Radar and laser altimeter measurements over Arctic sea ice
To validate sea ice models, basin wide sea ice thickness measurements with an accuracy of 0.5 m are required to analyse trends in sea ice thickness, it is necessary to detect changes in sea ice thickness of 4 cm per year on a basin wide scale. The estimated error on satellite radar altimeter estimates of sea ice thickness is 0.45 m and the estimated error on satellite laser altimetry estimates of sea ice thickness is 0.78 m. The Laser Radar Altimetry (LaRA) field campaign took place in the Arctic during 2002. It was the first experiment to collect coincident radar and laser altimetry over sea ice. This thesis analyses the data from LaRA to explore the potential of combining radar and laser altimetry to reduce the uncertainties in measurements of sea ice thickness. Two new methods to analyse the LaRA data are described. The first is the University College London (UCL) Delay/Doppler radar altimeter (D2P) re-tracking algorithm and the second is the UCL D2P power simulator. Each method is calibrated and the associated error is estimated. The UCL D2P power simulator reproduces the D2P returns closely, and is used to estimate the elevation difference between the reflecting surface of the radar and the laser with an accuracy of 0.07 m. The laser is shown to consistently reflect from a higher surface than the radar. The offset between the laser and the radar is consistent with observed snow depths and compares well to snow depth distributions from in-situ data. We find that reducing the error in snow depth to 7 cm reduces the radar error in sea ice thickness from 0.45 m to 0.37 m and the laser error in sea ice thickness from 0.78 m to 0.55 m.