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This study evaluates the ability of Earth System Models (ESMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to simulate biogeochemical variables in the southern South China Sea (SCS). The analysis focuses on chlorophyll, phytoplankton, nitrate, and oxygen at annual and seasonal scales. The models' performance is assessed against Copernicus Marine Environment Monitoring Service (CMEMS) data using statistical metrics such as the Taylor diagram and Taylor skill score. The results show that the models generally capture the observed spatial patterns of biogeochemical variables but exhibit varying degrees of overestimation or underestimation. The performance of the models is also influenced by the season, with some models showing better performance during the southwest monsoon than the northeast monsoon. Overall, the top five best-performing models for biogeochemical variables are MIROC-ES2H, GFDL-ESM4, CanESM5-CanOE, MPI-ESM1-2-LR, and NorESM2-LM. The findings of this study have implications for researchers and end-users of the datasets, providing guidance for model improvement and understanding the impacts of climate change on the SCS ecosystem. [ABSTRACT FROM AUTHOR]

Mansor, K.N.A.A.K.; Roseli, N.H.; Ali, F.S.M., and Akhir, M.F.M., 2023. Physical properties of seawater in Malacca Strait (Southeast Asia) during monsoon seasons. Journal of Coastal Research, 39(5), 921–932. Charlotte (North Carolina), ISSN 0749-0208. Malacca Strait (MS) is a narrow passage in Southeast Asia mainly influenced by the Asian monsoon system. As a busy international maritime route, MS is highly exposed to seawater pollution, harmful algal blooms, and jellyfish blooms. To understand the physical properties of the water column in MS, scientific cruise data were used to examine mixed layer depth, stratification frequency, and water mass distribution during two monsoon seasons (March and August). Results showed that surface water in March is fresher and warmer than in August, whereas the bottom depth in March is more saline and cooler than in August. The mixed layer depth for both months did not exceed approximately 15 m for temperature and salinity, with thermocline and halocline layers observed below the mixed layer depth. The temperature and salinity diagram classified three water masses from the cruise dataset—surface warm water, mixed water, and subsurface water—with the potential density anomaly ranging between about 15.5 and 24 kg/m3. The highest density of water mass, subsurface water, was found only in March at a depth between 54 and 80 m. This cool, high-salinity water is the remaining NE monsoon water mass that settled near the bottom because March is the period of change from NE monsoon to SW monsoon. During this time, winds weaken and solar radiation increases, thus creating stable warm surface water. Strong stratification observed in March prevented mixing between warm surface water and cool bottom water. Meanwhile, August is characterized by a warm SW monsoon; thus, the whole MS is occupied by warmer water. This research presents the variation of physical properties in the water column and reveals the influences of monsoon season on shifts of stratification and water mass distribution. [ABSTRACT FROM AUTHOR]

This paper describes the morphodynamic changes that took place along Kuala Terengganu coastline over daily periods during seasonal monsoons (onset of Northeast Monsoon in October 2014 and during Southwest Monsoon in May 2015). Cross-shore beach profiles had been determined and foreshore sediments were sampled from two selected beaches; north of Kuala Terengganu at Pengkalan Maras (PM) and another to the south at Kuala Ibai (KI). Based on the beach classification scheme, PM appeared to be a spilling breaker type beach (ξb) with an Intermediate state (Ω), whereas KI belonged to the plunging breaker type (ξb) with Intermediate-Dissipative state (Ω). The beaches were dominated by coarse and fine sands at PM and KI, respectively. The wave hydrodynamics on the southern beach (KI) was characterised by higher Hb values, when compared to that in the north (PM). This study investigated the impact of morphodynamic changes during seasonal monsoons, regardless of the presence of coastal defence structures. Without any coastal defence structure (revetment), the PM beach exhibited attainment of equilibrium state, when compared to the KI beach. Therefore, coastal structures, such as revetments, directly modified the morphodynamics at KI beach. The PM beach displayed the tendency for occurrence of erosion during the Northeast Monsoon, while exhibited accretion during the Southwest Monsoon. This scenario differed from that noted at the KI beach, which signified erosion during both seasonal monsoons. The study outcomes may assist in formulating an effective coastal zone management plan for monsoon-dominated coasts, particularly sandy beaches. [ABSTRACT FROM AUTHOR]

This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM) is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW) indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST) was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast. [ABSTRACT FROM AUTHOR]