WP1: Exposure to MHW thermal stress

Two Simultaneous Climate Events Trigger a Catastrophic Marine Heatwave

In 2016, the Southwest Pacific experienced an unprecedented marine heatwave caused by the co-occurrence of two major climate phenomena: El Niño and the negative phase of the Madden-Julian Oscillation. This exceptional situation led to an abnormal increase in ocean surface water temperatures (30-50 m), which remained at record-high levels throughout February 2016.

MAHEWA: Monthly Monitoring in the Nouméa Lagoon Combining Physical and Biological Parameters to Assess and Understand the Impact of Marine Heatwaves

A monthly monitoring effort in the Nouméa lagoon, combining physical and biological parameters to assess and understand the impact of marine heatwaves.

With sea outings scheduled monthly throughout the project—and more frequently during marine heatwaves—these missions bring together researchers, engineers, and divers from IFREMER and IRD to collect physical and biological data. The aim is to understand the influence and impact of marine heatwaves on lagoon ecosystems and their signatures from the coast to the open sea.

The MaHeWa Project in Action in Lifou – MaHeWa

The MaHeWa project kicked off in Lifou, Loyalty Islands Province! At the end of November 2024, a team of two IFREMER scientists embarked on a mission with two key objectives: 1) to inform managers and stakeholders from local communities about the general goals of the MaHeWa project, and 2) to deploy thermographs at two sites of interest.

Deployment of an Argo Float to Monitor the Marine Heatwave South of New Caledonia

As part of WP1, which focuses on exposure to thermal stress, an Argo float was deployed on 30 November 2025 from the research vessel Antea during the KASEAOPE3 mission, in order to document the ongoing marine heatwave south of New Caledonia. This event is currently classified as moderate to strong, with temperature anomalies reaching +3°C at the surface according to OSTIA analyses from 25 November 2025 (Copernicus Marine Service). This deployment offers a unique opportunity to observe the vertical structure of the warming associated with this MHW.