on the hydrography of puyuhuapi channel chilean patagonia abstract this work describes the hydrographic conditions found in puyuhuapi channel northern chilean patagonia during recent years on a seasonal scale puyuhuapi channel was once a glacial valley but the retreating ice allowed the inflow of marine waters five surveys were conducted between 2008 and 2012 historical data from 1995 to 2007 were included a meteorological oceanographic buoy was also installed in the northern section of puyuhuapi channel and was operational beginning on april 12th 2011 puyuhuapi channel s surface characteristics highlight a fresher northern part and a more haline southern part except during winter when the pattern can reverse due to the intrusion of oceanic water via jacaf channel the channel exhibits a highly variable meridional and seasonal vertical stratification especially in its northern part where during spring and summer the water column is highly stratified but partially mixed during winter puyuhuapi channel is the only fjord channel with severe hypoxic conditions in all of chilean patagonia

sea surface and subsurface circulation dynamics off equatorial peru during the last 17 kyr the complex deglacial to holocene oceanographic development in the gulf of guayaquil eastern equatorial pacific is reconstructed for sea surface and subsurface ocean levels from isotope geochemical proxies based on marine sediment cores at sea surface southern sourced cold coastal water and tropical equatorial surface water tropical surface water are intimately related in particular since 10 ka independent sea surface temperature proxies capturing different seasons emphasize the growing seasonal contrast in the gulf of guayaquil which is in contrast to ocean areas further offshore cold coastal water became rapidly present in the gulf of guayaquil during the austral winter season in line with the strengthening of the southeast trades while coastal upwelling off peru gradually intensified and expanded northward in response to a seasonally changing atmospheric circulation pattern affecting the core locations intensively since 4 ka bp equatorial surface water instead was displaced and tropical surface water moved northward together with the equatorial front at subsurface the presence of equatorial under current sourced equatorial subsurface water was continuously growing prominently since 10 8 ka b p during heinrich stadial 1 and large parts of the bolling allerod and similarly during short holocene time intervals at 5 1 4 ka b p and 1 5 0 5 ka b p the admixture of equatorial subsurface water was reduced in response to both short term weakening of equatorial under current strength from the northwest and emplacement by tropical equatorial surface water considerably warming the uppermost ocean layers

distribution of pleuroncodes monodon larvae over the continental shelf of south central chile field and modeling evidence for partial local retention and transport abstract in situ and modeled spatial distribution of squat lobster pleuroncodes monodon larvae over the continental shelf off south central chile 35 37 s was analyzed along with currents and hydrography we aimed to identify the main larval transport retention characteristics in the study area which constitutes the southernmost p monodon fishing grounds embedded in the humboldt current system we hypothesized that the main contribution to population renewal originates in the two persistent adult aggregations close to the nursery ground that occurs over a continental shelf terrace limited by two submarine canyons two extensive bio physical field campaigns were carried out during the main 2001 2002 upwelling season field data indicated that larvae were released from late austral winter to spring from spots to the north and south of the nursery zoea i were found mainly below 50 m depth in southward flowing waters whereas older zoea dominated in northward flowing layers above 50 m larvae were circumscribed between the coast and the shelf break front and pelagic retention areas were identified over the widest shelf area megalopa and juveniles during march were only found over the nursery area individual based simulations coupled to the output of a hydrodynamic model climatological configuration for the studied area showed that the release sites close to the nursery made the largest contribution to recruitment sites further north could also contribute to recruitment if hatching occurred later in the upwelling season the contribution of vertical behavior to larval success was also important as was the former s interaction with the site and time of larval release our results support the relevance of coastal circulation affected by topography on the persistence of p monodon populations off southern chile and the modulation of temporal variability these results might apply to other abundant species in the area

rare earth element concentrations and nd isotopes in the southeast pacific ocean 1 three vertical profiles of rare earth element concentrations and nd isotopic compositions have been measured in the remote southeast pacific ocean the three stations represent contrasting environments the oligotrophic center of the gyre station gyr the transition zone east of the south tropical front station egy and the peru chile upwelling marked by a pronounced oxygen minimum station upx rare earth concentrations display nutrient like vertical profiles except at upx where surface waters are enriched at this station nd isotopic compositions are clearly more radiogenic than in the open ocean suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic andes unexpected radiogenic values end reaching 3 7 are also observed at 2000 m at station gyr in the upper circumpolar deep water that commonly have end values around 6 exchange processes related to hydrothermal activity are suspected to produce this increase in end in the vicinity of the east pacific rise these results provide some guidance for higher resolution studies planned in this region by the international geotraces program

characteristics and formation of eastern south pacific intermediate water 1 newly gathered hydrographic data from the eastern south pacific is combined with other high quality data mainly woce to reassess the properties and boundaries of the eastern south pacific intermediate water espiw to date the espiw has been only poorly described the espiw core is found off central and northern chile between the coast and 90 w and 20 38 s located at 50 400 m of depth its temperature varies between 11 13 c salinity ranges from 34 1 34 3 and its sigma t lies between 25 75 26 25 kgm 3 espiw spreads with the subtropical gyre circulation and can be traced to at least 150 w formed through the process of subduction southeastward of the wind driven gyre circulation the espiw communicates surface properties of the waters off central chile to tropical latitudes

the role of the magellan strait on the southwest south atlantic shelf abstract we analyze historical hydrographic data together with recent high resolution hydrographic and underwater glider observations collected in the magellan strait to determine the water mass characteristics and exchanges between the continental shelves of the southeast south pacific and southwest south atlantic around southern south america the near surface salinity distribution and water mass analyses indicate a strong interoceanic connectivity associated with diluted subantarctic waters of the pacific ocean through the magellan strait which in turn are further diluted largely by inflows from the almirantazgo fjord via the whiteside channel the lowest salinity waters reach the atlantic shelf via the magellan strait this core of low salinity waters s

semidiurnal internal tides in a patagonian fjord abstract the fjords of central chilean patagonia 47 s receive fresh water from both precipitation and the baker river this buoyancy input generates a two layer hydrographic system characterized by strong salinity stratification 30 g kg 1 over a depth range of 7 15 m which favors baroclinic conditions in the fjord hourly current velocity profiles were collected with an acoustic doppler current profiler adcp moored at a depth of 40 m during march april 2009 and complemented by 11 ctd profiles and hourly sea level time series these data allowed the detection of semidiurnal internal tidal waves for the first time in this region wavelength and horizontal phase speeds were determined by the dynamical mode 1 for internal waves maximum wavelength was 52 km travelling at a horizontal phase speed of 1 16 m s 1 wavelet spectral and empirical orthogonal function eof analysis techniques applied to the echo anomaly signal and to the baroclinic velocity showed largest semidiurnal amplitudes near the pycnocline out of three modes obtained from the eof analysis two modes displayed a two or three layer flow structure with flow direction reversing at the pycnocline the semidiurnal internal waves were found as fluctuations near the pycnocline in sporadic packets correlated to high discharge pulses of the baker river r2 0 77 additionally internal froude number calculations at the mouth of the baker river indicated critical flow conditions which allowed for generation of internal waves at the plume front these waves are separated from the river plume after internal wave phase speeds surpassed frontal speeds this suggests that the internal waves were modulated by pulses in high river discharge rather than the interaction of barotropic tide with bathymetry a sill an implication of these internal waves would be to increase vertical mixing of nutrients toward the surface through shear instabilities which would favor primary production

apatite weathering and the phanerozoic phosphorus cycle despite widespread debate in the literature there is still considerable uncertainty concerning which nutrient ultimately controls marine net ecosystem production nep over geologic time geochemical arguments suggest that phosphorus is the culprit the weathering of apatite the primary phosphorus sink in earth s exosphere controls long term phosphorus availability if phosphorus is the ultimate controlling nutrient over geologic time scales then long term marine nep is coupled to the release of phosphorus from apatite weathering the most abundant apatite compositions found in nature are igneous fluorapatite and marine sedimentary carbonate fluorapatite sparse data exist on how these compositions dissolve under earth s surface conditions to demonstrate a need for these data and their application we present a kinetic treatment of existing data augmented by new results we then use these results in a weathering model designed to illustrate the control exerted by temperature via activation energy and surface area on the phosphorus flux from apatite dissolution during the phanerozoic our conclusion is that activation energy and hence temperature and apatite surface area are important parameters governing the phosphorus flux from apatite weathering and therefore marine nep during phanerozoic time

changes in biological productivity and ocean climatic fluctuations during the last 1 5 kyr in the humboldt ecosystem off northern chile 27 s a multiproxy approach abstract a sedimentary box core biac072014 collected in a coastal environment in the humboldt current ecosystem hce inglesa bay 27 s northern chile was used to reconstruct the changes in biological productivity and ocean climate fluctuations during the last 1 5 kyr via geochemical mineralogical and micropaleontological analyses from 510 ce to 930 ce el nino like conditions prevailed while during the medieval climate anomaly mca 950 ce to 1450 ce la nina like conditions predominated this pattern might have resulted from weakening strengthening of the walker cell contraction expansion of the south pacific sub tropical high spsh and a predominance of warm cold phases of the pacific decadal oscillation pdo between 1820 ce and the present inglesa bay experienced a reduction in the oxygen minimum zone omz intensity and biological productivity an increase in the detritic input and a decrease in sea surface temperature sst despite the regional intensification and secular cooling 14 s and 27 s of coastal upwelling the similarity between the reduction in biological productivity and omz intensity in this region and that in the central zone of chile 36 s suggests that inglesa bay acts a transition zone in relation to the oceanographic behaviour of the hce the reduction in the omz intensity and biological productivity during the last 200 years could be explained by greater subsurface ventilation in intermediate depths due to more northward displacement of the subduction region of the eastern south pacific intermediate water espiw near 30 s in response to the strengthening of the circulation of the subtropical gyre the coastal cooling observed in the northern section of hce during the current warm period suggests that it is not possible to demonstrate that el nino like conditions promoted the reduction in biological productivity and omz intensity in inglesa bay

variability of 14c reservoir age and air sea flux of co2 in the peru chile upwelling region during the past 12 000 years abstract the variability of radiocarbon marine reservoir age through time and space limits the accuracy of chronologies in marine paleo environmental archives we report here new radiocarbon reservoir ages r from the central coast of chile 32 s for the holocene period and compare these values to existing reservoir age reconstructions from southern peru and northern chile late holocene r values show little variability from central chile to peru prior to 6000 cal yr bp however r values were markedly increased in southern peru and northern chile while similar or slightly lower than modern r values were observed in central chile this extended dataset suggests that the early holocene was characterized by a substantial increase in the latitudinal gradient of marine reservoir age between central and northern chile this change in the marine reservoir ages indicates that the early holocene air sea flux of co2 could have been up to five times more intense than in the late holocene in the peruvian upwelling while slightly reduced in central chile our results show that oceanic circulation changes in the humboldt system during the holocene have substantially modified the air sea carbon flux in this region

chromophoric and fluorescent dissolved organic matter in and above the oxygen minimum zone off peru key points two amino acid like and three humic like fdom components were found in and above the oxygen minimum zone off the coast of peru the distribution of cdom and amino acid like fdom covaried with chl a suggesting phytoplankton as their major source presence of dom microbial reworking and dom release by anoxic sediment was illustrated by the distribution of humic like fdom as a result of nutrient upwelling the peruvian coastal system is one of the most productive regions in the ocean sluggish ventilation of intermediate waters characteristic for the eastern tropical south pacific etsp and microbial degradation of a high organic matter load promotes deoxygenation at depth dissolved organic matter dom plays a key role in microbial respiration and carbon cycling but little is known on dom distribution and cycling in the etsp dom optical properties give important insights on dom sources structure and biogeochemical reactivity here we present data and a conceptual view on distribution and cycling of chromophoric cdom and fluorescent fdom dom in and above the oxygen minimum zone omz off peru five fluorescent components were identified during parafac analysis highest intensities of cdom and of the amino acid like fluorescent component c3 occurred above the omz and coincided with maximum chl a concentrations suggesting phytoplankton productivity as major source high intensities of a marine humic like fluorescent component c1 observed in subsurface waters indicated in situ microbial reworking of dom fdom release from inner shelf sediment was determined by seawater analysis and continuous glider sensor measurement and included a humic like component c2 with a signature typical for terrestrially derived humic acids upwelling supplied humic like substances to the euphotic zone photo reactions were likely involved in the production of a humic like fluorescent component c5 our data show that variable biological and physical processes need to be considered for understanding dom cycling in a highly dynamic coastal upwelling system like the etsp off peru

interannual variability of the subsurface eddy field in the southeast pacific the southeast pacific which encompasses the coasts of peru and chile is one of the world s most productive regions resulting principally from the upwelling of subsurface nutrient rich waters over the satellite altimetry era there have been numerous evidence that surface mesoscale eddies play an important role in the offshore transport of rich coastal waters but it has been only recently that few observational numerical studies have highlighted the importance of the subsurface eddies the eddy field variability is explored using the results of a high resolution model experiment from 1979 to 2012 the model results indicate an asymmetry of the surface and subsurface eddy fields while surface intensified cyclones are slightly more frequent than anticyclones the subsurface field is dominated by anticyclones intrathermoclineeddies ites triggered by the instability of the subsurface peru chile undercurrent pcuc composite maps are consistent with in situ observations ites are associated with maximum vorticity around 150 200 m depth warmer and more saline core characteristic of the equatorial subsurface water from the pcuc we find that the variability of the ites is significantly correlated with the enso equatorial signal during strong el nino events e g 1982 1998 we find that while the pcuc transport increases the volume of coastal waters transported by ites however decreases during those periods we find that the relaxation of the isopycnals along the coast during el nino events leads to weakened baroclinic instability and to a decrease of the ites transport

the distribution of neodymium isotopes and concentrations in the eastern equatorial pacific water mass advection versus particle exchange the radiogenic isotope composition of the rare earth element ree neodymium nd is a powerful water mass proxy for present and past ocean circulation the processes controlling the nd budget of the global ocean are not quantitatively understood and in particular source and sink mechanisms are still under debate in this study we present the first full water column data set of dissolved nd isotope compositions and nd concentrations for the eastern equatorial pacific eep where one of the globally largest oxygen minimum zones omz is located this region is of particular interest for understanding the biogeochemical cycling of rees because anoxic conditions may lead to release of rees from the shelf whereas high particle densities and fluxes potentially remove the rees from the water column data were obtained between 1 40 n and 16 s along a nearshore and an offshore transect near surface zonal current bands such as the equatorial undercurrent euc and the subsurface countercurrent sscc which are supplying oxygen rich water to the omz are characterized by radiogenic nd isotope signatures end 2 surface waters in the northernmost part of the study area are even more radiogenic end 3 most likely due to release of nd from volcanogenic material deep and bottom waters at the southernmost offshore station 14 s are clearly controlled by advection of water masses with less radiogenic signatures end 7 originating from the southern ocean towards the equator however the deep waters show a clear trend towards more radiogenic values of up to end 2 the northernmost station located in the panama basin shows highly radiogenic nd isotope signatures in the entire water column which indicates that particle scavenging downward transport and release processes play an important role this is supported by relatively low nd concentrations in deep waters 3000 6000 m in the eep 20 pmol kg compared to locations in the northern and central pacific 40 60 pmol kg which suggests enhanced removal of nd in the eep

distribution of siphonophores chaetognaths euphausiids and oceanographic conditions in the fjords and channels of southern chile abstract interior waters of the fjords and channels of southern chile 41 5 s 56 s receive inputs of subantarctic water equatorial subsuperficial water and western pacific subsurface water from the adjacent pacific ocean by means of numerous connecting channels that lead inward from the ocean margin these waters become mixed in the interior zone with freshwater from precipitation river flow and meltwater from cordilleran glaciers a two layered positive estuarine circulation becomes established with a superficial layer having a net movement towards the adjacent ocean and a deep layer with net movement towards the fjords the biomass of the interior waters is composed principally of planktonic crustaceans copepods and euphausiids chaetognaths and gelatinous carnivores in a southerly direction decreases are observed in biomass in relative abundance and in species diversity of siphonophores chaetognaths and euphausiids only a few species have been able to adapt successfully to the extreme oceanographic conditions typical of the region reflected in dominant monospecific populations such as muggiaea atlantica sagitta tasmanica and euphausia vallentini the zooplankton fauna of interior waters characterized by its low degree of specific richness is made up of a mixture of species typical of subantarctic water sagitta tasmanica s decipiens euphausia lucens nematoscelis megalops thysanoessa gregaria antarctic water pyrosthephos vanhoeffeni dimophyes arctica sagitta marri s gazellae eukrohnia hamata e bathyantarctica euphausia vallentini temperate and warm epipelagic waters eudoxoides spiralis lensia conoidea chelophyes appendiculata muggiaea atlantica sphaeronectes gracilis s fragilis abylopsis tetragona sagitta enflata and mesopelagic water physophora hydrostatica stylocheiron maximum vogtia pentacantha v serrata

the formation of a subsurface anticyclonic eddy in the peru chile undercurrent and its impact on the near coastal salinity oxygen and nutrient distributions the formation of a subsurface anticyclonic eddy in the peru chile undercurrent pcuc in january and february 2013 is investigated using a multi platform four dimensional observational approach research vessel multiple glider and mooring based measurements were conducted in the peruvian upwelling regime near 12 30 s the dataset consists of 10000 glider profiles and repeated vessel based hydrography and velocity transects it allows a detailed description of the eddy formation and its impact on the near coastal salinity oxygen and nutrient distributions in early january a strong pcuc with maximum poleward velocities of 0 25 m s at 100 to 200 m depth was observed starting on january 20 a subsurface anticyclonic eddy developed in the pcuc downstream of a topographic bend suggesting flow separation as the eddy formation mechanism the eddy core waters exhibited oxygen concentrations 1 mol kg an elevated nitrogen deficit of 17 mol l and potential vorticity close to zero which seemed to originate from the bottom boundary layer of the continental slope the eddy induced across shelf velocities resulted in an elevated exchange of water masses between the upper continental slope and the open ocean small scale salinity and oxygen structures were formed by along isopycnal stirring and indications of eddy driven oxygen ventilation of the upper oxygen minimum zone were observed it is concluded that mesoscale stirring of solutes and the offshore transport of eddy core properties could provide an important coastal open ocean exchange mechanism with potentially large implications for nutrient budgets and biogeochemical cycling in the oxygen minimum zone off peru

mass loss of totten and moscow university glaciers east antarctica using regionally optimized grace mascons author s mohajerani y velicogna i rignot e abstract 2018 american geophysical union all rights reserved totten and moscow university glaciers in the marine based sector of east antarctica contain enough ice to raise sea level by 5 m obtaining precise measurements of their mass balance is challenging owing to large area of the basins and the small mass balance signal compared to west antarctic glaciers here we employ a locally optimized processing of gravity recovery and climate experiment grace harmonics to evaluate their mass balance at the sub basin scale and compare the results with mass budget method mbm estimates using regional atmospheric climate model version 2 3 racmo2 3 or modele atmospherique regional version 3 6 4 mar3 6 4 the sub basin mass loss estimate for april 2002 to november 2015 is 14 8 4 3 gt yr which is weakly affected by glacial isostatic adjustment uncertainties 1 4 gt yr this result agrees with mbm racmo2 3 15 8 2 0 gt yr whereas mbm mar3 6 4 underestimates the loss 6 6 1 6 gt yr for the entire drainage the mass loss for april 2002 to august 2016 is 18 5 6 6 gt yr or 15 4 of its ice flux these results provide unequivocal evidence for mass loss in this east antarctic sector

how biophysical interactions associated with sub and mesoscale structures and migration behavior affect planktonic larvae of the spiny lobster in the juan fernandez ridge a modeling approach abstract the juan fernandez ridge jfr is a chain of topographical elevations in the eastern south pacific 33 35 s 76 81 5 w rich in endemic marine species this ridge is frequently affected by the arrival of mesoscale eddies originating in the coastal upwelling zone off central southern chile the impacts of these interactions on the structure and dynamics of the jfr pelagic system have however not been addressed yet the present model based study is focused on the coupled influence of mesoscale submesoscale processes and biological behavior i e diel vertical migration on the horizontal distribution of planktonic larvae of the spiny lobster jasus frontalis around the jfr waters two case studies were selected from a hydrodynamic regional ocean modeling system to characterize mesoscale and submesoscale structures and an individual based model ibm to simulate diel vertical migration dvm and its impact on the horizontal distribution and the patchiness level dvm behavior of these larvae has not been clearly characterized therefore three types of vertical mechanisms were assessed on the ibm 1 no migration lg 2 a short migration 0 50 m depth dvm1 and 3 a long migration 10 200 m depth dvm2 the influence of physical properties eddy kinetic energy stretching deformation and divergence on larval aggregation within meso and submesoscale features was quantified the patchiness index assessed for mesoscale and submesoscale structures showed higher values in the mesoscale than in the submesoscale however submesoscale structures revealed a higher accumulation of particles by unit of area both vertical migration mechanisms produced larger patchiness indices compared to the no migration experiment dvm2 was the one that showed by far the largest aggregation of almost all the aggregation zones larval concentrations were highest in the submesoscale structures these zones were characterized by low eddy kinetic energy negative stretching deformation and slight convergence stretching deformation flow appeared to be triggered by the eddy eddy interactions and the robinson island barrier effect and it likely promotes the aggregation of the spiny lobster larvae in the juan fernandez system these results highlighted the importance of the coupled effect of physical mesoscale and submesoscale oceanographic features and biological processes dvm in the generation of larval patchiness and concentration of spiny lobster larvae around the jfr which could be key for their survival and retention in those waters

dissolved iron and iron isotopes in the southeastern pacific ocean the southeast pacific ocean is a severely understudied yet dynamic region for trace metals such as iron since it experiences steep redox and productivity gradients in upper waters and strong hydrothermal iron inputs to deep waters in this study we report the dissolved iron dfe distribution from seven stations and fe isotope ratios 56fe from three of these stations across a near zonal transect from 20 to 27 s we found elevated dfe concentrations associated with the oxygen deficient zone odz with light 56fe implicating porewater fluxes of reduced fe however temporal dfe variability and rapid 56fe shifts with depth suggest gradients in odz fe source and or redox processes vary over short depth spatial scales the dfe concentrations decreased rapidly offshore and in the upper ocean dfe was controlled by biological processes resulting in an fe c ratio of 4 2 mol mol calculated vertical diffusive fe fluxes were greater than published dust inputs to surface waters but both were orders of magnitude lower than horizontal diffusive fluxes which dominate dfe delivery to the gyre the 56fe data in the deep sea showed evidence for a 0 2 antarctic intermediate water end member and a heavy 56fe of 0 55 for distally transported hydrothermal dissolved fe from the east pacific rise these heavy 56fe values were contrasted with the near crustal 56fe recorded in the hydrothermal plume reaching station aloha in the north pacific the heavy hydrothermal 56fe precludes a nanopyrite composition of hydrothermal dfe and instead suggests the presence of oxides or more likely binding of hydrothermal dfe by organic ligands in the distal plume

hydrography of the eastern south pacific ocean results from the sonne 102 cruise may june 1995 abstract full depth conductivity temperature depth hydrographic measurements were taken in may june 1995 along 28 15 35 15 and 43 15 s from the chilean coast to 86 88 w from the r v sonne sections of potential temperature salinity neutral density and oxygen are presented to illustrate the water column structure in this sparsely sampled region a more comprehensive database on all available hydrographic data from the region was compiled these data and available meteorological data are used to help in the interpretation of the sonne results a number of important features found in the sections are discussed including a shallow salinity minimum apparently ventilated from south of 37 s salt fingering as a possible mechanism to transport high salinity subtropical water into the shallow salinity minimum equatorial subsurface water subantarctic mode water and antarctic intermediate water geostrophic calculations of alongshore flow show the poleward peru chile undercurrent at each of the three sections with a poleward descending core and peak velocities of 10 cm s 1 as in earlier works a deep pacific outflow is found near the chilean coast part of a clockwise deep circulation in the chile basin

elevated trace metal content of prokaryotic communities associated with marine oxygen deficient zones little is known about the trace metal content of marine prokaryotes in part due to their co occurrence with more abundant particulate phases in the upper ocean such as phytoplankton and biogenic detritus lithogenic minerals and authigenic mn and fe oxyhydroxides we attempt to isolate these biomass signals in particulate data from the us geotraces eastern pacific zonal transect cruise gp16 in the eastern tropical south pacific etsp which exhibited consistent maxima in p and other bioactive trace metals and minima in particulate mn in the oxygen deficient zones odzs of 13 stations nitrite maxima and nitrate deficits indicated the presence of denitrifying prokaryotic biomass within etsp odzs and deep secondary fluorescence maxima at the upper odz boundaries of 10 stations also suggested the presence of low light autotrophic communities odzs were observed as far west as 99 w more than 2300 km from the south american coast where eolian lithogenic and lateral resuspended sedimentary inputs were negligible presenting a unique opportunity to examine prokaryotic metal stoichiometries odz particulate p maxima can rival gyre mixed layer biomass concentrations are highly sensitive to oxygen and are in excess of amounts scavengable by local fe oxyhydroxides and acid volatile sulfides even after correction for lithogenic and ferruginous scavenged metals odz p maxima are often enriched in cd co cu ni v and zn exhibiting particulate trace metal ratios to p that exceed mixed layer biomass ratios by factors of 2 9 odz prokaryotic communities may be largely hidden tm rich pools involved in the marine cycles of these bioactive trace metals

water masses in the humboldt current system properties distribution and the nitrate deficit as a chemical water mass tracer for equatorial subsurface water off chile abstract three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern south pacific and their distributions oceanographic data were taken from the scorpio may june 1967 piquero may june 1969 and krill june 1974 cruises vertical sections of temperature salinity dissolved oxygen nitrate nitrite phosphate and silicate were used to analyze the water column structure five water masses were identified in the zone through t s diagrams subantarctic water subtropical water equatorial subsurface water antarctic intermediate water and pacific deep water their proportions in the sea water mixture are calculated using the mixing triangle method vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m several characteristic oceanographic features in the study area were analyzed the shallow salinity minimum displacement towards the equator the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south and the equatorward intermediate antarctic salinity minimum associated with a dissolved oxygen maximum the nitrate deficit generated in the denitrification area off peru and northern chile is proposed as a conservative chemical tracer for the equatorial subsurface waters off the coast of chile south of 25 s

isotopic evidence for complex biogeochemical cycling of cd in the eastern tropical south pacific abstract over the past decades observations have confirmed decreasing oxygen levels and shoaling of oxygen minimum zones omzs in the tropical oceans such changes impact the biogeochemical cycling of micronutrients such as cd but the potential consequences are only poorly constrained here we present seawater cd concentrations and isotope compositions for 12 depth profiles at coastal nearshore and offshore stations from 4 s to 14 s in the eastern tropical south pacific where one of the world s strongest omzs prevails the depth profiles of cd isotopes display high 114 110 cd at the surface and decreasing 114 110 cd with increasing water depth consistent with preferential utilization of lighter cd isotopes during biological uptake in the euphotic zone and subsequent remineralization of the sinking biomass in the surface and subsurface ocean seawater displays similar 114 110 cd signatures of 0 47 0 23 to 0 82 0 05 across the entire eastern tropical south pacific despite highly variable cd concentrations between 0 01 and 0 84 nmol kg this observation best explained by an open system steady state fractionation model contrasts with previous studies of the south atlantic and south pacific oceans where only cd deficient waters have a relatively constant cd isotope signature for the subsurface to about 500 m depth the variability of seawater cd isotope compositions can be modeled by mixing of remineralized cd with subsurface water from the base of the mixed layer in the intermediate and deep eastern tropical south pacific 500 m seawater cd and 114 110 cd appear to follow the distribution and mixing of major water masses we identified modified aaiw of the etsp to be more enriched in cd than aaiw from the source region whilst both water masses have similar 114 110 cd a mass balance estimate thus constrains a 114 110 cd of between 0 38 and 0 56 for the accumulated remineralized cd in the etsp nearly all samples show a tight coupling of cd and po4 concentrations whereby surface and deeper waters define two distinct linear trends however seawater at a coastal station located within a pronounced plume of h2s is depleted in cd and features significantly higher 114 110 cd this signature is attributed to the formation of authigenic cds with preferential incorporation of lighter cd isotopes the process follows a rayleigh fractionation model with a fractionation factor of 114 110 cd seawater cds 1 00029 further deviations from the deep cd po4 trend were observed for samples with o2

nitrogen biogeochemical cycling in the northwestern indian ocean abstract the vertical distribution and fine scale structure of nitrate no 3 nitrite no 2 nitrous oxide n 2 o phosphate po 4 oxygen o 2 and chlorophyll chl were determined in the north western indian ocean nwio along a meridional section 67 e from the equator to the gulf of oman using an autoanalyser for micromolar levels of nutrients and chemiluminescence and gas chromatographic methods for nanomolar levels of no 3 and no 2 and n 2 o respectively three biogeochimically contrasting regimes were investigated 1 the highly oligotrophic nutrient depleted subtropical gyre 2 the nonsoonal upwelling of nutrient rich intermediate waters of the southeastern arabian coast and 3 the denitrifying o 2 depleted zone odz ca 150 1200 m depth in the arabian sea concentrations of no 3 and no 2 were severely depleted in surface oligotrophic waters from the equator average 43 and 3 6 nm respectively to the subtropical gyre 12 15 n average 13 3 and 2 0 nm respectively with similar levels in the more stratified gulf of oman upwelling waters off southern arabia had three orders of magnitude higher no 3 levels and throughout the nwio the calculated no 3 fuelled primary production appeared to be regulated by no 3 concentration existing redfield o 2 no 3 regeneration ratios 9 1 previously derived for the deep indian ocean were confirmed 9 35 within the oxic upper layers of the nwio the no potential temperature relationship broecker 1974 earth and planetary science letters 23 100 107 needed for the derivation of expected no 3 and no 3 deficits within the denitrifying odz were refined using an isopycnal binary mixing model along the 26 6 density layer to take into account the inflowing contribution of no 3 depleted persian gulf water vertically integrated no 3 deficits increased northwards from 0 8 mol no 3 n m 2 at sta 2 04 n up to 6 49 mol no 3 n m 2 at sta 9 at the mouth of the gulf of oman then decreased to 4 10 moles no 3 n m 2 toward sta 11 near the straits of hormuz when averaged for the denitrification area of the arabian sea this corresponds to a deficit of 118 tg no 3 n adopting a recent freon 11 based estimate of water residence time of 10 years olson et al 1993 deep sea research ii 40 673 685 for the o 2 depleted layer we calculate an annual net denitrification flux of 11 9 tg n to the atmosphere or approximately 10 of the global water column denitrification rates supersaturated n 2 o concentrations were found in both surface oxic and upwelling waters up to 246 and peaked at the base of the odz up to 1264 in the northern arabian sea both nitrification in oxic waters and denitrification in hypoxic layers can be invoked as sources of n 2 o the inventory of excess n 2 o amounted to 2 55 1 3 tg n 2 o n corresponding to annual production of 0 26 0 13 tg from denitrification this is comparable to earlier law and owens 1990 nature 346 826 828 estimates of the ventilation flux of n 2 o 0 22 0 39 tg yr 1 from the upwelling region of the arabian sea the decadal response times for circulation deoxygenation denitrification and ventilation of the odz derived n 2 o and co 2 greenhouse gases and their monsoonal coupling implies the arabian sea is a sensitive oceanic recorder of global climate change

low nutrient and high chlorophyll a coastal upwelling system a case study in the southern taiwan strait using the field data during four summer cruises of 2005 2006 2008 and 2013 an interesting phenomenon of low nutrient and high chl a lnhc was observed in the coastal upwelling system off dongshan in the southern taiwan strait the results indicated that the upwelling region was dominated by cold 33 9 psu upwelled water and the concentration of nitrate 1 m and phosphate 0 1 m was very low while with high chl a content mean 1 98 3 56 g l 1 maximum 8 3 g l 1 during the stronger summer upwelling cruise of 2005 2006 and 2008 the upwelled water originated from the 50 100 m layer off shanwei with a low concentration of nitrate 7 5 mol l 1 and phosphate 0 5 mol l 1 which was transported to shantou dongshan by the northeastward bottom current during the time that the upwelled water moved the long distance 150 300 km from shanwei to shantou dongshan and was transported through the euphotic zone alongshore the phytoplankton grew rapidly due to the favorable temperature n p ratio and illumination and consumed most of the nutrients in the upwelled water these unique physical chemical and biological processes are the main reasons for the formation of the low nutrients high chlorophyll a in this coastal upwelling system in the southern taiwan strait

modification of no po and no po during flow across the bering and chukchi shelves implications for use as arctic water mass tracers the no and po tracers 9 no3 o2 and 135 po4 o2 respectively and their derivative no po have found increasing use in arctic water mass analyses for identifying the specific basin or shelf areas from which surface waters originate based upon assumed differences in pacific and atlantic derived content and basin to basin differences within the arctic following shipboard sampling in june september 1993 and may june 1994 both north and south of bering strait we have found evidence that pacific derived waters flowing north to bering strait do not necessarily have any unique no po or no po identity that would permit unequivocal use as a water mass tracer in particular no po ratios in the bering sea continental shelf 150 m waters varied from 0 7 to 1 1 which encompasses ratios previously reported for arctic continental shelf and atlantic origin waters in the arctic ocean the highest no po ratios 1 in the bering sea were observed to the southwest of st lawrence island close to where high nutrient waters are first upwelled onto the shelf and seasonally early in the biological production cycle by contrast later in the summer north of bering strait at the depth of the arctic ocean nutrient maximum the highest concentrations of silica 60 m were associated with low no po ratios 0 7 apparent increases in the proportions of sea ice melt in these waters inferred from 18o and salinity regressions were associated with lower no po ratios this pattern the potential for sea air exchange and a significant relationship between decreases in nitrate phosphate ratios and both no po ratios and silica concentrations indicate that biological and physical processes north and south of bering strait affect the fidelity of these nutrient based tracers these results indicate the need for consideration of shelf based processes before no po ratios and other nutrient based tracers can be successfully applied as arctic circulation tracers

seasonal climatology of hydrographic conditions in the upwelling region off northern chile over 30 years of hydrographic data from the northern chile 18os 24os upwelling region are used to calculate the surface and subsurface seasonal climatology extending 400 km offshore the data are interpolated to a grid with sufficient spatial resolution to preserve cross shelf gradients and then presented as means within four seasons austral winter july september spring october december summer january march and fall april june climatological monthly wind forcing surface temperature and sea level from three coastal stations indicate equatorward upwelling favorable winds throughout the year weakest in the north seasonal maximum alongshore wind stress is in late spring and summer december march major water masses of the region are identified in climatological t s plots and their sources and implied circulation discussed surface fields and vertical transects of temperature and salinity confirm that upwelling occurs year round strongest in summer and weakest in winter bringing relatively fresh water to the surface nearshore surface geostrophic flow nearshore is equatorward throughout the year during summer an anticyclonic circulation feature in the north which extends to at least 200 rn depth is evident in geopotential anomaly and in both temperature and geopotential variance fields subsurface fields indicate generally poleward flow throughout the year strongest in an undercurrent near the coast this undercurrent is strongest in summer and most persistent and organized in the south south of 21os a subsurface oxygen minimum centered at 250 m is strongest at lower latitudes low salinity subsurface water intrudes into the study area near 100 m predominantly in offshore regions strongest during summer and fall and in the southernmost portion of the region the climatological fields are compared to features off baja within the somewhat analogous california current and to measurements from higher latitudes within the chile peru current system

changes in the advection of antarctic intermediate water to the northern chilean coast during the last 970 kyr 1 the antarctic intermediate water aaiw is a key player in global scale oceanic overturning processes and an important conduit for heat fresh water and carbon transport the aaiw past variability is poorly understood mainly due to the lack of sedimentary archives at intermediate water depths we present records of benthic stable isotopes from sediments retrieved with the seafloor drill rig marum mebo at 956 m water depth off northern chile geob15016 27 29 48 s 71 07 58 w that extend back to 970 ka the sediments at this site are presently deposited at the boundary between aaiw and pacific deep water pdw for previous peak interglacials our results reveal similar benthic 13c values at site geob15016 and of a newly generated stack of benthic 13c from various deep pacific cores representing the average pdw this suggests unlike today the absence of aaiw at the site and the presence of nearly pure pdw in contrast more positive 13c values at site geob15016 compared to the stack imply a considerable aaiw contribution during cold phases of interglacials and especially during glacials besides we used three short sediment cores to reconstruct benthic 13c values from the aaiw core during the last glacial and found a 13c signature similar to today s assuming that this was the case also for the past 970 kyr we demonstrate that sea level changes and latitudinal migrations of the aaiw formation site can only account for about 50 of the full range of past 13c increases at site geob15016 during cold periods other processes that could explain the remaining of the positive 13c anomalies are increases in glacial aaiw production and or deeper convection of the aaiw with respect to preceding interglacials

freshwater structure and its seasonal variability off western patagonia abstract climatological hydrographic data for the southeastern pacific from the world ocean atlas show an extended low salinity region associated with high rainfall river runoff along the chilean patagonia coast however the structure and variability of this extensive freshwater area is poorly understood due to the lack of periodic hydrographic observations here we use 15 years of satellite observations in combination with hydrographic data from argo profiling floats to increase our understanding of the freshwater structure and its seasonal variability off western patagonia satellite derived seasonal fields of surface salinity from aquarius sac d and smap soil moisture active passive satellite missions reveal a prominent coastal band of low salinity water year round fresher during spring and summer hydrographic profiles from argo floats confirm this coastal freshening the major content of freshwater is located off central patagonia where the low salinity surface layer dominates the stratification of the upper ocean in contrast the freshwater content plays a minor role in setting up the stratification off northern and southern patagonia a warm surface layer greatly increases the stability of the upper 500 m in the northern sector especially in summer and fall whereas cold temperatures in the southern region tend to damp zonal density gradients and decrease the stratification future studies at interannual scales are suggested considering the melting of patagonian icefields since the 1960s

main eddy vertical structures observed in the four major eastern boundary upwelling systems in the four major eastern boundary upwelling systems ebus mesoscale eddies are known to modulate the biological productivity and transport near coastal seawater properties toward the offshore ocean however little is known about their main characteristics and vertical structure this study combines 10 years of satellite altimetry data and argo float profiles of temperature and salinity and our main goals are i to describe the main surface characteristics of long lived eddies formed in each ebus and their evolution and ii to depict the main vertical structure of the eddy types that coexist in these regions a clustering analysis of the argo profiles surfacing within the long lived eddies of each ebus allows us to determine the proportion of surface and subsurface intensified eddies in each region and to describe their vertical structure in terms of temperature salinity and dynamic height anomalies in the peru chile upwelling system 55 of the sampled anticyclonic eddies aes have subsurface intensified maximum temperature and salinity anomalies below the seasonal pycnocline whereas 88 of the cyclonic eddies ces are surface intensified in the california upwelling system only 30 of the aes are subsurface intensified and all of the ces show maximum anomalies above the pycnocline in the canary upwelling system 40 of the aes and 60 of the ces are subsurface intensified with maximum anomalies extending down to 800 m depth finally the benguela upwelling system tends to generate 40 50 of weak surface intensified eddies and 50 60 of much stronger subsurface intensified eddies with a clear geographical distribution the mechanisms involved in the observed eddy vertical shapes are discussed

front eddy influence on water column properties phytoplankton community structure and cross shelf exchange of diatom taxa in the shelf slope area off concepcion 36 37 s in eastern boundary current systems ebcss submesoscale to mesocale variability contributes to cross shore exchanges of water properties nutrients and plankton data from a short term summer survey and satellite time series january february 2014 were used to characterize submesoscale variability in oceanographic conditions and phytoplankton distribution across the coastal upwelling and coastal transition zones north of punta lavapie and to explore cross shelf exchanges of diatom taxa a thermo haline front frn 1 flanked by a mesoscale anticyclonic intrathermocline eddy ite 1 or mode water eddy persisted during the study period and the survey was undertaken during a wind relaxation event at the survey time ite 1 contributed to an onshore intrusion of warm oceanic waters southern section and an offshore advection of cold coastal waters northern section with the latter forming a cold high chlorophyll a filament in situ phytoplankton and diatom biomasses were highest at the surface in frn 1 and at the subsurface in ite 1 whereas values in the coastal zone were lower and dominated by smaller cells diatom species typical of the coastal zone and species dominant in oceanic waters were both found in the frn 1 and ite 1 interaction area suggesting that this mixture was the result of both offshore and onshore advection overall front eddy interactions in ebcss could enhance cross shelf exchanges of coastal and oceanic plankton as well as sustain phytoplankton growth in the slope area through localized upward injections of nutrients in the frontal zone combined with ite induced advection and vertical nutrient inputs to the surface layer

warming and circulation change in the eastern south pacific ocean deep ocean temperature salinity and dissolved oxygen observations in the eastern south pacific ocean collected during the late austral fall in 1995 are compared with observations made there 28 years earlier during the same season and similar el nino southern oscillation phase warming observed above 800 m at 43 s reflects the production of warmer subantarctic mode water in recent decades warming observed above 1600 m at 28 s is due to downward isotherm displacement and southward movement of water masses by 100 200 km as revealed by joint analysis of temperature and oxygen data such changes would be expected for a weaker subtropical gyre in the south pacific an observed oxygen decrease between about 1800 m and 2900 m at 28 s may indicate enhanced southward boundary current flow at mid depths off chile

mesoscale variability and nutrient phytoplankton distributions off central southern chile during the upwelling season the influence of mesoscale eddies abstract mesoscale features are recurrently found in the coastal transition zone ctz off central southern chile 35 40 s a region characterized by seasonal wind driven coastal upwelling in this study oceanographic data from two consecutive cruises carried out during the upwelling season january 2009 were combined with satellite time series data in order to characterize the structure and evolution of mesoscale eddies and to explore their influence on phytoplankton structure and nutrient distribution in the context of organic carbon exchanges between the coastal upwelling zone and the ctz two coastally generated contiguous mesoscale eddies 2 months old were characterized a surface cyclonic eddy cc1 and a subsurface anticyclonic eddy aa1 the distributions of salinity and dissolved oxygen together with nutrients suggested that both eddies were sites of vertical injection of high nutrient concentrations from the equatorial subsurface water mass essw into the upper layer in the ctz in addition eddy aa1 in combination with an upwelling plume was involved in the offshore advection of nutrients from the core of the essw located in the coastal zone at shallow depths

a pacific hydrographic section at 88 w water property distribution full depth conductivity temperature depth ctd hydrographic measurements with high horizontal and vertical resolution were made in february april 1993 along a line lying at a nominal longitude of 88 w and extending from southern chile 54 s to guatemala 14 n it crossed five major deep basins southeast pacific chile peru panama and guatemala basins east of the east pacific rise vertical sections of potential temperature salinity potential density oxygen silica phosphate nitrate and nitrite are presented to illustrate the structure of the entire water column some features of interest found in the sections are described and an attempt is made to interpret them in terms of the isopycnal property distributions associated with the large scale ocean circulation these features include various near surface waters observed in the tropical and subtropical regions and the fronts that mark the boundaries of these waters the possible importance of salt fingering to the downward salt transfer from the high salinity subtropical water a shallow thermostad pycnostad developed at 16 18 5 c in the subtropical water low salinity surface water in the subantarctic zone west of southern chile large domains of extremely low oxygen in the subpycnocline layer on both sides of the equator and a secondary nitrite maximum associated with a nitrate minimum in these low oxygen domains high salinity low oxygen high nutrient subpycnocline water that is carried poleward along the eastern boundary by the peru chile undercurrent the subantarctic mode and antarctic intermediate waters middepth isopycnal property extrema observed at the crest of the sala y gomez ridge influences of the north pacific and the north atlantic upon deep waters along the section and the characteristics and sources of the bottom waters in the five deep basins along the section

intrathermocline eddies in the coastal transition zone off central chile 31 41 s 1 the three dimensional structure and the origin of mesoscale anticyclonic intrathermocline eddies ites in the coastal transition zone ctz off central chile 31 41 s were analyzed through the combination of data from oceanographic cruises and satellite altimetry and the application of an eddy resolving primitive equation ocean model coupled with a numerical experiment using a passive tracer in this region ites are represented by subsurface lenses 100 km diameter 500 m thickness or vertical extension of nearly homogeneous salinity 34 5 and oxygen deficient 1 0 ml l 1 waters properties which are linked to the equatorial subsurface water mass essw transported poleward by the peru chile undercurrent pcuc in the coastal band at least five to seven ites were observed simultaneously in the area between 31 and 38 s during winter cruises in 1997 and 2009 satellite data indicated that the ites identified from in situ data moved westward each at a mean speed of 2 km d 1 and transported a total volume of 1 106 m3 s 1 1 sv the lifespan of each ite ranged from a few months to 1 year model results indicate that ites become detached from the pcuc under summer upwelling conditions in the coastal zone

observed property changes in eastern south pacific antarctic intermediate water 1 we compared potential temperature and salinity of antarctic intermediate water along 32 30 s from the coast of chile to the central south pacific ocean between 2003 and 1992 based on two vertically and horizontally high resolution repeat sections each being 6795 km long the temperature of antarctic intermediate water considering the entire body of the water mass along the section increased by 0 048 c and salinity by 0 002 the increase in salinity could be explained by a slight shift in the evaporation precipitation balance of the south pacific ocean

late quaternary variability of sedimentary nitrogen isotopes in the eastern south pacific ocean 1 we present high resolution bulk sedimentary 15n data from the southern edge of the present day oxygen minimum zone of the eastern south pacific the record is interpreted as representing changes in water column nitrogen removal during the last 70 000 years we found significant fluctuations in the isotopic signal that suggest major reorganizations of the oxygen minimum zone at millennial timescales these fluctuations were not related to other millennial scale changes like the northern hemisphere s dansgaard oeschger climate swings or local changes in primary productivity so appear to be dictated by the southern hemisphere s climate rhythm this is preliminarily corroborated by an overall agreement between our 15n data and the sedimentary proxy of ice sheet dynamics in patagonia which is in turn correlated with surface water properties at the midlatitude subduction region of the eastern south pacific intermediate waters finally potential implications on late quaternary changes in atmospheric co2 concentrations are discussed

air sea co2 fluxes along the coast of chile from co2 outgassing in central northern upwelling waters to co2 uptake in southern patagonian fjords 1 carbon system parameters measured during several expeditions along the coast of chile 23 s 56 s have been used to show the main spatial and temporal trends of air sea co2 fluxes in the coastal waters of the eastern south pacific chilean coastal waters are characterized by strong pco2 gradients between the atmosphere and the surface water with high spatial and temporal variability on average the direction of the carbon flux changes from co2 outgassing at the coastal upwelling region to co2 sequestering at the nonupwelling fjord region in chilean patagonia estimations of surface water pco2 along the patagonian fjord region showed that while minimum pco2 levels strong co2 undersaturation occurs during the spring and summer period maximum levels including co2 supersaturation occur during the austral winter co2 uptake in the patagonia fjord region during spring summer is within the order of 5 mol c m 2 yr 1 indicating a significant regional sink of atmospheric co2 during that season we suggest that the co2 sink at patagonia most probably exceeds the co2 source exerted by the coastal upwelling system off central northern chile

hypoxia in chilean patagonian fjords abstract chilean patagonia is one of the largest estuarine systems in the world it is characterized by a complex geography of approximately 3300 islands a total surface area of 240 000 km2 and 84 000 km of coast line including islands peninsulas channels fjords and sounds the chilean patagonia interior sea is filled with a mixture of sea estuarine and fresh waters and is characterized by a two layer vertical general circulation dissolved oxygen do conditions in these fjords were analyzed based on historic salinity dissolved oxygen and nutrient data from 1200 oceanographic stations horizontal advection of adjacent well oxygenated subantarctic waters 5 6 ml l 1 was the mayor source of do in the deep layers of the interior sea incoming do was consumed by the respiration of autochthonous and allochthonous particulate organic matter as ocean water flows towards the continental fjord heads reaching near hypoxic 2 3 ml l 1 or hypoxic levels 2 ml l 1 and four hypoxic

distribution of 236u in the u s geotraces eastern pacific zonal transect and its use as a water mass tracer abstract we report dissolved concentrations of the long lived radioisotope 236u measured in the water column along the 2013 us geotraces eastern pacific zonal transect gp16 this transect followed a 10 15 s line from manta ecuador to papeete haiti french polynesia crossing the southern east pacific rise intercepting one of the largest hydrothermal plumes as well as a productivity gradient which includes the upwelling zone and associated low oxygen waters offshore from peru and the oligotrophic sub tropical gyre accelerator mass spectrometry was used to measure dissolved seawater 236u concentrations as low as 1 103 atom kg 1 which are among the lowest levels reported to date differences in upper water column 236u distributions from east to west are a result of variable contributions from different surface and intermediate waters encountered along the transect the distribution of 236u both in depth and geographically provides complementary information to that obtained from 14c and helium isotopes demonstrating that 236u concentrations are diagnostic in the identification of and contributions from the different deep and bottom water masses encountered along the epzt jenkins et al 2017 for example we observe minimum 236u concentrations along the epzt between 2000 and 3000 m that are consistent with contributions attributed to pacific deep water we also observe increases in 236u below 3000 m at the eastern and western termini of the epzt this is consistent with contributions associated with antarctic bottom water and lower circumpolar deep water our results indicate that 236u may be used in conjunction with 14c and 3he isotopes as an additional tool with which to identify and resolve contributions from different water masses in the pacific ocean this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

on subsurface cooling associated with the biobio river canyon chile submarine canyons cutting across the continental shelf can modulate the cross shelf circulation being effective pathways to bring water from the deep ocean onto the shelf here we use 69 days of moored array observations of temperature and ocean currents collected during the spring of 2013 and winter spring 2014 as well as shipboard hydrographic surveys and sea level observations to characterize cold oxygen poor and nutrient rich upwelling events along the biobio submarine canyon bbc the bbc is located within the gulf of arauco at 36 50 s in the central chilean coast the majority of subtidal temperature at 150 m depth is explained by subtidal variability in alongshore currents on the canyon with a lag of less than a day r2 0 65 using the vertical displacement of the 10 and 10 5 c isotherms we identified nine upwelling events lasting between 20 h to 4 5 days that resulted in vertical isothermal displacements ranging from 29 to 137 m the upwelled water likely originated below 200 m majority of the cooling events were related with strong northward opposite kelvin wave propagation flow and low pressure at the coast most of these low pressure events occur during relatively weak local wind forcing conditions and were instead related with coastal trapped waves ctws propagating southwards from lower latitudes these cold high nutrient low oxygen waters may be further upwelled and advected into the gulf of arauco by wind forcing thus canyon upwelling may be a key driver of biological productivity and oxygen conditions in this gulf

controls on sedimentary nitrogen isotopes along the chile margin chilean margin sedimentary n isotope records have been the focus of paleoceanographic studies examining the extent of water column denitrification in the eastern south pacific in the past here we use 15n 14n of nitrate and surface sedimentary n along the chilean coast to investigate the relative contributions of water column denitrification and surface nitrate assimilation by phytoplankton to the sedimentary n isotope record off northern and central chile subsurface enrichment of 15no3 is associated with the lowest oxygen concentrations and maximum nitrate deficits the product of water column denitrification locally at 21 s and through the transport of denitrified waters to the south while elevated the 15n of pycnocline nitrate shows no distinct trend with distance from the omz and is nearly homogenous within the shallow subsurface layer presumably due to lateral circulation along the margin moreover an isotopically depleted and relatively uniform layer exists within the shallow subsurface possibly as a result of the remineralization of newly fixed nitrogen that may work to further homogenize the 15n of the upwelling nitrate whereas the high 15n of sedimentary n in the region is clearly a product of denitrification and its isotopic imprint on nitrate along the margin the northward increase in sedimentary 15n from higher southern latitudes also reflects the degree of surface layer nitrate consumption by phytoplankton the northward increase in sedimentary 15n corresponds to a regional decrease in the surface nitrate concentration and isotopic fractionation during nitrate assimilation is apparent in shallow nitrate 15n a comparison of the 15n in shallow subsurface nitrate and sedimentary n suggests that north of 30 s nearly complete nitrate consumption causes the 15n of sediments to converge on that of the nitrate supply such that denitrification should be the dominant signal in downcore 15n records from these latitudes moreover the lateral homogeneity of the denitrification signal in the subsurface within this region suggests that such records will provide robust reconstructions of denitrification intensity

on the pathways of the equatorial subsurface currents in the eastern equatorial pacific and their contributions to the peru chile undercurrent 1 theconnections between theequatorial currentsystem andtheperu currentsystem in the eastern tropical pacific etp are examined with a primitive equations eddy resolving regional model the quasi equilibrium solutions reproduce three eastward equatorial subsurface currents of interest the equatorial undercurrent euc located between 1 n and 1 s the primary southern subsurface countercurrent psscc between 3 and 4 s and farther south the secondary southern subsurface countercurrent ssscc between 7 and 8 s using a lagrangian tracking procedure the fate of these currents in the etp and their contribution to the peru chile undercurrent pcuc are studied lagrangian diagnostics show that for the most part the euc water contributes to westward flows including the south equatorial current and deeper flows below it and strikingly only a very little fraction feeds the pcuc while a significant part of both ssccs contribute substantially mesoscale eddies are shown to exert an effect on these connections in addition about 30 of the pcuc is fed by the three subsurface equatorial flows euc psscc ssscc the remaining part of the pcuc comes from an alongshore recirculation associated with flows below it and from the southern part of the domain south of 9 s