As part of the MaHeWa project, an Argo float was deployed on 30 November 2025 from the research vessel Antea, during the KASEAOPE3 mission, south of New Caledonia. This deployment takes place in the midst of a marine heatwave, currently classified as moderate to strong, with temperature anomalies reaching up to +3°C at the surface.
Monitoring the marine heatwave… beneath the surface
Satellites can measure sea-surface temperature, but they do not provide information on what is happening deeper in the water column, where marine organisms live, move, and experience thermal stress. The deployed Argo float will:
measure temperature, salinity and pressure down to 2,000 m depth,
document the vertical structure of the ongoing marine heatwave by profiling daily down to 500 m for 15 days,
monitor the evolution of the water column during the event, from the surface to the ocean interior.
These repeated profiles will provide essential data to understand how heat accumulates or dissipates in the ocean around New Caledonia.
An opportunistic and strategic deployment
The float was released at night from the vessel’s aft deck, thanks to a coordinated operation between the scientific team of the KASEAOPE3 mission and the crew on board. This deployment also contributes to the global Argo network, an international reference programme for ocean monitoring.
Photo credit: Inès Mangolte
In line with the MaHeWa project, these data will complement the information required for WP1.
Regarding the current marine heatwave around New Caledonia, and based on the OSTIA analyses of 25 November 2025 (Copernicus Marine Service):
The region shows a positive average anomaly,
Some areas in the west, south and southwest of Grande Terre reach +3°C at the surface,
Marine heatwave categories range from moderate to strong, with localized severe cores in the southwest.
These conditions confirm the need to monitor the event at depth — exactly what this Argo float will enable.
