Updated outline of climate and oceanic conditions to March 2022 for the Indian Ocean, with perspectives on climate change effects on fish catch potential in Maldives and in three coastal upwelling systems

The updated descriptors of ocean status indicate that the Indian Ocean Dipole has been in a neutral phase since 2020, with dominant normal conditions in sea surface temperature. The Dipole is predicted to enter a negative phase in May 2022 until the end of the year, potentially causing thermocline shoaling in the West IO and deepening in the East IO. The thermocline fluctuated in opposite ways between East and West IO. Shallow thermocline conditions took place in the Central IO from March to October 2021, shifting to the West IO in the first quarter of 2022. A strong positive dipole in 2019 boosted (depleted) the plankton production in the East IO (West IO). In 2021, there was higher chlorophyll concentration than normal in the East (+12%) and in the West IO (+8%), and values around the average in the ISSG (+3%) and the Mozambique Channel (-2%). Potential impacts of projected climate change scenarios on fish catch potential over the 21st century are discussed in several regions. In Maldives, the net primary production is projected to decline by ~50% under a high warming scenario (RCP 8.5) and an unsuitable habitat for skipjack tuna to expand over the 21st century. In Oman, the coastal upwelling is projected to intensify, potentially stimulating the biological response at the base of the food web. Conversely, the same simulations foresee a weakening of the Somali upwelling. The South Java upwelling would intensify under the influence of more frequent strong positive Dipole events through the century. There, the response in terms of fish catch potential is subject to debate, either a continuous decline over the century, or an increase to 2025 with a return to current situation in 2050, depending on the structure and the spatial resolution of the ecosystem model used.