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This paper reviews both the recent and longer-term (Holocene) ecological history of coral reefs in the South China Sea (SCS). (1) Local ecological monitoring since the 1960s shows that the coral reefs in the South China Sea have declined dramatically, reflecting the rapid decrease of living coral cover and the great loss of symbiotic zooxanthellae. Collectively, this has led to a significant decrease of annual CaCO production. Heavy anthropogenic activities and global warming are recognized as major triggers of the observed coral reef degradation. Observations show that the modern coral reefs in the SCS are a source of atmospheric CO in summer. (2) Coral reefs of the SCS have been widely used to reveal longer-term environmental variations, including Holocene high-resolution sea surface temperature (SST) and abrupt climate events, millennial-scale El Niño variations, millennial- and centennial-scale sea level oscillations, strong and cyclic storm activities, East Asian monsoon intensities, variation in seawater pH, and recent seawater pollution. (3) Coral reefs of the southern SCS have experienced repeated episodes of bleaching over the last 200 years due to high SST and intense El Niño events; coral reefs of the northern SCS suffered high levels of mortality during several abrupt winter cold-water bleaching events during the middle Holocene warm period. On average, recovery after the middle Holocene cold-bleaching took 20-30 years; recovery following other middle Holocene environmental stresses took approximately 10-20 years. Such findings have significantly contributed to the understanding of the present ecological pressures faced by the coral reefs in the SCS, the histories of Holocene climate/environment changes, and the long-term models of coral reef responses to various past environmental changes. [ABSTRACT FROM AUTHOR]

The two key mechanisms for biologically driven carbon sequestration in oceans are the biological pump (BP) and the microbial carbon pump (MCP); the latter is scarcely simulated and quantified in the China seas. In this study, we developed a coupled physical-ecosystem model with major MCP processes in the South China Sea (SCS). The model estimated a SCS-averaged MCP rate of 1.55 mg C m−2 d−1, with an MCP-to-BP ratio of 1:6.08 when considering the BP at a depth of 1000 m. Moreover, the ecosystem responses were projected in two representative global warming scenarios where the sea surface temperature increased by 2 and 4°C. The projection suggested a declined productivity associated with the increased near-surface stratification and decreased nutrient supply, which leads to a reduction in diatom biomass and consequently the suppression of the BP. However, the relative ratio of picophytoplankton increased, inducing a higher microbial activity and a nonlinear response of MCP to the increase in temperature. On average, the ratio of MCP-to-BP at a 1000-m depth increased to 1:5.95 with surface warming of 4°C, indicating the higher impact of MCP in future ocean carbon sequestration. [ABSTRACT FROM AUTHOR]

Whether the Madden‐Julian oscillation (MJO) propagates into the western Pacific or is blocked by the Maritime Continent (MC) can have great impacts on global weather and climate. This study investigates the extratropical circulations associated with the MJO events that propagate across the MC (MJO‐C) and those blocked by the MC (MJO‐B), respectively, during the boreal winter. The results show that there are significant northeasterly anomalies over the South China Sea and tropical western North Pacific when MJO‐C events propagate through the MC. The MJO‐C events are much more likely to be accompanied by cold surges during its propagation over the MC, following the intensification of the Siberian High. This study suggests that cold surges, which have been documented as a trigger of tropical convection, can help the MJO propagate across the MC. [ABSTRACT FROM AUTHOR]

Global gridded daily mean data from the NCEP/NCAR Reanalysis (1948–2012) are used to obtain the onset date, retreat date and duration time series of the South China Sea summer monsoon (SCSSM) for the past 65 years. The summer monsoon onset (retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly (westerly) to westerly (easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K (less than 335 K) in the South China Sea area [110–120° E (10–20° N)]. The clockwise vortex of the equatorial Indian Ocean region, together with the cross-equatorial flow and the subtropical high, plays a decisive role in the burst of the SCSSM. The onset date of the SCSSM is closely related to its intensity. With late (early) onset of the summer monsoon, its intensity is relatively strong (weak), and the zonal wind undergoes an early (late) abrupt change in the upper troposphere. Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity. With climate warming, the number of early-onset (-retreat) years of the SCSSM is clearly greater (less), and the SCSSM is clearly weakened. [ABSTRACT FROM AUTHOR]

The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate. [ABSTRACT FROM AUTHOR]