GEOCEAN-NC 2019 - Sea level evolution in Noumea Lagoon, an approach using high resolution along-track altimetry and in-situ measurements

Clémence Chupin (LIENSs, UMR CNRS - La Rochelle Université, France)


Valérie Ballu (LIENSs, UMR CNRS - La Rochelle Université, France); Laurent Testut (LEGOS/CNES, 31404 Toulouse, France); Yann-Treden Tranchant (LIENSs, UMR CNRS - La Rochelle Université, France); Jerome Aucan (LEGOS/Centre IRD de Nouméa, New Caledonia)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Coastal Altimetry

Presentation type: Type Forum only

Coastal sea-level evolution in the Pacific area is an unresolved issue, as altimetric, tide gauge and GNSS data on land do not provide consistent information (Aucan et al., 2017, Martinez-Asensio et al., 2019). The absolute sea-level rise estimated by altimetry differs from that given by the Noumea tide gauge of about 1.4mm/year (Aucan et al, 2017) and this difference is not explained by vertical movement trends estimated by GPS (Ballu et al., 2019).
For the moment, the processing of altimetric data in this area does not integrate either a local geoid or hydrodynamic model or a tropospheric correction different from the radiometer: there are therefore opportunities for improvements in the time series produced by satellite altimetry. Another unknown is related to the value and trend of the local elevation of the water body (setup) which may vary between the area where the tide gauge is installed and that sampled by the altimetry products.
The objective of the GEOCEAN-NC 2019 mission is to acquire in-situ measurements to answer these questions. To this end, we install 5 pressure sensors in the lagoon to quantify the setup and its variations. We also map sea-level height variations under 3 satellite tracks with the CalNaGeo coastal GNSS carpet and the Cyclopée system. In the scope of altimetry validation, we also acquire in-situ sea-level measurements during 4 satellites passes.
The purpose of this presentation is to present the first analyses of the altimetric data available in the Noumea area and to discuss these results. In particular, we look at the impact of the land when approaching the coast for the different satellites and the variation in SL trends with distance to the coast.
Clémence Chupin
LIENSs, UMR CNRS - La Rochelle Université