Coastal Kelvin Research Articles

Negative Surface Chlorophyll Concentration Anomalies in the Southeast Arabian Sea During Summer in 2015 and 2019

AbstractSatellite observations revealed two extremely low surface chlorophyll concentration (SCC) events with a warm sea surface temperature anomaly in the southeastern Arabian Sea (SEAS, 6°–15°N, 72°–77°E) during the summer (July–August–September) in 2015 and 2019. We find that the physical processes leading to these two similar low SCC events are remarkably different. The low SCC in the SEAS during summer 2019 is mainly related to the weakened upwelling and deepening of the thermocline depth due to the combined effects of the local wind anomalies and the arrival of westward‐propagating downwelling coastal Kelvin wave driven by easterly anomalies near the eastern Sri Lanka during an extreme positive Indian Ocean Dipole (IOD) event. In summer 2015, a weaker positive IOD‐induced easterly anomalies in the southern Bay of Bengal also drives downwelling coastal Kelvin waves westward, deepening the thermocline in the SEAS. But unlike that in summer 2019, the local wind stress curl anomalies in the SEAS during summer 2015 favors upwelling, which counteracts the downward motion of the coastal Kelvin waves, leading to weaker downward transport (one‐third of that in 2019). Meanwhile, the upper ocean layer in the SEAS experiences extreme warming during summer owing to the development of 2015/2016 super El Niño. This substantial warming enhances upper oceanic stratification, which results in weaker vertical mixing and reduces the SCC to an extremely low level despite the much weaker IOD strength in 2015.

The influence of climate variability events on the mesoscale eddies in the Bay of Bengal

This study investigates the temporal variability of mesoscale eddies in the Bay of Bengal (BoB) over a 29-year period (1993–2021) using satellite altimeters. High-resolution daily sea level anomaly data are considered to identify the mesoscale eddies in the BoB utilizing py-eddy-tracker, an automated eddy detection and tracking method. Wavelet coherence analysis was conducted to find a statistically significant relation between eddy properties and climate indices. The findings indicate that anti-cyclonic eddies are more susceptible to the consequence of the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO) than cyclonic eddies. Additionally, the joined impact of ENSO and IOD conceivably alters eddy activities across the BoB, as the second downwelling coastal Kelvin wave (dCKW) were absent. The mesoscale eddies exhibit correlations with climate indicators, suggesting that eddies get stronger during La Niña and negative IOD years and get weaker during El Niño and positive IOD years. This is because La Niña and negative IOD events intensify the second dCKW, while it weakens or becomes completely absent during El Niño and positive IOD years. Random Forest model was used to compare the influence of ENSO and IOD on the forecasting performance of the eddy properties. It was demonstrated that a unique positive IOD (+IOD) negatively affects the forecasting of eddy properties when using Sea Surface Temperature (SST) and SST anomalies. The findings bear importance in verifying and confirming the interactions between the ocean and climate.

Bulk-edge correspondence recovered in incompressible geophysical flows

Bulk-edge correspondence is a cornerstone in topological physics, establishing a connection between the number of unidirectional edge modes in physical space and a Chern number, an integer that counts phase singularities of the eigenmodes in parameter space. In continuous media, violation of this correspondence has been reported when some of the frequency wave bands are unbounded, resulting in weak topological protection of chiral edge states. Here, we propose a strategy to reestablish strong bulk-edge correspondence in incompressible rotating stratified flows, taking advantage of a natural cutoff frequency provided by density stratification. The key idea involves the introduction of an auxiliary field to handle the divergence-free constraint. This approach highlights the resilience of internal coastal Kelvin waves near vertical walls under varying boundary conditions. Published by the American Physical Society 2024

The Bonney Coast upwelling: How physical processes shape the feeding behaviour of blue whales

This study employs a fully coupled physical-biological model to explore the oceanic dynamics and phytoplankton production in one of Australia’s most prominent coastal upwelling systems, the Bonney Coast Upwelling, that has barely been studied before. The study focusses on how physical processes provide two different food sources for blue whales (Balaenoptera musculus), namely, krill (treated as nonbuoyant particles) and zooplankton, both feeding on phytoplankton. While plankton grows in the euphotic zone in response to nutrient enrichment on time scales of weeks, krill can only be transported into the region via ambient currents. Findings of this study suggest that phytoplankton blooms appear slowly in the main upwelling plume on timescales of 4-8 weeks. Dynamical influences from incoming coastal Kelvin waves significantly weaken or strengthen this classical upwelling plume and its plankton productivity. On the other hand, the upwelling-favourable wind induces a continuous coastal current that also extends eastward past the Bonney Coast. This current operates to transport and distribute krill (that cannot swim horizontally) westward along the shelf, which explains the apparent conundrum why blue whales also feed on the upstream side of the upwelling plume. The author postulates that the variability of both plankton production and the intensity of the upwelling flow (passing krill swarms along the shelf) control the feeding locations of blue whales and other baleen whales on Australia’s southern shelves.

A Verification Suite of Test Cases for the Barotropic Solver of Ocean Models

AbstractThe development of any atmosphere or ocean model warrants a suite of test cases (TCs) to verify its spatial and temporal discretizations, order of accuracy, stability, reproducibility, portability, scalability, etc. In this paper, we present a suite of shallow water TCs designed to verify the barotropic solver of atmosphere and ocean models. These include the non‐dispersive coastal Kelvin wave; the dispersive inertia‐gravity wave; the dispersive planetary and topographic Rossby waves; the barotropic tide; and a non‐linear manufactured solution. These TCs check the implementation of the linear pressure gradient term; the linear constant or variable‐coefficient Coriolis and bathymetry terms; and the non‐linear advection terms. Simulation results are presented for a variety of time‐stepping methods as well as two spatial discretizations: a mimetic finite volume method based on the TRiSK scheme, and a high‐order discontinuous Galerkin spectral element method. The experimental procedure for conducting these numerical experiments is detailed. It underscores several key considerations that vary depending on the chosen spatial discretization method. Finally, convergence studies of every TC are conducted with refinement in both space and time, only in space, and only in time. The convergence slopes match the expected theoretical predictions.

Role of Intersecting Equatorial and Coastal Waveguides Near Sri Lanka on Intraseasonal Sea Level Variability Along the West Coast of India

AbstractThe sea level variations along the west coast of India (WCI) significantly affect the ecosystems and fisheries, because of their tight coupling with the oxycline depths in this region, which hosts the world's largest natural hypoxic system. Here, we investigate the main causes of the WCI sea level variability. Using idealized experiments with a linear, continuously stratified ocean model, we first demonstrate that there is a direct pathway between the equatorial waveguide and the WCI, in addition to the well‐documented pathway that aligns with the coastal waveguide in the Bay of Bengal. This direct connection results from the intersection of equatorial and coastal waveguides near Sri Lanka. The forced and reflected equatorial Rossby waves induce sea level variations at the Sri Lankan coast around 6°N, which propagate directly to the WCI as coastal Kelvin waves, without transiting through the Bay of Bengal coastal waveguide. Using model experiments with realistic coastline and forcing, we then illustrate that this direct pathway is the primary contributor (0.4 regression coefficient) to the WCI intraseasonal (20–150 days) sea level variability, followed by the Bay of Bengal coastal waveguide pathway (0.3) and the wind forcing in a small region near Sri Lanka (0.25). The remote forcing originating from the rest of the Bay of Bengal and the WCI local wind forcing have weaker influence. We conclude by discussing why this direct connection exhibits strong impact on sea level variability at the intraseasonal timescale, while its influence is considerably weaker at the longer seasonal and interannual timescales.

An Eddy Pair in the Northwestern Bay of Bengal: Characteristics, Dynamics and Interannual Variability

AbstractMesoscale eddies are active in the Bay of Bengal and have profound effects on the dynamic conditions, the transport of heat and salt, and the primary productivity. We report a pair of periodic eddies in the Bay of Bengal and examine their characteristics, dynamic mechanisms and interannual variability based on satellite observations and a nonlinear 1.5‐layer reduced‐gravity model. The eddy pair mainly occupies the northwestern Bay of Bengal from March to May and consists of a cyclonic eddy in the north and an anticyclonic eddy in the south. The anticyclonic eddy is generated by local wind forcing, whereas the cyclonic eddy is significantly contributed by equatorial and coastal Kelvin waves. On an interannual scale, the eddy pair was exceptionally weak in 1999, 2000 and 2008 due to the extreme La Niña events in these years when the westerly wind anomaly over the equatorial Indian Ocean weakened the local wind forcing and coastal Kelvin waves. This study provides new knowledge on periodic eddies in the Bay of Bengal and advances our understanding of the dynamic connections between this marginal sea and the equator.

Gauge theories for fluids in 2 + 1 dimensions through master actions

Two actions which are functionals of different variables but describing the same dynamical system can be shown to possess the same origin by constructing a master action which generates both of them. We first present the master action which produces an action depending on the fluid variables and a gauge theory action whose equations of motion are equivalent to the incompressible fluid Euler equations in 2+1 dimensions. We then introduce the master action generating the actions which on shell provide the linearized shallow water equations. One of them is a functional of the variables of the shallow water and the other one is the Maxwell-Chern-Simons gauge theory action. The maps between gauge vector fields and fluid variables are obtained for both of the systems. We employ them to derive the corresponding gauge theory solutions of the Hopfion and the coastal Kelvin wave solutions.

The Effect of an Exponentially Decaying Upper-Ocean Vertical Mixing on the Pacific Tropical Sea Surface Temperature

Abstract We investigate the mechanisms with which the sea surface temperature (SST) in the tropical Pacific responds to the perturbation of an exponential form to the background vertical mixing of the upper ocean. For a surface value of 0.005 m2 s−1 and a scale depth of 10 m (as typically used in the so-called nonbreaking wave parameterization), it is found that only ocean temperature within the equatorial eastern Pacific (EEP) is directly impacted; surface cooling and thermocline warming anomalies are produced. These signals propagate poleward as coastal Kelvin waves and then westward as equatorial Rossby waves. The surface cooling is severely damped while the thermocline warming is able to reach the western coast. This warm anomaly is brought up to the surface by equatorial upwelling more strongly around 110°W than at other places. In the coupled model, such equatorial warming induces an El Niño–like large-scale warming through Bjerknes feedback. Increasing the surface value of vertical mixing by a factor of 10 does not increase the equatorial surface warming while increasing the scale depth to 20 m does. Increasing the scale depth generates thermocline warming also in the subtropical region, which then propagates to the equatorial thermocline and enhances the warming there. Moreover, the off-equatorial cooling is enhanced, which makes the final warming anomaly narrower meridionally compared to an El Niño pattern.

Intraseasonal oscillations of the Andaman Sea thermocline

Variations in the upper ocean thermal structure have significant implications for air-sea interaction and upper-ocean ecosystem processes. Vertical profiles of temperature measured by a moored buoy located at 10.5°N, 94°E in the Andaman Sea and simulation by an Indian Ocean model are used in this study to characterise the intraseasonal variations (ISV) in the Andaman Sea (AndS) thermal structure and identify their sources. The seasonal variations in the upper ocean thermal structure show a strong semi-annual cycle driven by monsoons. The sub-surface temperature shows significant intraseasonal oscillations within a band of 40–110 days, which are de-coupled from that in the mixed layer, which has dominant periodicity in the band of 90–120 days. Thermocline ISV are seasonally modulated with a primary peak during August–September and a secondary peak during February–March, with significant year-to-year variations. A cross-wavelet analysis shows that ISV in the 40–60 days period is in phase with that at the eastern boundary and they are locally forced by the passage of eddies. The 60–110 day band is out of phase with the eastern boundary and is forced by Rossby waves radiated from the equatorially generated intraseasonal coastal Kelvin waves.

Summertime discontinuity of Western Boundary Current in the Bay of Bengal during contrasting Indian Ocean Dipole events of 2008 and 2010

The East India Coastal Current (EICC), the Western Boundary Current (WBC) in the Bay of Bengal (BOB) is continuous northward and southward during pre- and post-Indian Summer Monsoon (ISM), respectively. The discontinuity in EICC occurs during ISM (June–September) when the boundary current remains inconsistent with various cyclonic and anticyclonic eddies in presence of a southward flow from 21°N and a northward flow from 10°N along the boundary. The variations in this summertime EICC discontinuity during the contrasting Indian Ocean Dipole (IOD) events of 2008 (positive) and 2010 (negative) are investigated here. The study uses a 1/12° Regional Ocean Modelling System (ROMS) simulation, available observations and reanalysis data. The study reveals that the strong coastal Kelvin and reflected Rossby waves during 2010, supported by strong winds in the equatorial Indian Ocean, helped to strengthen the spring and winter time continuous EICC. The continuous EICC remained very weak with the weaker equatorial remote forcing signals in 2008. The southward and northward flows from 21°N and 10°N, respectively were much stronger during 2010 ISM. However, strong eddy activities along the boundary reduced these two flows in 2008. The year 2010 showed relatively weak, but well-distributed eddy activity over the whole western BOB during ISM. Conversely, pronounced eddy activity near the western boundary with high eddy kinetic energy accumulation increases the inconsistency in boundary current flow during ISM of 2008. Therefore, the study suggests that the contrasting IOD modes have significant and complementary influence on WBC discontinuity in the BOB.

A gauge theory for shallow water

The shallow water equations describe the horizontal flow of a thin layer of fluid with varying height. We show that the equations can be rewritten as a d=2+1d=2+1 dimensional Abelian gauge theory. The magnetic field corresponds to the conserved height of the fluid, while the electric charge corresponds to the conserved vorticity. In a certain linearised approximation, the shallow water equations reduce to relativistic Maxwell-Chern-Simons theory. This describes Poincaré waves. The chiral edge modes of the theory are identified as coastal Kelvin waves.

Role of local and remote forcing on the decadal variability of Mixed Layer Depth in the Bay of Bengal

The Mixed Layer Depth (MLD) of an ocean acts as a storage of the incoming heat and releases via air-sea exchange processes. The present study tries to understand the decadal variability of MLD over the Bay of Bengal (BoB) and its association with local as well as external forcing. The time series and wavelet analysis confirm the significant decadal signals for the period from 1980 to 2015. The BoB MLD is found to have opposing trend prior to and post of 1998. In the decadal timescale, the BoB MLD is found to be comparably deep for regime-1 (1980–1998) and shallow for regime-2 (1999–2014) with stronger variation in the western bay. The local forcing like wind, wind-related processes, and Evaporation minus Precipitation (E-P) are found to have a prominent role to modulate the decadal variability of BoB MLD. The leading mode of the decadal Empirical Orthogonal Function (EOF-1) of MLD over the BoB shows a strong spatial pattern with the strongest in the western part of the Bay. The corresponding principal component shows a similar variability to Interdecadal Pacific Oscillation (IPO) signal. The enhancement of descending (ascending) branch of the Indian branch of Walker circulation (IWC) in the positive (negative) phase of IPO influences the changes over the equatorial Indian Ocean remotely modulate MLD of the coastal region of the BoB via the propagating coastal Kelvin waves. The decadal variability of MLD in the coastal region of the BoB is caused mainly by remote effect but the interior BoB is by the local factors.

Influence of Winter Subsurface on the Following Summer Variability in Northern California Current System

AbstractTemperature variations in the North and tropical Pacific contribute to the predictability of temperatures along the 26.4σ isopycnal layer off the Northern California Current System (N‐CCS). Monthly temperature variations at this depth in the N‐CCS are related to a linear combination of factors, including North Pacific spice anomalies, and the PDO and ENSO climate indices. However, the mechanisms for seasonal predictability of subsurface temperatures, are not well explored. While wind and buoyancy driven deep winter mixing influence subsurface temperatures during the following summer in the deep basin of the North Pacific, a coupled atmosphere‐ocean reanalysis (the CFSR) reveals that winter prior surface temperatures explain only 25% of the summer subsurface temperatures in the N‐CCS. A heat budget of the intermediate layer between a temporally varying mixed layer and the 26.4σ level is diagnosed here to explore the possible role of oceanic advection in explaining the remaining variance. Warmer waters from the south near the coast drive temperature changes in ENSO‐neutral winters, thereby preconditioning temperatures for the following summer. During ENSO winters, isopycnal variations associated with propagating coastal kelvin waves and other sources of heaving, along with anomalous alongshore currents, drive convergence/divergence of the advective fluxes, thereby reducing the local memory of the winter subsurface temperatures. Variations in winter advection could account for almost 36% of the summer subsurface temperature variability in the N‐CCS; this exceeds the portion explained by the heat fluxes associated with deep winter mixing.

Influence of the El Niño-Southern Oscillation on SST Fronts Along the West Coasts of North and South America.

Along the west coasts of North, Central, and South America, sea surface temperature (SST) fronts are important for circulation dynamics and promoting biological activity. Prevailing equatorward winds during summer results in offshore Ekman transport and upwelling along the coast, where fronts often form between cold, upwelled water and warmer offshore waters. The interannual variability in winds, coastal upwelling, sea level anomalies, and SST in these regions have been linked to the El Niño-Southern Oscillation (ENSO), however SST fronts have received less attention. Here, we investigate the interannual variability of SST fronts off North, Central, and South America using satellite SST data spanning 1982-2018. Anomalies of fronts within 0-300km offshore indicate interannual variability that coincides with ENSO events in most regions. Frontal activity generally decreases during El Niño events and increases during La Niña events. The decrease in fronts off Peru and Chile during El Niño coincides with the seasonal peak in frontal activity, while off the United States the decrease occurs when frontal activity is at a seasonal minimum. We also utilized satellite measurements of wind stress and sea level anomaly to investigate how ENSO oceanic and atmospheric forcing mechanisms affect frontal activity. Decreases in frontal activity during El Niño events are largely due to oceanic forcing (i.e., coastal Kelvin waves) off Central and South America and to both oceanic forcing and atmospheric teleconnections off the United States. This study furthers our understanding of the influence of ENSO on coastal upwelling regions in the eastern Pacific Ocean.

The Characteristics and Variability of Intraseasonal Coastal Kelvin Waves in the Bay of Bengal under Hindcast Conditions and the RCP8.5 Scenario

Abstract The characteristics and variability of intraseasonal internal coastal Kelvin waves (CKWs) along the Bay of Bengal (BoB) waveguide are investigated in the context of global warming by employing a regional ocean model. The analyzed period covers 120 years from 1980 to 2099, which includes the historical scenario and the RCP8.5 scenario. CKW information is successfully extracted from the temperature anomalies along the pycnocline by applying a newly developed methodology. The analysis reveals that intraseasonal CKWs in the BoB are highly in accordance with the intraseasonal zonal wind stress in the western equatorial Indian Ocean; the downwelling CKW lags the equatorial intraseasonal westerly winds, and the upwelling CKW lags the equatorial intraseasonal easterly winds. The CKWs significantly affect subsurface characteristics at the eastern BoB boundary, and the weakening of CKWs near the Irrawaddy Delta tip is a general feature occurring in the subsurface. With respect to the long-term scale, the occurrence of significant CKWs is predicted to be more frequent in the future under the high emissions pathway. Remarkably, the monthly climatology of CKWs varies over time; unlike the first two 30-yr analyzed periods, significant CKWs are predicted to mainly occur around August during the last two 30-yr periods due to the corresponding variabilities in the equatorial wind field, suggesting that the BoB characteristics may greatly deviate from the current climatological state.

Coastlines at Risk of Hypoxia From Natural Variability in the Northern Indian Ocean

AbstractCoastal hypoxia—harmfully low levels of oxygen—is a mounting problem that jeopardizes coastal ecosystems and economies. The northern Indian Ocean is particularly susceptible due to human‐induced impacts, vast naturally occurring oxygen minimum zones, and strong variability associated with the seasonal monsoons and interannual Indian Ocean Dipole (IOD). We assess how natural factors influence the risk of coastal hypoxia by combining a large set of oxygen measurements with satellite observations to examine how the IOD amplifies or suppresses seasonal hypoxia tied to the Asian Monsoon. We show that on both seasonal and interannual timescales hypoxia is controlled by wind‐ and coastal Kelvin wave‐driven upwelling of oxygen‐poor waters onto the continental shelf and reinforcing biological feedbacks (increased subsurface oxygen demand). Seasonally, the risk of hypoxia is highest in the western Arabian Sea in summer/fall (71% probability of hypoxia). Major year‐to‐year impacts attributed to the IOD occur during positive phases along the eastern Bay of Bengal (EBoB), where the risk of coastal hypoxia increases from moderate to high in summer/fall (21%–46%) and winter/spring (31%–42%), and along the eastern Arabian Sea (i.e., India, Pakistan) where the risk drops from high to moderate in summer/fall (53%–34%). Strong effects are also seen in the EBoB during negative IOD phases, when the risk reduces from moderate to low year‐round (∼25% to ∼5%). This basin‐scale mapping of hypoxic risk is key to aid national and international efforts that monitor, forecast, and mitigate the impacts of hypoxia on coastal ecosystems and ecosystem services.

Propagation of barotropic Kelvin waves around Antarctica

Barotropic (i.e., depth-uniform) coastal oceanic Kelvin waves can provide rapid teleconnections from climate and weather events in one location to remote regions of the globe. Studies suggest that barotropic Kelvin waves observed around Antarctica may provide a mechanism for rapidly propagating circulation anomalies around the continent, with implications for continental shelf temperatures along the West Antarctic Peninsula and thus Antarctic ice mass loss rates. However, how the propagation of Kelvin waves around Antarctica is influenced by features such as coastal geometry and variations in bathymetry remains poorly understood. Here we study the propagation of barotropic Antarctic Kelvin waves using a range of idealized model simulations. Using a single-layer linear shallow water model with 1∘ horizontal resolution, we gradually add complexity of continental configuration, realistic bathymetry, variable planetary rotation, and forcing scenarios, to isolate sources and sinks of wave energy and the mechanisms responsible. We find that approximately 75% of sub-inertial barotropic Kelvin wave energy is scattered away from Antarctica as other waves in one circumnavigation of the continent, due mostly to interactions with bathymetry. Super-inertial barotropic Kelvin waves lose nearly 95% of their energy in one circumpolar loop, due to interactions with both coastal geometry and bathymetry. These results help to explain why only sustained signals of low-frequency resonant barotropic Kelvin waves have been observed around Antarctica, and contribute to our understanding of the role of rapid, oceanic teleconnections in climate.

Lakshadweep High Propagation and Impacts on the Somali Current and Eddies During the Southwest Monsoon

AbstractClimatological eddies in the Arabian Sea (AS), including the Lakshadweep High (LH) and the Great Whirl (GW), play major roles in the regional fluxes of upper ocean properties. For the first time, we apply an eddy tracking algorithm to the LH using altimetric sea surface height observations from 1993 through 2019. We additionally analyze the LH's water mass composition throughout its life cycle using the 1/12° Global eddy resolving physical ocean and sea ice reanalysis (GLORYS12). We observe that the second annual downwelling coastal Kelvin wave's (CKW) arrival during the winter monsoon is primarily responsible for generating the LH. In March, Rossby waves propagate along 8°N at the same speed of that of the LH. In 17 of 27 years, the LH maintains coherence across the AS. The LH sustains a shallow lens of lower salinity Bay of Bengal water up to 68°E in these years. In the remaining 10 years, the LH dissipates between 60°E and 70°E or fails to propagate beyond the southwest Indian coast. We attribute the differences between propagation types to fluctuations in the CKW strength, differences in wind stress between the southern tip of India and Sri Lanka, and the variable distribution of wind stress curl around the LH. We also find that longer propagating LH types negatively correlate with the eddy kinetic energy of the Somali Current region during the summer monsoon. We conclude that, upon its arrival in late July, the LH either merges with or replaces the GW, disrupting the cyclone that normally orbits the GW.

Simulation and analysis of marine hydrodynamics based on the El Niño scenario

BACKGROUND AND OBJECTIVESEl Nino - Southern Oscillation is known to affect the marine and terrestrial environment in Southeast Asia, Australia, northern South America, and southern Africa. There has been much research showing that the effects of El Nino - Southern Oscillation are extensive. In this study, a simulation of an El Nino event is carried out, which is ideal in the vertical layer of the Pacific Ocean (0-250 meters). The fast Fourier transform is used to process the vertical modeling data so that the results can accurately represent El Nino.METHODSA non-hydrostatic 3-dimensional numerical model is used in this research. To separate the signal produced and obtain the quantitative difference of each sea layer, the simulation results are analyzed using the fast Fourier transform. Winds blow from the west to the east of the area in perfect El Nino weather, with a reasonably high wind zone near the equator (forming a cosine). Open fields can be found on the north and south sides, while closed fields can be found on the west and east sides. Density is uniform up to a depth of 100 meters, then uniformly increases by 1 kilogram per cubic meter from 100 to 250 meters. FINDINGSThe results of the model simulation show that one month later (on the 37th day), the current from the west has approached the domain's east side, forming a complete coastal Kelvin wave. The shape of coastal Kelvin waves in the eastern area follows a trend that is similar to the OSCAR Sea Surface Velocity plot data obtained from ERDDAP in the Pacific Ocean in October 2015. In this period, the density at a depth of 0-100 meters is the same, while the density at the depth layer underneath is different. CONCLUSIONStrong winds could mix water masses up to a depth of 100 meters, implying that during an ideal El Nino, the stratification of the water column is influenced by strong winds. The eastern domain has the highest sea level amplitude, resulting in perfect mixing up to a depth of 100 m, while wind effect is negligible in the lower layers. The first layer (0-50 m) and the second layer (50-100 m) have the same density and occur along the equator, according to FFT. The density is different and much greater in the third layer (100-150 m).