IIOSC - 2025

The Indian Ocean benefits millions of people through livelihoods, food security, transport and tourism. However, stressors in marine and estuarine ecosystems have increased in frequency or severity as a result of human activities. Marine ecosystem stressors that are of particular concern in the Indian Ocean include warming, sea-level rise, deoxygenation, acidification, eutrophication, atmospheric, hydrocarbon and plastic pollution, coastal erosion, mining, overfishing and habitat loss. These stressors, combined with other physical consequences of human activities, are affecting marine ecological processes from genes to ecosystems, over scales from lagoons to ocean basins, impacting ecosystem health and services and threatening human food security, which requires more observation and monitoring in coastal waters.

The session invites abstracts that explore the impacts of human-induced ocean stressors on the atmosphere, biogeochemistry, ecology and people of the Indian Ocean using observational data, monitoring, modelling, and management strategies including marine spatial planning to address these complex challenges

The Indian Ocean basin exhibits a unique geomorphology, and hosts a complex system of boundary currents, upwelling, and downwelling circulation processes. In the northern Indian Ocean, several boundary current systems are seasonally reversing, a a unique feature of monsoon-driven systems with profound biogeochemical and ecological consequences. These dynamic current systems strongly influence marine productivity. Many fisheries in the region are closely linked to boundary current behavior and upwelling variability, resulting in direct societal impacts.

The session invites abstracts that address the features and physics of boundary currents, eddies, and upwelling as well as their interactions with marine biogeochemical cycles, ecosystem processes, and resource use of the Indian Ocean. We particularly welcome contributions exploring the interaction of currents, upwelling variability, and ecosystems with events that span from local weather to climate scales.

The monsoon domain in the Indian Ocean is usually defined as northward of 10°S, where the circulation is characterised by seasonal reversing circulation patterns tied to the annual monsoon cycle. These monsoonal winds, exhibiting the largest annual amplitude of any subtropical and tropical climate feature, profoundly impact not only the Arabian Sea, the Bay of Bengal and the surrounding continent, but also the eastern side of the Indian Ocean basin, including Southeast Asia and Australia. Given that a significant fraction of the world's population lives in the coastal and interior regions of Indian Ocean rim countries, understanding monsoonal variability are critical as they directly impact ecosystems, food, freshwater and energy security as well as human health and livelihoods.

The session invites abstracts that address the drivers of monsoonal variability - present, past and future - and its influence on ocean physics, chemistry and biogeochemistry of the Indian Ocean, along with the effects on ecosystem response including fisheries and implications for human populations and regional economies.

The general circulation of the Indian Ocean remains the least understood among the open ocean basins. Its surface and deep currents are complex, variable with the monsoon winds driving seasonally reversing surface currents of the northern part of the Indian Ocean. In contrast, the southern part of the basin extending to the subtropical convergence is influenced by the zone of subtropical high atmospheric pressure, which forms a continuous belt around the globe during the Southern Hemisphere winter. A key feature of the global thermohaline circulation is the transport of warm, relatively fresh upper-ocean waters from the Pacific through the Indonesian Seas to the Indian Ocean. This transport, known as the Indonesian Throughflow is strongly modulated by large-scale climatic phenomena such as the East Asian monsoon, the Indian Ocean Dipole and the El Niño-Southern Oscillation all of which exert a strong influence on the transport, water properties and vertical stratification in this critical region.

The session invites abstracts to address past, current and expected future changes in the atmospheric and ocean circulation of the Indian Ocean, its relation to topography and connectivity with the Pacific, Atlantic and Southern Ocean and impact on biological productivity, carbon cycling, human activities and livelihoods including fisheries.

Extreme events can have disastrous effects on vulnerable populations, leading to loss of life, damage to infrastructure, habitat destruction and at times severe economic damage and financial burdens. These events are often driven by meteorological, seismic and hydrological processes such as severe tropical cyclones, extreme rainfall events, marine heat waves and cold water episodes, floods, droughts, tsunamis, storm surges with severe ecosystem consequences that include coral bleaching, ocean acidification, harmful algal blooms, and deoxygenation. The occurrence of these events ranges spatially from local to basin scales and temporally from days to climatic scales. The Indian Ocean region is particularly susceptible to these extremes, because of its unique oceanic and atmospheric circulation patterns, geomorphology and the large populations living in the coastal region making them particularly vulnerable. Many middle- and low-income countries with sizeable populations bordering the Indian Ocean face disproportionate risks, with cascading impacts on ecosystem as well as the human well-being.

The session invites abstracts to address the frequency and/or severity of extreme events and their subsequent impacts on coastal and open ocean ecosystems. We also welcome abstracts addressing the impacts of rare but high impact events such as volcanic eruptions, tsunamis and storm surges, with particular focus on human vulnerability, adaptation, and mitigation strategies in low-lying coastal zones and small island nations of the Indian Ocean region.

The Indian Ocean hosts a range of unique geomorphological features, such as seamounts, ridges, plateaus and shelf canyons that strongly influence circulation, mixing and upwelling that result in unusual and contrasting productivity regimes that are atypical of surrounding areas. They often serve as important habitats and provide aggregation sites for feeding and reproduction of migratory biota. The tectonically active mid-ocean ridges and their associated hydrothermal vent circulations inject trace metals and reduced compounds into the deep ocean, yet their biogeochemical impacts remain largely unknown. Similarly, the subtropical gyre, shaped by large-scale atmospheric circulation, sustains an expansive oligotrophic zone that profoundly influences regional biogeochemistry, although its trophic implications are still not well understood. The session invites abstracts to address the unique geological, physical, biogeochemical, and ecological features of the Indian Ocean and their influential roles in circulation, mixing, carbon and oxygen dynamics, ocean-atmosphere coupling, biogeochemistry, habitats, taxonomy of new species and ecological processes.

The United Nations Decade of Ocean Science for Sustainable Development (2021-2030) seeks to catalyze transformative ocean science and knowledge that halts or reverses the decline of ocean health and unlocks new opportunities for sustainable use of massive marine ecosystems and resources. Serving as a global framework, the Ocean Decade aims to foster collaboration among scientists and stakeholders from diverse sectors to develop the scientific knowledge, and the partnerships needed to accelerate and harness advances in ocean science to achieve a better understanding of the ocean system and deliver science-based solutions to the challenges and contribute to achieving the 2030 Agenda for Sustainable Development.

The session invites abstracts to address the benefits to society of the knowledge gained from the various studies of IIOE-2 and how they can be maximised and sustained. Contributions could include innovative ideas to generate useful information/products and actionable tools from existing knowledge at the science / policy and science innovation interfaces. The session also invites abstracts proposing new observations, innovative approaches, modelling frameworks or data integration efforts that enhance the translation of science to benefit society, particularly in support of the blue economy, sustainable fisheries and climate resilience.

The marginal seas are partially enclosed bodies of water adjacent to the main ocean basin and play a vital role in regulating regional climate, supporting marine biodiversity and sustaining the livelihoods of coastal populations In the Indian Ocean, major marginal seas include the Andaman Sea, the Arabian/Persian Gulf, the Gulf of Aden, the Red Sea, and the Sea of Oman. Despite their significance, these dynamic and ecologically rich systems remain relatively underexplored compared to other regions of the Indian Ocean. Advancing our understanding of their complex physical, biogeochemical and ecological processes is critical for informed stewardship and regional sustainability.

The session invites abstracts to address key areas such as geological, physical, chemical and biological oceanography in the marginal seas of the Indian Ocean. We welcome studies that assess the impacts of climate change and human activities on the marginal seas and those that propose strategies for conservation, sustainable management, and resilience building in these vital and vulnerable regions of the Indian Ocean.

Mapping of the Indian Ocean seabed and associated habitats is crucial for understanding geological structures, marine biodiversity, and environmental change. The seabed is characterized by a wide array of features, including abyssal plains, mid-ocean ridges, deep trenches, and submerged plateaus that play a significant role in oceanic circulation and marine ecosystems. Further, the Indian Ocean hosts various habitats, including coral reefs, coastal seagrass meadows, hydrothermal vents, and deep-sea habitats, which require mapping to assess their distributions and ecosystem health. Recent advancements in satellite technology, sonar imaging, and underwater exploration have enhanced the resolution and accuracy of seabed and benthic habitat mapping, offering new opportunities for assessment of ecosystem health, informing conservation planning and guiding of efforts for sustainable resource management. The Indian Ocean has considerable ecological and economic importance, and thus, comprehensive mapping will assist in protecting marine biodiversity, mitigating climate change effects, and supporting sustainable resource use.

The session invites abstracts to address the distribution and variability of various seabed features and ecological habitats of the Indian Ocean by using various techniques such as satellite-based mapping, sonar imaging, modelling and other modern analytical tools.