Climate‐Driven Stratification Intensifies Internal Wave Cooling on a Shallow Island Reef

• Published in: Geophysical research letters Vol. 52; no. 14
• Main Authors: Rogers, Justin S., Tan, Shuwen, Davis, Kristen A., Pawlak, Geno, Fringer, Oliver B.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.07.2025; Wiley
• Subjects: Atolls; Benthic environment; Benthos; Bottom temperature; Climate; climate change; Cooling; coral reef; Global warming; Internal tides; Internal waves; Ocean temperature; Ocean warming; Oceans; Refuges; Refugia; Stratification; Surface temperature; Temperature changes; upwelling; Wave propagation; Waves
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2025GL115458

As ocean temperatures rise, understanding the cooling role of internal waves is crucial for reef preservation. Climate‐induced surface warming increases stratification, altering internal wave propagation. We use high‐resolution, nonhydrostatic simulations at Dongsha Atoll in the South China Sea to explore seasonal bottom temperature changes affecting benthic ecosystems for climate scenario SSP5‐8.5 for 2020 and 2100. Our findings show internal waves transport cooler, deeper waters into shallow areas, reducing warming by up to 2.3°C relative to conditions without waves. Enhanced stratification and internal tide forcing in a warmer, more strongly stratified ocean increases wave‐driven cooling by up to 0.5°C in shallow zones. Variability in bottom temperature are also enhanced by up to 4.5°C. However, net warming by 2100 is projected at up to 2.8°C in shallow areas and 0.9°C in deeper regions. Areas with strong internal wave activity could serve as thermal refugia, despite overall trends pointing to continued ocean warming. Plain Language Summary Coral reefs are some of the most vulnerable ecosystems to ocean warming, which is driven by climate change. In this study, we explore how underwater waves, called internal waves, affect water temperatures around Dongsha Atoll in the South China Sea. Using a model of the ocean, we looked at how internal waves and climate warming might impact water temperatures near the reef in 2020 and 2100. Internal waves bring cooler, deeper waters to the surface, which helps cool the shallows of the reef by up to 2.3°C compared to conditions without these waves. In a warmer future, stronger layering in the ocean enhances this cooling effect, adding another 0.5°C of cooling in shallow areas. We also found that future ocean warming will increase temperature fluctuations near the bottom, making them more variable by up to 4.5°C. Despite the cooling effects of internal waves, overall temperatures are expected to rise—up to 2.8°C in shallow areas and 0.9°C in deeper ones by 2100. While internal waves may create cool areas that help some reefs survive, the long‐term trend of ocean warming highlights the urgent need to address climate change. Key Points Internal waves create cooling effect up to 2.3°C compared to background with no waves Increased stratification in a warmer ocean enhances nonlinear wave cooling effect by up to 0.5°C Overall trend points to continued warming, emphasizing the critical need mitigate climate change