The Coastal Mean Dynamic Topography in Norway Observed by CryoSat-2 and GOCE

Vegard Ophaug, M. Idžanović, O. Andersen

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Abstract

The Norwegian Coastal Current (NCC) transports warm and relatively fresh water along the Norwegian coast and into the Barents Sea, with its origin in Baltic water entering Skagerrak. Along its way northward it is fed by additional freshwater discharge. The NCC is important for the regional marine ecosystem and contributes to the poleward transport of warm Atlantic Water, maintaining the relatively mild climate in northwest Europe. Although satellite altimetry is a mature technique, globally observing the sea surface height with an accuracy of a few centimeters, numerous effects degrade the observations in the coastal zone. For example, the radar footprint is contaminated by land and bright targets, and the range and geophysical corrections become difficult to model. The rugged Norwegian coast presents a further challenge, and the NCC, at times only a few tens of kilometers wide, typically falls into a zone where conventional altimeters do not deliver reliable observations. The European Space Agency's CryoSat-2 (CS2) satellite is the first to carry a SAR altimeter instead of the conventional pulse-limited system, resulting in higher range precision and along-track resolution. This allows for tracking finer structures of the sea surface and get closer to the coast. We use CS2 low resolution and SARIn observations along the Norwegian coast and determine a mean dynamic topography (MDT) that is validated using tide gauges. In turn, geostrophic surface currents are derived from both the CS2 MDT and the operational coastal numerical ocean model of the Norwegian Meteorological Institute, and compared. For the first time, the NCC is revealed by space-geodetic techniques, giving confidence in the new-generation SAR altimeters for coastal sea level recovery.
Original languageEnglish
Publication date2018
Number of pages1
Publication statusPublished - 2018
Event25 years of progress in radar altimetry symposium - , Portugal
Duration: 24 Sep 201829 Sep 2018

Conference

Conference25 years of progress in radar altimetry symposium
CountryPortugal
Period24/09/201829/09/2018

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