The 24th IAHR-APD Congress (24th IAHR-APD Congress)

180 / 2024-02-26 20:55:11

Assessing the Possibility of Summer Hypoxia Occurrence Due to Flooding Events in Coastal Waters Under Current Climate Projections

climate change,hypoxia,coastal water

Subtheme 5: Climate Change: Adaptation, Mitigation and Resilience > Topic 1: Hydrology and Water Resources response to climate change

Numerous studies have highlighted the profound impact of climate change-induced shifts in precipitation patterns on river and marine ecosystems. Recent years have witnessed hypoxic events in prominent water bodies such as the Gulf of Mexico, Mississippi, and Yangtze River basins, exacerbating the deterioration in water quality and posing a significant threat to fisheries, especially due to the adverse effects of hypoxia on benthic species and the broader ecosystem. The Ariake Sea, situated in Kyushu Island, western Japan, holds pivotal importance as a vital estuarine or inner bay-type region of freshwater influence (ROFI), crucial for sustaining fisheries and seaweed production. Climate change projections indicate an escalation in the frequency and intensity of flooding events, leading to heightened discharges from urban areas into the estuary. This surge in river discharge diminishes salinity levels and disrupts the halocline, hindering the vertical transfer of dissolved oxygen (DO) from surface layers to the seabed, thereby exacerbating hypoxia near the seafloor.

To assess the possibility of hypoxia events during the rainy season, this study utilizes an ensemble climate prediction database (d4PDF), which offers regional downscaling simulations covering the Japan area. Integrating a three-dimensional hydrodynamic model (employing Delft3D-FLOW) with a lower-trophic ecosystem model (employing Delft3D-WAQ), the study simulates DO dynamics in the Ariake Sea under current climate predictions. The findings suggest an increased possibility of hypoxia events, particularly larger-scale occurrences, with flood scale positively correlated with the likelihood of hypoxic events. This underscores the urgent need for implementing effective adaptation measures to mitigate the impacts of climate change on marine ecosystems and fisheries sustainability.