Circulation in a Tidally-Flushed Atoll Lagoon

Sarah Ruth Merrigan, University of California, Irvine, Civil & Environmental Engineering, Irvine, CA, United States, Kristen A Davis, University of California Irvine, Civil and Environmental Engineering, Irvine, United States, Geno R Pawlak, University of California San Diego, Mechanical and Aerospace Engineering, La Jolla, CA, United States and Gregory Sinnett, University of California Irvine, Civil and Environmental Engineering Department, Irvine, CA, United States
Abstract:
The tidally flushed lagoon of the Dongsha Atoll, located in the South China Sea, is at times hypoxic and is also affected by variable wind patterns, internal wave interaction, and flow over the reef crest making it an ideal environment for characterizing causes of hypoxia. During 2014 a significant hypoxic event occurred in the atoll lagoon, causing seagrass die off and fish kills. To examine driving physical forces associated with these types of events, a field experiment was conducted during the summer of 2019 instrumenting the lagoon and outer forereef. Here we show how circulation patterns and stratification influenced by wind, tides, and temperature variability within and surrounding the lagoon and apply findings to understand the cause of hypoxic pocket events inside the lagoon.
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