Summary
Techniques to calculate sea ice thickness from measurements of sea ice freeboard from spacebome radar and laser altimeters in the Arctic have the potential to be used in the Antarctic. The conversion of freeboard, measured by the altimeter, to thickness uses estimates of snow depth and density, and water and ice density, from a climatology. In order to use these estimates of sea ice thickness we must understand the errors associated with the conversion of ice freeboard to ice thickness and in particular how the errors of each of the constituent parameters co-vary. In particular the data must be averaged in space and time to reduce the errors in the freeboard measurement, and in the parameters involved in the conversion to thickness. Knowledge of how these parameters co-vary in space and time and with each other is essential in properly calculating an error in the retrieval. Therefore, ground truth measurements must be carefully designed to validate estimates of ice thickness and in particular to analyse covariance of the errors. We describe the principles of the error evaluation of estimates of sea ice thickness from satellite measurements of ice freeboard and outline the in-situ measurements required to validate such estimates.