Who first tried to derive sea ice freeboard from satellite radar altimetry measurements? I always thought it was Laxon et al. (e.g. 1990), but I read his PhD thesis last year and found there was backstory! It has a nice figure taken from Stanley et al. (1979) showing the height profiles from two GEOS-3 tracks in the Bering Sea, before and after the sea ice melted away. The March track with sea ice present exhibits higher elevations. Much higher…
The freeboard implied by this figure is unrealistically big, and was attributed to unspecified “instrumental errors” related to operation over sea ice. I strongly suspect that this involves the need for different retracking approaches for leads and floes. But it’s still a landmark paper for me in terms of the method. I wasn’t able to find this paper anywhere online, so my thanks to Vishnu Nandan who retrieved and sent me a copy from the U. Calgary library. I’ve staged it online here so folks can read it.
On the topic of interesting references, while rooting around in Seymour Laxon’s thesis I came across what might be the first definition of “pulse peakiness” by Laxon and Rapley (1987). An ever growing number of pulse peakiness (and “stack peakiness”) definitions are entering the altimetry literature, and I’m finding it quite confusing to be honest. So I think it’s valuable to know where this all started.
Finally, on waveform retracking trivia, another paper cited in Laxon’s thesis was news to me. I don’t feel bad about it, because Laxon and Rapley (1986) has only ever received that singular citation from Laxon himself in his thesis (per Google Scholar). The paper discusses how radar waves reflect from sea ice and ocean surfaces, and how we should handle that. Interestingly, it includes the words:
“Here we show that retracking may be achieved through the use of a library of model return waveforms fitted to the data using a least squares method”.
The more things change…
References
Stanley, R.H., Brooks, R.L and Brown, G.S “Ice Freeboard Determination by Satellite Altimetry” (1979) Proceedings of the International Workshop on Remote Estimation of Sea Ice Thickness, St. John’s, Newfoundland, Canada.
Laxon, S. W., and C. G. Rapley. "Radar altimeter data quality flagging." (1987) Advances in Space Research 7.11: 315-318.
Laxon, S. W., and C. G. Rapley. "Satellite altimeter measurements of the geoid in sea ice zones." Advances in space research 6.9 (1986): 99-102.
Laxon, Seymour William Clarke. Satellite radar altimetry of sea ice. PhD Thesis, University of London, University College London (United Kingdom), 1990.