estimation of the agulhas ring impacts on meridional heat fluxes and transport using argo floats and satellite data 1 a method that combines vertical profiles from the argo floats program and satellite sea surface height ssh data is used to reconstruct the vertical structure of the agulhas rings all eddies shed by the agulhas retroflection in the period between january 2005 and december 2008 were successfully reconstructed the velocity structures obtained are tilted and phase shifted in relation to the temperature anomalies resulting in an annual mean eddy meridional heat flux across the ring paths of 0 062 0 012 pw northward a first order estimate indicates 0 07 pw entering the atlantic from the indian ocean through agulhas rings the volume transport by agulhas rings is believed to play a central role in the overturning circulation being the main process responsible for the leakage of indian ocean waters to the atlantic the new estimates of the time mean ring volume transport of 9 8 sv from the indian to the atlantic ocean fall in the range obtained by previous works these estimates include a better representation of the trapped water region in the eddies a large inter annual variability in the volume transport was observed with a maximum of 11 21 sv in 2007 this variability is related to the number of structures shed by the agulhas retroflexion per year the ring shapes play a secondary though important role

rainfall intensity and slope gradient effects on sediment losses and splash from a saline sodic soil under coastal reclamation abstract rainfall intensity and slope gradient play important roles in soil erosion processes this study was conducted to investigate the effects of rainfall intensity and slope gradient as well as of their interactions on splash and overland flow transport on saline sodic soil slopes rainfall intensities of 85 95 110 and 125 mm h 1 were applied to slope gradients of 6 11 22 and 35 splash was partitioned into four directional components runoff sediment and splash samples were collected throughout the rainstorms and infiltration was calculated the final infiltrations under the lower rainfall intensities of 85 mm h 1 were the largest for every slope gradient but they decreased by 39 3 as the slope gradient increased from 6 to 35 however the final infiltration rates exhibited an increasing decreasing trend for rainfall intensities higher than 85 mm h 1 as the slope gradient increased the critical slope gradient was about 11 the influence of rainfall intensity on runoff was considerably reduced at the higher slope gradients due to increased infiltration the influence of slope gradient on sediment loss was reduced as rainfall intensity increased while the effect of rainfall intensity on sediment losses was greater on the gentler slopes than on the steeper slopes the upslope splash mean value initially increased from 4 8 to 7 2 g m 1 h 1 before it decreased to 3 g m 1 h 1 as the slope gradient increased the maximum measured value occurred when the slope gradient was 22 total splash increased to maximum levels as the slope gradient increased to 11 but decreased with further increases in gradient these results indicated that the effects of slope gradient and rainfall intensity on sediment losses runoff and splash were interconnected

effects of erosion degree rainfall intensity and slope gradient on runoff and sediment yield for the bare soils from the weathered granite slopes of se china abstract soil erosion caused by rainfall is a dominant driving force of ecosystem degradation and has become a worldwide environmental issue however few studies have been conducted to investigate the effect of erosion degree on the characteristics of soil erosion this study aims to investigate the effects of erosion degree rainfall intensity and slope gradient on erosion processes on bare weathered granite slopes of southeast china the method of simulated rainfalls was applied with two soil tanks under three slope gradients 8 15 25 four rainfall intensities 60 90 120 150 mm h and three erosion degrees slight e1 moderate e2 severe e3 the rainfall time lasted 90 min and the paddy samples were collected at every 3 min to determine the runoff rate for surface flow rr s and interflow rr i sediment rate sr sediment concentration sc and particle size distribution psd the enrichment ratio er and mean weigh diameter mwd of different particles were finally calculated and evaluated the occurring time of surface flow tr s and interflow tr i presented a negative relationship with rainfall intensity and slope gradient while tr s presented an order of e2 e1 e3 and tr i was negatively related to erosion degree rr s increased with runoff duration and was positively correlated to rainfall intensity and slope gradient but negatively correlated to erosion degree but rr i displayed single peak curves with runoff duration and was positively related to erosion degree sr showed an increasing deceasing trend with runoff duration and was positively correlated to rainfall intensity and slope gradient sr on different slopes displayed an order of e1 e2 e3 at the 60 and 90 mm h rainfalls while it reversed at heavier rainfalls sc decreased with runoff duration with light fluctuations it was found that sediment psd was corresponding to original soils to a definite extent while mwd and er were positively correlated to erosion degree these results facilitate the understandings of runoff and soil erosion processes in the weathered granite regions and erosion degree should be considered in future erosion prediction and modeling

coherent mesoscale eddies in the north atlantic subtropical gyre 3 d structure and transport with application to the salinity maximum the mean vertical structure and transport properties of mesoscale eddies are investigated in the north atlantic subtropical gyre by combining historical records of argo temperature salinity profiles and satellite sea level anomaly data in the framework of the eddy tracking technique the study area is characterized by a low eddy kinetic energy and sea surface salinity maximum although eddies have a relatively weak signal at surface amplitudes around 3 7 cm the eddy composites reveal a clear deep signal that penetrates down to at least 1200 m depth the analysis also reveals that the vertical structure of the eddy composites is strongly affected by the background stratification the horizontal patterns of temperature salinity anomalies can be reconstructed by a linear combination of a monopole related to the elevation depression of the isopycnals in the eddy core and a dipole associated with the horizontal advection of the background gradient by the eddy rotation a common feature of all the eddy composites reconstructed is the phase coherence between the eddy temperature salinity and velocity anomalies in the upper 300 m layer resulting in the transient eddy transports of heat and salt as an application a box model of the near surface layer is used to estimate the role of mesoscale eddies in maintaining a quasi steady state distribution of salinity in the north atlantic subtropical salinity maximum the results show that mesoscale eddies are able to provide between 4 and 21 of the salt flux out of the area required to compensate for the local excess of evaporation over precipitation

vertical structure of mesoscale eddies in the eastern south pacific ocean a composite analysis from altimetry and argo profiling floats 1 the mean vertical structure of mesoscale eddies in the peru chile current system is investigated by combining the historical records of argo float profiles and satellite altimetry data a composite average of 420 526 profiles acquired by argo floats that surfaced into cyclonic anticyclonic mesoscale eddies allowed constructing the mean three dimensional eddy structure of the eastern south pacific ocean key differences in their thermohaline vertical structure were revealed the core of cyclonic eddies ces is centered at 150 m depth within the 25 2 26 0 kg m 3 potential density layer corresponding to the thermocline in contrast the core of the anticyclonic eddies aes is located below the thermocline at 400 m depth impacting the 26 0 26 8 kg m 3 density layer this difference was attributed to the mechanisms involved in the eddy formation while intrathermocline ces would be formed by instabilities of the surface equatorward coastal currents the subthermocline aes are likely to be shed by the subsurface poleward peru chile undercurrent in the eddy core maximum temperature and salinity anomalies are of 1 c and 0 1 with positive negative values for aes ces this study also provides new insight into the potential impact of mesoscale eddies for the cross shore transport of heat and salt in the eastern south pacific considering only the fraction of the water column associated with the fluid trapped within the eddies each ce and ae has a typical volume anomaly flux of 0 1 sv and yields to a heat and salt transport anomaly of 1 3 1011 w and 3 8 103 kg s 1 respectively

anomalous eddy heat and freshwater transport in the gulf of alaska characteristics of eddies in the gulf of alaska are assessed from january 2003 through april 2012 ensemble statistics for eddy subsurface water properties on isopycnals are computed using temperature and salinity profiles from argo profiling floats located within eddies which are identified in sea surface height using objective techniques ninety cyclonic and 154 anticyclonic eddies are identified during this period the anticyclonic eddies are strongly nonlinear and exhibit significant warm subsurface temperature anomalies and associated salty anomalies on isopycnals while no clear distinguishing subsurface anomalies on isopycnals are detected in association with the cyclonic eddies heat and freshwater fluxes for the eddies are estimated from integrations in depth coordinates the anticyclonic eddies transport heat both westward off the continental shelf into the subarctic gyre and westward within the alaskan stream however they transport salt into the subarctic gyre and freshwater within the alaskan stream in both pathways eddy heat and freshwater transport show possible year to year fluctuations varying from 0 to 50 4 1018 j a 1 and 16 8 to 7 4 km3 a 1 respectively the anticyclonic eddies are capped by relatively fresh water year round

effect of rainfall intensity slope and antecedent moisture content on sediment concentration and sediment enrichment ratio abstract the transportability of sediment by runoff and its potential for subsequent deposition is dependent on the size and distribution of the transported material and the sediment concentration the size distribution of the eroded sediment is also expected to vary depending on which erosion process is predominant this study discusses the results of laboratory analysis to evaluate the effect of rainfall intensity slope steepness soil types and antecedent moisture content on sediment concentration runoff coefficients and sediment enrichment ratios to achieve the objectives laboratory experiments were conducted using fel 3 rainfall simulator and erosion pan rainfall intensity of 120 70 and 55 mm h was applied sequentially at 9 25 and 45 slope for three soil types found in alemaya watershed eastern ethiopia alemaya black soil soil a regosols soil b and cambisols soil c varied from clay to sandy clay loam in texture with wet and dry antecedent moisture contents the rate of sediment concentration significantly varied with moisture contents for soil a sediment concentrations 24 3 g l from an initially air dry surface and 18 7 g l from an initially wet surface were observed wetting decreased sediment concentration of soil a b and c by 23 45 7 and 1 3 respectively sediment concentration didn t show any trend with rainfall intensities for soil b the highest average silt enrichment ratio of 2 15 was observed followed by average clay enrichment ratio of 1 61 for soil a and soil c average clay enrichment ratios of 1 13 and 1 91 were observed respectively initial moisture contents had effect on the enrichment ratio however the actual effect varied with soil type and the size of the particle results of the study indicated that the actual effect of slope as well as rainfall intensity on sediment concentration and sediment yield vary with soil types and moisture contents

southern ocean eddy phenomenology mesoscale eddies are ubiquitous features in the southern ocean yet their phenomenology is not well quantified to tackle this task we use satellite observations of sea level anomalies and sea surface temperature sst as well as in situ temperature and salinity measurements from profiling floats over the period 1997 2010 we identified over a million mesoscale eddy instances and were able to track about 105 of them over 1 month or more the antarctic circumpolar current acc the boundary current systems and the regions where they interact are hot spots of eddy presence representing also the birth places and graveyards of most eddies these hot spots contrast strongly to areas shallower than about 2000 m where mesoscale eddies are essentially absent likely due to topographical steering anticyclones tend to dominate the southern subtropical gyres and cyclones the northern flank of the acc major causes of regional polarity dominance are larger formation numbers and lifespans with a contribution of differential propagation pathways of long lived eddies areas of dominance of one polarity are generally congruent with the same polarity being longer lived bigger of larger amplitude and more intense eddies extend down to at least 2000 m in the acc eddies show near surface temperature and salinity maxima whereas eddies in the subtropical areas generally have deeper anomaly maxima presumably inherited from their origin in the boundary currents the temperature and salinity signatures of the average eddy suggest that their tracer anomalies are a result of both trapping in the eddy core and stirring

eddy induced heat transport in the subtropical north pacific from argo tmi and altimetry measurements basin scale heat transport induced by mesoscale oceanic eddies is estimated by combining satellite derived sea surface height and temperature temperature data are from the trmm microwave imager tmi data with argo float temperature salinity data in the north pacific ocean subtropical gyre warm cold temperature anomalies of mesoscale eddies are found to be consistently located to the west of high low ssh anomalies the phase misalignment between the temperature and velocity anomalies however is largely confined to the seasonal thermocline causing most of the eddy induced heat transport to be carried in the surface 200 m layer by establishing a statistical relationship between the surface and depth integrated values of the eddy heat transport the basin scale eddy heat transport is derived from the concurrent satellite ssh sst data of the past six years in the kuroshio extension region the meandering zonal jet is found to generate oppositely signed eddy heat fluxes as a result the zonally integrated poleward heat transport associated with the kuroshio extension is at a level o 0 1 pw smaller than the previous estimates based on turbulent closure schemes large poleward eddy heat transport is also found in the subtropical north pacific along a southwest northeast tilting band between taiwan and the midway islands this band corresponds to the region of the subtropical front and it is argued that the relevant temperature field for identifying this band in the turbulent closure scheme models should be that averaged over the seasonal thermocline

lignin biomarker and isotopic records of paleovegetation and climate changes from lake erhai southwest china since 18 5kabp abstract a sound knowledge of paleovegetation is fundamental to better understanding of past climate variability and provides necessary background for improving predictions of future climate changes in the present study stable isotopes 13c and 15n and lignin biomarker of sedimentary organic matter som from lake erhai 25 50 n 100 10 e southwest china were determined to reconstruct paleovegetation and to find vegetation climate relationships the stable carbon isotope signatures suggested that the organic matter mostly derived from c3 plants throughout the depositional periods since 18 5 ka bp the variability of isotopic values of carbon 13c 28 8 to 23 9 and nitrogen 15n 1 2 4 1 might be related to changes in terrestrial runoff i e precipitation compositions of the alkaline cuo oxidation products of lignin showed a significant change in terrestrial vegetation from gymnosperm rich to angiosperm rich plants at lake catchments in the early holocene the lignin phenol vegetation index lpvi also indicated changes in terrestrial vegetation with few more subtle changes during the last 18 5 ka as a single proxy of entire characteristic of terrestrial vegetation in comparison to past asian monsoon records 18o record in stalagmite of dongge cave lpvi suggested a direct linkage between vegetation changes and asian monsoon variability that might be influenced by global climate changes

an improved approach for evaluating the time dependent stability of colluvial landslides during intense rainfall the paper presents an improved analytical approach for evaluating the time dependent stability of colluvial landslides during intense rainfall infiltration the approach comprises two steps first to simulate rainfall infiltration and then to compute the safety factor in terms of the irregularity of the natural landslide surface in implementation of the method the landslide is divided into several soil slices with approximately straight sides each single slice is regarded as a finite slope so that the infiltration formula and safety factor can be deduced the infiltration formula is derived with combination of the green ampt model and mass conservation law considering seepage perpendicular and parallel to slope surface simultaneously in the modified infiltration model both size effect and angle effect are vividly observed in the process of rainfall infiltration into the finite slope while the former of which is not presented in the original green ampt model the safety factor is computed using the limit equilibrium method with the influence of infiltrating water on the shear strength gravity and seepage force of soil slices considered by case study of the shuping landslide in three gorges decline in the safety factor and the decrease in the tendency are definite specifically under the rainfall intensity of 50 mm h the failure of shuping landslide is most likely to occur at the time of 102 h in addition the results highlight shallow failure along the wetting front under intense rainfall

a 45 kyr laminae record from the dead sea implications for basin erosion and floods recurrence abstract recording and analyzing how climate change impacts flood recurrence basin erosion and sedimentation can improve our understanding of these systems the aragonite detritus laminae couplets comprising the lacustrine formations that were deposited in the dead sea are considered as faithful monitors of the freshwater supply to the lakes we count a total of 5600 laminae couplets deposited in the last 45 kyr mis3 mis1 at the dead sea center which encompass the upper 142 m of the icdp core 5017 1 the present study shows that aragonite and detritus laminae are thinner and occur at high frequency during mis 3 2 while they are much thicker and less frequent during mis 1 by analyzing multiple climate connected factors we propose that significant lake level drops enhanced dust input and low vegetative cover in the drainage basin during the last deglaciation 22 11 6 ka have considerably increased erodible materials in the dead sea watershed we find a decoupling existed between the significant lake level drop lake size reduction and lamina thickness change during the last deglaciation we argue that during the last glacial and the holocene the variation of lamina thickness at the multiple millennium scale was not controlled directly by the lake level size change we interpret this decoupling implying the transport capacity of flash floods is low and might be saturated by the oversupply of erodible materials and indicating a transport limited regime during the time period we suggest the observed thickness and frequency distribution of aragonite detritus laminae points to the high frequency of small magnitude floods during the last glacial in contrast to low frequency but large magnitude floods during the holocene

a global analysis of sverdrup balance using absolute geostrophic velocities from argo using observations from the argo array of profiling floats the large scale circulation of the upper 2000 decibars db of the global ocean is computed for the period from december 2004 to november 2010 the geostrophic velocity relative to a reference level of 900db is estimated from temperature and salinity profiles and the absolute geostrophic velocity at the reference level is estimated from the trajectory data provided by the floats combining the two gives the absolute geostrophic velocity on 29 pressure surfaces spanning the upper 2000db of the global ocean these velocities together with satellite observations of wind stress are thenusedtoevaluatesverdrupbalance thesimplecanonicaltheoryrelatingmeridionalgeostrophictransport to wind forcing observed transports agree well with predictions based on the wind field over large areas primarily in the tropics and subtropics elsewhere especially at higher latitudes and in boundary regions sverdrup balance does not accurately describe meridional geostrophic transports possibly due to the increased importance of the barotropic flow nonlinear dynamics and topographic influence thus while it provides an effective framework for understanding the zero order wind driven circulation in much of the global ocean sverdrup balance should not be regarded as axiomatic

vertical structure and temporal evolution of an anticyclonic eddy in the balearic sea western mediterranean 1 an anticyclonic eddy in the balearic sea western mediterranean was described using data from a mooring line deployed at the northern slope of mallorca island at about 900 m deep its surface signature was investigated using sea surface height and sea surface temperature images the eddy which lasted around 1 month modified the thermohaline characteristics and the currents of the entire water column levantine intermediate waters usually resident in the region were displaced by colder and fresher western mediterranean intermediate waters associated with the eddy along slope main currents toward ne were completely reversed at 500 m and significantly deviated at 900 m interestingly near bottom velocities were found to be systematically larger than those at intermediate depths furthermore during the eddy velocities reached values up to 26 cm s at the bottom 5 times larger than the bottom average speed the recurrence of the phenomenon was explored with an eddy detection tool applied to satellite observations results indicated that anticyclonic eddies are common structures in the balearic current

effects of rain intensity slope gradient and particle size distribution on the relative contributions of splash and wash loads to rain induced erosion abstract soil erosion during rainfall is a complex phenomenon resulting from detachment by raindrop impact and overland flow the objective of this study is to investigate the transportation rate of splash load sl and that of wash load wl and their relative contributions to the rain induced erosion rate affected by rain intensity slope gradient and particle size distribution a total of 60 simulation runs were carried out using a detachment tray under simulated rainfall with no inflow the experiments were done on two soil samples aggregate sizes finer than 2 and 4 75 mm from an agricultural land use at different rain intensities 57 and 80 mm h 1 and varying slope gradients 0 5 2 5 5 10 and 20 under unsteady state conditions wl showed relatively high dependency on slope gradient whereas approaching steady state conditions nearly similar values of wl occurred at different slopes sl and wl increased with increasing rain intensity and slope gradient implying the importance of rain induced erosion on bare agriculture lands especially at steeper slopes the ratio of wl sl decreased when slope gradient increased however wl increased more significantly than sl as soil aggregates became finer the result indicates that at all the slope gradients wl was much larger than sl indicating that wash load significantly contributes to the rain induced erosion in the agricultural soil furthermore with increasing slope gradient the contribution of wash load to rain induced erosion decreased while it was greater in the soil containing finer aggregates also with increasing rain intensity at lower slope gradients 10 the finding of this study revealed that the rain induced erosion was transport limited at the gentler slopes whereas at the steeper slopes it shifted to detachment limited conditions

advective timescales and pathways of agulhas leakage current research indicates an increase in agulhas leakage for the past and coming decades this change potentially alters the strength of the atlantic meridional overturning circulation in particular through advection of positive density anomalies into the north atlantic to explore the fate of agulhas leakage results from a lagrangian analysis were evaluated with virtual floats advected within an eddy permitting ocean model orca025 a considerable fraction of agulhas leakage reached the subtropical north atlantic of a mean agulhas leakage transport of 15 3 sv entering the south atlantic 9 7 7 7 and 6 1 sv crossed sections at 6 degrees s 6 degrees n and 26 degrees n respectively the most probable transit time of leakage to reach the respective latitudes is one to two decades we suggest that changes in agulhas leakage could manifest in the gulf stream regime most probably within two decades these results were supported by an eddy resolving implementation of the ocean model inalt01

long range transport of a quasi isolated chlorophyll patch by an agulhas ring 1 using satellite retrievals of sea surface chlorophyll and geostrophic currents we study the evolution of a distinct chlorophyll patch transported by an agulhas ring along a 1 500 km track throughout an 11 months period of the total 2 years eddy lifetime the shape of the chlorophyll patch is consistently delimited by the horizontal transport barriers associated with the eddy analysis of lagrangian time series of sea surface variables in and around the eddy suggests that the evolution of the chlorophyll patch is driven by two processes i slow lateral mixing with ambient waters mediated by horizontal stirring in filaments and ii rapid events of wind induced vertical mixing these results support the idea that mesoscale eddies shape biological production through the combination of horizontal and vertical dynamical processes and emphasize the important role of horizontal eddy transport in sustaining biological production over the otherwise nutrient depleted subtropical gyres

rings in the ocean certain robust long lived eddy features in t he world s ocean have come to be k nown as rings the nomenclature stems from fuglister 1 1972 who c oined t he name based on the c ircle or ring of gulf stream waters t hat surrounded a class of eddies formed from t he g ulf stream through the pinch off of meanders here it s uffices to define rings as intense eddies or vortices that represent a wrapped up piece of a major ocean c urrent they t ranslate over space scales of hundreds to thousands of k ilometers and exist for periods lasting from months to years rings move t hrough the ocean carrying anomalies s imilar to the contrasts in physical biological and chemical properties observed across the major ocean c urrents while the term ring is t ied to fuglister t he existence ofthese features was evident at least as early as t he 1930s when iselin 2 1936 1940 encountered strong cold anomalies in the region south of the gulf stream that we would identify as c old corc cyclonic rings today iselin fully rec ognized these features as part of the highly time dependent eddy motion in the ocean later iselin fuglister 1948 were the first to survey what is now k nown as a warm core anticyc lonic ring there are tw o types of rings cold core rings are made up of w aters from the poleward s ide of c urrents like the gulf stream that are introduced to

three compartment structure of subsurface intensified mesoscale eddies in the ocean mesoscale eddies are energetically dominant and pervasive over most of the world s oceans among them many are subsurface intensified with strongest signals in the ocean interior such as mode water eddies which trap water masses with distinctive properties and carry them over long distances with both argo profiling floats and atmospheric reanalysis data we showed that the structure of these eddies obeys a universal rule hence their three dimensional hydrographic fields can be readily reconstructed from very limited information more interestingly the volume of water trapped and moved by a mode water eddy is much greater than previously thought it has a three compartment structure in the vertical with the mode water being sandwiched between two layers of notably different properties and accounting for only a portion of the total trapped volume this article is protected by copyright all rights reserved

hydrological responses on saline sodic soil slopes in a coastal reclamation area of china abstract evaluation of the effects of slope gradient and rainfall intensity on the hydrological responses on slopes can provide important information for soil and water conservation we conducted simulated rainfall experiments to study the hydrological response of a saline sodic soil on slopes with different gradients 6 11 22 and 35 and rainfall intensities 85 95 110 and 125 mm h 1 higher effective rainfall intensities significantly reduced the times to ponding and runoff while the infiltration coefficient did not always increase with increasing slope gradient it consistently increased with increasing rainfall intensity on slopes of 6 11 or 22 the mean flow velocities and stream power values tended to increase with increasing slope gradient but did not change consistently with changes in rainfall intensity hydraulic shear stress and its logarithm could predict sediment losses that were 1 h 1 however stream power and its logarithm were better predictors of a wider range of sediment losses from slopes with saline sodic soil these results suggest that existing hydrological and erosion models should be adjusted to take into account the effects of salinity and sodicity

laboratory investigations of rill dynamics on soils of the loess plateau of china abstract we conducted a laboratory study on rill network evolution with detailed measurements under controlled experimental conditions the concepts of fractal geometry entropy and topology were used to quantify rill erosion intensity and morphology the objectives of this study are to reveal rill erosion processes and rill network development under different rainfall intensities and to present some indicators to provide a quantitative description of rill morphology a soil pan 5 m long 1 m wide and 0 6 m deep with slope gradient of 20 was subjected to three successive rainfall events under rainfall intensities of 66 94 and 127 mm h 1 the results showed that rainfall intensity played a major role in rill erosion the development of a rill network is most rapid under medium intensity rainfall rainfall intensity that is too weak or too strong is not conducive to rill development as rainfall duration increased under the same rainfall intensity the values of soil loss rill density geomorphologic comentropy and nodes increased rill network development was slow at the early stage but became more rapid at a later stage the results also indicated that the geomorphologic comentropy was the best basic morphological indicator of rill erosion and the number of rill nodes was the best derived morphological indicator of rill morphology which was followed in descending order by the fractal dimension rill density and bifurcation ratio

mesoscale eddies off peru in altimeter records identification algorithms and eddy spatio temporal patterns relatively little is known about coherent vortices in the eastern south pacific along the peruvian coast even with regard to basic facts about their frequency of occurrence longevity and structure this study addresses these issues with nearly 15 years of relatively high resolution satellite altimetry measurements we first compare two distinct automated methods for eddy identification the objective validation protocol shows that the rarely used geometrical or winding angle method based on the curvature of the streamline functions is more accurate than the commonly used okubo weiss algorithm which defines a vortex as a simple connected region with values of okubo weiss parameter weaker than a given threshold we then investigate vortices off peru using more than 20 000 mesoscale eddies identified by the winding angle method coherent eddies characterized by a high ratio of vorticity to deformation rate are typically formed along the coast and propagate westward at 3 6 cm s 1 the vortices have a mean radius of 80 km increasing northward and are most frequently observed off of chimbote 9s and south of san juan 15s the mean eddy lifetime is about 1 month but if eddies survive at least 2 months the probability for surviving an additional week or month is constant at 90 or 67 anticyclonic eddies tend to propagate northwestward whereas cyclonic vortices migrate southwestward in general cyclones and anticyclones are similar except for eddies surviving at least 6 months in this case after a similar 3 4 months of radius and amplitude growth amplitudes or sizes decay particularly rapidly for anticyclonic or cyclonic eddies in terms of intensity cyclonic eddies show a rapid decay during the first 3 months before arriving at a quasi constant value whereas anticyclones exhibit steady decline finally eddy temporal variations were examined at seasonal and interannual scales in the coastal region favorable to the formation of energetic mesoscale structures on seasonal scales eddy activity is maximal in fall and minimum in spring at interannual scales the eddy activity index was maximal during the strong el nino of 1997 1998 but another strong maximum of eddy activity also occurred late in 2004 these temporal variations are probably associated with the intensification of the upwelling thermal front and with the passage of coastal trapped waves which generate baroclinic instabilities further investigation of the mechanisms involved on the eddy genesis is needed

agulhas ring transport efficiency from combined satellite altimetry and argo profiles agulhas rings are one of the main processes contributing to the westward transport of agulhas leakage water across the south atlantic basin here we quantified the water transported and exchanged by three agulhas rings by combining remote sensing altimetry and in situ argo observations satellite velocities showed that two of the eddies formed within the cape basin west of south africa at the beginning of 2013 and reached the mid atlantic ridge by the end of 2014 there they merged forming the third eddy which dissipated a year later when it approached the brazilian continental shelf eddy structure reconstructed from argo profiles showed that the eddies were at least 1500 m deep and that their dynamics was strongly affected by the two open ocean ridges encountered along their path between the ridges eddy volumes were mostly conserved but waters were continuously exchanged during eddy dissipation volume losses and water exchanges were more pronounced at depth these findings highlight the importance of combining surface with in situ information to accurately represent agulhas ring transport and exchanges overall the eddies transported roughly 0 5 1013 m3 of water from the cape basin to west of 30 w in a 3 year span lagrangian diagnostics indicated that after an initial period of instability the surface waters exchanged by the eddies along their tracks dispersed roughly in the same direction as the eddies albeit at a much slower rate these results further confirm that agulhas eddies are the most efficient process for westward transport across the south atlantic basin