Seasonal variation of mesoscale eddy intensity in the global ocean

Mesoscale eddies are a prominent oceanic phenomenon that plays an important role in oceanic mass transport and energy conversion.Characterizing by rotational speed,the eddy intensity is one of the most fundamental properties of an eddy.However,the seasonal spatiotemporal variation in eddy intensity has not been examined from a global ocean perspective.In this study,we unveil the seasonal spatiotemporal characteristics of eddy intensity in the global ocean by using the latest satellite-altimetry-derived eddy trajectory data set.The results suggest that the eddy intensity has a distinct seasonal variation,reaching a peak in spring while attaining a minimum in autumn in the Northern Hemisphere and the opposite in the Southern Hemisphere.The seasonal variation of eddy intensity is more intense in the tropical-subtropical transition zones within latitudinal bands between 15°and 30°in the western Pacific Ocean,the northwestern Atlantic Ocean,and the eastern Indian Ocean because baroclinic instability in these areas changes sharply.Further analysis found that the seasonal variation of baroclinic instability precedes the eddy intensity by a phase of 2–3 months due to the initial perturbations needing time to grow into mesoscale eddies.

Eddy diffusivity and coherent mesoscale eddy analysis in the Southern Ocean

The spatial distribution of eddy diffusivity,basic characteristics of coherent mesoscale eddies and their relationship are analyzed from numerical model outputs in the Southern Ocean.Mesoscale fluctuation information is obtained by a temporal-spatial filtering method,and the eddy diffusivity is calculated using a linear regression analysis between isoneutral thickness flux and large-scale isoneutral thickness gradient.The eddy diffusivity is on the order of O(103 m2/s)with a significant spatial variation,and it is larger in the area with strong coherent mesoscale eddy activity.The mesoscale eddies are mainly located in the upper ocean layer,with the average intensity no larger than 0.2.The mean radius of the coherent mesoscale cyclonic(anticyclonic)eddy gradually decays from(121.2±10.4)km((117.8±9.6)km)at 30°S to(43.9±5.3)km((44.7±4.9)km)at 65°S.Their vertical penetration depths(lifespans)are deeper(longer)between the northern side of the Subpolar Antarctic Front and 48°S.The normalized eddy diffusivity and coherent mesoscale eddy activity show a significant positive correlation,indicating that coherent mesoscale eddy plays an important role in eddy diffusivity.

Three-dimensional mesoscale eddy identification and tracking algorithm based on pressure anomalies Liming

The Kuroshio Extension(KE)is one of the most eddy-energetic regions in the global ocean.However,most mesoscale eddy studies in the region are focused on surface eddies and the structure and characteristics of three-dimensional(3-D)eddies require additional research.In this study,we proposed a 3-D eddy identification and tracking algorithm based on pressure anomalies,similar to sea level anomalies(SLAs)for surface eddy identification.We applied this scheme to a 5-year(2008-2012)high-resolution numerical product to develop a 3-D eddy dataset in the KE.The reliability of the numerical product was verified by the 5-year temperature/salinity hydrological characteristics and surface eddy distribution.According to the 3-D eddy tracking dataset,the number of eddies decreased dramatically as the eddy existence-time increased and more anticyclonic eddies(AEs)had an existence-time longer than 1 week than cyclonic eddies(CEs).We presented daily variations in the 3-D structure of two 3-D eddy-tracking trajectories that exhibit a certain jump in depth and a shift toward the west and equator.In addition to the bowl,lens,and cone eddies that have been discovered by previous researchers,we found that there is a cylindrical eddy,and its eddy radii are almost consistent across all layers.CEs cause significant negative temperature anomalies,“negative-positive”salinity anomalies,and sinking current fields in the KE region,while AEs cause positive temperature anomalies,“positive-negative”salinity anomalies,and upward current fields.The four types of eddies have different effects on the temperature/salinity anomalies and current field distribution which are related to their structure.

Dynamical analysis of mesoscale eddy-induced ocean internal waves using linear theories

This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar （SAR） observations of mesoscale eddies with diameter of several tens of kilometers to hundreds of kilometers show that the internal wave packets with wavelength of hundreds of meters to kilometer exist inside the mesoscale eddies. This coexistence phenomenon and inherent links between the two different scale processes are revealed in the solutions of governing equations and boundary conditions for the internal wave disturbance with a horizontally slowly variable amplitude in a cylindrical coordinate system. The theoretical solutions indicate that the instability of eddy current field provides the dynamical mechanism to internal wave generation. The derived dispersion relation indicates that the internal wave propagation is modified by the eddy current field structure. The energy equation of the internal waves clearly shows the internal wave energy increment comes from the eddy. The theoretical models are used to explain the observation of the mesoscale eddy-induced internal waves off the Norwegian coast. The two-dimensional waveform solution of the anticyclonic eddy-induced internal wave packet appears as ring-shaped curves, which contains the typical features of eddy stream lines. The comparison of theoretical solutions to the structure of the internal wave packets on SAR image shows a good agreement on the major features.

Impact of warm mesoscale eddy on tropical cyclone intensity

The spatial-temporal patterns of tropical cyclone(TC) intensity changes caused by the warm ocean mesoscale eddy(WOME) distribution are evaluated using two sets of idealized numerical experiments. The results show that the TC was intensified and weakened when a WOME was close to and far away from the TC center, respectively.The area where the WOME enhanced(weakened) TC intensity is called the inner(outer) area in this study.Amplitudes of the enhancement and weakening caused by the WOME in the inner and outer area decreased and increased over time, while the ranges of the inner and outer area diminished and expanded, respectively. The WOME in the inner area strengthened the secondary circulation of the TC, increased heat fluxes, strengthened the symmetry, and weakened the outer spiral rainband, which enhanced TC intensity. The effect was opposite if the WOME was in the outer area, and it weakened the TC intensity. The idealized simulation employed a stationary TC, and thus the results may only be applied to TCs with slow propagation. These findings can improve our understanding of the interactions between TC and the WOME and are helpful for improving TC intensity forecasting by considering the effect of the WOME in the outer areas.

Spatial structure of turbulent mixing of an anticyclonic mesoscale eddy in the northern South China Sea

Upper turbulent mixing in the interior and surrounding areas of an anticyclonic eddy in the northern South China Sea(SCS)was estimated from underwater glider data(May 2015)in the present study,using the Gregg-HenyeyPolzin parameterization and the Thorpe-scale method.The observations revealed a clear asymmetrical spatial pattern of turbulent mixing in the anticyclonic eddy area.Enhanced diffusivity(in the order of 10–3 m2/s)was found at the posterior edge of the anticyclonic mesoscale eddy;on the anterior side,diffusivity was one order of magnitude lower on average.This asymmetrical pattern was highly correlated with the eddy kinetic energy.Higher shear variance on the posterior side,which is conducive to the triggering of shear instability,may be the main mechanism for the elevated diffusivity.In addition,the generation and growth of sub-mesoscale motions that are fed by mesoscale eddies on their posterior side may also promote the occurrence of strong mixing in the studied region.The results of this study help improve our knowledge regarding turbulent mixing in the northern SCS.

Observation of an anti-cyclonic mesoscale eddy in the subtropical northwestern Pacific Ocean from altimetry and Argo profiling floats

The comprehensive three-dimensional structures of an anti-cyclonic mesoscale eddy(AE)in the subtropical northwestern Pacific Ocean were investigated by combining the Argo floats profiles with enhanced vertical and temporal sampling and satellite altimetry data.The AE originated near the Kuroshio Extension and then propagated westward with mean velocity of 8.9 cm/s.Significant changes and evolutions during the AE’s growing stage(T1)and further growing stage(T2)were revealed through composite analysis.In the composite eddy core,maximum temperature(T)and salinity(S)anomalies were of 1.7(1.9)℃ and 0.04(0.07)psu in T1(T2)period,respectively.The composite T anomalies showed positive in almost whole depth,but the S anomalies exhibited a sandwich-like pattern.The eddy’s intensification and its influence on the intermediate ocean became more significant during its growth.The trapping depth increased from 400×10^4 Pa to 580×10^4 Pa while it was growing up,which means more water volume,heat and salt content in deeper layers can be transported.The AE was strongly nonlinear in upper oceans and can yield a typical mean volume transport of 0.17×10^6 m^3/s and a mean heat and salt transport anomaly of 3.6×10^11 W and–2.1×10^3 kg/s during the observation period.The Energy analysis showed that eddy potential and kinetic energy increased notably as it propagated westward and the baroclinic instability is the major energy source of the eddy growth.The variation of the remained Argo float trapped within the eddy indicated significant water advection during the eddy’s propagation.

Revisiting mesoscale eddy genesis mechanism of nonlinear advection in a marginal ice zone

A three-dimensional（3-D） ocean model is coupled with a two-dimensional（2-D） sea ice model, to revisit a nonlinear advection mechanism, one of the most important mesoscale eddy genesis mechanisms in the marginal ice zone. Two-dimensional ocean model simulations suggest nonlinear advection mechanism is more important when the water gets shallower. Instead of considering the ocean as barotropic fluid in the 2-D ocean model, the 3-D ocean model allows the sea ice to affect the current directly in the surface layer via ocean-ice interaction. It is found that both mesoscale eddy and sea surface elevation are sensitive to changes in a water depth in the 3-D simulations. The vertical profile of a current velocity in 3-D experiments suggests that when the water depth gets shallower, the current move faster in each layer, which makes the sea surface elevation be nearly inverse proportional to the water depth with the same wind forcing during the same time. It is also found that because of the vertical motion, the magnitude of variations in the sea surface elevation in the 3-D simulations is very small,being only 1% of the change in the 2-D simulations. And it seems the vertical motion to be the essential reason for the differences between the 3-D and 2-D experiments.

Three-dimensional structure of an observed cyclonic mesoscale eddy in the Northwest Pacific and its assimilation experiment

Mesoscale eddies play an important role in modulating the ocean circulation.Many previous studies on the threedimensional structure of mesoscale eddies were mainly based on composite analysis,and there are few targeted observations for individual eddies.A cyclonic eddy surveyed during an oceanographic cruise in the Northwest Pacific Ocean is investigated in this study.The three-dimensional structure of this cyclonic eddy is revealed by observations and simulated by the four-dimensional variational data assimilation(4 DVAR)system combined with the Regional Ocean Modeling System.The observation and assimilation results together present the characteristics of the cyclonic eddy.The cold eddy has an obvious dual-core structure of temperature anomaly.One core is at 50–150 m and another is at 300–550 m,which both have the average temperature anomaly of approximately-3.5℃.The salinity anomaly core is between 250 m and 500 m,which is approximately-0.3.The horizontal velocity structure is axis-asymmetric and it is enhanced on the eastern side of the cold eddy.In the assimilation experiment,sea level anomaly,sea surface temperature,and in situ measurements are assimilated into the system,and the results of assimilation are close to the observations.Based on the high-resolution assimilation output results,the study also diagnoses the vertical velocity in the mesoscale eddy,which reaches the maximum of approximately 10 m/d.The larger vertical velocity is found to be distributed in the range of 0.5 to 1 time of the normalized radius of the eddy.The validation of the simulation result shows that the 4 DVAR method is effective to reconstruct the three-dimensional structure of mesoscale eddy and the research is an application to study the mesoscale eddy in the Northwest Pacific by combining observation and assimilation methods.

Variations of mesoscale eddy SST fronts based on an automatic detection method in the northern South China Sea

SST fronts at the mesoscale eddy edge(ME fronts)were investigated from 2007–2017 in the northern South China Sea(NSCS)based on an automatic method using satellite sea level anomaly(SLA)and SST data.The relative probabilities between the number of anticyclonic/cyclonic ME fronts(AEF/CEF)and the number of anticyclones/cyclones reached 20%.The northeastern and southwestern parts of these anticyclones had more fronts than the northwestern and southeastern parts,although CEFs were nearly equally distributed in all directions.The number of ME fronts had remarkable seasonal variations,while the eddy kinetic energy(EKE)showed no seasonal variations.The total EKE at the ME fronts was three times of that within the MEs,and it was much stronger in AEFs than in CEFs.The interannual variability in the number of ME fronts and EKE had no significant correlation with the El Ni?o-Southern Oscillation(ENSO)index.Possible mechanisms of ME fronts were discussed,but the contributions of mesoscale eddies to SST fronts need to be quantified in future studies.

Mass transport of a mesoscale eddy in the South China Sea identified by a simulated passive tracer

To quantitatively investigate the water mass transport of mesoscale eddies,the mass transport induced by a simulated anticyclonic eddy in the South China Sea was evaluated by using the Regional Ocean Modelling System(ROMS)and a built-in passive tracer module.The results indicate that the eddy can trap and transport 51%of the initial water in the eddy core to 689 km from its origin during its lifetime of 100 days,with a stable loss rate of 6‰per day.During propagation,there is drastic horizontal water exchange between the inside and outside of the eddy.Meanwhile,the vertical mass transport is signifi cant,and 65%of the water initially in the mixed layer of the eddy is eventually detrained into the subsurface.A tracer budget analysis of eddy shows that advection is the dominant dynamic process of transport,while the eff ect of mixing is weak,and horizontal process plays a controlling role.Horizontal and vertical advection exhibit opposite patterns and strongly off set each other.Particularly,a distinct dipole pattern is found in the local velocity fi eld of the eddy,with signifi cant convergence(downwelling)and divergence(upwelling)zones in the anterior and posterior of the eddy,respectively,which is likely related to the driving mechanism of the westward propagation of the eddy.The dipole further induces a vertical overturning cell,through which the surface water in the anterior of the eddy detrains into the subsurface by downwelling and resurface from the posterior of the eddy by upwelling and gradually spreads out of the eddy.The temporal variability in the tracer budget is signifi cant,in which horizontal advection is dominant.The propagation acceleration and temporal derivative of the deformation rate are highly correlated with tracer transport,suggesting the potential eff ect of the temporal instability of eddies on the eddy mass transport.

A new algorithm for reconstructing the three-dimensional flow field of the oceanic mesoscale eddy

A new algorithm for reconstructing the three-dimensional flow field of the oceanic mesoscale eddies is proposed in this paper,based on variational method.Firstly,with the numerical differentiation Tikhonov regularizer,we reconstruct the continuous horizontal flow field on discrete grid points at each layer in the oceanic region,in terms of the horizontal flow field observations.Secondly,benefitting from the variational optimization analysis and its improvement,we reconstruct a three-dimensional flow field under the constraint of the horizontal flow and the vertical flow.The results of simulation experiments validate that the relative error of the new algorithm is lower than that of the finite difference method in the case of high grid resolution,which still holds in the case of unknown observational errors or in the absence of vertical velocity boundary conditions.Finally,using the reanalysis horizontal data sourcing from SODA and the proposed algorithm,we reconstruct three-dimensional flow field structure for the real oceanic mesoscale eddy.

Multisatellite observations of smaller mesoscale eddy generation in the Kuroshio Extension

Smaller mesoscale eddies(SMEs)have an important effect on the transmission of ocean temperatures,salinity,energy,and marine biochemical processes.However,traditional altimeters,the dominant sensors used to identify and track eddies,have made it challenging to observe SMEs accurately due to resolution limitations.Eddies drive local upwelling or downwelling,leaving signatures on sea surface temperatures(SSTs)and chlorophyll concentrations(Chls).SST can be observed by spaceborne infrared sensors,and Chl can be measured by ocean color remote sensing.Therefore,multisatellite observations provide an opportunity to obtain information to characterize SMEs.In this paper,an eddy detection algorithm based on SST and Chl images is proposed,which identifies eddies by characterizing the spatial and temporal distribution of SST and Chl data.The algorithm is applied to characterize and analyze SMEs in the Kuroshio Extension.Statistical results on their distribution and seasonal variability are shown,and the formation processes are preliminarily discussed.SMEs generation may be contributed by horizontal strain instability,the interaction of topographic obstacles and currents,and wind stress curl.

The characteristics of spontaneous near-inertial wave generation from an anticyclonic mesoscale eddy

The generation and propagation characteristics of near-inertial waves(NIWs)generated spontaneously from a quasi-geostrophic anticyclonic mesoscale eddy in a rotating and stratifi ed fl uid were investigated by three-dimensional numerical modeling.NIWs are generated over a long time interval as a forced response to balanced baroclinic mesoscale eddies.For such eddies,NIW generation from balanced flow is an inevitable result as the evolution of eddies.Moreover,the baroclinicity of mesoscale eddies is an essential condition for this NIW generation mechanism.The spontaneously generated NIWs radiate horizontally toward the eddy center and propagate upward in vertical direction.The forcing of the NIWs moves downward along the eddy axis from the location of maximum temperature anomaly of the mesoscale eddy.The moving speed of the forcing is independent on the balanced mesoscale eddies but is determined by the ratio of buoyancy to inertial frequency.When the forcing reaches the bottom of the mesoscale eddy,the spontaneous NIW generation process terminates.NIW intensity in this spontaneous generation process is strengthened with the increase of the Rossby and Froude numbers.Further research to gain a solid understanding of the role of the Rossby and Froude numbers is necessary for the parameterization of spontaneous NIW generation from quasi-geostrophic mesoscale eddies in general circulation model.

Seasonal Behaviour of Mesoscale Eddy Trajectories in the North Indian Ocean Based on Satellite Altimetry

In the north Indian Ocean (NIO), maps of sea level anomaly from satellite altimetry were analysed from January-1995 to December-2000. The study attempted to trace the trajectories of the individual mesoscale anomalies manually and to understand seasonal changes in terms of phase speed. Mesoscale anomalies are detected as concentric circular shapes and diameters of ~90 km to 600 km and the minimum 30 days life cycle. Relatively higher eddy kinetic energy was noticed in the northwestern region of the NIO. Individual mesoscale anomalies, namely positive (warm, anticyclonic eddies) and negative (cold, cyclonic eddies) showing travelling direction westward in the NIO basins. In autumn, the number of negative anomalies detected is more than positive anomalies and vice versa during summer. The westward propagating positive (negative) anomalies in the Arabian Sea start appearing in winter (spring) along (away from) the west coast of India and west of 65°E;individual anomalies move to the west in spring/summer/autumn and collide along Somalia’s & Arabian coast. A group of positive (negative) anomalies trajectories appears as a tail at the southern tip of India are located west of the Laccadive ridge in winter (summer to autumn) associated with LH (LL). The Bay of Bengal (BB) trajectories show southwestward in northern BB, westward in central BB and northwestward in southern BB;individual anomalies are appearing along the west coast of Andaman & Nicobar ridge. The zonal phase speed decreases away from the equator, and the magnitude varies longitudinally in each season in the form of a wave-like pattern propagating westward from autumn to summer;the life cycle of the wave is almost 365 days (a year). The theoretical phase speed of the first mode of the baroclinic Rossby waves is quite similar to that of averaged zonal speed. Therefore mesoscale anomalies (eddies) are embedded into the large waves like phenomenon (Rossby waves), responsible for creating high variability and EKE in the region of NIO along the western boundaries.

Statistical analysis of mesoscale eddy propagation velocity in the South China Sea deep basin

Using mesoscale eddy trajectory product derived from satellite altimetry data from 1993 to 2017,this study analyzes the statistical characteristics of spatiotemporal distribution of mesoscale eddy propagation velocities(C)in the South China Sea(SCS)deep basin with depths>1000 m.Climatologically,the zonal propagation velocities(cx)are westwards in the whole basin,and the meridional velocities(cy)are southwards in the northwestern basin,and northwards in the southeastern basin.The variation of cy with longitude is consistent with that of the background meridional currents with correlation coefficient R2 of 0.96,while the variation of cx is related both to the background zonal currents andβeffect.The propagation velocities characterize significant seasonality with the minimum magnitude occurring in summer and the maximum in winter for cx and C.Interannually,larger values of cx and cy mostly occurred in La Ni?a years in the negative phase of the Pacific Decadal Oscillation(PDO).Mesoscale eddies move fast at the beginning and end of their life span,i.e.,at their growth and dissipation periods,and slowly during their stable"midlife"period.This trend is negatively correlated with the rotating tangential velocity with R2 of–0.93.Eddies with extreme propagation velocities are defined,which are slower(faster)than 1.5 cm/s(15.4 cm/s)and take 1.5%(1.9%)of the total eddies.The extremely slow-moving(fastmoving)eddies tend to appear in the middle(on the edge)of the basin,and mostly occur in summer(winter).The mechanism analysis reveals that the spatiotemporal distributions of the propagation velocities of mesoscale eddies in the SCS are modulated by the basin-scale background circulation.

Three-Dimensional Climatological Structures of the Arabian Sea Eddies and Eddy-Induced Flux

This study explores the spatial structure and transport characteristics of eddies in the Arabian Sea(AS)using Argo profiles and satellite measurements.The majority of eddies occur in the northern AS,especially along its northeastern boundary.In contrast,the western AS had a relatively higher eddy kinetic energy compared to the eastern part.Particularly,the strongest energetic eddies were present in the Somali Current system.The composite results revealed the evident thermohaline anomalies caused by cyclonic eddies(CEs)and anticyclonic eddies(AEs)in the upper 300m layers.The anomalous temperature structure within CEs and AEs showed a dominant dipole structure in the near-surface layer and a monopole structure below,with maximum temperature anomalies of approximately−0.8℃and+1.0℃located at depths of 100–150m,respectively.The composited salinity structures for CEs and AEs exhibited monopole vertical structures and sandwich-like patterns.For AEs,large positive salinity anomalies occurred at subsurface layers of 60–180 m with a peak value of about 0.07,and weak negative values were observed above 60m and below 180 m.A similar vertical structure but with an opposite sign operates for CEs.The composited CE and AE caused an equatorward salt flux with values of−8.1×10^(4)and−2.2×10^(4)kg s^(−1),respectively.CEs caused an equatorward heat flux of−7.7×10^(11)W,and AEs induced a poleward flux of 1.5×1011 W.

Three-dimensional properties of mesoscale cyclonic warm-core and anticyclonic cold-core eddies in the South China Sea

In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anticyclonic)eddies associated with warm(cold)cores in the South China Sea(SCS).These"abnormal"eddies pose a challenge to previous works on eddy detection,characteristic analysis,eddy-induced heat and salt transports,and even on mesoscale eddy dynamics.Based on a 9-year(2000–2008)numerical modelling data,the cyclonic warm-core eddies(CWEs)and anticyclonic cold-core eddies(ACEs)in the SCS are analyzed.This study found that the highest incidence area of the"abnormal"eddies is the northwest of Luzon Strait.In terms of the eddy snapshot counting method,8620 CWEs and 9879 ACEs are detected,accounting for 14.6%and 15.8%of the total eddy number,respectively.The size of the"abnormal"eddies is usually smaller than that of the"normal"eddies,with the radius only around 50 km.In the generation time aspect,they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan.The survival time of CWEs(ACEs)occupies 16.3%(17.1%)of the total eddy lifespan.Based on two case studies,the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these"abnormal"eddies near the northeastern SCS.

A statistical analysis of mesoscale eddies in the Bay of Bengal from 22–year altimetry data

Eddy properties in the Bay of Bengal are studied from 22 a archiving, validation and interpretation of satellite oceanographic（AVISO） data using a sea level anomaly（SLA）-based eddy identification. A geographical distribution and an eddy polarity, an eddy lifetime and propagation distances, eddy origins and terminations,eddy propagation directions and trajectories, eddy kinetic properties, the evolution of eddy properties,seasonal and interannual variabilities of eddy activities are analyzed in this area. Eddies exist principally in the western Bay of Bengal and most of them propagate westward. The polarity distribution of eddies shows cyclones prefer to occur in the northwest and south of the Bay of Bengal, while anticyclones mainly occur in the east of the bay. Five hundred and sixty-five cyclones and 389 anticyclones with the lifetime that exceeds 30 d are detected during the 22 a period, and there is a preference for the cyclones for all lifetime and propagation distances. The kinetic properties of all observed eddies show the average amplitude of the cyclones is larger than that of the anticyclones, whereas that is opposite for average radius, and their average velocities are basically the same. Moreover, the evolution of eddies properties reveals that the eddies with a long lifetime that exceeds 90 d have a significant double-stage feature of the former 50 d growth period and the dying period after 50 d. For the seasonal variability of the eddies, the cyclones occur more often in spring while the anticyclones occur more often in summer. The analysis of long-lived eddy seasonal distributions shows that there is the obvious seasonal variation of the eddy activities in the Bay of Bengal. The interannual variability of an eddy number shows an obvious negative correlation with the EKE variation.

Estimation of eddy heat transport in the global ocean from Argo data

The Argo data are used to calculate eddy（turbulence） heat transport（EHT） in the global ocean and analyze its horizontal distribution and vertical structure.We calculate the EHT by averaging all the v ′,T ′ profiles within each 2 ×2 bin.The velocity and temperature anomalies are obtained by removing their climatological values from the Argo ＂instantaneous＂ values respectively.Through the Student＇s t-test and an error evaluation,we obtained a total of 87% Argo bins with significant depth-integrated EHTs（D-EHTs）.The results reveal a positive-and-negative alternating D-EHT pattern along the western boundary currents（WBC） and Antarctic Circumpolar Current（ACC）.The zonally-integrated D-EHT（ZI-EHT） of the global ocean reaches 0.12 PW in the northern WBC band and –0.38 PW in the ACC band respectively.The strong ZI-EHT across the ACC in the global ocean is mainly caused by the southern Indian Ocean.The ZI-EHT in the above two bands accounts for a large portion of the total oceanic heat transport,which may play an important role in regulating the climate.The analysis of vertical structures of the EHT along the 35 N and 45 S section reveals that the oscillating EHT pattern can reach deep in the northern WBC regions and the Agulhas Return Current（ARC） region.It also shows that the strong EHT could reach 600 m in the WBC regions and 1 000 m in the ARC region,with the maximum mainly located between 100 and 400 m depth.The results would provide useful information for improving the parameterization scheme in models.