Development of an ENVISAT altimetry processor providing sea level continuity between open ocean and Arctic leads

• Published in: IEEE Transactions on Geoscience and Remote Sensing
• Main Authors: Poisson, JC, Quartly, GD, Kurekin, A, Thibaut, P, Hoang, D, Nencioli, F
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Earth Observation - Remote Sensing; Oceanography; Arctic; Arctic Ocean; Climate change; Sea ice
• Online Access: http://plymsea.ac.uk/id/eprint/7750/; http://plymsea.ac.uk/id/eprint/7750/13/Published%20version.pdf; http://ieeexplore.ieee.org/document/8328007/; https://doi.org/10.1109/TGRS.2018.2813061

Over the Arctic regions, current conventional altimetry products suffer from a lack of coverage or from degraded performance due to the inadequacy of the standard process- ing applied in the ground segments. This paper presents a set of dedicated algorithms able to process consistently returns from open ocean and from sea ice leads in the Arctic Ocean (detection of water surfaces and derivation of water levels using returns from these surfaces). This processing extends the area over which a precise sea level can be com- puted. In the frame of the ESA Sea Level Climate Change Initiative (CCI, http://cci.esa.int), we have first developed a new surface identification method combining two complementary solutions, one using a multiple criteria approach (in particular the backscattering coefficient and the peakiness coefficient of the waveforms) and one based on a supervised neural net- work approach. Then, a new physical model has been developed (modified from the Brown model to include anisotropy in the scattering from calm protected water surfaces) and has been implemented in a Maximum Likelihood Estimation retracker. This allows us to process both sea-ice lead waveforms (characterized by their peaky shapes) and ocean waveforms (more diffuse returns), guaranteeing, by construction, continuity between open ocean and ice-covered regions. This new processing has been used to produce maps of Arctic sea level anomaly from 18Hz ENVISAT/RA-2 data