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RWP-RK proteins are important factors involved in nitrate response and gametophyte development in plants, and the functions of RWP-RK proteins have been analyzed in many species. However, the characterization of peanut RWP-RK proteins is limited. In this study, we identified 16, 19, and 32 RWP-RK members from Arachis duranensis, Arachis ipaensis, and Arachis hypogaea, respectively, and investigated their evolution relationships. The RWP-RK proteins were classified into two groups, RWP-RK domain proteins and NODULE-INCEPTION-like proteins. Chromosomal distributions, gene structures, and conserved motifs of RWP-RK genes were compared among wild and cultivated peanuts. In addition, we identified 12 orthologous gene pairs from the two wild peanut species, 13 from A. duranensis and A. hypogaea, and 13 from A. ipaensis and A. hypogaea. One, one, and seventeen duplicated gene pairs were identified within the A. duranensis, A. ipaensis, and A. hypogaea genomes, respectively. Moreover, different numbers of cis-acting elements in the RWP-RK promoters were found in wild and cultivated species (87 in A. duranensis, 89 in A. ipaensis, and 92 in A. hypogaea), and as a result, many RWP-RK genes showed distinct expression patterns in different tissues. Our study will provide useful information for further functional and evolutionary analysis of the RWP-RK genes.

The China Seas include the South China Sea, East China Sea, Yellow Sea, and Bohai Sea. Located off the Northwestern Pacific margin, covering 4700000 km2 from tropical to northern temperate zones, and including a variety of continental margins/basins and depths, the China Seas provide typical cases for carbon budget studies. The South China Sea being a deep basin and part of the Western Pacific Warm Pool is characterized by oceanic features; the East China Sea with a wide continental shelf, enormous terrestrial discharges and open margins to the West Pacific, is featured by strong cross-shelf materials transport; the Yellow Sea is featured by the confluence of cold and warm waters; and the Bohai Sea is a shallow semi-closed gulf with strong impacts of human activities. Three large rivers, the Yangtze River, Yellow River, and Pearl River, flow into the East China Sea, the Bohai Sea, and the South China Sea, respectively. The Kuroshio Current at the outer margin of the Chinese continental shelf is one of the two major western boundary currents of the world oceans and its strength and position directly affect the regional climate of China. These characteristics make the China Seas a typical case of marginal seas to study carbon storage and fluxes. This paper systematically analyzes the literature data on the carbon pools and fluxes of the Bohai Sea, Yellow Sea, East China Sea, and South China Sea, including different interfaces (land-sea, sea-air, sediment-water, and marginal sea-open ocean) and different ecosystems (mangroves, wetland, seagrass beds, macroalgae mariculture, coral reefs, euphotic zones, and water column). Among the four seas, the Bohai Sea and South China Sea are acting as CO2 sources, releasing about 0.22 and 13.86– 33.60 Tg C yr−1 into the atmosphere, respectively, whereas the Yellow Sea and East China Sea are acting as carbon sinks, absorbing about 1.15 and 6.92 –23.30 Tg C yr−1 of atmospheric CO2, respectively. Overall, if only the CO2 exchange at the sea-air interface is considered, the Chinese marginal seas appear to be a source of atmospheric CO2, with a net release of 6.01 –9.33 Tg C yr−1 , mainly from the inputs of rivers and adjacent oceans. The riverine dissolved inorganic carbon(DIC) input into the Bohai Sea and Yellow Sea, East China Sea, and South China Sea are 5.04, 14.60, and 40.14 Tg C yr−1 , respectively. The DIC input from adjacent oceans is as high as 144.81 Tg C yr−1 , significantly exceeding the carbon released from the seas to the atmosphere. In terms of output, the depositional fluxes of organic carbon in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea are 2.00, 3.60, 7.40, and 5.92 Tg C yr−1 , respectively. The fluxes of organic carbon from the East China Sea and South China Sea to the adjacent oceans are 15.25–36.70 and 43.93 Tg C yr−1 , respectively. The annual carbon storage of mangroves, wetlands, and seagrass in Chinese coastal waters is 0.36 –1.75 Tg C yr−1 , with a dissolved organic carbon (DOC) output from seagrass beds of up to 0.59 Tg C yr−1 . Removable organic carbon flux by Chinese macroalgae mariculture account for 0.68 Tg C yr−1 and the associated POC depositional and DOC releasing fluxes are 0.14 and 0.82 Tg C yr−1 , respectively. Thus, in total, the annual output of organic carbon, which is mainly DOC, in the China Seas is 81.72 –104.56 Tg C yr−1 . The DOC efflux from the East China Sea to the adjacent oceans is 15.00 –35.00 Tg C yr−1 . The DOC efflux from the South China Sea is 31.39 Tg C yr−1 . Although the marginal China Seas seem to be a source of atmospheric CO2 based on the CO2 flux at the sea-air interface, the combined effects of the riverine input in the area, oceanic input, depositional export, and microbial carbon pump (DOC conversion and output) indicate that the China Seas represent an important carbon storage area.

Conductivity-temperature-depth (CTD) data obtained during the 2010 La Nina winter and the 2012 normal winter, combined with concurrent Argo profiling float data, provide a quasi-synoptic description of the water mass distributions and their variations in the far western equatorial Pacific Ocean. The water mass connection between the western Pacific and the east Indonesian seas is emphasized. Analysis indicates that the North Pacific Tropical Water (NPTW, S >34.9) carried by the Mindanao Current southward and the South Pacific Tropical Water (SPTW, S >35.1) from the southern hemisphere meet in the area. Observations suggest that the southward transport of the NPTW is stronger in 2010 than in 2012 due to enhanced advection of the Mindanao Current. The distribution of SPTW, which crosses the equator in the northwest direction and retroflects back to the interior Pacific Ocean, is found to retreat from 4°–5°N in 2012 to 2°–3°N in 2010 La Nina peak in the 130°E section. A relatively fresh tropical subsurface water is identified in between the NPTW and the SPTW, moving eastward with the North Equatorial Countercurrent into the equatorial Pacific Ocean. However, the salinity maximum of this subsurface fresh water is found to decrease eastward, suggesting that the salinity maximum is generated either by strong diapycnal mixing or by isopycnal mixing of temporally entrained Indonesian sea water into the area.

The rectification of intraseasonal wind forcing on interannual sea surface temperature anomalies (SSTA) and sea level anomalies (SLA) associated with El Nino–Southern Oscillation (ENSO) during 1993–2016 are investigated using the LICOM ocean general circulation model forced with daily winds. The comparisons of the experiments with and without the intraseasonal wind forcing have shown that the rectified interannual SSTA and SLA by the intraseasonal winds are much weaker than the total interannual SSTA and SLA in the cold tongue, due to the much weaker rectified than the total interannual Kelvin and Rossby waves in the equatorial Pacific Ocean. The dynamics of the rectification are through the nonlinear zonal and vertical advection by the background currents, which produces downwelling equatorial Kelvin waves during El Nino. The meridional advection is much smaller than the zonal and vertical advection, suggesting that the rectification is not induced by the Ekman dynamics or the thermocline rectification. The rectified interannual Kelvin waves are found to be much smaller than reflected at the Pacific western boundary and those forced by the interannual winds, suggesting that the latter two play a much more important role in ENSO dynamics than the intraseasonal winds. The results of this study suggest an unlikely significant role of oceanic nonlinear rectification by intraseasonal winds during the onset and cycling of El Nino.

The meridional geostrophic transport (MGT) in the interior tropical North Pacific Ocean is estimated based on global ocean heat and salt content data. The decadal variations of the zonally and vertically integrated MGT in the tropical North Pacific Ocean are found to precede the Pacific decadal oscillation (PDO) by 1–3 years. The dynamics of the MGT are analyzed based on Sverdrup theory. It is found that the total meridional transport variability (MGT plus Ekman) is dominated by the MGT variability having positive correlations with the PDO index. The Sverdrup transports differ from the total meridional transport significantly and have insignificant correlations with PDO index, suggesting that the MGT variability is not controlled by the Sverdrup dynamics. In comparison, the simulated meridional transport variability in the models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and the Ocean General Circulation Model for the Earth Simulator are dominated by the Sverdrup transports, having insignificant correlations with the simulated PDO indices. The comparison suggests that the non-Sverdrup component in the MGT is important for the predictability of PDO and that significant deficiencies exist in these models in simulating a realistic structure of the tropical ocean gyre variability and predicting the decadal climate variations associated with it.

Based on Marx-Planck coupled model simulations and in situ hydrography measurements, the volume transport of ocean currents and associated carbon fluxes across the continental margin from the continental shelf to the deep ocean in the East China Sea during winter are estimated. Because cross-shelf currents in the Yellow and East China seas are much stronger in winter than in other seasons and are subducted into the subsurface Kuroshio, the cross-shelf burial of carbon takes place mainly in winter. The analyses show prominent cross-shelf transports during winter in the Yellow and East China seas, with annual mean offshore transport across a section from Taiwan to Cheju at 3.92 Sv (1 Sv=106 m3 s−1). Net transport across the section was 0.82 Sv off the shelf, determined by the difference between Taiwan and Cheju strait transports. Net cross-shelf transports of dissolving inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) in winter were 98, 12, and 0.1 million tons, respectively. Under global greenhouse gas emission reduction (RCP4.5) and continuous increase (RCP8.5) scenarios, this cross-shelf transport has an increasing trend. The transports across the Taiwan-Cheju section in winter are predicted to increase by 0.54 and 0.65 Sv from 2006 to 2099, with rates of increase 15.3% and 19.6%, respectively. Associated with the transport increase, the cross-shelf fluxes of DIC, DOC and POC increase by as much as 15.4–25.2%. Cross-shelf carbon fluxes in the East China Sea during winter are evaluated for the first time under the global warming scenarios, showing the importance of cross-shelf transport in the carbon cycle of the China marginal seas.

The influence of western boundary reflection (WBR) of Rossby waves on the seasonal circulation in the equatorial Indian Ocean is investigated using an ocean model LICOM , forced by daily winds and surface fluxes of the National Centers for Environmental Prediction (NCEP) reanalysis I during 2000–2010. LICOM has reproduced seasonal variations of Ocean Surface Current Analysis Real-time (OSCAR) zonal currents and satellite altimeter sea level well. Comparisons of the experimental results with and without WBR suggest that the WBR enhances the zonal currents and sea level variations in the central and eastern equatorial Indian Ocean. Long equatorial wave dynamics analyses suggest that the difference of the second baroclinic mode waves with and without WBR are evidently larger than those of the first baroclinic mode, suggesting the importance of the second baroclinic mode waves in controlling the sea level and zonal current seasonal variations. Analyses also suggest that reflected Kelvin waves from the first and second baroclinic modes have a much larger contribution to the semiannual oscillations of the sea level than Rossby waves. The first meridional Rossby wave of the first and second baroclinic modes have larger contribution to zonal currents than the Kelvin waves from the WBR. These results suggest the important role of the WBR in controlling the seasonal circulation in the equatorial Indian Ocean.

The global carbon cycle has played a key role in mitigating global warming and climate change. Long-term natural and anthropogenic processes influence the composition, sources, burial rates, and fluxes of carbon in sediments on the continental shelf of China. In this study, the rates, fluxes, and amounts of carbon storage at the centennial scale were estimated and demonstrated using the case study of three fine-grained sediment cores from the central South Yellow Sea area (SYSA) and Min-Zhe belt (MZB), East China Sea. Based on the high-resolution temporal sequences of total carbon (TC) and total organic carbon (TOC) contents, we reconstructed the annual variations of historical marine carbon storage, and explored the influence of terrestrial and marine sources on carbon burial at the centennial scale. The estimated TC storage over 100 years was 1.18×108 t in the SYSA and 1.45×109 t in the MZB. The corrected TOC storage fluxes at the centennial scale ranged from 17 to 28 t/(km2·a)in the SYSA and from 56 to 148 t/(km2·a) in the MZB. The decrease of terrestrial materials and the increase of marine primary production suggest that the TOC buried in the sediments in the SYSA and MZB was mainly derived from the marine autogenetic source. In the MZB, two depletion events occurred in TC and TOC storage from 1985 to 1987 and 2003 to 2006, which were coeval with the water impoundment in the Gezhouba and Three Gorges dams, respectively. The high-resolution records of the carbon storage rates and fluxes in the SYSA and MZB reflect the synchronous responses to human activities and provide an important reference for assessing the carbon sequestration capacity of the marginal seas of China.

The dynamics of the teleconnection between the Indian Ocean Dipole (IOD) in the tropical Indian Ocean and El Nino-Southern Oscillation (ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.

The coastal ocean circulation off the Chinese Subei (north Jiangsu Province) coasts in the southwestern Yellow Sea in summer is studied using hydrographic data from four research cruises, moored current meter data in the Lunan (south Shandong Province) trough, and Lagrangian trajectories of satellite-tracked ARGOS surface drifters in the summers of 2008 and 2009. The hydrographic data indicate a fresh water plume extending offshore in the northeastward direction from the Sheyang River mouth and a belt of relatively cold surface temperature from the surrounding areas located offshore of the Subei coasts to the south of the plume in summer. The drifter trajectories show that the Subei coastal current, which is traditionally thought to flow southward year round, flows northward in June through July under the forcing of the southerly monsoon. A northward intrusion along the submarine valley off the Changjiang mouth is indicated by the movement of the drifters, which is persistently strong and independent of the winds. Associated with the northward flow, coastal upwelling is generated offshore of the Subei coast to the south of the Sheyang River plume, below which upwelling is generated but is shut down by the buoyancy of the fresh water at the surface. Coastal upwelling is also observed off the coast of Qingdao city in middle July through early August of 2008, which is forced by the along-shore component of the southerly and southwesterly winds. The Qingdao upwelling in summer is reported for the first time in history.

Offshore extension of the fresh Subei coast water is identified in winter based on in site salinity observation data in this and previous studies. A high-resolution regional ocean circulation model is used to investigate the cross-isobath movement of low salinity-water over the Yellow and East China Seas, and it has reproduced the salinity distribution observed in the winter of 2014–2015 successfully. The model suggests that the low-salinity water is basically degenerated back to the eastern coast of China in winter because of strong northeasterly wind. However, a part of the low-salinity water extends offshore in the southeast direction across the 20–50 m isobaths over the Yangtze Bank, which cannot be explained by either the northerly winter monsoon or the Changjiang discharge. Numerical experiments suggest that the cross-isobath transport of the soluble substances is highly attributed to the tidal residual current, flowing southeastward across 20–50 m isobaths over the whole Yangtze Bank. The results of controlled experiments also indicate that the bottom shear of the tidal current, rather than the tidal mixing, plays a significant role in the cross-isobath current during winter.

Impacts of the Indonesian Throughflow (ITF) on seasonal circulation in the equatorial eastern Indian Ocean are investigated using the ocean-only model LICOM by opening and closing ITF passages. LICOM had daily forcing from NCEP reanalysis data during 2000–2011. It can reproduce vertical profiles of mean density and buoyancy frequency of World Ocean Atlas 2013 data. The model also simulates well annual oscillation in the central Indian Ocean and semiannual oscillation in the eastern Indian Ocean of sea level anomalies (SLA) using satellite altimeter data, as well as the semiannual oscillation of surface zonal equatorial currents of Ocean Surface Current Analyses Real Time current data in the equatorial Indian Ocean. The wave decomposition method is used to analyze the propagation and reflection of equatorial long waves based on LICOM output. Wave analysis suggests that ITF blockage mainly influences waves generated from the Indian Ocean but not the Pacific Ocean, and eastern boundary reflections play an important role in semiannual oscillations of SLA and zonal current differences in the equatorial Indian Ocean associated with ITF. Reconstructed ITF-caused SLA using wave decomposition coefficient differences between closed and open ITF-passage experiments suggest both Kelvin and Rossby waves from the first baroclinic mode have comparable contributions to the semiannual oscillations of SLA difference. However, reconstructed ITF-caused surface zonal currents at the equator suggest that the first meridional-mode Rossby wave has much greater contribution than the first baroclinic mode Kelvin wave. Both reconstructed sea level and zonal currents demonstrate that the first baroclinic mode has a greater contribution than other baroclinic modes.

Subseasonal-to-seasonal (S2S) forecasts have the potential to provide advance information about weather and climate events. The high heat capacity of water means that the subsurface ocean stores and re-releases heat (and other properties) and is an important source of information for S2S forecasts. However, the subsurface ocean is challenging to observe, because it cannot be measured by satellite. Subsurface ocean observing systems relevant for understanding, modeling, and forecasting on S2S timescales will continue to evolve with the improvement in technological capabilities. The community must focus on designing and implementing low-cost, high-value surface and subsurface ocean observations, and developing forecasting system capable of extracting their observation potential in forecast applications. S2S forecasts will benefit significantly from higher spatio-temporal resolution data in regions that are sources of predictability on these timescales (coastal, tropical, and polar regions). While ENSO has been a driving force for the design of the current observing system, the subseasonal time scales present new observational requirements. Advanced observation technologies such as autonomous surface and subsurface profiling devices as well as satellites that observe the ocean-atmosphere interface simultaneously can lead to breakthroughs in coupled data assimilation (CDA) and coupled initialization for S2S forecasts. These observational platforms should also be tested and evaluated in ocean observation sensitivity experiments with current and future generation CDA and S2S prediction systems. Investments in the new ocean observations as well as model and DA system developments can lead to substantial returns on cost savings from disaster mitigation as well as socio–economic decisions that use S2S forecast information.

An experiment using the Community Climate System Model (CCSM4), a participant of the Coupled Model Intercomparison Project phase-5 (CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole (IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the “oceanic channel dynamics” and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.

A set of absolute geostrophic current (AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profiles in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin (except the North Indian Ocean, where the circulation is dominated by monsoons). The identified non-Sverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom (JEBAR) and mesoscale eddy nonlinearity.

Absolute geostrophic currents in the North Pacific Ocean are calculated using the P-vector method and gridded Argo profiling data from January 2004 to December 2012. Three-dimensional structures and seasonal variability of meridional heat transport (MHT) and meridional salt transport (MST) are analyzed. The results show that geostrophic and Ekman components are generally opposite in sign, with the southward geostrophic component dominating in the subtropics and the northward Ekman component dominating in the tropics. In combination with the net surface heat flux and the MST through the Bering Strait, the MHT and MST of the western boundary currents (WBCs) are estimated for the first time. The results suggest that the WBCs are of great importance in maintaining the heat and salt balance of the North Pacific. The total interior MHT and MST in the tropics show nearly the same seasonal variability as that of the Ekman components, consistent with the variability of zonal wind stress. The geostrophic MHT in the tropics is mainly concentrated in the upper layers, while MST with large amplitude and annual variation can extend much deeper. This suggests that shallow processes dominate MHT in the North Pacific, while MST can be affected by deep ocean circulation. In the extratropical ocean, both MHT and MST are weak. However, there is relatively large and irregular seasonal variability of geostrophic MST, suggesting the importance of the geostrophic circulation in the MST of that area.

The cross-shelf circulation and its transport in the Yellow and East China Seas (YECSs) are very important to global ocean material exchanges and regional environment. A field survey including a long-term mooring, 89 sample stations, 25 drifters, etc., was conducted in the YECSs in the winter of 2015 to investigate the cross-shelf transport of the sediment plume over the Changjiang Bank. The observation shows that the northern East China Sea (ECS) current carries low temperature, low salinity, and high turbidity coastal waters southeastward from the radial tidal sand ridge off the Jiangsu coast to the outer shelf south of Cheju Island. The northern ECS current with an average speed of 4.7 cm/s and in the average direction of 100° from due north is not only measured directly by the 21-day mooring, but also recorded in trajectories of 6 satellite-tracked surface drifters. The mean current of the northern ECS current flows roughly along the 30–50 m isobaths with a small cross-isobath component. The mooring data indicate that the sediment flux is dominated by the mean advection of mean sediment concentration, resulting in an average suspended sediment flux of 52.23 g s−1 m−1 in the direction of 105°. According to the suspended sediment flux decomposition, the flux due to tidal currents is calculated to be one order of magnitude smaller than the advection by subtidal currents, implying that the sediment plume is unlikely generated by the tidal pumping, but is likely maintained by the advection. The amount of the suspended sediments carried by the northern ECS current is estimated to reach 40.62 million tons assuming an average width of 100 km of the turbid plume during December through February. The transport by the northern ECS current is suggested to provide sufficient amount of sediments for the Southwestern Cheju Island Mud to grow in time.

The regional INDESO model configured in the Indonesian seas from 2008 to 2016 is used to study the mechanisms responsible for the variability of the currents in the Sulawesi Sea of the Indonesian seas. The model simulation compares reasonably with the seasonal to interannual variability of the moored current meter observations in the upper 350m or so of the Maluku Channel during 2015 and 2016. The interannual variability of the currents in the eastern Sulawesi Sea in the model is found to be associated with both the Pacific and Indian Ocean remote forcing. Lag correlation analysis and a theoretical linear wave model simulation suggest that both the equatorial Kelvin waves from the Indian Ocean and the coastally trapped Kelvin waves from the western Pacific along the Philippine coast can propagate through the Indonesian seas and arrive at the Maluku Channel. In particular, from mid-2015 to 2016 the Indian Ocean Kelvin waves are found to significantly impact the sea level anomaly variability in the Maluku Channel. The results indicate the importance of Indo-Pacific planetary waves to the interannual variability of the currents in the Sulawesi Sea at the entrance of the Indonesian seas. Plain Language Summary The Indonesian seas provide a tropical connection for the climate systems over the tropical Pacific and Indian Oceans, the dynamics of which are not clear so far. This study uses a high-resolution computer model to simulate the currents measured by an acoustic current meter attached to a deep ocean mooring in the Maluku Channel of the northeastern Indonesian seas. Based on the successful simulation, the dynamics of the interannual variations of the circulation in the Maluku Channel are studied using the model and a simplified theoretical linear model. The interannual currents and sea level variability in the Maluku Channel are found to be affected by both the Indian Ocean Kelvin waves and the Philippine coastal Kelvin waves. It is found that the Indian Ocean Kelvin waves dominate the sea level variability in the Maluku Channel from mid-2015 to 2016. In early 2015, the sea level variability in the Maluku Channel is dominated by the coastal Kelvin waves from the east Philippine coasts. The results are important for the understanding of the circulation at the entrance of the Indonesian seas and of the Indo-Pacific interactions through the propagation of the planetary waves.

The Maluku Channel is a major opening of the eastern Indonesian Seas to the western Pacific Ocean, the upper-ocean currents of which have rarely been observed historically. During December 2012–November 2016, long time series of the upper Maluku Channel transport are measured successfully for the first time using subsurface oceanic moorings. The measurements show significant intraseasonal-to-interannual variability of over 14 Sv (1 Sv ≡ 106 m3 s−1) in the upper 300 m or so, with a mean transport of 1.04–1.31 Sv northward and a significant southward interannual change of over 3.5 Sv in the spring of 2014. Coincident with the interannual transport change is the Mindanao Current, choked at the entrance of the Indonesian Seas, which is significantly different from its climatological retroflection in fall–winter. A high-resolution numerical simulation suggests that the variations of the Maluku Channel currents are associated with the shifting of the Mindanao Current retroflection. It is suggested that the shifting of the Mindanao Current outside the Sulawesi Sea in the spring of 2014 elevates the sea level at the entrance of the Indonesian Seas, which drives the anomalous transport through the Maluku Channel. The results suggest the importance of the western boundary current nonlinearity in driving the transport variability of the Indonesian Throughflow.

The equatorial wave dynamics of sea level variations during negative Indian Ocean dipole (nIOD) events are investigated using the LICOM ocean general circulation model forced with the European Centre for Medium-Range Weather Forecast reanalysis wind stress and heat flux from 1990 to 2001. The work is a continuation of the study by Yuan and Liu, in which the equatorial wave dynamics during positive IOD events are investigated. The model has reproduced the sea level anomalies of satellite altimeter data well. Long equatorial waves extracted from the model output suggest two kinds of negative feedback during nIOD events: the western boundary reflection and the easterly wind bursts. During the strong 1998–99 nIOD event, the downwelling anomalies in the eastern Indian Ocean are terminated by persistent and strong upwelling Kelvin waves from the western boundary, which are reflected from the wind-forced equatorial Rossby waves over the southern central Indian Ocean. During the 1996–97 nIOD, however, the reflection of upwelling anomalies at the western boundary is terminated by the arrival of downwelling equatorial Rossby waves from the eastern boundary reflection in early 1997. Therefore, the negative feedback of this nIOD event is not provided by the western boundary reflection. The downwelling anomalies in the eastern basin during the 1996–97 nIOD event are terminated by easterly wind anomalies over the equatorial Indian Ocean in early 1997. The disclosed equatorial wave dynamics are important to the simulation and prediction of IOD evolution.

Lag correlations between sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean (STIO) in fall and Nino 3.4 SSTA in the eastern equatorial Pacific in the following fall are subjected to decadal variation, with positive correlations during some decades and negative correlations during others. Negative correlations are smaller and of shorter duration than positive correlations. Variations in lag correlations suggest that the use of the Indian Ocean Dipole (IOD) as a predictor of the El Nino-Southern Oscillation (ENSO) at a lead time of one year is not effective during some decades. In this study, lag correlations between IOD and ENSO anomalies were analyzed to investigate why the IOD-ENSO teleconnection disappears during decades with negative correlations. Anomalies induced by the IOD in the equatorial Pacific Ocean during decades with negative correlations are still present, but at a greater depth than in decades with positive correlations, resulting in a lack of response to oceanic channel dynamics in the cold tongue SSTA. Lag correlations between oceanic anomalies in the west Pacific warm pool in fall and the equatorial Pacific cold tongue with a one-year time lag are significantly positive during decades with negative correlations. These results suggest that oceanic channel dynamics are overwhelmed by ocean-atmosphere coupling over the equatorial Pacific Ocean during decades with negative correlations. Therefore, the Indonesian throughflow is not effective as a link between IOD signals and the equatorial Pacific ENSO.

The nonlinear collision of two western boundary currents (WBCs) of Munk thickness LM colliding near a gap of width 2a is studied using a 1.5-layer, reduced-gravity, quasigeostrophic ocean model. The work is a continuation of our recent study on nonlinear collision of two equal-strength WBCs at a wide gap. It is found that, for narrow gaps, a < 5.7LM, and both of the WBCs fail to penetrate into the western basin due to the restriction of friction; for intermediate size gaps, 5.7LM ≤ a < 9.6LM, and multiple equilibrium states exist for the colliding WBCs: the penetrating state, the choking state, and the eddy-shedding state. The current system transits between them through a hysteresis procedure, with transitions at different Reynolds numbers from those in the equal-transport case. The stronger WBC tends to intrude more deeply into the western basin than the weaker WBC; for wide gaps, a > 9.6LM, and only penetrating and eddy-shedding states exist. No choking state is identified for either WBC. It is found that the critical gap width for the disappearance of the choking state decreases with the asymmetry of the WBC system. The theory is used to explain some of the circulation features at the entrance of the Indonesian Throughflow in the western Pacific Ocean recently observed with satellite-tracked surface drifters.

The mean structure and variability of the currents east of Mindanao are investigated through 2 year mooring observations at about 8 degrees N, 127 degrees 3' E from December 2010 to December 2012. The strong southward Mindanao Current (MC) exists in the upper 600 m with a maximum mean velocity of 73 cm/s and a standard deviation of 17 cm/s at 100 m. A northward mean flow is observed below 600 m to the depth deeper than 1000 m, which has been called the Mindanao Undercurrent (MUC) with a maximum mean velocity of about 10 cm/s at 950 m and a standard deviation of 19 cm/s. Further analysis with hydrographic data and an eddy-resolving model outputs also suggests this northward mean current to be the MUC. Intraseasonal variability with a period of 60-80 days is revealed through the whole water column from 200 m down to about 900 m. This intraseasonal variability appears to be closely related to subthermocline eddies, which translate westward and intensify near the Mindanao coast.

The article of record as published may be found at http://dx.doi.org/10.1175/JPO-D-12-0230.1 Absolute geostrophic currents in the North Pacific Ocean are calculated from the newly gridded Argo profiling float data using the P-vector method for the period of 2004–11. The zonal geostrophic currents based on the Argo profile data are found to be stronger than those based on the traditional World Ocean Atlas 2009 (WOA09) data. A westward mean geostrophic flow underneath the North Equatorial Countercurrent is identified using the Argo data, which is evidenced by sporadic direct current measurements and geostrophic calculations in history. This current originates east of the date line and transports more than 4 3 106 m3 s 21 of water westward in the subsurface northwestern tropical Pacific Ocean. The authors name this current the North Equatorial Subsurface Current. The transport in the geostrophic currents is compared with the Sverdrup theory and found to differ significantly in several locations. Analyses have shown that errors of wind stress estimation cannot account for all of the differences. The largest differences are found in the area immediately north and south of the bifurcation latitude of the North Equatorial Current west of the date line and in the recirculation area of the Kuroshio and its extension, where nonlinear activities are vigorous. It is, therefore, suggested that the linear dynamics of the Sverdrup theory is deficient in explaining the geostrophic transport of the tropical northwestern Pacific Ocean. National Basic Research Program of China Naval Oceanographic Office NSFC Grants 40888001 NSFC Grants 41176019 CMA Grant GYHY201306018 CAS Strategic Priority Project XDA11010301 KLOCAW Grant 1208 Municipal Science and Technology Project 2011C32015 Municipal Science and Technology Project 2012C33033 NSF Grants OCE-0960500 NSF Grants OCE-1049131

Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10-20 years) and multidecadal (> 20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the "out of phase" relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces "in phase" effects on the WTP sea level variability.

The performance of the eddy-resolving LICOM2.0 in simulating the Indonesian Throughflow has been evaluated against the INSTANT data in the present study. The mean vertical structures of the along strait velocities are simulated well in LICOM2.0, but the large velocities at the bottom of the Lifamatola Passage and the Timor Passage cannot be reproduced by LICOM2.0. The causes are considered to be both the errors in the topography and the tidal mixing at the bottom. Despite several biases in the mean velocities, the mean inflow and outflow volume transports in LICOM2.0 are almost identical to the INSTANT data. Compared with the lower resolution LICOM, the most significant improvement is the better simulation of the partitions of the inflow and outflow transports in individual straits. The outflow for low-resolution LICOM is mainly through the Ombai and Lombok Strait, whereas that for LICOM2.0 is mainly through the Timor Passage. The variability of the vertical structure of velocities and the volume transport are also investigated. LICOM2.0 overestimates the magnitude of the upper-layer currents and the amplitude of the variation. We also found that the largest correlation coefficient occurs in the shallowest strait, the Lombok, whereas the lowest occurs in the Timor Passage, especially in the upper layer. The latter may be caused by the unrealistic transport through the Torres Strait in LICOM2.0.

The Luzon Undercurrent (LUC) was discovered about 20 years ago by geostrophic calculation from conductivity–temperature–depth (CTD) data. But it was not directly measured until 2010. From November 2010 to July 2011, the LUC was first directly measured by acoustic Doppler current profiler (ADCP) from a subsurface mooring at 18.0°N, 122.7°E to the east of Luzon Island. A number of new features of the LUC were identified from the measurements of the current. Its depth covers a range from 400 m to deeper than 700 m. The observed maximum velocity of the LUC, centered at about 650 m, could exceed 27.5 cm s−1, four times stronger than the one derived from previous geostrophic calculation with hydrographic data. According to the time series available, the seasonality of the LUC strength is in winter > summer > spring. Significant intraseasonal variability (ISV; 70–80 days) of the LUC is exposed. Evidence exists to suggest that a large portion of the intraseasonal variability in the LUC is related to the westward propagation of mesoscale eddies from the east of the mooring site.

Lag correlations of sea surface temperature anomalies (SSTAs), sea surface height anomalies (SSHAs), subsurface temperature anomalies, and surface zonal wind anomalies (SZWAs) produced by the Flexible Global Ocean-Atmosphere-Land System model: Grid-point Version 2 (FGOALS-g2) are analyzed and compared with observations. The insignificant, albeit positive, lag correlations between the SSTAs in the southeastern tropical Indian Ocean (STIO) in fall and the SSTAs in the central-eastern Pacific cold tongue in the following summer through fall are found to be not in agreement with the observational analysis. The model, however, does reproduce the significant lag correlations between the SSHAs in the STIO in fall and those in the cold tongue at the one-year time lag in the observations. These, along with the significant lag correlations between the SSTAs in the STIO in fall and the subsurface temperature anomalies in the equatorial Pacific vertical section in the following year, suggest that the Indonesian Throughflow plays an important role in propagating the Indian Ocean anomalies into the equatorial Pacific Ocean. Analyses of the interannual anomalies of the Indonesian Throughflow transport suggest that the FGOALS-g2 climate system simulates, but underestimates, the oceanic channel dynamics between the Indian and Pacific Oceans. FGOALS-g2 is shown to produce lag correlations between the SZWAs over the western equatorial Pacific in fall and the cold tongue SSTAs at the one-year time lag that are too strong to be realistic in comparison with observations. The analyses suggest that the atmospheric bridge over the Indo-Pacific Ocean is overestimated in the FGOALS-g2 coupled climate model.

The authors’ previous dynamical study has suggested a link between the Indian and Pacific Ocean interannual climate variations through the transport variations of the Indonesian Throughflow. In this study, the consistency of this oceanic channel link with observations is investigated using correlation analyses of observed ocean temperature, sea surface height, and surface wind data. The analyses show significant lag correlations between the sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean in fall and those in the eastern Pacific cold tongue in the following summer through fall seasons, suggesting potential predictability of ENSO events beyond the period of 1 yr. The dynamics of this teleconnection seem not through the atmospheric bridge, because the wind anomalies in the far western equatorial Pacific in fall have insignificant correlations with the cold tongue anomalies at time lags beyond one season. Correlation analyses between the sea surface height anomalies (SSHA) in the southeastern tropical Indian Ocean and those over the Indo-Pacific basin suggest eastward propagation of the upwelling anomalies from the Indian Ocean into the equatorial Pacific Ocean through the Indonesian Seas. Correlations in the subsurface temperature in the equatorial vertical section of the Pacific Ocean confirm the propagation. In spite of the limitation of the short time series of observations available, the study seems to suggest that the ocean channel connection between the two basins is important for the evolution and predictability of ENSO.

The responses to tidal and/or wind forces of Lagrangian trajectories and Eulerian residual velocity in the southwestern Yellow Sea are investigated using a high-resolution circulation model. The simulated tidal harmonic constants agree well with observations and existing studies. The numerical experiment reproduces the long-range southeastward Eulerian residual current over the sloping bottom around the Yangtze Bank also shown in previous studies. However, the modeled drifters deployed at the northeastern flank of the Yangtze Bank in the simulation move northeastward, crossing over this strong southeastward Eulerian residual current rather than following it. Additional sensitivity experiments reveal that the influence of the Eulerian tidal residual currents on Lagrangian trajectories is relatively weaker than that of the wind driven currents. This result is consistent with the northeastward movement of ARGOS surface drifters actually released in the southwestern Yellow Sea. Further experiments suggest that the quadratic nature of the bottom friction is the crucial factor, in the southwestern Yellow Sea, for the weaker influence of the Eulerian tidal residual currents on the Lagrangian trajectories. This study demonstrates that the Lagrangian trajectories do not follow the Eulerian residual velocity fields in the shallow coastal regions of the southwestern Yellow Sea.

A nested circulation model system based on the Princeton ocean model (POM) is set up to simulate the currentmeter data from a bottom-mounted Acoustic Doppler Profiler (ADP) deployed at the 30 m depth in the Lunan(South Shandong Province, China) Trough south of the Shandong Peninsula in the summer of 2008, and to study the dynamics of the circulation in the southwestern Huanghai Sea (Yellow Sea). The model has reproduced well the observed subtidal current at the mooring site. The results of the model simulation suggest that the bottom topography has strong steering effects on the regional circulation in summer. The model simulation shows that the Subei (North Jiangsu Province, China)coastal current flows northward in summer, in contrast to the southeastward current in the center of the Lunan Trough measured by the moored currentmeter. The analyses of the model results suggest that the southeastward current at the mooring site in the Lunan Trough is forced by the westward wind-driven current along the Lunan coast, which meets the northward Subei coastal current at the head of the Haizhou Bay to flow along an offshore path in the southeastward direction in the Lunan Trough. Analysis suggests that the Subei coastal current, the Lunan coastal current, and the circulation in the Lunan Trough are independent current systems controlled by different dynamics. Therefore, the current measurements in the Lunan Trough cannot be used to represent the Subei coastal current in general.

Using conductivity-Temperature-depth data of a recent cruise during July 22-28, 2008 and historical data, it is found that temperature inversions occur from time to time in the Huanghai Sea(Yellow Sea) cold water mass (HSCWM) in summer. The temperature inversions are produced by the movement of the fresh and cold HSCWM masses above the warm and saline Huanghai Sea Warm Current water at the central bottom of the Huanghai Sea Trough. The non-homogeneous profiles of the temperature and the salinity suggest that vertical mixing in the HSCWM, which is of great importance to the circulation in the Huanghai Sea in summer, is weak. Trajectories of satellite-tracked surface drifters suggest that waters in the northern reach of the Huanghai Sea move southward along the 40-50 m isobaths and descend into the southern Huanghai Sea to form the western core of the HSCWM.

Unfortunately for all articles of Vol. 35 No. 1 the future journal title “Journal of Oceanology and Limnology” was used instead of the current journal title “Chinese Journal of Oceanology and Limnology”. All articles in the issue are affected. Please make sure to cite the articles with the following Vol. and No. info: Chinese Journal of Oceanology and Limnology, Vol. 35 No. 1, [page range].

Controlled numerical experiments using ocean-only and ocean–atmosphere coupled general circulation models show that interannual sea level depression in the eastern Indian Ocean during the Indian Ocean dipole (IOD) events forces enhanced Indonesian Throughflow (ITF) to transport warm water from the upper-equatorial Pacific Ocean to the Indian Ocean. The enhanced transport produces elevation of the thermocline and cold subsurface temperature anomalies in the western equatorial Pacific Ocean, which propagate to the eastern equatorial Pacific to induce significant coupled evolution of the tropical Pacific oceanic and atmospheric circulation. Analyses suggest that the IOD-forced ITF transport anomalies are about the same amplitudes as those induced by the Pacific ENSO. Results of the coupled model experiments suggest that the anomalies induced by the IOD persist in the equatorial Pacific until the year following the IOD event, suggesting the importance of the oceanic channel in modulating the interannual climate variations of the tropical Pacific Ocean at the time lag beyond one year.

Hysteresis of a western boundary current (WBC) flowing by a wide gap of a western boundary and the dynamics of the WBC variations associated with the impingement of mesoscale eddies from the eastern side of the gap are studied using a 1.5-layer reduced-gravity quasigeostrophic ocean model. The study focuses on two issues not covered by existing studies: the effects of finite baroclinic deformation radii and time dependence perturbed by mesoscale eddies. The results of the study show that the hysteresis of the WBC of finite baroclinic deformation radii is not controlled by multiple steady-state balances of the quasigeostrophic vorticity equation. Instead, the hysteresis is controlled by the periodic penetrating and the leaping regimes of the vorticity balance. The regime of the vorticity balance inside the gap is dependent on the history of the WBC evolution, which gives rise to the hysteresis of the WBC path. Numerical experiments have shown that the parameter domain of the hysteresis is not sensitive to the baroclinic deformation radius. However, the domain of the periodic solution, which is determined by the lower Hopf bifurcation of the nonlinear system, is found to be sensitive to the magnitude of the baroclinic deformation radius. The lower Hopf bifurcation from steady penetration to periodic penetration is found to occur at lower Reynolds numbers for larger deformation radii. In general, the lower Hopf bifurcation stays outside the hysteresis domain of the Reynolds number. However, for very small deformation radii, the lower Hopf bifurcation falls inside the hysteresis domain, which results in the transition from the leaping to the penetrating regimes of the WBC to skip the periodic regime and hence the disappearance of the upper Hopf bifurcation. Mesoscale eddies approaching the gap from the eastern basin are found to have significant impact on the WBC path inside the gap when the WBC is at a critical state along the hysteresis loop. Cyclonic (anticyclonic) eddies play the role of reducing (enhancing) the inertial advection of vorticity in the vicinity of the gap so that transitions of the WBC path from the leaping (periodic penetrating) to the periodic penetrating (leaping) regimes are induced. In addition, cyclonic eddies are able to induce transitions of the WBC from the periodic penetrating to the leaping regimes through enhancing the meridional advection by its right fling. The transitions are irreversible because of the nonlinear hysteresis and are found to be sensitive to the strength, size, and approaching path of the eddy.

Satellite images and in situ hydrography and nutrient observations are used to study the three-dimensional structure of a penetrating front off the Changjiang mouth in the East China Sea. The satellite images of MODIS/Terra on October 16, 2006 show anomalously high concentrations of chlorophyll and total suspended sediments extending offshore from the mean coastal front off the Chiangjiang mouth. However, the sea-surface temperature image of the same satellite shows no signature of this extension at all. The in situ hydrography measured during the same time as the satellite images discloses that the surface layer of the front is occupied by low-salinity waters from the nearshore area, which suggests a cross-shelf jet covering a distance of about 50 km. A counter intrusion underneath the surface offshore jet is indicated by an increase of the subsurface temperature and salinity during the offshore excursion of the front, which leads to a significant temperature inversion at the head of the front. The vertical temperature and salinity distribution shows propensity of double diffusive processes, which may contribute to the ensuing evolution of the front. The nutrient distribution of the front is consistent with the cross-shelf jet derived from the hydrographic data, with surface and bottom intensified concentrations and minimum mid-depth concentrations, suggesting that the primary transport of the surface nutrients is in the horizontal cross-shelf direction. The potential dynamics of the frontal intrusion is discussed in light of wind forcing and frontal instability. The intrusion is found to be very important to cross-shelf and cross-front exchanges in the East China Sea. (C) 2010 Elsevier Ltd. All rights reserved.

A general ocean circulation model is used to study the dynamics of the cross-shelf circulation in the Yellow and East China Seas in winter. The model results show that the shelf circulation in winter is induced primarily by the northerly monsoonal winds. Compared with the wind-driven circulation, the Kuroshio-forced circulation over the shelf is very weak. The westward shift of the Yellow Sea Warm Current is produced by the northerly winds through the generation of a sea-level trough off the Subei coasts and a sea-level ridge along the center of the Yellow Sea topographic trough. The sea-level trough off the Subei coasts is produced because the sea level at the coast is tied to the depression in the northern Yellow Sea and is moderated by the surface Ekman transport of the northerly monsoon. The sea-level ridge along the center of the Yellow Sea topographic trough is produced because the sea level along both the east China and the west Korea coasts decreases. The structure of the sea level gives rise to a geostrophic intrusion against the wind along the western side of the Yellow Sea trough and southward movement of the Korean coastal currents along the eastern side of the trough.

Images of 8-day mean chlorophyll-a concentrations of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard of Aqua Satellite from 2002 to 2007 and of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite from 1998 to 2007 are used to study the variability of the cross-shelf penetrating fronts (CPFs) in the East China Sea. The analysis suggests that the generation of the CPFs has strong seasonal-to-interannual variations, with more CPFs in summer and winter than in spring and fall. Each CPF lasts for a few days to a month. The majority of the fronts are triangle-shaped with their broad bases nearby the coast and their sharp heads penetrating into the middle shelf. There are over 40 CPFs with penetrating distances exceeding 100 km over the East China Sea during the past 10 years of the satellite era, with the maximum ones reaching the Kuroshio at the edge of the continental shelf. Of all the low cloud scenes of the satellite images, more than 25% contain at least one CPF. The high-frequency occurrence of the CPFs suggests that the CPFs play an important role in cross-shelf transport of heat, effluent, and land-derived materials in the East China Sea.

Strong El Nino and positive Indian Ocean Dipole (pIOD) events in 2015/2016 followed by relatively strong negative Indian Ocean Dipole (nIOD) and weak La Nina in 2016 events have affected hydrography conditions in the Indonesian Throughflow (ITF) region. Two research cruises were conducted using RV Baruna Jaya VIII in August and November 2016. These cruises aim to evaluate possible impact of those two climate mode events on the water mass characteristic in the outflow region of the ITF. Hydrographic data from those two cruises were combined with the sea surface temperature (SST) from the Advanced Very High Resolution Radiometer (AVHRR) and surface wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The results showed that in the 2016 anomaly year, the cooler sea surface temperature was observed during the negative IOD (nIOD) event while the warmer temperature was found in the post of nIOD event. The observed water mass characteristics in the outflow region of the ITF revealed that the upper layer was dominated by the Indian Ocean water mass, while the Pacific Ocean water mass was observed in the deeper layer. The observed current data across the Sumba Strait showed that the South Java Coastal Current (SJCC) was observed in the upper layer, propagating eastward toward the Savu Sea. A few days later, the observed currents in the upper layer of the Ombai Strait revealed the ITF flow towards the Indian Ocean. Meanwhile, the lower layer showed an eastward flow towards the Ombai Strait.

The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. The trajectories of the Argo floats provided robust evidence that there does exist southward flowing current along the Vietnam coast. The southward current begins at about 15°N, 111°E, flowing along the 1 000 m isobath and extending to 5°N south. The estimated surface and parking depth velocities obtained from the floats suggest that this southward current can extend to 1 000 m depth. The mean surface velocity of the western boundary current is about 49 cm/s, with the maximum speed exceeding 100 cm/s occurring at 11.6°N, 109.5°E in the direction of 245°. The mean parking depth (1 000 m) velocity is 12–16 cm/s with the maximum speed of 36 cm/s occurring at 12.1°N, 109.7°E in the direction of 239°.

Using a 1.5-layer reduced-gravity nonlinear shallow-water equation model, we studied the effect of the meridional wind on the western boundary currents (WBC) at critical states with hysteresis courses. The results of the simulation indicate that the WBC is prone to penetrating into the gap under northerly winds, and its path is more difficult to alter due to the larger interval between the two critical transition curves (C (1) P and C (1) L). For southerly winds, the WBC is prone to leaping across the gap, and its path is easier to alter due to the smaller interval between the two critical transition curves. The simulation results also indicate that the meridional winds over the southern region of the gap are the dominant factor determining the formation of the WBC. The dynamic mechanism influencing the transport of WBC near the gap is both Ekman transport and the blocking of Ekman transport. Ekman transport induced by northerly winds may reduce the transport of the WBC, causing the beta-effect to dominate the meridional advection (promoting the penetration). Southerly winds, however, may enhance the transport of the WBC, causing the meridional advection to dominate the beta-effect (promoting the leaping state). These results explain some structural features of the Kuroshio at the Luzon Strait.

Long-wave dynamics of the interannual variations of the equatorial Indian Ocean circulation are studied using an ocean general circulation model forced by the assimilated surface winds and heat flux of the European Centre for Medium-Range Weather Forecasts. The simulation has reproduced the sea level anomalies of the Ocean Topography Experiment (TOPEX)/Poseidon altimeter observations well. The equatorial Kelvin and Rossby waves decomposed from the model simulation show that western boundary reflections provide important negative feedbacks to the evolution of the upwelling currents off the Java coast during Indian Ocean dipole (IOD) events. Two downwelling Kelvin wave pulses are generated at the western boundary during IOD events: the first is reflected from the equatorial Rossby waves and the second from the off-equatorial Rossby waves in the southern Indian Ocean. The upwelling in the eastern basin during the 1997–98 IOD event is weakened by the first Kelvin wave pulse and terminated by the second. In comparison, the upwelling during the 1994 IOD event is terminated by the first Kelvin wave pulse because the southeasterly winds off the Java coast are weak at the end of 1994. The atmospheric intraseasonal forcing, which plays an important role in inducing Java upwelling during the early stage of an IOD event, is found to play a minor role in terminating the upwelling off the Java coast because the intraseasonal winds are either weak or absent during the IOD mature phase. The equatorial wave analyses suggest that the upwelling off the Java coast during IOD events is terminated primarily by western boundary reflections.

The interannual anomalies of horizontal heat advection in the surface mixed layer over the equatorial Pacific Ocean in an assimilation experiment are studied and compared with existing observational analyses. The assimilation builds upon a hindcast study that has produced a good simulation of the observed equatorial currents and optimizes the simulation of the Reynolds sea surface temperature (SST) data. The comparison suggests that the assimilation has improved the simulation of the interannual horizontal heat advection of the surface mixed layer significantly. During periods of interrupted current measurements, the assimilation is shown to produce more meaningful anomalies of the heat advection than the interpolation of the observational data does. The assimilation also shows that the eddy heat flux due to the correlation between high-frequency current and SST variations, which is largely overlooked by the existing observational analyses, is important for the interannual SST balance over the equatorial Pacific. The interannual horizontal heat advection anomalies are found to be sensitive to SST errors where oceanic currents are strong, which is a challenge for ENSO prediction. The study further suggests that the observational analyses of the tropical SST balance based on the TAO and the Reynolds SST data contain significant errors due to the large gradient errors in the Reynolds SST data, which are amplified into the advection anomalies by the large equatorial currents.

Satellite and in situ observations in the equatorial Atlantic Ocean during 2002–03 show dominant spectral peaks at 40–60 days and secondary peaks at 10–40 days in sea level and thermocline within the intraseasonal period band (10–80 days). A detailed investigation of the dynamics of the intraseasonal variations is carried out using an ocean general circulation model, namely, the Hybrid Coordinate Ocean Model (HYCOM). Two parallel experiments are performed in the tropical Atlantic Ocean basin for the period 2000–03: one is forced by daily scatterometer winds from the Quick Scatterometer (QuikSCAT) satellite together with other forcing fields, and the other is forced by the low-passed 80-day version of the above fields. To help in understanding the role played by the wind-driven equatorial waves, a linear continuously stratified ocean model is also used. Within 3°S–3°N of the equatorial region, the strong 40–60-day sea surface height anomaly (SSHA) and thermocline variability result mainly from the first and second baroclinic modes equatorial Kelvin waves that are forced by intraseasonal zonal winds, with the second baroclinic mode playing a more important role. Sharp 40–50-day peaks of zonal and meridional winds appear in both the QuikSCAT and Pilot Research Moored Array in the Tropical Atlantic (PIRATA) data for the period 2002–03, and they are especially strong in 2002. Zonal wind anomaly in the central-western equatorial basin for the period 2000–06 is significantly correlated with SSHA across the equatorial basin, with simultaneous/lag correlation ranging from −0.62 to 0.74 above 95% significance. Away from the equator (3°–5°N), however, sea level and thermocline variations in the 40–60-day band are caused largely by tropical instability waves (TIWs). On 10–40-day time scales and west of 10°W, the spectral power of sea level and thermocline appears to be dominated by TIWs within 5°S–5°N of the equatorial region. The wind-driven circulation, however, also provides a significant contribution. Interestingly, east of 10°W, SSHA and thermocline variations at 10–40-day periods result almost entirely from wind-driven equatorial waves. During the boreal spring of 2002 when TIWs are weak, Kelvin waves dominate the SSHA across the equatorial basin (2°S–2°N). The observed quasi-biweekly Yanai waves are excited mainly by the quasi-biweekly meridional winds, and they contribute significantly to the SSHA and thermocline variations in 1°–5°N and 1°–5°S regions.