This document presents a preliminary climate change characterization of the Southern Indian Ocean focusing on temperature-related climatic impact-drivers, notably warming, climate velocities, and marine heatwaves. The analysis is performed on both observations and CMIP6 model outputs.
• A CMIP6 multi-model analysis over the Southern Indian Ocean indicates an average surface temperature further increase of about 1°C (relative to 1995-2014) and approximately 200 days per year affected by marine heatwaves by the end of the century and under the modest mitigation scenario (SSP2-4.5).
• The subantarctic zone, north of the Antarctic Circumpolar Current, is the most affected by warming (models and observations).
• Isotherms are drifting poleward at an average speed of about 10 km/decade (observations, 1982-2021).
• Mesopelagic (200 - 1000 m) temperatures are expected to change faster than surface (0 - 200 m) temperatures (up to 1.8 times faster under SSP2-4.5 at the end of the century) .
• Future warming trends between SSP-4.5 and SSP1-2.6 are similar on the short or medium term but diverge in the long term (end of century).
• Essential to more effective and future-proof conservation is (i) a better understanding of warming and marine heatwaves impacts on ecosystems, (ii) the maintaining of long term (multi-decadal) observing systems and (iii) the development of regional climate change modelling tools.