Peacock, Neil Robert; (1998) Arctic sea ice and ocean topography from satellite altimetry. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis explores novel applications of data from the ERS-1 and 2 satellite altimeters in the Arctic. The use of such data in this region has been restricted in the past by the presence of sea ice, which vastly affects the radar echo received from the surface. The altimeter instruments are optimised for operation in ice-free seas, which generate diffuse, low power echoes. When sea ice is present, higher powered specular echoes are observed. Evidence is presented to support the hypothesis that these echoes originate from regions of calm water between ice floes, thus allowing the direct measurement of sea surface height in areas of very high ice concentration. Results from a full simulation of the ERS altimeter tracking system have enabled the development of processing algorithms which dramatically reduce short wavelength instrument noise. This has enabled direct measurements of sea surface height to be made for the first time in ice-covered seas. Maps of sea surface height variability and eddy kinetic energy are presented, and compared with the corresponding output from two Arctic Ocean models. An empirical tide model based purely on the altimeter data has also been developed and is compared with existing models. Open ocean-like echoes have been observed in areas of 100% ice cover, and are shown to originate from the surfaces of ice floes. The associated height measurements are seen to deviate from those of the surrounding water by an amount which is attributed to ice elevation. From these measurements, estimates of ice thickness have been made, allowing the first direct large-scale observations of this parameter from space. A preliminary validation of these measurements is performed using in situ observations from upward-looking sonar (ULS) instruments.

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