The Estimation of the Total Freeboard of Arctic Sea Ice in Winter Using Passive Microwave Satellite Measurements

A method for estimating the total freeboard h f of the sea ice in the Arctic basin was developed in this study. To utilize the dielectric properties of microwave measurements on the sea ice freeboard, we adopted the spectral difference between the microwave frequencies (e.g., the gradient ratio). Satellite lidar altimetry data were utilized as a reference, and two pairs of gradient ratios [GR(36.5, 18.7) and GR(10.7, 6.9)] and an optional brightness temperature for first-year ice [that is, TB H (6.9)] were converted from passive microwave sensors into h f using the multiple linear regression equation. Using this method, we estimated h f without direct altimetry measurements. The developed method was evaluated using Operation IceBridge data and the relationship between the regressed h f and Operation IceBridge h f had a correlation coefficient R of 0.761 and a nearly unbiased (approximately −0.4 cm) pattern. Because passive microwave measurements are taken in the Arctic daily, the approach presented in this study has the potential to enable daily h f estimations for the Arctic.