat-2 observations in space and time over the Arctic. This study investigates the CRYO2ICE radar and laser freeboards acquired by CryoSat-2 and ICESat-2, respectively, during the full winter season of 2020–2021, and derives snow depths from their differences. As expected, the ICESat-2 signal is backscattered at a surface above the elevation of the CryoSat-2 signal. CRYO2ICE snow depths are thinner than the daily model- or passive-microwave-based snow depth composites used for comparison, where differences are most pronounced in the Atlantic and Pacific Arctic. These observations show the exciting potential for along-track dual-frequency observations of snow depth from the future Copernicus mission CRISTAL; but also highlight uncertainties in radar penetration and the length scales of snow topography that still require further research.