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The North Equatorial Subsurface Current (NESC) is a subthermocline ocean current uncovered recently in the tropical Pacific Ocean, flowing westward below the North Equatorial Countercurrent. In this study, the dynamics of the seasonal cycle of this current are studied using historical shipboard acoustic Doppler current profiler measurements and Argo absolute geostrophic currents. Both data show a westward current at the depths of 200–1000 m between 4° and 6°N, with a typical core speed of about 5 and 2 cm s−1, respectively. The subsurface current originates in the eastern Pacific, with its core descending to deeper isopycnal surfaces and moving to the equator as it flows westward. The zonal velocity of the NESC shows pronounced seasonal variability, with the annual-cycle harmonics of vertical isothermal displacement and zonal velocity presenting characters of vertically propagating baroclinic Rossby waves. A simple analytical Rossby wave model is employed to simulate the propagation of the seasonal variations of the westward zonal currents successfully, which is the basis for exploring the wind forcing dynamics. The results suggest that the wind curl forcing in the central-eastern basin between 170° and 140°W associated with the meridional movement of the intertropical convergence zone dominates the NESC seasonal variability in the western Pacific, with the winds west of 170°W and east of 140°W playing a minor role in the forcing.

The ocean currents in the Halmahera Sea are studied using a subsurface mooring deployed in the Jailolo Strait from November 2015 to October 2017. The subtidal currents of the mooring measurements are characterized by a two-layer system, with the current variability below about 200 m in opposite phases to that in the upper layer. The mean along-strait velocity (ASV) is toward the Indonesian seas in the whole water column, producing an estimated mean transport of 2.44 ± 0.42 Sv (1 Sv ≡ 106 m3 s−1). The errors of the transport calculation based on the single mooring measurements are estimated to be less than 15% using simulations of high-resolution ocean models. A weak current is observed to flow northward during 2017 at the bottom of the strait. The ASV variability is found to be dominated by an annual cycle both in the upper and lower layers. The total transport, however, is dominated by semiannual variability because of the cancelation of the annual transports in the upper and lower layers. The variability of the transport is suggested to be driven by the pressure difference between the Pacific Ocean and the Indonesian seas, as evidenced by the agreement between the satellite pressure gradient and the two-layer transports. The transport of the Jailolo Strait during the 2015/16 super El Niño is found to be nearly the same as that during the 2016 La Niña, suggesting that the interannual variability of the transport is much smaller than the seasonal cycle.

This paper examines whether private entrepreneurs with communist party member status affect corporate social responsibility (CSR) performance of private enterprises. Our empirical result reveals that firms led by private entrepreneurs of communist party members are significantly associated with higher CSR score. The result is robust to confronting several sources of endogeneity, e.g., re-examining the result using propensity score matching (PSM), entropy balancing (EB) and Heckman two-stage estimation, removing the influence of local religious culture. Further, the observed positive relation is particularly sharper for firms with party organization embedding and a good external legal environment. Our findings highlight entrepreneur political affiliation as an important driver of socially responsible corporate decision making.

Global sea level rise (SLR) associated with a warming climate exerts significant stress on coastal societies and low-lying island regions. The rates of coastal SLR observed in the past few decades, however, have large spatial and temporal differences from the global mean, which to a large part have been attributed to basin-scale climate modes. In this paper, we review our current state of knowledge about climate modes' impacts on coastal sea level variability from interannual-to-multidecadal timescales. Relevant climate modes, their impacts and associated driving mechanisms through both remote and local processes are elaborated separately for the Pacific, Indian and Atlantic Oceans. This paper also identifies major issues and challenges for future research on climate modes' impacts on coastal sea level. Understanding the effects of climate modes is essential for skillful near-term predictions and reliable uncertainty quantifications for future projections of coastal SLR.

The North Equatorial Subsurface Current (NESC) has recently been found to flow westward below the North Equatorial Countercurrent in the subsurface layer across the Pacific Ocean. The structure, water mass properties, and the dynamics of the NESC are studied using Argo profiles and geostrophic currents, combined with moored current meter observations. The mean westward geostrophic currents of the NESC has been validated with moored current meter measurements at 4.7° N, 142° E in the far western tropical Pacific Ocean. Sizable seasonal-to-interannual variability of the NESC is indicated by the observations, with strong transports in boreal summer and during La Niña events, whereas weak transports in boreal winter and during El Niño events. The water masses of the NESC appear to be the mixture of the North and South Pacific intermediate waters, with the waters immediately below the thermocline closer to the North than to the South Pacific waters. A simulation using a linear continuously stratified model of ocean circulation suggests that the mean NESC is forced by wind curl through low baroclinic mode responses of the ocean.

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 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.

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.

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.

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

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.

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.

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.

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.