Asymmetric chlorophyll responses enhanced by internal waves near the Dongsha Atoll in the South China Sea

Internal waves(IWs)are small-scale physical processes that occur frequently in stratified marginal seas.IWs are ubiquitous and well documented in the northern South China Sea(n SCS),but few studies have explored the ecosystem responses to the IWs.MODISA chlorophyll-a(Chl-a)data from 2002 to 2014 were used to examine the distribution of Chl a near the Dongsha Atoll(DSA).Composite Chl a from about 40 IWs during spring and summer showed stronger response on the northern side than on the southern side of the DSA.One day after the passage of IWs,composite surface Chl a on the northern side increased from 0.11 mg/m3 to a maximum mean value of 0.18 mg/m3.It decreased to 0.13 mg/m3 after two days and maintained that level for several days after the passage of IWs.The enhanced surface Chl a likely caused subsurface Chl-a maximum and nutrients in the surface layer.Approximately 64%of the increase in surface Chl a was due to the uplift of the subsurface Chl-a maximum one day after the passage of IWs,while nutrient-induced new phytoplankton growth contributed about 18%of the increase a few days later.When the IWs occurred frequently in spring and summer,Chl-a level on the northern side was about 30%higher than that on the southern side.IW dissipation and its impact on nutrients and chlorophyll were stronger on the northern side of the DSA than on the south,which caused a north-south asymmetric distribution of Chl a in the region.

Cross-shelf variation of internal tides west of the Dongsha Plateau in the northern South China Sea

We examine the cross-shelf variation of internal tides(ITs)west of the Dongsha Plateau in the northern South China Sea based on observations from 4 moorings deployed between August 2017 and September 2018.On the slope,the amplitude of diurnal baroclinic current ellipses are 5 times larger than that of barotropic currents.The baroclinic energy quickly dissipates during cross-shelf propagation,and barotropic currents become dominant on the shelf outside of the Zhujiang River Estuary,with the amplitude of semidiurnal barotropic current ellipses being 10 times larger than that of the baroclinic ones.Dynamic modal decomposition indicates the first baroclinic mode is dominant for both diurnal and semidiurnal ITs.The total horizontal kinetic energy(HKE)of the first three baroclinic modes shows spatiotemporal differences among the 4 moorings.On the slope,the HKE for diurnal ITs is stronger in summer and winter,but weaker in spring and autumn;for semidiurnal ITs there is a similar seasonal variation,but the HKE in winter is even stronger than that in summer.On the shallow shelf,both diurnal and semidiurnal ITs maintain a certain intensity in summer but almost disappear in winter.Further analysis shows that only the upper water column is affected by seasonal variation of stratification on the slope,variation of diurnal ITs is thus controlled by the semi-annual cycle of barotropic energy input from the Luzon Strait,while the incoherent baroclinic currents make a major contribution to the temporal variation of semidiurnal ITs.For the shelf region,the water column is well mixed in winter,and the baroclinic energy largely dissipates when ITs propagate to the shelf zone despite of a strong barotropic energy input from the Luzon Strait.

Properties of Phase Transformation of Ferroelectric Thin Films with Surface Layers

Using the generalized Ginzburg-Landau-Devonshire theory, the characteristics of phase transformation of a ferroelectric thin film with surface layers are investigated. We study the effect of the surface layer on the properties (coercive field, critical thickness) of a ferroelectric thin film. Our theoretical results show that the surface layer is likely to answer for the emergence of phase transformation.

Saco-Casco Bays Inundation Modeling of Five Winter Storms

Coastal inundation along the northeast coast of the United States is usually caused by strong winter storms(WS).However,the accurate prediction of coastal inundation due to the WS is challenging.Therefore,our study aims to develop a unique high-resolution modeling system to accurately predict the coastal inundation in the ungauged coastal areas of Saco-Casco Bays and map the flood risk zones to potential sea level rise due to these storms.Hindcasts of five classic WS in 2014-2015 were studied.The inundation models are based on FVCOM that uses unstructured grid to capture the minor to significant flooding near the shallow areas of the bays,harbor entrance and river banks.In this study,topography has been generated from the NOAA’s integrated dataset of Portland,ME 1/3 arc-second MHW digital elevation model.The model runs were driven by two different sets of meteorological(NECOFS WRF and NOAA’s NAM WRF)forcing to examine the effect of spatial resolution on the predicted inundation.The study reveals that among the five storm surge cases,WS-III produces a maximum surge of 0.7 m and WS-II cause a minimum surge of 0.3 m.In all scenarios,southward wind-driven coastal current flowing towards Biddeford Pool,Pine Point and Camp Ellis forms a small-scale eddy which causes significant inundation however strength of the current varies accordingly.Sensitivity experiments have been carried out using NECOFS WRF simulation products with varying parameters of marshland elevation and bottom friction to understand the influence of intertidal storage on the predicted flooding.

Integrating multi-modal information to detect spatial domains of spatial transcriptomics by graph attention network

Recent advances in spatially resolved transcriptomic technologies have enabled unprecedented opportunities to elucidate tissue architecture and function in situ.Spatial transcriptomics can provide multimodal and complementary information simultaneously,including gene expression profiles,spatial locations,and histology images.However,most existing methods have limitations in efficiently utilizing spatial information and matched high-resolution histology images.To fully leverage the multi-modal information,we propose a SPAtially embedded Deep Attentional graph Clustering(SpaDAC)method to identify spatial domains while reconstructing denoised gene expression profiles.This method can efficiently learn the low-dimensional embeddings for spatial transcriptomics data by constructing multi-view graph modules to capture both spatial location connectives and morphological connectives.Benchmark results demonstrate that SpaDAC outperforms other algorithms on several recent spatial transcriptomics datasets.SpaDAC is a valuable tool for spatial domain detection,facilitating the comprehension of tissue architecture and cellular microenvironment.The source code of SpaDAC is freely available at Github(https://github.com/huoyuying/SpaDAC.git).

Advances in research of the mid-deep South China Sea circulation

The South China Sea(SCS)is a large marginal sea connecting the Indian and Pacific oceans.Under the factors of monsoons,strait transport,and varied bathymetry,the SCS presents a three-layer structure and strong diapycnal mixing which is far greater than that in the open ocean.Theoretical analysis and observations reveal that internal tides,internal solitary waves,and strong winds are the sources of the strong mixing in the northern SCS.A major consequence of the strong mixing is an active mid-deep circulation system.This system promotes exchange of water between the SCS and adjacent oceans,and also regulates the upper layer of wind-driven circulation,making the 3 dimensional SCS circulation clearly different from that in other tropical and subtropical marginal seas.The mass transport capacity of the mid-deep circulation has a substantial impact on marine sedimentation,the biogeochemical cycle,and other processes in the SCS.This paper summarizes the recent advances in middeep sea circulation dynamics of the SCS,and discusses the opportunities and challenges in this area.