Yellow Sea Bottom Cold Water Research Articles

Dissolved organic matter in the northwestern Pacific marginal seas: Insight into the distribution of its optical properties

Dissolved organic carbon (DOC) and the optical properties of dissolved organic matter (chromophoric- and fluorescent dissolved organic matter; CDOM and FDOM) were measured to determine the distributions and drivers of DOM in the northwestern Pacific marginal seas, including the East China Sea, the Yellow Sea, and the East/Japan Sea, in August 2020. In this study, the concentrations of DOC and CDOM/FDOM in surface water showed good correlations with salinity, indicating a predominant contribution from the Changjiang River. However, significantly high concentrations of DOC and FDOM were also observed in the central Yellow Sea region, which seems to be produced mainly from the continental shelf-water and enriched over the water residence time of the Yellow Sea, while the lowest concentrations of DOC and CDOM/FDOM were found in high-salinity waters near the southern sea of Korea. In addition, the East/Japan Sea showed relatively low DOC concentrations and high FDOM values. To distinguish the physical mixing and biogeochemical processes of DOM, we estimated the water mass fractions using an optimum multi-parameter analysis with hydrological and DOM parameters of the major water masses in this region. Our results showed that five primary external drivers of DOM distribution were intrusions of (1) the Changjiang diluted water and (2) the Kuroshio Current water in the surface water, the mixing of (3) the Yellow Sea bottom cold water and (4) the Kuroshio sub-surface water in the bottom layer, and (5) upwelling of the East/Japan Sea water. We conclude that the distribution of DOM is significantly influenced by the mixing of multiple water masses, and the optical signature of DOM can be an effective proxy for tracing the origins and characteristics of DOM in this region.

Variations in aragonite saturation state and its controlling factors in the South Yellow Sea in spring and autumn

To assess the progression of ocean acidification in the South Yellow Sea (SYS), the aragonite saturation state (Ωarag) was determined from dissolved inorganic carbon (DIC) and total alkalinity (TA) in the surface and bottom waters of the SYS in spring and autumn. The Ωarag exhibited large spatiotemporal variations in the SYS; DIC was a major factor controlling the Ωarag variations, whereas temperature, salinity, and TA were minor factors. Surface DIC concentrations were mainly influenced by the lateral transport of the DIC-enriched Yellow River waters and DIC-depleted East China Sea Surface Water; bottom DIC concentrations were affected by aerobic remineralization in spring and autumn. Ocean acidification is now seriously progressing in the SYS, particularly in the Yellow Sea Bottom Cold Water (YSBCW) where the mean value of Ωarag substantially decreased from 1.55 in spring to 1.22 in autumn. All Ωarag values measured in the YSBCW in autumn were lower than the critical threshold value of 1.5 necessary for the survival of calcareous organisms.

A Biological Indication of Vertical Mixing of the Yellow Sea Bottom Cold Water

A Biological Indication of Vertical Mixing of the Yellow Sea Bottom Cold Water

Southward Migration of Arctic Ocean Species During the Last Glacial Period

AbstractThe East Asian winter monsoon (EAWM) is associated with northerly surface winds affecting crop and livestock productivity and social and economic activities across East Asia. However, the relationship between EAWM dynamics and marine biota remains poorly understood. In this study, we analyzed fossil ostracods from sediment cores collected in the northwestern Pacific Ocean to detect the appearance/disappearance of circumpolar species during the late Quaternary. We compared our ostracod records, including dating results, with ice‐rafted debris records from the Sea of Japan, and identified two southward migration events of Arctic ostracods at 120–100 ka (Marine Isotope Stage [MIS] 5d stadial) and 30–15 ka (MIS 3 and 2, peak Last Glacial), which corresponded to a strengthened EAWM system. Our results indicate that an intensified EAWM influenced the Yellow Sea Bottom Cold Water formation, lowered the winter water temperatures, and allowed Arctic ostracods to migrate southward into the Yellow Sea.

Benthic polychaete community structure in the Yellow Sea Bottom Cold Water zone (YSBCW): Species diversity, temporal-spatial distribution, and feeding guilds

The Yellow Sea Bottom Cold Water zone (YSBCW) is a unique seasonal phenomenon in the Yellow Sea, where sea-floor cold water formed in winter is maintained until summer. This survey was conducted at 36 sites from 2018 to 2020. We identified 130 species of polychaetes, with an average density of 275 individuals/m2. The number of species and density were different outside and inside of the YSBCW, and the outside was generally high. The remaining dominant species were all deposit feeders, although differences were observed in the surface or subsurface (burrowers). Correlations between polychaete community and environmental variables strongly correlated with depth, temperature, gravel, and sand. This study investigated polychaete community distribution, environmental characteristics, and feeding guilds in the YSBCW and can be used as a basic database for comprehensive research related to the Yellow Sea in the future.

Spatiotemporal Distribution Characteristics of Copepods in the Water Masses of the Northeastern East China Sea

To understand the effects of variable water masses in the northeastern East China Sea (Korea South Sea), planktonic copepods were seasonally sampled. Out of a total of 106 copepod species, 85 were oceanic warm-water species, and the number of species varied in summer, autumn, spring, and winter. The study area was divided into two or three regions according to the degree of influence of the water masses. Canthocalanus pauper, Clausocalanus furcatus, Oithona plumifera, Oncaea venella, Oncaea venusta, and Paracalanus aculeatus showed a positive correlation with water temperature and salinity and were indicator species of warm currents. Calanus sinicus, known as an indicator species of the Yellow Sea Bottom Cold Water, showed a high abundance and occurrence ratio in the western sea of the study area from spring to autumn. Moreover, Acartia pacifica indicated the extension of coastal waters to offshore areas. Several oceanic warm-water species (A. danae, Centropages gracilis, Labidocera acuta, Rhincalanus nasutus, and Temoropia mayumbaensis) were considered indicator species of the Taiwan Warm Current. Our results suggest that the spatiotemporal distribution patterns of indicator species are partly explained by different water masses.

Assessments of Nitrate Budgets in the Yellow Sea Based on a 3D Physical-Biogeochemical Coupled Model

Nitrate (NO3–) plays an important role in ecosystems and aquaculture in the Yellow Sea (YS). Sparse observational data suggest that ocean currents and nitrification are crucial to NO3– flux in the YS; however, a quantitative assessment of these fluxes has not yet been performed. This study investigates seasonal and spatial variations in NO3– flux via currents and biological processes in the YS from 2006 to 2019 using a physical-biogeochemical coupled model. The model results show that the current-driven fluxes exceeded biological processes in the eastern and central regions of the YS, unlike in the western and northern regions. Advection of NO3– in the YS is mainly driven by cyclonic circulation in summer and fall, and anticyclonic circulation in spring and winter. The Subei Coastal Current along the coast of China plays a primary role in net advective influx of NO3– to the YS year round. The NO3– influx by the Yellow Sea Warm Current along the lower layer of the southcentral YS is offset by outflux through wind-driven surface currents in winter. The southward movements of the Yellow Sea Bottom Cold Water in summer and the Korean Coastal Current in winter are major NO3– outfluxes to the East China Sea. In terms of biological processes, NO3– is mainly consumed by phytoplankton during the spring bloom and supplied through organic matter decomposition and nitrification. Net supply of NO3– by biological processes was the greatest in the southcentral YS where the Yellow Sea Bottom Cold Water is present.

Spatial Distribution of Sound Scattering Layer and Density Estimation of Euphausia pacifica in the Center of the Yellow Sea Bottom Cold Water Determined by Hydroacoustic Surveying

The Yellow Sea Bottom Cold Water (YSBCW) refers to seawater with a water temperature of 10 °C or less found at the bottom of the center of the Yellow Sea. The spatiotemporal variability of the YSBCW directly affects the distribution of organisms in the marine ecosystem. In this study, hydroacoustic and net surveys were conducted in April (spring) to understand the spatial distribution of the sound scattering layer (SSL) and estimate the density of Euphausia pacifica (E. pacifica) in the YSBCW. Despite the shallow water in the YSBCW region, E. pacifica formed an SSL, which was distributed near the bottom during the daytime; it showed a diel vertical migration (DVM) pattern of movement toward the surface during the nighttime. The mean upward and downward swimming speeds around sunset and sunrise were approximately 0.6 and 0.3–0.4 m/min, respectively. The E. pacifica density was estimated in the central, western, and eastern regions; the results were approximately 15.8, 1.3, and 10.3 g/m2, respectively, indicating significant differences according to region. The results revealed high-density distributions in the central and eastern regions related to the water temperature structure, which differs regionally in the YSBCW area. Additional studies are needed regarding the spatial distribution of E. pacifica in the YSBCW and its relationship with various ocean environmental parameters according to season. The results of this study contribute to a greater understanding of the structure of the marine ecosystem in the YSBCW.

Potential of a Tintinnid Species, Tintinnidium primitivum, as a Biological Indicator in the Yellow Sea Bottom Cold Water

Potential of a Tintinnid Species, Tintinnidium primitivum, as a Biological Indicator in the Yellow Sea Bottom Cold Water

Diversity and Assemblage Structure of Marine Fish Species Collected by Set Net in Korean Peninsula During 2009–2013

Assemblage structure analysis was conducted based on seasonal fish species composition data collected four times a year during 2009–2013 from 10 stations around Korea (except the western coast of Korea) using set nets. A total of 154 fish species were identified, of which Trachurus japonicus (22.1%) was the most dominant, followed by Konosirus punctatus (9.2%) and Scomber japonicus (8.7%). Species richness was highest in Jumunjin (in the mid-eastern coast of Korea) and lowest in Gijang (in the east-southern coast of Korea), and species diversity was highest in Gangjeong (southern Jejudo Island) and lowest in Hanrim (northern Jejudo Island). Based on a Bray-Curtis similarity index value of 38%, the 10 stations were divided into three groups: group A comprised four stations in the eastern coast of Korea, group B comprised four stations in the east-southern coast of Korea and Jejudo Island, and group C comprised two stations in the westsouthern coast of Korea. One-way analysis of similarities showed significant differences among groups (global R: 0.822, p = 0.001). The characteristics of the sea currents (e.g., Tsushima Warm Current, North Korea Cold Current) and water masses (e.g., Yellow Sea Bottom Cold Water) might have influenced this grouping.

Complete mitochondrial genome sequence of Parumbrosa polylobata

The complete mitochondrial genome sequences of giant jellyfish Parumbrosa polylobata, a scyphozoan species inhabiting the Yellow Sea cold bottom water in China, is firstly described and analyzed in this research. It is 16,809 bp in length with a linear mitochondrial DNA. The base composition of the genome with A + T bias is 69.7%. There are 13 protein-coding genes (PCGs), 2 tRNAs, and 2 rRNAs. Another two special PCGs, ORF360 and ORF147 with telomeres were found at both ends. The neighbor-joining (NJ) phylogenetic tree among the related 13 species showed that P. polylobata is close to Aurelia spp.

Trans-dimensional Markov chain Monte Carlo inversion of sound speed and temperature: Application to Yellow Sea multichannel seismic data

Abstract Understanding the oceanographic features of the sea water is important for ecosystem studies. In seismic oceanography, structures are imaged and physical properties, such as the sound speed, temperature, or salinity, are calculated using multichannel seismic data. These data provide high lateral resolution information at the full depth of the ocean. However, when the sea water depth is shallow, such as in shallow basins, conventional seismic oceanographic data processing techniques might not provide accurate inversion results for oceanographic properties or accurate images of the sea water structures. In this study, we use the trans-dimensional Markov chain Monte Carlo inversion technique, which assumes both the dimension and properties of the model as unknowns in inversion problems, to estimate the sound speed and define the locations of layer interfaces of the Yellow Sea, which is a semi-enclosed shallow basin. The ocean temperature is calculated using the estimated sound speed and the sound speed-temperature relationship. The estimated sound speed and temperature are compared with the true sound speed and temperature obtained from an expendable bathythermograph. The result shows that the proposed algorithm correctly estimates the sound speed and temperature and accurately images the oceanic structure. As a result, the trans-dimensional Markov chain Monte Carlo inversion can accurately identify the distribution of the Yellow Sea bottom cold water.

Distribution of Different Biogeographical Tintinnids in Yellow Sea and Bohai Sea

There were different biogeographical tintinnids in the oceans. Knowledge of their distribution pattern and mixing was important to the understanding of ecosystem functions. Yellow Sea (YS) and Bohai Sea (BS) were semi-enclosed seas influenced by warm water intrusion and YS cold bottom water. The occurrence of tintinnids in YS and BS during two cruises (summer and winter) were investigated to find out: i) whether warm-water tintinnids appeared in YS and BS; ii) whether boreal tintinnids appeared in high summer; iii) the core area of neritic tintinnids and iv) how these different biogeographical tintinnids mixed. Our results showed that tintinnid community was dominated by neritic tintinnid. We confirmed the occurrence of warm-water tintinnids in summer and winter. In summer, they intruded into BS and mainly distributed in the upper 20 m where Yellow Sea Surface Warm Water (YSSWW) developed. In winter, they were limited in the surface water of central deep region (bottom depth > 50 m) of YS where were affected by Yellow Sea Warm Water (YSWW). Boreal tintinnids occurred in YS in high summer (August) and in winter, while they were not observed in BS. In summer, the highest abundance of boreal tintinnids occurred in Yellow Sea Bottom Cold Water, indicating the presence of an oversummering stock. In winter, they were concentrated in the north of YSWW. Vertically, neritic tintinnids abundance was high in the bottom layers. Horizontally, high neritic tintinnids abundance in bottom layers occurred along the 50 m isobath coinciding with the position of front systems. Front systems were the core distribution area of neritic tintinnids. High abundance areas of warm-water and boreal tintinnids were clearly separated vertically in summer, and horizontally in winter. High abundance of neritic tintinnids rarely overlapped with that of warm-water or boreal tintinnids.

Imaging the Yellow Sea Bottom Cold Water from multichannel seismic data

The Yellow Sea Bottom Cold Water (YSBCW) is a large cold water mass lying in the deep part of the Yellow Sea during the warm season. We acquired multichannel seismic (MCS) data using an air gun source to image the structure of the YSBCW. The MCS data recorded reflections from sea water. The recognition of these reflections was confirmed by finite-difference seismic modeling in the frequency-domain. The seismic section from MCS data enabled discrimination of water masses distinctly separated by reflecting horizons. The structure of the water masses is fairly consistent with temperature-depth variations obtained using expandable bathythermograph (XBT) casts. The YSBCW is imaged as the lowermost water mass, maximally 40 m thick, that extends as a lens-like form along the sea bottom under the warm mixed layer. The correlation of XBT measurements and the seismic section indicates a rapid decrease in temperature from around 11 to 8 °C in the uppermost part of the YSBCW. A transition zone between the mixed layer and the underlying YSBCW is also defined. This transition zone has fairly uniform thickness of 14–18 m and marks an interval of rapid temperature drop, indicating vigorous thermal mixing. Our study demonstrates that MCS profiling is a useful and reliable tool for imaging fine structures in the shallow Yellow Sea.

Interannual Variability of Subsurface Intrusion of Low-Temperature and Salinity Shelf Water into the Kuroshio in the East China Sea

Interannual Variability of Subsurface Intrusion of Low- Temperature and Salinity Shelf Water into the Kuroshio in the East China Sea Spatiotemporal characteristics of salinity and temperature on isopycnal surfaces and subsurface exchange of Kuroshio and ECS shelf water are investigated based on Simple Ocean Data Assimilation (SODA) reanalysis data from January 1958 to December 2008. Applying a neutral density variable γn and Empirical Orthogonal Function (EOF) analysis, dominant spatial features and corresponding temporal variability on both seasonal and interannual time scales are revealed on neutral surfaces 23.0-24.5 γn. The most remarkable characteristic of variability on interannual time scale is the anomalous strengthening of subsurface intrusion of less saline shelf water into the shelf edge and the Kuroshio region during strong La Nina years. Possible causes inducing the strengthening are found to be associated with extraordinarily large discharge of the Changjiang in the following years of strong El Nino as well as the variability of the Yellow Sea bottom cold water modulated by La Nina Events.

Lipids and fatty acids in Calanus sinicus during oversummering in the southern Yellow Sea

Over-summering is a crucial period for Calanus sinicus in the southern Yellow Sea, where it is a key member of the zooplankton community. Lipids play an important role in copepod diapause, which is part of their over-summering strategy. We investigated how different fatty acids and lipid classes, including wax esters, changed during over-summering of C. sinicus during three cruises in June and August 2011 and November 2010, corresponding to the pre-, during and post-diapause periods, respectively. Large amounts of lipids were accumulated, mainly wax esters as previously found in C. finmarchicus during its diapause, and most of the storage lipids were used during over-summering. Wax ester polyunsaturated fatty acids (PUFAs) showed the most variation of the fatty acids (FAs), while the percentage composition of FAs in polar lipids was relatively stable. Selective use of wax ester PUFAs has already been shown to play important roles in the winter diapause of Calanus species in other regions, and our FA results show that this is the case for the Yellow Sea Cold Bottom Water (YSCBW) population that diapauses in summer.

Contribution of the Yellow Sea bottom cold water to the abnormal cooling of sea surface temperature in the summer of 2011

AbstractSatellite‐based sea surface temperature (SST) measurements revealed an abnormal cooling anomaly over the Yellow Sea (YS) in the summer of 2011. Using in situ hydrographic profiles, meteorological fields, and an ocean circulation model with a passive tracer experiment, we identified the cold SST anomaly and its connection with the YS Bottom Cold Water (YSBCW), which occupies the central part of the YS below the thermocline in the summer. The summer SST anomalies in the YS showed three cold peaks in 1993, 2003, and 2011 over the past 20 years, but the reasons for the cooling events were different, as one was due to weakened surface heating and the other was attributed to mixing with the YSBCW. In 1993 and 2003, relatively weak surface heating made the surface water cooler compared with that during the other years, whereas in 2011, a strong vertical mixing of water was induced by a typhoon that passed through the central YS, causing the surface water to cool by ∼8°C and the bottom water to warm up by ∼4°C. A tracer experiment further confirmed that the vertical heat transfers between the warm surface and the cold bottom water masses when the typhoon passed through the YS interior.

황해저층냉수에 따른 참조기(Larimichthys polyactis) 어황의 변화와 예측 가능성

We consider changes in the fishing ground of the small yellow croaker Larimichthys polyactis and discuss their utility in predicting fishing conditions for this species. The fishing ground, which having been formed around Jeju Island since the 1970s, is dominated by the Yellow Sea Bottom Cold Water (YSBCW), and variation in its southward expansion from the Yellow Sea is the single most key environmental factor affecting the L. polyactis catch. When the YSBCW showed strong expansion and the fishing ground shifted to the west and southwest of Jeju Island, as occurred in the late 1980s, late 1990s, and early 2000s, the L. polyactis catch was low; conversely, when expansion was weak, as in the early 1990s and late 2000s, the L. polyactis catch was high. This relationship was statistically significant and should be useful in predicting fishing conditions for L. polyactis.

Seasonal migration of the Yellow Sea Bottom Cold Water

AbstractThe three‐dimensional motion of the Yellow Sea Bottom Cold Water (YSBCW) and the relevant dynamical factors are studied using a regional circulation model and the two‐way Lagrangian particle tracking method (PTM). The simulated results are in good agreement with hydrographic observations. The trajectories of the modeled particles show that the subsurface cold heavy water mass from the northern part of the Yellow Sea gradually sinks into deeper layers along the western slope of the Yellow Sea trough with a southward movement from spring to summer. The cold water mass gradually gathers speed from early March to July or August, and eventually reaches its southernmost location in late September or early October. Furthermore, sensitivity experiments demonstrate that tide‐induced residual currents under baroclinic conditions are the dominant factor driving deep circulation during summertime in the Yellow Sea. The summer southerly wind and strong surface solar radiation are the secondary factors influencing the southward migration. This study also proposes an improved delimitation for the YSBCW based on temperature statistics in the central basin (deeper than 40 m) between 35°N and 39°N in March with an increase in rate of approximately 0.7°C/month, which is more appropriate than the constants of the 8°C or 10°C isotherms frequently used.

Climate change projection in the Northwest Pacific marginal seas through dynamic downscaling

AbstractThis study presents future climate change projections in the Northwest Pacific (NWP) marginal seas using dynamic downscaling from global climate models (GCMs). A regional climate model (RCM) for the Northwest Pacific Ocean was setup and integrated over the period from 2001 to 2100. The model used forcing fields from three different GCM simulations to downscale the effect of global climate change. MIROC, ECHAM, and HADCM were selected to provide climate change signals for the RCM. These signals were calculated from the GCMs using Cyclostationary Empirical Orthogonal Function analysis and added to the present lateral open boundary and the surface forcing. The RCM was validated by comparing hindcast result with the observation. It was able to project detailed regional climate change processes that GCMs were not able to resolve. A relatively large increases of water temperature were found in the marginal seas. However, only a marginal change was found along the Kuroshio path. Heat supply to the atmosphere decreases in most study areas due to a slower warming of the sea surface compared to the atmosphere. The RCM projection suggests that the temperature of the Yellow Sea Bottom Cold Water will gradually increase by 2100. Volume transports through major straits except the Taiwan Strait in the marginal seas are projected to increase slightly in future. Increased northeasterly wind stress in the East China Sea may also result in the transport change.