Rapport de mesures dans le lagon de Hienghène-Touho - Province Nord - Nouvelle-Calédonie. SPHYNX - Suivi des Paysages HYdrologiques des lagons Nord

Ce rapport fait partie du projet de recherche PRESENCE (PRessions sur les Ecosystèmes récifaux et lagonaires de Nouvelle-CalédoniE). L'objectif de ce projet est de mieux appréhender le fonctionnement des lagons de Nouvelle-Calédonie à partir d’observations in-situ, de télédétection et de modélisation hydrodynamique. Ce rapport présente les mesures effectuées sur les lagons de Touho à Pouébo situés sur la côte Est de la Province Nord de Nouvelle-Calédonie, secteur sur lequel les connaissances et observations du fonctionnement hydrodynamique étaient assez parcellaires. Les données seront utilisées par la suite pour mieux appréhender la dynamique de ce grand lagon mais également à des fins de calibration et de validation de modèle hydrodynamique

Hydrodynamic and hydrological processes within a variety of coral reef lagoons: Field observations during 6 cyclonic seasons in New Caledonia

Abstract. From 2014 to 2021, extensive monitoring of hydrodynamics was deployed within a variety of lagoons of New Caledonia during 6 tropical cyclone seasons. Globally, those coastal physical observations encompassed five different lagoons (four of which were never monitored before) and at least eight major atmospheric events ranging from tropical depression to category 4 cyclone. The main objectives were to characterize the processes at stake controlling hydrodynamics and hydrology of these lagoons (e.g ocean-lagoon exchanges, circulation, level dynamics, temperature and salinity variability) and capture their magnitude of change during extreme events. An additional objective was to build an adequate data set for assessment of high-resolution hydrodynamics models. Those field experiments took place within the PRESENCE project (PRESsures on coral Ecosystems of New CalEdonia) which aimed at building an efficient representation of the land-lagoon-ocean continuum of Grande Terre (main land) lagoons. Autonomous oceanographic instruments were moored at strategic locations to collect time-series of temperature, salinity, pressure, eulerian currents which characterize hydrodynamics at best. During field trips, whenever possible, lagrangian drifters releases and cross-shore hydrological profiles radials were additionally carried out. Surveys begun chronologically with SPHYNX campaign which lasted 15 months (December 2014 to February 2016) in the Hienghène-Touho lagoon followed with 5 months records in NOUMEA lagoon (December 2016 to April 2017). ELADE campaign in Poe lagoon encompassed 2 periods of measure (February to April 2018 and June to August 2018). In Koumac lagoon, CADHYAK survey was carried out between December 2019 until the end of May 2020 and finally, data have been recorded continuously for 9 months in Moindou lagoon (NEMO) (September 2020 to April 2021). In addition to characterize these lagoons, this data set stresses out some important features and processes, such as the presence of internal waves on reef slopes, wave-driven fluxes over reef barrier and exchanges through passes. It also contains the signatures of strong events materialized by surges, thermal drops inside lagoons or massive flash flood plumes dispersion. Raw data sets were processed, quality-controlled and validated, and processed files are publicly available in dedicated repositories on Seanoe in NetCDF format. Links (DOI) of individual data sets are provided herein