A study in Scientific Reports shows the potential of passive microwave observations from satellites to estimate the thickness and winter volume of Arctic sea ice.
The pack ice, formed by freezing sea water, covered most of the basin Arcticthe essence of theyearuntil the beginning of this century. However, since the end of the 1970s, the Arctic sea ice has been gradually melting, especially in summer, as measurements have revealed. satellites of ice cover by passive microwaves.
These observations show a reduction of more than 10%, per decade, in the surface summer of the sea ice, equivalent to more than five times the surface of France since 1979. This melting, reproduced by the models of the climateis attributed to CO2 emissions from human activities.
However, the measurement of the cover says nothing about the thickness of the ice, which would allow a better understanding of the melting, and especially the determination of the volume of the ice shelf.
Estimates of sea ice thickness are obtained from space by altimeters (lidar and radar), but these observations are not available continuously over long periods; and until now, only numerical simulations from physical models estimate the volume of the Arctic sea ice, with an uncertainty of around 50%.
Reduction in the volume of sea ice in the Arctic between 1992 and 2020 for the months of October and March, estimated by microwave satellite observations (PMW) and by a physical model (PIOMAS). Associated trends are shown.
© CNRS Images
The study in which the Laboratory for the Study of Radiation and Matter is involved in astrophysics and atmospheres – LERMAParis Observatory – PSL, shows the potential of passive microwave observations from satellites to estimate the thickness and winter volume of Arctic sea ice. The method is based on an algorithmartificial intelligencetrained on data ice thickness lidar, and takes advantage of the length time series of microwave observations.
The ice thicknesses obtained and the resulting sea ice volumes agree with simulations over the last 30 years: the two sources agree better than expected on ice volumes, and are close in terms of trends in sea ice volume and of its changes from one year to the next.
Passive microwave satellite data thus make it possible to substantially reduce uncertainties on the volume of the Arctic sea ice and its evolution, and should improve the precision of forecasts of the future of the sea ice.
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