Alexei Kouraev (LEGOS/UPS, France); Inna Krylenko (IWP RAS, Russia); Nicholas Hall (LEGOS/UPS, France); Jean-Francois Crétaux (LEGOS/CNES, France)

Many rivers and lakes in the Northern Hemisphere are seasonally ice-covered. Ice presence is long and may last for almost half of the year. Ice cover dramatically affects energy exchange between water and atmosphere. Ice formation and break-up, as well as ice thickness, are good indicators of regional and large-scale climate variability. River ice is a key component of the river hydrology as it affects streamflow via immobilization/release, modification of the water velocity field, creation of a backwater during freezing and melting. For lakes, ice thickness and duration of ice period affect timing of vertical overturning, duration of summer warming period and thus water temperature and evaporation rate. Ice is also important for establishing transport on ice, for fishing activities and tourism.
Satellite monitoring of river and lake ice is a rapidly developing area. At the same time for active microwave remote sensing the presence of ice significantly affects the returning radar signal and could result in erroneous interpretation of satellite altimetry measurements. We present results of comparison of field observations on ice and snow structure done on Lake Hovsgol (Mongolia) in winter with SWOT measurements and use complementary satellite imagery in different bands to help the interpretation of spatial heterogeneity of SWOT observations.
In the Middle Lena River we compare the SWOT water level measurements with in situ observations at the gauging stations and with the simulations of the hydrodynamic model STREAM 2D along 300 km-long river reach. We put a specific focus on the winter period.
This research was supported by the CNES TOSCA Lakeddies, Lakeddies II, TRISHNA and SWIRL projects, and RAS Governmental Order FMWZ-2025-0003 for IWP.