Climate modulates internal wave activity in the Northern South China Sea

Abstract

Internal waves (IWs) generated in the Luzon Strait propagate into the Northern South China Sea (NSCS), enhancing biological productivity and affecting coral reefs by modulating nutrient concentrations and temperature. Here we use a state-of-the-art ocean data assimilation system to reconstruct water column stratification in the Luzon Strait as a proxy for IW activity in the NSCS and diagnose mechanisms for its variability. Interannual variability of stratification is driven by intrusions of the Kuroshio Current into the Luzon Strait and freshwater fluxes associated with the El Niño-Southern Oscillation. Warming in the upper 100 m of the ocean caused a trend of increasing IW activity since 1900, consistent with global climate model experiments that show stratification in the Luzon Strait increases in response to radiative forcing. IW activity is expected to increase in the NSCS through the 21st century, with implications for mitigating climate change impacts on coastal ecosystems.

Mass coral mortality under local amplification of 2 °C ocean warming

“…Strategies designed to cap ocean warming have potential to reduce or at least delay these impacts1011, and some corals may be able to adapt to moderate rates of warming1012. Critically however, the thermal environments of many tropical coral reef ecosystems do not resemble those of the open ocean13141516171819. Limited by availability of light, tropical reefs form relatively shallow structures, even those perched atop undersea volcanoes whose bases stretch kilometers to the seafloor.…”

Validation of the remotely sensed nighttime sea surface temperature in the shallow waters at the Dongsha Atoll

“…Qualitatively, similar major distributional patterns were depicted in both cases. Thus, the coldest waters were found along the fore-reef and the reef-flat, where cold subsurface water might have been uplifted to the surface and washed over the reef-flat by the combined actions of the incoming and breaking internal waves, and tides (Pan et al 2012;DeCarlo et al 2015). The signal was especially prominent at the eastern and northeastern fore-reef and reef-flat, which were in the direct path of propagation of the internal waves.…”

“…In addition to exchanges through the North and South Channel at the western side of the DSA, tidal actions can also lead to exchanges between the water inside and outside of the lagoon over the reef-flat. Internal waves that are generated at the Luzon Straits propagate westward and impinge upon the DSA where they may undergo transformation and even destruction (Li et al 2008;Alford et al 2015;DeCarlo et al 2015). In fact, some of the strongest internal waves in the world are found in the waters around the DSA (Zhao and Alford 2006;Farmer et al 2011;Alford et al 2015).…”

“…1, Table 1) by using Onset Corporation HOBO U22 temperature loggers, which had been calibrated in a constant temperature bath to an accuracy of ±0.1°C (DeCarlo et al 2015(DeCarlo et al , 2017. The locations, nominal moored depths relative to the sea surface and the time-periods of the deployment of these loggers are shown in Table 1 and Fig.…”

Earth observation from the manned low Earth orbit platforms

“…It had been fully functional for nearly 5 years and collected approximately 10,000 hyperspectral scenes of the Earth from October 1, 2009 to its shutdown in September 2014 which was caused by an X-class solar storm. The HICO data have been used for various studies, including sensor calibration (Chen and Lucke, 2013;Gao et al, 2012), atmospheric correction (Amin et al, 2014), ocean internal waves (DeCarlo et al, 2015;Szekielda, 2012), seagrass mapping (Cho et al, 2014), seasonal changes in bathymetry (Garcia et al, 2014), water quality (Braga et al, 2013;Keith et al, 2014) and chlorophyll retrieval (Gitelson et al, 2011).…”