Seismicity in ocean ridge-transform systems reveals fundamental processes of mid-ocean ridges,while comparisons of seismicity in different oceans remain rare due to a lack of detection of small events.From 1996 to 200...Seismicity in ocean ridge-transform systems reveals fundamental processes of mid-ocean ridges,while comparisons of seismicity in different oceans remain rare due to a lack of detection of small events.From 1996 to 2003,the Pacific Marine Environmental Laboratory of the National Oceanic and Atmospheric Administration(NOAA/PMEL)deployed several hydrophones in the eastern Pacific Ocean and the northern Atlantic Ocean.These hydrophones recorded earthquakes with small magnitudes,providing us with opportunities to study the seismic characteristics of ridge-transform systems at different spreading rates and make further comparisons of their differences.This study comparatively analyzed hydroacoustic and teleseismic data recorded on the fast-spreading East Pacific Rise(EPR,10°S to 12°N),intermediate-spreading Galapagos Ridge(103°W to 80°W),and slow-spreading Mid-Atlantic Ridge(MAR,15°N to 37°N).We present a systematic study of the spatial and temporal distribution of events,aftershock seismicity,and possible triggering mechanisms of aftershock sequences.Our analysis yields the following conclusions.(1)From the hydroacoustic data,the EPR transform faults had the highest average seismicity rate among the three regions.(2)Along-ridge event distributions show that a high number of earthquakes were concentrated on the EPR,while they became dispersed on the GR and fewer and more scattered on the MAR,reflecting that the different tectonic origins were closely correlated with the spreading rate.(3)Analysis from mainshock-aftershock sequences shows no significant differences in the aftershock decay rate among the three regions.(4)Multiple types of aftershock triggering models were inferred from Coulomb stress changes:strike-slip mainshocks triggered strike-slip aftershocks and normal faulting aftershocks,and normal faulting mainshocks triggered normal faulting aftershocks.Although these results are case studies,they may be applicable to other ocean ridge-transform systems in future investigations.Our results provide important new insights into the seismicity of global ocean ridge-transform systems.展开更多
As part of an ongoing comprehensive inventory of Galapagos lichens,a first assessment of the morphology and anatomy of basidiolichens from the archipelago is presented here.It is the basis for further studies of the t...As part of an ongoing comprehensive inventory of Galapagos lichens,a first assessment of the morphology and anatomy of basidiolichens from the archipelago is presented here.It is the basis for further studies of the taxonomy,ecology and biogeography of this poorly known group of lichens.Four genera,all in Hygrophoraceae,can be distinguished:Acantholichen,Cora,Cyphellostereum and Dictyonema.Both Acantholichen and Cora are characterized by chroococcoid cyanobionts and a heteromerous thallus with a distinct upper cortex and photobiont layer.The monotypic Acantholichen pannarioides is entirely composed of small,branched,inflated squamules that appear densely pruinose because their cortical hyphae bear characteristically swollen,densely spinose end cells(acanthohyphidia);this species has never been observed fertile.The common Cora glabrata is foliose,forming large,radially zonate,conch-like,often tiled thalli,when fertile with circular lines of basidiocarps on its lower side.Dictyonema is distinguished by filamentous cyanobionts and distinctly filamentous thalli that are homomereous(i.e.,not distinctly layered);all species of Dictyonema s.str.have trichomes(filamentose cyanobacterial photobionts)closely enveloped by fungal cells of a jigsaw pattern.In D.sericeum thallus filaments(i.e.,individual fibrils)aggregate to form shelf-like structures similar in appearance to polyporoid bracket fungi;basidiocarps develop in irregular patches on the lower side of these shelves.In contrast,fibrils of D.schenkianum grow encrusting their substrate with irregularly to suberect trichomes,occasionally bearing basidiocarps dispersed across the thallus.Two other species in Galapagos show adpressed growth form and are described here as new:Dictyonema pectinatum,which is characterized by large parallel fibrils with paler,papillate tips,and D.galapagoense,characterized by thin trichomes of more squarrish elongate cells.The genus Cyphellostereum is represented by two species:the newly described C.imperfectum and an unnamed Cyphellostereum sp.,both phenotypically similar to free-living cyanobacterial filaments.Cyphellostereum imperfectum has narrow photobiont filaments with irregular hyphal sheath leaving interspaces;macroscopically it shows a bluish green thallus with a distinct prothallus.Cyphellostereum sp.has a rather uncommon basidiolichen appearance:thin sctytonematoid fibrils surrounded by straight fungal cells forming shiny tufts.The new combination Cyphellostereum nitidum is also proposed.The ecology and taxonomy of Galapagos basidiolichens is briefly discussed and a key and short descriptions of all species are presented.展开更多
The fishery of the sea cucumber Isostichopus fuscus was the most important one in the early 2000s in the Galapagos Marine Reserve.Its overexploitation leads to its total closure from 2016 to 2021.At the end of this pe...The fishery of the sea cucumber Isostichopus fuscus was the most important one in the early 2000s in the Galapagos Marine Reserve.Its overexploitation leads to its total closure from 2016 to 2021.At the end of this period,if the co-management system of the Galapagos Marine Reserve decides to open this fishery,a total allowed catch must be established using the methodology of Wolff,Schuhbauer,and Castrejón(2012).The objective of this paper is to evaluate this methodology and improve the total allowed catch calculation.We replicated Wolff et al.‘s methodology that uses the Cadima equation of Maximum Sustainable Yield(in Troadec,1977).We determined the age and growth parameters of I.fuscus to estimate total mortality and improved the calculation of the area of fishing and habitat of this species in Galapagos to estimate its abundance.We found inconsistences in Wolff et al.‘s estimations of mortality and abundance and we recommend that the Maximum Sustainable Yield be used not as the total allowed catch,but as a limit reference point for this fishery.We propose,instead,to use a dynamic abundance model that is capable of estimating a variety of reference points,including the fishing mortality for optimal fishing that is recommended to use to establish a total allowed catch.In addition,for the first time,the age and growth parameters of I.fuscus for Galapagos and the eastern-central region of the Pacific Ocean are determined(L∞=42.5 cm;K=0.21/year).展开更多
This study is a re-assessment of basidiolichen diversity in the Galapagos Islands.We present a molecular phylogenetic analysis,based on 92 specimens from Galapagos,using two nuclear ribosomal DNA markers(ITS and nuLSU...This study is a re-assessment of basidiolichen diversity in the Galapagos Islands.We present a molecular phylogenetic analysis,based on 92 specimens from Galapagos,using two nuclear ribosomal DNA markers(ITS and nuLSU).We also re-examined the morphology and anatomy of all sequenced material.The molecular results confirm our previous assessment that all Galapagos basidiolichens belong to the Dictyonema clade,which in Galapagos is represented by four genera:Acantholichen,Cora,Cyphellostereum,and Dictyonema.Most species previously reported from Galapagos in these genera were at the time believed to represent widely distributed taxa.This conclusion,however,has changed with the inclusion of molecular data.Although almost the same number of species is distinguished,the phylogenetic data now suggest that all are restricted to the Galapagos Islands.Among them,six species are proposed here as new to science,namely Cora galapagoensis,Cyphellostereum unoquinoum,Dictyonema barbatum,D.darwinianum,D.ramificans,and D.subobscuratum;and four species have already been described previously,namely Acantholichen galapagoensis,Cora santacruzensis,Dictyonema pectinatum,and D.galapagoense,here recombined as Cyphellostereum galapagoense.Our analysis is set on a very broad phylogenetic framework,which includes a large number of specimens(N=826)mainly from Central and South America,and therefore strongly suggests an unusually high level of endemism previously not recognized.This analysis also shows that the closest relatives of half of the basidiolichens now found in Galapagos are from mainland Ecuador,implying that they reached the islands through the shortest route,with all species arriving on the islands through independent colonization events.展开更多
Hydrothermal plume is an important constituent of seabed hydrothermal circulation and is also one of the characteristics of active hydrothermal vents. Portable Miniature Autonomous Plume Recorders （MAPR） attached to...Hydrothermal plume is an important constituent of seabed hydrothermal circulation and is also one of the characteristics of active hydrothermal vents. Portable Miniature Autonomous Plume Recorders （MAPR） attached to a towed deep-sea instrument was used to search for hydrothermal plumes and hydrothermal vents. We introduced the basic principle of MAPR based on deep towing technology to detect plumes, then analyzed the factors affecting the quality of the MAPR data and presented a data correction method for MAPR, including instrument location correction, noise reduction processing, system error elimination and seawater background reduction. Finally we applied the method to analyze MAPR data obtained during the Chinese DY115-21 cruise on R/VDayang Iin the “Precious Stone Mountain” hydrothermal field on the Gala-pagos Microplate. The results provided a better understanding of the distribution of the hydrothermal activ-ity in this field, indicating the presence of a new hydrothermal vent.展开更多
Many recent studies of ecological speciation have focused on ＂magic trait＂ scenarios, in which divergent selection on viability traits leads inextricably to corresponding divergence in mechanisms, especially mate re...Many recent studies of ecological speciation have focused on ＂magic trait＂ scenarios, in which divergent selection on viability traits leads inextricably to corresponding divergence in mechanisms, especially mate recognition systems, that facilitate assortative mating. Speciation however may also proceed via other scenarios, such as when populations experience directly se- lected or random divergence in mate recognition systems. The relative contributions of magic trait versus other scenarios for speciation remain virtually unexplored. The present study aims to test the relative contribution of the magic trait scenario in the divergence of populations of the medium ground finch Geospiza fortis of Santa Cruz Island, Galapagos. First, we assess differ- ences in G. fortis song between a northern population （Borrero Bay） and a southeastern population （El Garrapatero）, differences that we propose （along with other within-island geographic song variations） have arisen via scenarios that do not involve a magic trait scenario. Pairwise comparisons of raw and composite （PC） song parameters, as well as discriminant functions analyses, re- veal significant patterns of song divergence between sites. Second, we test the ability of territorial males at Borrero Bay to dis- criminate songs from the two sites. We find that G. fortis males can discriminate within-island song variants, responding more strongly to local than to ＂foreign＂ songs, along 3 raw and 1 composite response measures. Third, we compare these findings to prior data sets on song divergence and discrimination in Santa Cruz G. fortis. These comparisons suggest that song divergence and discrimination are shaped less strongly by geographic sources than by morphological （beak-related） sources. We thus argue that interpopulation song divergence and discrimination, fundamental elements of assortative mating in Darwin＇s finches, can be fos- tered in early stages of divergence under magic trait as well as alternative scenarios for speciation, but with more emphasis on the magic trait scenario, at least for this species on this island [Current Zoology 59 （1）： 8-19, 2013].展开更多
Seasonal variations of the equatorial undercurrent(EUC) termination in the Eastern Pacific,and their mechanism were examined using the Estimating the Circulation and Climate of the Ocean,PhaseⅡ(ECCO2).The ECCO2 repro...Seasonal variations of the equatorial undercurrent(EUC) termination in the Eastern Pacific,and their mechanism were examined using the Estimating the Circulation and Climate of the Ocean,PhaseⅡ(ECCO2).The ECCO2 reproduced a weak and shallow eastward EUC east of the Galapagos Islands,with annual mean transport of half of EUC to the west of the Islands.The diagnosis of zonal momentum equation suggests that the zonal advection(nonlinear terms) drives the EUC beyond the Islands rather than the pressure gradient force.The EUC in the Far Eastern Pacific has the large st core velocity in boreal spring and the smallest one in boreal summer,and its volume transport exhibits two maxima in boreal spring and autumn.The seasonal variability of the EUC in the Eastern Pacific is dominated by the Kelvin and Rossby waves excited by the zonal winds anomalies in the central and Eastern Pacific that are associated with the seasonal relaxation or intensification of the trade wind.In the Far Eastern Pacific to the east of 120°W,the eastward propagation Kelvin waves play a dominate role in the seasonal cycle of the EUC,results in a semiannual fluctuation with double peaks in boreal spring and autumn.A construction of water mass budget suggests that approximately 24.1% of the EUC water east of 100°W has upwelled to the mixed layer by0.35 m/d.The estimated upwelling is stronge st during boreal autumn and weake st during boreal winter.It is also found that approximately 42.6% of the EUC turns westward to feed the south equatorial current(SEC),13.2% flows north of the equator,and 20.1% flows south of the equator,mainly contributing to Peru-Chile undercurrent.展开更多
基金The Fund of the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0205the National Natural Science Foundation of China under contract Nos 42006055,41704049,41890813,41976066,and 41976064+3 种基金The Fund of the State Key Laboratory of Marine Geology,Tongji University under contract No.MGK202011the Scholarship of China Scholarship Councilthe Program of Chinese Academy of Sciences under contract Nos Y4SL021001,QYZDYSSW-DQC005,131551KYSB20200021,133244KYSB20180029,and ISEE2021PY03the International Conference Communication Fund for Graduate Students,Tongji University.
文摘Seismicity in ocean ridge-transform systems reveals fundamental processes of mid-ocean ridges,while comparisons of seismicity in different oceans remain rare due to a lack of detection of small events.From 1996 to 2003,the Pacific Marine Environmental Laboratory of the National Oceanic and Atmospheric Administration(NOAA/PMEL)deployed several hydrophones in the eastern Pacific Ocean and the northern Atlantic Ocean.These hydrophones recorded earthquakes with small magnitudes,providing us with opportunities to study the seismic characteristics of ridge-transform systems at different spreading rates and make further comparisons of their differences.This study comparatively analyzed hydroacoustic and teleseismic data recorded on the fast-spreading East Pacific Rise(EPR,10°S to 12°N),intermediate-spreading Galapagos Ridge(103°W to 80°W),and slow-spreading Mid-Atlantic Ridge(MAR,15°N to 37°N).We present a systematic study of the spatial and temporal distribution of events,aftershock seismicity,and possible triggering mechanisms of aftershock sequences.Our analysis yields the following conclusions.(1)From the hydroacoustic data,the EPR transform faults had the highest average seismicity rate among the three regions.(2)Along-ridge event distributions show that a high number of earthquakes were concentrated on the EPR,while they became dispersed on the GR and fewer and more scattered on the MAR,reflecting that the different tectonic origins were closely correlated with the spreading rate.(3)Analysis from mainshock-aftershock sequences shows no significant differences in the aftershock decay rate among the three regions.(4)Multiple types of aftershock triggering models were inferred from Coulomb stress changes:strike-slip mainshocks triggered strike-slip aftershocks and normal faulting aftershocks,and normal faulting mainshocks triggered normal faulting aftershocks.Although these results are case studies,they may be applicable to other ocean ridge-transform systems in future investigations.Our results provide important new insights into the seismicity of global ocean ridge-transform systems.
基金supported by two National Science Foundation(NSF)projects entitled“Neotropical Epiphytic Microlichens-An Innovative Inventory of a Highly Diverse yet Little Known Group of Symbiotic Organisms”(DEB 0715660 to The Field Museum,PI Robert Lücking)and“Phylogenetic Diversity of Mycobionts and Photobionts in the Cyanolichen Genus Dictyonema,with Empasis on the Neotropics and the Galapagos Islands”(DEB 0841405 to George Mason UniversityPI James Lawrey,subcontract to the Charles Darwin Foundation,local coordinator Frank Bungartz).
文摘As part of an ongoing comprehensive inventory of Galapagos lichens,a first assessment of the morphology and anatomy of basidiolichens from the archipelago is presented here.It is the basis for further studies of the taxonomy,ecology and biogeography of this poorly known group of lichens.Four genera,all in Hygrophoraceae,can be distinguished:Acantholichen,Cora,Cyphellostereum and Dictyonema.Both Acantholichen and Cora are characterized by chroococcoid cyanobionts and a heteromerous thallus with a distinct upper cortex and photobiont layer.The monotypic Acantholichen pannarioides is entirely composed of small,branched,inflated squamules that appear densely pruinose because their cortical hyphae bear characteristically swollen,densely spinose end cells(acanthohyphidia);this species has never been observed fertile.The common Cora glabrata is foliose,forming large,radially zonate,conch-like,often tiled thalli,when fertile with circular lines of basidiocarps on its lower side.Dictyonema is distinguished by filamentous cyanobionts and distinctly filamentous thalli that are homomereous(i.e.,not distinctly layered);all species of Dictyonema s.str.have trichomes(filamentose cyanobacterial photobionts)closely enveloped by fungal cells of a jigsaw pattern.In D.sericeum thallus filaments(i.e.,individual fibrils)aggregate to form shelf-like structures similar in appearance to polyporoid bracket fungi;basidiocarps develop in irregular patches on the lower side of these shelves.In contrast,fibrils of D.schenkianum grow encrusting their substrate with irregularly to suberect trichomes,occasionally bearing basidiocarps dispersed across the thallus.Two other species in Galapagos show adpressed growth form and are described here as new:Dictyonema pectinatum,which is characterized by large parallel fibrils with paler,papillate tips,and D.galapagoense,characterized by thin trichomes of more squarrish elongate cells.The genus Cyphellostereum is represented by two species:the newly described C.imperfectum and an unnamed Cyphellostereum sp.,both phenotypically similar to free-living cyanobacterial filaments.Cyphellostereum imperfectum has narrow photobiont filaments with irregular hyphal sheath leaving interspaces;macroscopically it shows a bluish green thallus with a distinct prothallus.Cyphellostereum sp.has a rather uncommon basidiolichen appearance:thin sctytonematoid fibrils surrounded by straight fungal cells forming shiny tufts.The new combination Cyphellostereum nitidum is also proposed.The ecology and taxonomy of Galapagos basidiolichens is briefly discussed and a key and short descriptions of all species are presented.
文摘The fishery of the sea cucumber Isostichopus fuscus was the most important one in the early 2000s in the Galapagos Marine Reserve.Its overexploitation leads to its total closure from 2016 to 2021.At the end of this period,if the co-management system of the Galapagos Marine Reserve decides to open this fishery,a total allowed catch must be established using the methodology of Wolff,Schuhbauer,and Castrejón(2012).The objective of this paper is to evaluate this methodology and improve the total allowed catch calculation.We replicated Wolff et al.‘s methodology that uses the Cadima equation of Maximum Sustainable Yield(in Troadec,1977).We determined the age and growth parameters of I.fuscus to estimate total mortality and improved the calculation of the area of fishing and habitat of this species in Galapagos to estimate its abundance.We found inconsistences in Wolff et al.‘s estimations of mortality and abundance and we recommend that the Maximum Sustainable Yield be used not as the total allowed catch,but as a limit reference point for this fishery.We propose,instead,to use a dynamic abundance model that is capable of estimating a variety of reference points,including the fishing mortality for optimal fishing that is recommended to use to establish a total allowed catch.In addition,for the first time,the age and growth parameters of I.fuscus for Galapagos and the eastern-central region of the Pacific Ocean are determined(L∞=42.5 cm;K=0.21/year).
基金thank National Science Foundation for financial support through a Division of Environmental Biology grant(DEB 0841405,PI:J.LawreyCoPIs:R.Lücking,P.Gillevet)+1 种基金a Postdoctoral Research Fellowship in Biology(PRFB 1609022,PI:M.Dal Forno)supported by the Mohamed bin Zayed Species Conservation Fund,Project 152510692。
文摘This study is a re-assessment of basidiolichen diversity in the Galapagos Islands.We present a molecular phylogenetic analysis,based on 92 specimens from Galapagos,using two nuclear ribosomal DNA markers(ITS and nuLSU).We also re-examined the morphology and anatomy of all sequenced material.The molecular results confirm our previous assessment that all Galapagos basidiolichens belong to the Dictyonema clade,which in Galapagos is represented by four genera:Acantholichen,Cora,Cyphellostereum,and Dictyonema.Most species previously reported from Galapagos in these genera were at the time believed to represent widely distributed taxa.This conclusion,however,has changed with the inclusion of molecular data.Although almost the same number of species is distinguished,the phylogenetic data now suggest that all are restricted to the Galapagos Islands.Among them,six species are proposed here as new to science,namely Cora galapagoensis,Cyphellostereum unoquinoum,Dictyonema barbatum,D.darwinianum,D.ramificans,and D.subobscuratum;and four species have already been described previously,namely Acantholichen galapagoensis,Cora santacruzensis,Dictyonema pectinatum,and D.galapagoense,here recombined as Cyphellostereum galapagoense.Our analysis is set on a very broad phylogenetic framework,which includes a large number of specimens(N=826)mainly from Central and South America,and therefore strongly suggests an unusually high level of endemism previously not recognized.This analysis also shows that the closest relatives of half of the basidiolichens now found in Galapagos are from mainland Ecuador,implying that they reached the islands through the shortest route,with all species arriving on the islands through independent colonization events.
基金The National Basic Research Program of China(973 Program)under contract No.2012CB417305China Ocean Mineral Resources R&D Association"Twelfth Five-Year"Major Program under contract Nos DY125-11-R-01 and DY125-11-R-05+1 种基金the Natural Science Foundation of Zhejiang Province under contract No.LY12D06006the scientific research fund of the Second Institute of Oceanography under contract No.JG1203
文摘Hydrothermal plume is an important constituent of seabed hydrothermal circulation and is also one of the characteristics of active hydrothermal vents. Portable Miniature Autonomous Plume Recorders （MAPR） attached to a towed deep-sea instrument was used to search for hydrothermal plumes and hydrothermal vents. We introduced the basic principle of MAPR based on deep towing technology to detect plumes, then analyzed the factors affecting the quality of the MAPR data and presented a data correction method for MAPR, including instrument location correction, noise reduction processing, system error elimination and seawater background reduction. Finally we applied the method to analyze MAPR data obtained during the Chinese DY115-21 cruise on R/VDayang Iin the “Precious Stone Mountain” hydrothermal field on the Gala-pagos Microplate. The results provided a better understanding of the distribution of the hydrothermal activ-ity in this field, indicating the presence of a new hydrothermal vent.
文摘Many recent studies of ecological speciation have focused on ＂magic trait＂ scenarios, in which divergent selection on viability traits leads inextricably to corresponding divergence in mechanisms, especially mate recognition systems, that facilitate assortative mating. Speciation however may also proceed via other scenarios, such as when populations experience directly se- lected or random divergence in mate recognition systems. The relative contributions of magic trait versus other scenarios for speciation remain virtually unexplored. The present study aims to test the relative contribution of the magic trait scenario in the divergence of populations of the medium ground finch Geospiza fortis of Santa Cruz Island, Galapagos. First, we assess differ- ences in G. fortis song between a northern population （Borrero Bay） and a southeastern population （El Garrapatero）, differences that we propose （along with other within-island geographic song variations） have arisen via scenarios that do not involve a magic trait scenario. Pairwise comparisons of raw and composite （PC） song parameters, as well as discriminant functions analyses, re- veal significant patterns of song divergence between sites. Second, we test the ability of territorial males at Borrero Bay to dis- criminate songs from the two sites. We find that G. fortis males can discriminate within-island song variants, responding more strongly to local than to ＂foreign＂ songs, along 3 raw and 1 composite response measures. Third, we compare these findings to prior data sets on song divergence and discrimination in Santa Cruz G. fortis. These comparisons suggest that song divergence and discrimination are shaped less strongly by geographic sources than by morphological （beak-related） sources. We thus argue that interpopulation song divergence and discrimination, fundamental elements of assortative mating in Darwin＇s finches, can be fos- tered in early stages of divergence under magic trait as well as alternative scenarios for speciation, but with more emphasis on the magic trait scenario, at least for this species on this island [Current Zoology 59 （1）： 8-19, 2013].
基金Supported by the National Key Research and Development Program of China(No.2017YFA0604600)the Fundamental Research Funds for the Central Universities(No.2019B63014)National Natural Science Foundation of China(No.41676019)。
文摘Seasonal variations of the equatorial undercurrent(EUC) termination in the Eastern Pacific,and their mechanism were examined using the Estimating the Circulation and Climate of the Ocean,PhaseⅡ(ECCO2).The ECCO2 reproduced a weak and shallow eastward EUC east of the Galapagos Islands,with annual mean transport of half of EUC to the west of the Islands.The diagnosis of zonal momentum equation suggests that the zonal advection(nonlinear terms) drives the EUC beyond the Islands rather than the pressure gradient force.The EUC in the Far Eastern Pacific has the large st core velocity in boreal spring and the smallest one in boreal summer,and its volume transport exhibits two maxima in boreal spring and autumn.The seasonal variability of the EUC in the Eastern Pacific is dominated by the Kelvin and Rossby waves excited by the zonal winds anomalies in the central and Eastern Pacific that are associated with the seasonal relaxation or intensification of the trade wind.In the Far Eastern Pacific to the east of 120°W,the eastward propagation Kelvin waves play a dominate role in the seasonal cycle of the EUC,results in a semiannual fluctuation with double peaks in boreal spring and autumn.A construction of water mass budget suggests that approximately 24.1% of the EUC water east of 100°W has upwelled to the mixed layer by0.35 m/d.The estimated upwelling is stronge st during boreal autumn and weake st during boreal winter.It is also found that approximately 42.6% of the EUC turns westward to feed the south equatorial current(SEC),13.2% flows north of the equator,and 20.1% flows south of the equator,mainly contributing to Peru-Chile undercurrent.
