International Journal of Marine Science, 2024, Vol.14, No.3, 182-192 http://www.aquapublisher.com/index.php/ijms 185 several major coastal regions, such as the California, Humboldt, and Benguela upwelling systems, over the past 60 years. This intensification is attributed to the growing differences in temperature and pressure between land and sea, which drive stronger winds. These changes have profound implications for marine productivity and biodiversity in these regions (Sydeman et al., 2014). Additionally, changes in wind patterns can affect the general circulation and residence time in semi-enclosed seas, as seen in the Persian Gulf, where future wind field changes could significantly alter the region's capacity to flush out dissolved pollutants (Ranjbar et al., 2020). 5.2 Sea level rise and its effects Sea level rise, driven by climate change, poses a substantial threat to coastal ecosystems. Rising sea levels can lead to the loss of marsh habitats, increased intrusion of marine waters, and changes in circulation patterns that affect the retention of indigenous species. These changes can exacerbate hypoxia and increase the frequency and intensity of storm surges, further impacting coastal and estuarine systems. In the southeastern United States, for example, rising sea levels combined with changes in the frequency and intensity of tropical storms and hurricanes are expected to have significant impacts on coastal wetland patterns and processes, affecting hydrology, geomorphology, and nutrient cycling. Moreover, sea level rise can slightly decrease current velocities, leading to increased residence times in certain regions, as observed in the Persian Gulf (Ranjbar et al., 2020). 5.3 Ocean temperature and salinity changes Rising ocean temperatures and changes in salinity are critical factors influencing coastal circulation. Increased global air and ocean temperatures are expected to alter estuarine stratification, residence time, and eutrophication, impacting estuarine productivity and the distribution of marine species. Higher ocean temperatures can also lead to poleward shifts in species ranges, affecting predator-prey dynamics and overall ecosystem functioning. Additionally, surface warming is a dominant factor accelerating upper ocean currents, particularly in the subtropical gyres and equatorial currents, due to increased vertical stratification (Peng et al., 2022). Changes in ocean salinity, driven by altered precipitation patterns and freshwater input, can further influence regional current systems and circulation patterns (Peng et al., 2022). In summary, climate change is driving significant changes in coastal circulation through alterations in wind patterns, sea level rise, and ocean temperature and salinity. These changes have wide-ranging implications for marine ecosystems, biodiversity, and the services they provide to human societies. Understanding and mitigating these impacts will require comprehensive and interdisciplinary research efforts. 6 Case Studies 6.1 Coastal circulation in different regions Understanding coastal circulation in various regions is crucial for predicting and managing the impacts of climate change on coastal ecosystems. A study focusing on the Vanuatu and New Caledonia archipelagos utilized an unstructured-mesh finite-volume modeling approach to simulate coastal circulation. The findings indicated that tidal residual circulation was influenced by flow separation at headlands and islands, while wind-residual circulation was sensitive to wind speed and direction. The study highlighted the importance of wind patterns and sea level rise (SLR) in altering coastal currents and processes, which are critical for sediment transport, pollutant dispersal, and larval transport in these regions (Figure 1) (Lee et al., 2021). Lee et al. (2021) provided valuable data on the ocean current patterns and seabed topography of the Vanuatu and New Caledonia island regions through detailed modeling and grid analysis. The marine and atmospheric conditions in this area have a significant impact on local communities, especially against the backdrop of global mean sea level rise (SLR) that is higher than average. The research team developed the Van-Fvcom model, validated the model's capability to simulate tidal behavior through tidal gauge observational data, and analyzed the strength and patterns of wind residual circulation by simulating coastal circulation changes under different wind speeds and directions. The study also simulated the impact of 1 m and 2 m SLR on tidal characteristics and coastal ocean currents, analyzing changes in maximum depth-averaged flow velocity. The results not only contribute to scientific understanding but also provide important foundations for regional ecological protection and resource management.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==