南海南部造山运动及其与古南海俯冲的成因联系

古南海的展布范围以及俯冲消亡过程等一直是地质学家们争论的焦点问题。这不仅与南海扩张诱因密切相关,而且对南海地球动力学研究有重大的指导意义。在研究前人文献的基础上,对南海南部造山运动以及古南海俯冲过程之间的关系进行详细的论述。结果表明,南海南部构造活动主要分为两期：第一期运动从早白垩纪到晚白垩纪,古太平洋的洋壳俯冲到婆罗洲岛下方,俯冲带位于现今卢帕尔线一带,引起了曾母-南沙地块不断向西南婆罗洲靠近,并于晚白垩纪引发了碰撞造山运动。由于婆罗洲自身是由众多地块拼合而成,所以在始新世期间发生了多期碰撞之后的地块变形重组事件。最终在晚始新世（37 Ma）完成最后一期变形（沙捞越运动）。第二阶段是晚始新世（35 Ma）到中中新世（15.5 Ma）,位于西巴拉姆线以东至菲律宾卡加延一带的古南海从西巴拉姆线以东,向婆罗洲岛下方俯冲,随后扩散到沙巴以及巴拉望岛以南的地区,直至菲律宾的民都洛岛一带停止俯冲。由此产生的拖曳力是南海扩张的主要诱因。与古太平洋板块俯冲产生的效果相似,古南海的俯冲使得婆罗洲岛与南沙地块不断靠近。在中中新世（15.5 Ma）,引起南沙地块与婆罗洲岛在沙巴地区的碰撞（沙巴造山）以及巴拉望北部陆壳与菲律宾岛弧的碰撞而停止。由此带来的不整合面在南海南部普遍可见,甚至到达了巴拉望岛一带。而现今南沙海槽与巴拉望海槽并非是俯冲带的前渊,前者是对沙巴新近纪增生楔重力驱动变形的响应,后者是巴拉望岛北侧伸展背景下产生的半地堑盆地,在后期增生楔的作用下发生强烈沉降所形成。真正的俯冲带则分别位于南沙海槽东南部以及巴拉望海槽东南部。据现有证据推测,最少在10 Ma之前古南海就在菲律宾民都洛一带停止俯冲,从而完成了整个古南海的封闭。     

南海新生代裂离地体

本文根据拖网取样和多道反射地震资料，结合前人工作，分析南海新生代裂离地体──中－西沙地体与南沙地体的特征、亲缘性及成因。     

The final rifting evolution in the South China Sea

Seismic reflection data imaging conjugate crustal sections at the South China Sea margins result in a conceptual model for rift-evolution at conjugate magma-poor margins in time and space.The wide Early Cenozoic South China Sea rift preserves the initial rift architecture at the distal margins. Most distinct are regular undulations in the crust–mantle boundary. Individual rift basins are bounded to crustal blocks by listric normal faults on either side. Moho uplifts are distinct beneath major rift basins, while the Moho is downbended beneath crustal blocks, with a wavelength of undulations in the crust–mantle boundary that approximately equals the thickness of the continental crust. Most of the basin-bounding faults sole out within the middle crust. At the distal margins, detachment faults are located at a mid-crustal level where a weak zone decouples crust and mantle lithosphere during rifting. The lower crust in contrast is interpreted as being strong. Only in the region within about 50 km from the Continent–Ocean Transition (COT) we suggest that normal faults reach the mantle, enabling potentially a coupling between the crust and the mantle. Here, at the proximal margins detachment fault dip either seaward or landward. This may indicate the presence of exhumed mantle bordering the continental margins.Post-rift shallow-water platform carbonates indicate a delay in subsidence during rifting in the South China Sea. We propose that this is an inherent process in highly extended continental margins and a common origin may be the influx of warm asthenospheric material into initially cool sub-lithospheric mantle.On a crustal-scale largely symmetric process predominate in the initial rifting stage. At the future COT either of the rift basin-bounding faults subsequently penetrates the entire crust, resulting in asymmetry at this location. However, asymmetric deformation which is controlled by large scale detachment faulting is confined to narrow areas and does not result in a margin-wide simple-shear model. Rather considerable along-margin variations are suggested resulting in alternating “upper and lower plate” margins.     

Structures of the northeasternmost South China Sea continental margin and ocean basin: geophysical constraints and tectonic implications

The northeastern part of the South China Sea is a special region in many aspects of its tectonics. Both recent drilling into the Mesozoic and new reflection seismic surveys in the area provide a huge amount of data, fostering new understanding of the continental margin basins and regional tectonic evolution. At least four half-grabens are developed within the Northern Depression of the Tainan Basin, and all are bounded on their southern edges by northwestward-dipping faults. One of the largest half-grabens is located immediately to the north of the Central Uplift and shows episodic uplift from the late Oligocene to late Miocene. Also during that period, the Central Uplift served in part as a material source to the Southern Depression of the Tainan Basin. The Southern Depression of the Tainan Basin is a trough structure with deep basement (up to 9 km below sealevel or 6 km beneath the sea bottom) and thick Cenozoic sedimentation (>6 km thick). Beneath the Southern Depression we identified a strong landward dipping reflector within the crustal layer that represents a significant crustal fault. This reflector coincides with a sharp boundary in crustal thicknesses and Moho depths. We show that the northeasternmost South China Sea basin, which may have undergone unique evolution since the late Mesozoic, is markedly different from the central South China Sea basin and the Huatung Basin, both geologically and geophysically. The Cenozoic evolution of the region was largely influenced by pre-existing weaknesses due to tectonic inheritance and transition. The South China Sea experienced multiple stages of Cenozoic extension.     

Deep structures of the Palawan and Sulu Sea and their implications for opening of the South China Sea

Compared to the northern South China Sea continental margin, the deep structures and tectonic evolution of the Palawan and Sulu Sea and ambient regions are not well understood so far. However, this part of the southern continental margin and adjacent areas embed critical information on the opening of the South China Sea (SCS). In this paper, we carry out geophysical investigations using regional magnetic, gravity and reflection seismic data. Analytical signal amplitudes (ASA) of magnetic anomalies are calculated to depict the boundaries of different tectonic units. Curie-point depths are estimated from magnetic anomalies using a windowed wavenumber-domain algorithm. Application of the Parker–Oldenburg algorithm to Bouguer gravity anomalies yields a 3D Moho topography. The Palawan Continental Block (PCB) is defined by quiet magnetic anomalies, low ASA, moderate depths to the top and bottom of the magnetic layer, and its northern boundary is further constrained by reflection seismic data and Moho interpretation. The PCB is found to be a favorable area for hydrocarbon exploration. However, the continent–ocean transition zone between the PCB and the SCS is characterized by hyper-extended continental crust intruded with magmatic bodies. The NW Sulu Sea is interpreted as a relict oceanic slice and the geometry and position of extinct trench of the Proto South China Sea (PSCS) is further constrained. With additional age constraints from inverted Moho and Curie-point depths, we confirm that the spreading of the SE Sulu Sea started in the Early Oligocene/Late Eocene due to the subduction of the PSCS, and terminated in the Middle Miocene by the obduction of the NW Sulu Sea onto the PCB.     

Seismic evidence and formation mechanism of gas hydrates in the Zhongjiannan Basin,Western margin of the South China Sea

An analysis of 3D seismic data from the Zhongjiannan Basin in the western margin of the South China Sea (SCS) reveals seismic evidence of gas hydrates and associated gases, including pockmarks, a bottom simulating reflector (BSR), enhanced reflection (ER), reverse polarity reflection (RPR), and a dim amplitude zone (DAZ). The BSR mainly surrounds Zhongjian Island, covering an area of 350 km² in this 3D survey area. The BSR area and pockmark area do not match each other; where there is a pockmark developed, there is no BSR. The gas hydrate layer builds upward from the base of the stability zone with a thickness of less than 100 m. A mature pockmark usually consists of an outside trough, a middle ridge, and one or more central pits, with a diameter of several kilometers and a depth of several hundreds of meters. The process of pockmark creation entails methane consumption. Dense faults in the study area efficiently transport fluid from large depths to the shallow layer, supporting the formation of gas hydrate and ultimately the pockmark.     

Middle to Late Cenozoic tectonic events in south and central Palawan (Philippines) and their implications to the evolution of the south-eastern margin of South China Sea: Evidence from onshore structural and offshore seismic data

Using recently gathered onland structural and 2D/3D offshore seismic data in south and central Palawan (Philippines), this paper presents a new perspective in unraveling the Cenozoic tectonic history of the southeastern margin of the South China Sea. South and central Palawan are dominated by Mesozoic ophiolites (Palawan Ophiolite), distinct from the primarily continental composition of the north. These ophiolites are emplaced over syn-rift Eocene turbidites (Panas Formation) along thrust structures best preserved in the ophiolite–turbidite contact as well as within the ophiolites. Thrusting is sealed by Early Miocene (∼20 Ma) sediments of the Pagasa Formation (Isugod Formation onland), constraining the younger limit of ophiolite emplacement at end Late Oligocene (∼23 Ma). The onset of ophiolite emplacement at end Eocene is constrained by thrust-related metamorphism of the Eocene turbidites, and post-emplacement underthrusting of Late Oligocene – Early Miocene Nido Limestone. This carbonate underthrusting at end Early Miocene (∼16 Ma) is marked by the deformation of a seismic unit corresponding to the earliest members of the Early – Middle Miocene Pagasa Formation. Within this formation, a tectonic wedge was built within Middle Miocene (from ∼16 Ma to ∼12 Ma), forming a thrust-fold belt called the Pagasa Wedge. Wedge deformation is truncated by the regionally-observed Middle Miocene Unconformity (MMU ∼12 Ma). A localized, post-kinematic extension affects thrust-fold structures, the MMU, and Late Miocene to Early Pliocene carbonates (e.g. Tabon Limestone). This structural set-up suggests a continuous convergent regime affecting the southeastern margin of the South China Sea between end Eocene to end Middle Miocene. The ensuing structures including juxtaposed carbonates, turbidites and shallow marine clastics within thrust-fold belts have become ideal environments for hydrocarbon generation and accumulation. Best developed in the Northwest Borneo Trough area, the intensity of thrust-fold deformation decreases towards the northeast into offshore southwest Palawan.     

Characteristics of Sea Surface Circulation and Eddy Field in the South China Sea Revealed by Satellite Altimetric Data

Temporal and spatial variations of sea surface circulation in the South China Sea were revealed with use of altimetric data provided by TOPEX/POSEIDON from December 1992 to October 1997. The estimated distribution of sea surface dynamic heights from altimetric data coincide well with the results of observation by Soong et al. (1995) and Chu et al. (1998). The RMS variability of sea surface dynamic height, which is obtained after tidal correction based on Yanagi et al. (1997), is high in the central part of the South China Sea, the Gulf of Tongking, the Sunda Shelf and the Gulf of Thailand. The high RMS variability in the Gulf of Tongking, the Sunda Shelf and the Gulf of Thailand is due to set up and set down of sea water by the East Asian monsoon, which is northeasterly during winter and southwesterly during summer. Also, the high RMS variability in the central part of the South China Sea is due to the variations of basin-wide circulation. The circulations are dominant in the central part of the South China Sea during summer and winter, an anticyclonic circulation during summer and a cyclonic circulation during winter. It is suggested that these circulations are controlled by the East Asian monsoon. Hence, there is an interannual variability of the basin-wide circulation associated with the variation of the East Asian monsoon.     

Rifted margin architecture and crustal rheology: Reviewing Iberia-Newfoundland,Central South Atlantic,and South China Sea

Crustal rheology controls the style of rifting and ultimately the architecture of rifted margins. Here we review the formation of three magma-poor margin pairs, Iberia-Newfoundland, the central segment of the South Atlantic Rift, and the South China Sea by integrating observational data into a numerical forward modelling framework. We utilise a 2D version of the finite element code SLIM3D, which includes nonlinear temperature- and stress-dependent elasto-visco-plastic rheology and is able to reproduce a wide range of rift-related deformation processes such as flexure, lower crustal flow, and faulting.Extension in cold, strong, or thin crust is accommodated by brittle faults and ductile shear zones that facilitate narrow rifts with asymmetric fault geometries. Hot, weak, or thick continental crust is dominated by ductile deformation and often extends symmetrically into a wide rift system. This simple recipe provides the standard framework to understand initial rift geometry, however, it is insufficient to account for the dynamics of intermediate and late rift stages that shape the final margin architecture.Asymmetric conjugate margins where one side is wide and the other narrow can be formed via both wide and narrow rift styles, which we reproduce with weak and strong crustal rheologies, respectively. Exemplified by the Iberia-Newfoundland conjugates and the Central South Atlantic, we define three characteristic rift phases: an initial phase of simultaneous faulting, an intermediate phase of rift migration that involves sequential fault activity, and finally, the breakup phase. Crustal rheology plays an overarching role in governing the dynamics of these asymmetric margins: we illustrate that weak rheologies generally prolong the phase of simultaneous faulting, while rift migration is enabled by initial fault asymmetry as well as relatively weak crust.Formation of the predominantly symmetric and wide margins of the South China Sea was controlled by extraordinarily weak crust that extended the phase of simultaneous faulting until breakup. The weak crustal rheology of this region relates to the South China Sea's pre-rift history where plate convergence lead to crustal thickening and magmatic additions in a back-arc regime shortly before the onset of rifting.     

南海名浅考

根据历史文献分析,已知南海海名最早出现于周宣王（827BC--782BC在位）时的《江汉》诗中。秦汉之间214BC—111BC时著的《山海经·海内东经》篇,记述了现时广东省三水和广州以南地区当时为海,称南海。这可从《史记》和《汉书》的记述,以及现代珠江三角洲的考古学、第四纪地质学和河口演变的研究成果所证实。南海古时别名涨海,明清时期外国人称为大明海和大清海。清朝以来,外国人把它翻译成（或称作）英文“South China Sea”,而近代某些中国人再把这个英文名词直译成汉文“南中国海”,忽视“南海”固有的中文名称。民国和中华人民共和国政府先后出版的地图和其他正式出版物,皆只用“南海”名。     

Distributions of nutrients in the East China Sea and the South China Sea connection

Surface maps of nitrate, phosphate and silicate of the East China Sea (ECS) have been constructed and are described. Reports on exchanges of material between the ECS and the South China Sea (SCS) through the Taiwan Strait are reviewed. Recent advances seem to have reversed the earlier view that the SCS exports nutrients to the ECS through the Taiwan Strait. This is because the northward flow of seawater in the summer carries little nutrient. On the other hand, the waters flowing southward along the coast of China in winter carry orders of magnitude higher nutrient concentrations. The outflow of subsurface waters from the SCS, however, is the major source of new nutrients to the ECS continental shelves because these subsurface waters flow out of the Luzon Strait, join the northwardly flowing Kuroshio and enter the Okinawa trough. Around 10% of the nutrients exported from the SCS through the Luzon Strait upwell onto the ECS shelf. These inputs are larger than the aggregate of all the rivers that empty into the ECS, contributing 49% of the externally sourced nitrogen, 71% of the phosphorous, and 54% of the silica for the ECS.     

Different expressions of rifting on the South China Sea margins

Rifting of continental margins is generally diachronous along the zones where continents break due to various factors including the boundary conditions which trigger the extensional forces, but also the internal physical boundaries which are inherent to the composition and thus the geological history of the continental margin. Being opened quite recently in the Tertiary in a scissor-shape manner, the South China Sea (SCS) offers an image of the rifting structures which varies along strike the basin margins. The SCS has a long history of extension, which dates back from the Late Cretaceous, and allows us to observe an early stretching on the northern margin onshore and offshore South China, with large low angle faults which detach the Mesozoic sediments either over Triassic to Early Cretaceous granites, or along the short limbs of broad folds affecting Palaeozoic to Early Cretaceous series. These early faults create narrow troughs filled with coarse polygenic conglomerate grading upward to coarse sandstone. Because these low-angle faults reactivate older trends, they vary in geometry according to the direction of the folds or the granite boundaries. A later set of faults, characterized by generally E–W low and high angle normal faults was dominant during the Eocene. Associated half-graben basement deepened as the basins were filling with continental or very shallow marine sediments. This subsequent direction is well expressed both in the north and the SW of the South China Sea and often reactivated earlier detachments. At places, the intersection of these two fault sets resulting in extreme stretching with crustal boudinage and mantle exhumation such as in the Phu Khanh Basin East of the Vietnam fault. A third direction of faults, which rarely reactivates the detachments is NE–SW and well developed near the oceanic crust in the southern and southwestern part of the basin. This direction which intersects the previous ones was active although sea floor spreading was largely developed in the northern part, and ended by the Late Miocene after the onset of the regional Mid Miocene unconformity known as MMU and dated around 15.5 Ma. Latest Miocene is marked by a regional basement drop and localized normal faults on the shelf closer to the coast. The SE margin of the South China Sea does not show the extensional features as well as the Northern margin. Detachments are common in the Dangerous Grounds and Reed Bank area and may occasionally lead to mantle exhumation. The sedimentary environment on the extended crust remained shallow all along the rifting and a large part of the spreading until the Late Miocene, when it suddenly deepened. This period also corresponds to the cessation of the shortening of the NW Borneo wedge in Palawan, Sabah, and Sarawak. We correlate the variation of margin structure and composition of the margin; mainly the occurrence of granitic batholiths and Mesozoic broad folds, with the location of the detachments and major normal faults which condition the style of rifting, the crustal boudinage and therefore the crustal thickness.     

A Review on the Currents in the South China Sea: Seasonal Circulation, South China Sea Warm Current and Kuroshio Intrusion

Researches on the currents in the South China Sea (SCS) and the interaction between the SCS and its adjacent seas are reviewed. Overall seasonal circulation in the SCS is cyclonic in winter and anticyclonic in summer with a few stable eddies. The seasonal circulation is mostly driven by monsoon winds, and is related to water exchange between the SCS and the East China Sea through the Taiwan Strait, and between the SCS and the Kuroshio through the Luzon Strait. Seasonal characteristics of the South China Sea Warm Current in the northern SCS and the Kuroshio intrusion to the SCS are summarized in terms of the interaction between the SCS and its adjacent seas.     

南海北部陆缘OBS2018-H2测线地壳结构初步结果

南海北部陆缘洋陆转换带实施的OBS2018-H2测线的地壳速度结构, 将为探讨南海张裂-破裂机制提供重要证据。文章介绍了OBS2018-H2测线前期数据处理流程, 包括多道反射地震数据处理、海底地震仪OBS (Ocean Bottom Seismometer)数据格式转换、炮点和OBS位置校正, 以及OBS震相的初步识别, 并对地壳结构进行了初步分析。结果表明: 炮点和OBS位置校正效果良好; 多道反射地震数据为建立初始速度模型提供了良好约束; OBS综合地震剖面识别了多组清晰的P波震相, 包括Pw、Pg、PmP和Pn震相。根据测线西侧OBS36、OBS37两台站的震相分布特征初步估算台站下方地壳厚度约为6~7km, 与根据多道地震剖面LW3的双程走时估算的厚度6~9km大致相符。     

A Bathymetric Model for the South China Sea from Satellite Altimetry and Depth Data

A bathymetric model for the South China Sea is computed from altimeter-derived gravity anomalies, shipborne depths, ETOPO5, and the GMT shorelines using a procedure that includes downward continuation, linear regression, and data merging. The model best fits the GMT shorelines and is a compromise between smoothness, degree of agreement with ship data, and the seafloor features we wish to retain. The model is proven useful in studying the tectonics and modeling the ocean tide of the South China Sea.     

The South China Sea thermohaline structure and circulation

In this study, we used the Navy' s Master Oceanographic Observation Data Set(MOODS), consisting of 116019 temperature and 9617 salinity profiles, during 1968- 1984 to investigate the temporal and spatial variabilities of South China Sea thermohaline structures and circulation. For temperature, profiles were binned into 204 monthly data sets from 1968 to 1984 (17 years). For salinity, profiles were binned into 12 climatological monthly data sets due to the data paucity. A two-scale optimal interpolation method was used to establish a three-dimensional monthly-varying gridded data set from MOODS, covering the area of 5°-25°N and 105° - 125°E and the depth from the surface to 400 m. After the gridded data set had been established, both composite analysis and the Empirical Orthogonal Function (EOF) analysis (for temperature only) were used to identify the major thermohaline fratures including annual mean, monthly anomalies, and interannual thermal variabilities. The inverted monthly circulation pattern     

南海海盆扩张成因质疑

从板块构造学、地球物理学和地球动力学等角度,结合南海中央海盆及其周边的地质、地球物理资料进行综合分析论证,对南海“扩张成因”模式提出质疑.认为南海“扩张成因说”不能成立,其中的几个核心问题是:(1)数学理论模型的边界参数选取存在多解性,其结果与地质地球物理资料不符或相去甚远;(2)无法解释海盆区地球物理探测和研究所表明的地壳结构及岩性特征,也无法解释海盆区的断裂分布和岩浆活动特征;(3)地球动力学诸方面难以支持南海“扩张成因说”成立;(4)南海海盆周边不存在与南海“扩张成因”相关的相互强烈作用的地球物理和地质构造特征;(5)南海海盆不具备大规模扩张的空间.南海“扩张成因说”已严重阻碍对南海和周边的地质与地球物理研究工作的深入和发展,应该放弃.     

The Laptev Sea Rift

In north-eastern Siberia the active mid-ocean Gakkel Ridge interacts with the continental shelf of the Laptev Sea. Extension has affected the shelf since at least the Early Tertiary and has resulted in the formation of a complex horst and graben system. We present new seismic data from the Laptev Sea including deep seismic soundings.The most prominent rift basin is the Ust' Lena Rift with a minimum E–W width of 300 km at latitude 75°N and a Cenozoic infill up to 13 km in thickness. The asymmetric shape of the basin and conclusive evidence for a detachment imply a simple-shear geometry. The suggested rift model combines a ramp and flat geometry for the detachment with ductile stretching beneath the detachment. A major west-dipping, hingeline, listric fault separates the Ust' Lena Rift from the Laptev Horst.The 100–150 km wide Laptev Horst is subdivided into three units by narrow rift grabens. Another prominent rift graben is the Anisin Basin, which is located in the northern shelf area.Though the Laptev Sea Rift formed in interaction with an active mid-oceanic ridge, there are indications that the Laptev Sea rift is of the ‘passive rift’ type. The rift was developed east of a SW–NE trending transfer zone which links the Gakkel Ridge to the Laptev Sea Rift.     

南海海表温时空演变与南海夏季风爆发早晚相关性初探

利用我国近海1986-2008年间的海温再分析资料,分析了南海海温异常的时空变化,重点揭示了南海夏季风爆发前后(4-6月)南海表层海温异常的时空演变特征,并探讨了其与南海夏季风爆发早晚的相关关系。结果显示,南海夏季风爆发前后南海表层海温异常存在一个显著时空演变模态,4月南海全域海表温度异常几呈负位相态势,其中正值信号首先出现于巴拉望岛以西海域,随后逐步向西向北扩展,5月南海大部已被海表温异常正位相控制,6月南海表层海温异常完成负-正位相转换。分析表明,南海表层海温异常时空演变的年际差异与南海夏季风爆发的早晚存在显著相关。综合已有研究认为,南海海表温异常时空演变所形成的季节内尺度的热力差异(主要包含演进趋势、速度和幅度等)可能是影响南海夏季风爆发早晚的一个重要因子,据此建立了海表温温差异常指标,其对南海夏季风爆发早晚具有较好的反映能力。此外,南海海表温异常时空演变与南海暖池的变化紧密关联。相关分析还发现,南海夏季风爆发前期南海暖池与印度洋暖池的海表温差异常存在显著正相关关系,而与西太平洋暖池为负相关关系。南海海表温异常季节内演变在印-太暖池区海表热力格局及差异形成背景下或可通过影响大尺度经向和纬向环流而引发南海夏季风爆发早晚之年际异常。     

Nutrient budgets for the South China Sea basin

Varying atmospheric forcing and an elaborate geography make for a complex flow in the South China Sea (SCS). Throughout the year, the surface waters of the Kuroshio flow into the SCS, while the surface waters of the SCS flow out through the Bashi Channel. Cumulatively, there is a small (1 Sv) net outflow of surface water (0–350-m depth) from the SCS in the wet season, but a net inflow (3 Sv) in the dry season through the Bashi Channel. The differences are mainly made up by inflow and outflow of Sunda Shelf Water in the wet and dry seasons, respectively.Seawater, phosphorus, nitrogen and silicate budgets were calculated based on a box model. The results point out an intermediate water outflow (350–1350-m depth) into the West Philippine Sea (WPS) through the Bashi Channel in both the wet and dry seasons, though this, along with the nutrients it carries, is slightly larger in the dry season (2 Sv) than in the wet (1.8 Sv). More importantly, the export of nutrient-laden SCS intermediate water through the Bashi Channel subsequently upwells onto the East China Sea (ECS) shelf. The denitrification rate for shelves in the SCS is 0.11 mol N m⁻² year⁻¹, calculated by balancing the nitrogen budget. The oxygen consumption and the nutrient regeneration rates, based on the mass-balance and the one-dimensional advection–diffusion models, stand between those for the Bering Sea and the Sea of Japan.