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Satellite-derived mean sea level anomalies were blended with mean dynamic topography to obtain seasonal climatologies of the eastern South Pacific Ocean's surface circulation with an emphasis on the Humboldt Current. The Humboldt Current is confined to a narrow northward flowing jet-like stream of about 350 km associated with maximum geostrophic ve...
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... Este indicador se propuso para evaluar la posición e intensidad del Anticiclón del Pacifico Sureste (APS), que representa el forzante dominante en el Sistema de Corrientes de Humboldt (Strub et al., 1998;Rutlant et al., 2004;Fuenzalida et al., 2008;Ancapichún y Garcés-Vargas, 2015;Rahn et al., 2015). El APS tiene ciclos estacionales, interanuales y decadales (interdecadales). ...
El presente informe entrega los resultados finales del proyecto de “Evaluación del stock desovante de anchoveta entre las regiones de Atacama y Coquimbo, año 2021.
La campaña 2021 se realizó en la zona comprendida entre 26°S y 32°10’S, desde la costa hasta las 20 mn, entre el 19 de agosto y 23 de septiembre de 2021 (semanas de 33 a 38).
... The SPSA is a thermal high system formed by the southern branch of the Hadley Cells, with its center located in the eastern portion of the south Pacific basin, where large-scale subsidence balances strong low-level divergence (Richter et al 2008). The SPSA is considered to be the dominant forcing of the subtropical gyre in the south Pacific, which in its right flank is formed by the southeastern Pacific current system, consisting of the Humboldt jet-like stream, Humboldt Current oceanic branch, Humboldt Current coastal branch, Peru-Chile Countercurrent, Peru-Chile Subsurface Current, Chile Coastal Current, South Pacific Current, and South Equatorial Current (Strub et al 1998, Fuenzalida et al 2008, and controlling the wind patterns, precipitations and SSTs. Therefore, any variation of the SPSA in position or intensity is most likely to evoke changes of the SPSAinduced meteorological elements. ...
Previous studies demonstrate that recent global warming hiatuses are associated with an ongoing cooling in the eastern Pacific. However, the possible driver for this cooling remains vigorously debated. Present theories can be generally categorized into three different frameworks, the most prevailing theory considering the increased heat uptake in ocean interior as a direct trigger in cooling the eastern equatorial Pacific, the next regarding the prolonged solar minimum as a potential driver in producing weak radiative forcing over the Pacific, while another suggesting that changes in atmospheric water vapour and aerosols play an unnegligible role in absorbing and reflecting solar radiation. Most recently, some studies argue that the ongoing cooling in the eastern Pacific is induced by a strengthening of the easterly trade winds. Nevertheless, observational records coming from the monitoring buoys deployed along the equator by NOAA since 1992 indicate that an intensification of the trade winds is only confined to the central tropical Pacific (around 170° E–170° W) during hiatus decades, elsewhere along the equatorial Pacific the trade winds exhibit a stable condition even a slight weakening in the eastern equatorial Pacific, rendering it as a trigger of this cooling in the eastern Pacific unlikely. Here we use a model and long-term observational data to demonstrate that a persistent cooling in the eastern Pacific is directly linked to an eastward displacement of the Southeast Pacific Subtropical Anticyclone (SPSA). Interactions between the Andes and an eastward shift of the SPSA generate greater pressure gradients in the eastern flank, in turn, stronger alongshore winds and more intense upwelling, ultimately contributing to hiatus decades.
... Species are also clustered, with the standard agglomerative method, based on the 'index of association'. The abundance of the pooled species is shown as in Fig. 4 Fig. 8 Non-metric multidimensional scaling graph (NMDS) based on the Bray-Curtis similarity index on transformed abundance data (fourth root) associated with the four pre-defined zones: upwelling zone, the mesotrophic zone, the oligotrophic zone, and the ultra-oligotrophic zone and salinity (for the entire gradient and the ultra-oligotrophic zone) indicated the changes in the composition and dominant species associated with subantarctic water (SAAW) in the upwelling zone (Reid 1973;Silva et al. 2009) and subtropical water (STW) (Schneider et al. 2007;Fuenzalida et al. 2008) in the oceanic areas of the SEP. This association had been described for euphausiids, copepods, and siphonophores (Palma and Silva 2006;Morales et al. 2010;Riquelme-Bugueño et al. 2012). ...
The subtropical region of the Southeast Pacific exhibits a strong onshore-offshore gradient in hydrographic conditions and biological production from the eutrophic upwelling zone to the ultra-oligotrophic oceanic area in the central South Pacific gyre (SPG). Across this gradient, zooplankton must cope with either gradual or abrupt changes in environmental conditions. Here, the distribution and diversity of hyperiid amphipods were assessed over this gradient in the upper 1000 m in relation to temperature, salinity, oxygen, chlorophyll-a, sea level anomalies, the bulk of mesozooplankton biomass and the biomass of salps, siphonophores, and other hydrozoans during October/November 2015 from the coastal zone off Chile (27° 00‵ S, 70° 52‵ W) to near Easter Island within the SPG (27° 10‵ S, 109° 20‵ W). The most frequent and abundant species were Hyperioides longipes Chevreux, 1900, Eupronoe minuta Claus, 1879, and Hyperioides sibaginis (Stebbing, 1888). Significant changes in abundance and community structure across the gradient with respect to the evaluated environmental variables and significant correlations of 17 hyperiid species with the gelatinous category other hydrozoans were found. These changes were closely linked to previously defined zonation patterns, which contained distinct species assemblages and a unique dominant species per zone. These zones represented ecoregions based on diversity patterns of hyperiids and other shared species among such ecoregions suggesting a possible ecological connectivity among the zones, promoted by mesoscale eddies travelling westward from the coastal upwelling zone to offshore waters. Environmentally forced zonation and the interactions with mesoscale features are thus suggested as the driving processes maintaining spatial patterns of diversity of the hyperiid community in the Southeast Pacific.
... Camus (2001) argues that these currents are responsible for the SEP biogeography and are the main reason for the IA biota's mixed character. We propose that the CCC and OCPC and their respective equatorward 0.2 ms -1 and 0.15 ms -1 flow (Marín & Delgado 2007;Fuenzalida et al. 2008), behave as a dispersal enhancer to the pelagic larval phase of A. spatuligera. ...
The pattern of the genetic structuring of marine species result from the relationship between homogenizing and structuring factors, together with historical and contemporary processes. Dispersal potential has been described as a homogenizing factor, corroborated by the connectivity paradigm, which states that high dispersers show low or no genetic differentiation. In contrast, biogeographic breaks and oceanic currents have an important role in limiting or enhancing connectivity, being structuring factors. We studied this relationship in Arbacia spatuligera, a subtidal echinoid with a planktonic larval stage, which is distributed along the Southeastern Pacific (SEP). The SEP is divided into two biogeographic provinces with an Intermediate Area between both them, which is delimited by two biogeographic breaks (~30° S and 40°-42° S). Moreover, much of the SEP coast, from ~42° S to 6° S, it is influenced by a complex system of marine currents known as the Humboldt Current System (HCS). Using molecular tools (mtDNA COI) we assessed the genetic diversity and structure of A. spatuligera and inferred its demographic history. Analyses showed that along ca. 3.200 km A. spatuligera has no genetic structure signals, has an unexpected low genetic diversity and a signal of recent demographic expansion dated ~33000 - 47000 years ago, probably related to the Marine Isotope Stage 3 (MIS3) climatic events. Our results support the hypothesis that dispersal potential is a determining factor of the phylogeographic patterns in the SEP, probably influenced by HCS. We propose that A. spatuligera is a high disperser.
... On average, one appendicularian can produce between 7.3 and 10.1 FPa h −1 27,57 or an average of 198.6 FPa d −1 or 72,500 FPa y −1 (Supplementary Table S4). We estimated a total area of the HCS off Chile of 910,000 km 2 , assuming a total latitudinal length of 2,600 km between 18.5° and 41.5°S and a width of 350 km 58 . Because most appendicularians occur within the upper 50 m of the water column 59,60 , an estimate of 1.08 × 10 9 appendicularians within this upper layer would produce 7.12 × 10 19 FPa y −1 along the whole HCS. ...
The role of appendicularian faecal pellet (FPa) size fractions on coccolithophore-derived particulate organic carbon (POC) and calcium carbonate (CaCO3) export to the deep sea was assessed from sediment traps within a period of ten years (1995–2004) off Coquimbo (CQ, 30°S) and five years (2005–2009) off Concepción (CC, 36°S) in the Humboldt Current System (HCS) off Chile. The composition and size distribution of 1,135 FPa samples from sediment traps deployed at 2,300 and 1,000 m depths showed non-linear, inverse relationships between the FPa size-fractions and their volume-specific POC and CaCO3 contents, which were up to ten times higher for small (<100 µm in diameter) than large (>100 µm) FPa. On average, 13 and 2% of the total POC and CaCO3 fluxes, respectively, were contributed mainly by small FPa (90%), with maxima during the autumn and summer. Thus, a non-linear, exponential model of volume-specific POC and CaCO3 contents of FPa substantially improved vertical flux rate estimates. In the HCS, annual carbon flux based on a non-linear FPa carbon load was double the estimate assuming a linear-volume to carbon load for FPa (345 and 172 kton C y−1). We recommend a widespread consideration of this non-linear model in global carbon estimates.
... The counterclockwise rotation of winds from the SPSA generates northerly winds along the coastlines of Chile and Peru, contributing to the maintenance of upwelling conditions all year and producing one of the highest productivity marine ecosystems in the world (Kämpf and Chapman, 2016). The system is well known for the contribution of the westerly winds and the SPSA to the circulation regimen (e.g., the formation of the Humboldt Current system) (Thiel et al., 2007;Fuenzalida et al., 2008). ...
... Even though maps similar to Fig. 2 were presented in Aguirre et al. (2012) and Saldías et al. (2018) using QuikSCAT data, details of the surface-wind behavior could not be determined. In addition, wind regime studies, which included derived variables such as EP and ET, focused on the central and northern regions of the Chilean and Peruvian coasts, north of 40 • S. The main goals of these studies were to explain the dynamic of the SPSA and improve the understanding of the wind's influence on this circulation regime (Ancapichun and Garcés-Vargas, 2015;Bravo et al., 2016;Fuenzalida et al., 2008;Schneider et al., 2017). Recently, the behavior and evolution of the ET in northern Patagonia and its implications in ocean response were investigated (Narváez et al., 2019). ...
In the Southern Hemisphere, macroscale atmospheric systems such as
westerly winds and the southeast Pacific subtropical anti-cyclone (SPSA)
influence the wind regime of the eastern austral Pacific Ocean. The average
and seasonal behaviors of these systems are well known, although wind
variability at different time and distance scales remains largely
unexamined. Therefore, the main goal of this study was to determine the
variabilities of surface winds on a spatiotemporal scale from 40 to 56∘ S,
using QuikSCAT, Advanced Scatterometer (ASCAT), and the fifth major global
European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) surface-wind
information complemented with in situ meteorological data. In addition,
interactions between the atmospheric systems, together with the
ocean–atmosphere response, were evaluated for the period 1999–2018. The
empirical orthogonal function detected dominance at the synoptic scale in
mode 1, representing approximately 30 % of the total variance. In this
mode, low and high atmospheric pressure systems characterized wind
variability for a 16.5 d cycle. Initially, mode 2 – which represents
approximately 22 % of the variance – was represented by winds from the
west/east (43–56∘ S), occurring mostly during spring
and summer/fall and winter at an annual timescale (1999–2008) until they
were replaced by systems cycling at 27.5 d (2008–2015). This reflects
the influence of the baroclinic annular mode in the Southern Hemisphere.
Mode 3, representing approximately 15 % of the variance, involved the
passage of small-scale low and high atmospheric pressure (LAP and HAP)
systems throughout Patagonia. Persistent Ekman suction occurred throughout
the year south of the Gulf of Penas and beyond the Pacific mouth of the
Strait of Magellan. Easterly Ekman transport (ET) piled these upwelled waters
onto the western shore of South America when winds blew southward. These
physical mechanisms were essential in bringing nutrients to the surface and
then transporting planktonic organisms from the oceanic zone to Patagonian
fjords and channels. In the zonal band between 41 and 43∘ S, the latitude of Chiloé Island, upward Ekman pumping and Ekman transport during spring and summer favored a reduced sea surface temperature and
increased chlorophyll a (Chl a) levels; this is the first time that such Ekman upwelling conditions have been reported so far south in the eastern Pacific Ocean. The influence of the northward-migrating LAP systems on the ocean–atmosphere interphase allowed us to understand, for the first time, their direct relationship with recorded nighttime air temperature maxima (locally referred to as “nighttime heatwave events”). In the context of global climate change, greater attention should be paid to these processes based on their possible impact on the rate of glacier melting and on the austral climate.
... This system supports Chile's principal fisheries according to 2014 Food and Agriculture Organization's statistics, including sardine and anchovy [5]. The HCS is driven principally by the SPSA, which controls winds along the coast [6,7]. During austral fall and winter, SPSA is located at low latitudes, with its center near 27-29 • S, which makes the winds favorable for upwelling only in Chile's northern region (18-28 • S). ...
The central and northern Chilean coasts are part of the Humboldt Current System, which sustains one of the largest fisheries in the world due to upwelling. There are several upwelling focal points along the Chilean coast; however, from a physical standpoint, the region between 39 • and 41 • S has not been studied in detail despite being one of the most productive zones for pelagic extraction in Chile. Here, we evaluated the seasonal variability of coastal upwelling off central-southern Chile using principally daily sea surface temperature (SST) and sea surface wind (SSW), and 8-day composite chlorophyll-a concentration between 2003 and 2017. Through the seasonal evaluation of the net surface heat flux and its relationship with the SST as well as daily SST variability, we determined the "maximum upwelling" on our area. The direction of surface winds is controlled throughout the year by the Southeast Pacific Subtropical Anticyclone, which produces a cold tongue and an upwelling shadow north of Punta Galera (40 • S) in austral spring and summer. A cross-correlation analysis showed a decrease of SST follow the alongshore SSW with a lag of 2 days in the months favorable to the upwelling. However, the correlations were not as high as what would be expected, indicating that there is a large advection of waters from the south that could be related to the greater volume of subantarctic water present in the zone.
... Off central Chile, upwelling events are mainly driven by South Pacific Subtropical Anticyclone seasonal fluctuations (Fuenzalida et al., 2008) that promote local southern winds concentrated in spring and summer (Sobarzo and Djurfeldt, 2004) and even synoptic variability with 3-12 day fluctuations leading active and relaxed upwelling events (Aguirre et al., 2014). In addition, upwelling events driven by the Biobío canyon (Sobarzo and Djurfeldt, 2004;Sobarzo et al., 2016) have been documented, as well as NPP enhancement due to the effect of geomorphological protection (Montecino et al., 2006;Henríquez et al., 2007). ...
The temporal variability of Net Primary Production (NPP) off central Chile (36°S, 73°W), an area subjected to seasonal coastal upwelling, was analyzed using monthly in situ ¹³C incubations within the photic zone, along with bio-oceanographic variables from a fixed time series station; and satellite NPP estimations (NPPE) from the Vertically Generalized Production Model between 2006 and 2015. NPP and NPPE rates varied from 0.03 to 18.29 and from 0.45 to 9.07 g C m⁻² d⁻¹, respectively. Both rates were fairly well correlated with each other (r² = 0.61), but when these data were separated into two periods, higher r² value was found during winter (r² = 0.70) with respect to the rest of the year (r² = 0.24); the latter correlation was partially due to increased weekly NPPE variability during active and relaxed upwelling events. NPP rates along with other biophysical variables allowed for a division of the annual cycle into three distinct periods: September to January (high productivity, mean integrated NPP rates of 4.0 g C m⁻² d⁻¹), February to March (intermediate productivity, mean integrated NPP rates of 1.4 g C m⁻² d⁻¹), and May to August (basal level, mean integrated NPP rates of 0.5 g C m⁻² d⁻¹). NPP appeared to be partially controlled by nutrient inputs, either from upwelling (September-April) and river discharge (May-August), maintaining high NPP rates throughout the entire year, with an annual mean NPP rate of 1.1 kg C m⁻² yr⁻¹. In this region, El Niño Southern Oscillation events did not appear to impact the NPP interannual variability.
... The ability of each of these data sets to resolve the mesoscale variability is likely a factor in the correlations. From the model perspective, lower correlations could be associated with both the Humboldt Current (Fuenzalida et al. 2008) and also the biases in heat and momentum fluxes. ...
... However, the spatial structure of the second eigenmode (not shown) shows maxima in MUR and NCEI that in general appear in Austral Winter (July). The maxima are consistent with known maxima in velocity of the Humboldt Current (Fuenzalida et al. 2008). ...
The upwelling system off Peru/Chile is characterized by significant mesoscale to submesoscale surface variability that results from the instability of the coastal currents (due to the strong vertical and horizontal shears) and to the marked density cross-shore gradients (associated with the mean upwelling). Here we investigate to what extent upwelling intensity can be inferred from sea surface temperature (SST) derived from remote sensing. As a first step in validation, a comparison between SST observations is performed, which indicates that the 1 km gridded multi-scale ultra-high-resolution (MUR) SST data set is defining a zone of maximum SST gradients closer to shore than the low-resolution National Centers for Environmental Information 0.25° resolution data set. Two model versions, at nominal resolutions of 2 km and 4 km, of the Massachusetts Institute of Technology general circulation model are analysed. A high-resolution version at 2 km is examined for the period 13 September 2011–23 January 2013, while a 4 km version is examined for 6 March 2011–22 April 2013. MUR shows maxima SST gradients in the range of 0.03 ± 0.02 K km⁻¹ while the model showed higher gradients around 0.05 ± 0.02 K km⁻¹. Based on coherence spectra, the relationship between upwelling rate (as inferred from the vertical velocity) and SST gradient is documented in the model from intraseasonal to annual timescales. It suggests that changes in SST gradient magnitudes are related to changes in the intensity of coastal upwelling off Peru and Chile. Such a relationship between SST gradients and vertical velocity would allow for the use of satellite-derived SSTs to monitor the intensity of coastal upwelling from the intraseasonal to annual timescales.
... Elevated values of eddy-kinetic energy (EKE), associated with increased mesoscale activity, have been described for the northern (Peru) and southern (central-southern Chile) HCS (Hormazabal et al., 2004;Vergara et al., 2016). In the strongly seasonal coastal upwelling region of the southern HCS (33-408S; Figure 1a), the equatorward Chile Coastal Current (CCC) dominates the surface flows, whereas the poleward Peru-Chile Undercurrent (PCUC) dominates the subsurface (100-400 m depth); the equatorward Chile-Peru surface Current (CPC) is located further offshore (Fuenzalida et al., 2008;Llanillo et al., 2012;Strub et al., 1998;Vergara et al., 2016). Eddies, fronts, jets, and filaments are regularly generated in this region, especially during the spring-summer upwelling season (Aguirre et al., 2012;Correa-Ramirez et al., 2012;Hormazabal et al., 2013;Letelier et al., 2009;Morales et al., 2007Wang et al., 2015). ...
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 Lavapié, 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.
