The coastal mean dynamic topography in Norway observed by CryoSat-2 and GOCE

Martina Idžanović, Vegard Ophaug, Ole Baltazar Andersen

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Abstract

New-generation synthetic aperture radar altimetry, as implemented on CryoSat-2, observes sea surface heights in coastal areas that were previously not monitored by conventional altimetry. Therefore,CryoSat-2 is expected to improve the coastal mean dynamic topography (MDT). However, the MDT remains highly reliant on the geoid. Using new regional geoid models as well as CryoSat-2 data, we determine three geodetic coastal MDT models in Norway and validate them against independent tide-gauge observations and the operational coastal ocean model NorKyst800. The CryoSat-2 MDTs agree on the ∼3–5 cm level with both tide-gauge geodetic and ocean MDTs along the Norwegian coast. In addition, we compute geostrophic surface currents to help identifying errors in the geoid models. We find that even though the regional geoid models are all based on the latest satellite gravity data as provided by GOCE, the resulting circulation patterns differ. We demonstrate that some of these differences are due to erroneous or lack of marine gravity data. This suggests that there is significant MDT signal at spatial scales beyond GOCE, and that the geodetic approach to MDT determination benefits from the additional terrestrial gravity information provided by aregional geoid model. We also find that the border of the geographical mode mask of CryoSat-2 coincides with the Norwegian Coastal Current, making it challenging to distinguish between artifacts in the CryoSat-2observations during mode switch and ocean signal.
Original languageEnglish
JournalGeophysical Research Letters
Volume44
Issue number11
Pages (from-to)5609-5617
Number of pages9
ISSN0094-8276
DOIs
Publication statusPublished - 2017

Bibliographical note

©2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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