This study characterizes the structure and variability of baroclinic semidiurnal tidal currents at the head of the Biobio Submarine Canyon (BbC), off central Chile, based on Acoustic Doppler Current Profiler (ADCP) and moored thermistor-chain observations from two deployments conducted in 2013 and 2014 under contrasting stratification conditions. The results show that the head of the BbC is a dynamically active site of semidiurnal variability, with markedly stronger and more coherent baroclinic motions during the more stratified winter–spring 2014 period. During that deployment, semidiurnal baroclinic current amplitudes reached up to 17 cm s−1, and the associated energy was concentrated near the surface and bottom. Rotary spectral analysis indicated that these semidiurnal baroclinic currents rotated anticyclonically and were closely aligned with the canyon axis. Empirical orthogonal function (EOF) analysis further showed that their vertical structure was dominated by a first baroclinic mode, which explained more than 70% of the semidiurnal baroclinic variance in 2014. In contrast, the 2013 deployment exhibited weaker and less coherent semidiurnal baroclinic variability. Taken together, these results indicate that stronger stratification favored the development of semidiurnal internal-tide-related motions over the canyon head and that the BbC provides a dynamically favorable setting for enhanced semidiurnal internal-tide activity and potentially elevated mixing, although direct turbulence or dissipation measurements were not available in this study. These findings have potential implications for local water-column structure, nutrient supply, and primary productivity in this highly productive coastal region.

Riverine organic matter strongly influences productivity and biogeochemical cycles in eastern boundary upwelling systems, enhancing microbial activity and carbon and nutrient cycling beyond natural upwelling inputs. To assess the impact of riverine organic matter from the Biob & iacute;o River on particulate organic carbon (POC) and the carbon biomass of higher trophic levels (zooplankton) in the adjacent coastal upwelling area off Central Chile, we conducted a year-long study (November 2009 to November 2010). Our study included analysis of land use, hydrographic data, nutrients, pigments, and POC and nitrogen, combined with geochemical tracers (i.e., carbon and nitrogen isotopes, and fatty acids). Results showed that nutrient and particulate organic matter (POM) fluxes, including phytoplankton biomass, peaked during periods of maximum rainfall and river discharge (winter and spring). A clear enrichment in delta 13C-POC from river to ocean during the upwelling season indicated that autochthonous production dominated the POM in the coastal zone. On average, terrestrial-originated material contributed 25% to the marine POC during spring, increasing to 73% in winter, when freshwater discharge was highest. Fatty acid analysis revealed a higher contribution of terrestrial carbon near the river mouth, with zooplankton incorporating 30%-40% of this carbon, mainly during winter. These findings suggest that terrestrial carbon enters the food web via freshwater phytoplankton, terrestrial POC, or microbial loops. Given climate change impacts on hydrology and upwelling, further studies are needed to assess the long-term effects of riverine carbon on coastal productivity and food webs in eastern boundary upwelling systems.

Submarine canyons are major topographic features that incise the continental shelf, modifying coastal ocean circulation and influencing the upwelling of subsurface slope waters onto the shelf. Interactions between Coastal Trapped Waves (CTWs) and tides at canyon heads can promote localized cooling events. Here, we evaluate how a negative-phase CTW interacts with the topography of the Biobio Canyon off central Chile, modulating cross-canyon circulation and the hydrographic structure at the canyon head. Our analysis is based on towed-ADCP observations collected along four transects, two moored ADCPs, a yo-yo CTD station, coastal tide gauges, and atmospheric and hydrological forcings (wind and Biobio River discharge). The towed-ADCP dataset was obtained on November 11–12, 2013, a few days after neap tide, during low upwelling-favorable winds (< 0.03 N/m ^2 ) and concurrent with the passage of a negative-phase CTW. We identified a mean asymmetric inflow–outflow circulation pattern in the zonal current, with a geostrophic northward flow confined near the coast. Most onshore flow occurred over the down-wave side (southern wall) of the canyon. Four cooling events were detected, each associated with coherent negative CTW signals. These events exhibited semidiurnal oscillations superimposed on diurnal variability and a pronounced subinertial band, particularly during events 2 and 4. The hydrographic response revealed the advection of cold, low-oxygen, nutrient-rich Equatorial Subsurface Water (ESSW) driven by the CTW passage and the accompanying semidiurnal oscillations, whose dominance varied across the events. Our results demonstrate that, even under weak wind conditions, CTWs and tidal forcing can enhance cross-shelf exchange, reinforcing the role of the Biobio Canyon in modulating cross-shore current variability and coastal ocean fertilization during local cooling events.

The Gulf of Arauco, a highly productive area, sustains some of the primary epipelagic, mesopelagic, and benthic resources in the Southern Humboldt Current System. It is also an important nursery and spawning area. High productivity is driven by seasonal and synoptic wind variability, coastal upwelling, topographic upwelling from the Biobio Submarine Canyon, and freshwater flow, mostly from the Biobio River. The effect of freshwater discharge on early-stage fisheries resources has been poorly studied in central Chile, making our research all the more significant. From 2014 to 2018, a high-resolution interannual biophysical simulation incorporating the Biobio River freshwater discharge was conducted. It allowed us to thoroughly examine the impact of the Biobio River on the abundance and transport of anchovy early-life stages in the Gulf of Arauco. To ensure the accuracy of our findings, we compared model results to in-situ biological/hydrographic data in the Gulf of Arauco from 2007 to 2019. The biophysical model was run with release pulses every five days from September 1 to October 31. In the research area, the months of September and October have traditionally been identified as anchovy spawning months. The simulation was evaluated using General Linear Models, which suggested that larval survival would be influenced by the spawning's temporal fluctuation (year and day of release). The extension of the Biobo River plume, identified using the potential energy anomaly, was found to be similar to the observations. The model results showed that larvae were largely transported northward, and spawning zones from the research period showed strong retention in the Gulf of Arauco. The highest abundances of anchovy early-life stages were found south of the Biobio River mouth, in highly stratified waters associated with the Biobio River plume in the Gulf of Arauco. Significant correlations between Biobio River's monthly mean discharge, river plume extension, and anchovy early-life stages abundance were observed from 2014 to 2018, both for simulated and in situ data. However, when considering a larger egg in situ abundance time series data in situ (from 2007 to 2019), significant correlations were observed between egg abundance and the river plume extension area (R2 = 0.7 p = 0.03) only up to a threshold value, which ranged from 338 to 357 km2); below and above this threshold, abundance dropped drastically. This research concludes that the Biobio River is an essential factor regulating the early stages of the life of anchovy in the Gulf of Arauco.

This study characterizes the hydrodynamics of the Dalcahue and Yal channels, key aquaculture areas within the Chiloe Inland Sea (CIS). It demonstrates the significant influence of bathymetric constrictions on local circulation patterns, tidal modulation, and biogeochemical variability. Dalcahue exhibits distinct bidirectional residual flows, characterized by intensified central inflows (NW-NE) and reinforced outflows (SE-SW) along the Quinchao coast, driven by channel curvature and bathymetry, with velocities reaching up to 70 cm/s in constrictions. In contrast, Yal shows a weak surface residual layer and persistent northwestward mid-depth flow, indicative of vertical tidal energy variations. Semidiurnal tidal forcing (M2, S2) predominantly drives current variability, explaining 50-75 % of observed fluctuations. A significant presence of the M4 overtide (up to 33 % in C2) highlights non-linear tidal interactions, crucial for understanding tidal asymmetry and net material transport. Weak correlations between sea level and dissolved oxygen suggest that strong tidal currents and mixing in constrictions counteract stratification, ventilating deeper layers. These findings enhance our understanding of physical oceanography in the context of the CIS, providing vital insights for environmental management and aquaculture planning by highlighting the role of constriction-induced hydrodynamics in estuarine systems worldwide.

This study examines the hydrodynamic response of the Gulf of Arauco, a semi-enclosed bay within the Humboldt Current System, to the passage of extratropical cyclones and their associated changes in wind patterns during the austral winter. Characterization of these cyclones over central Chile and their effect on the gulf's meridional wind was conducted using ERA5 atmospheric pressure fields in conjunction with a cyclone tracking algorithm. The hydrodynamic response was assessed through acoustic Doppler current profiler (ADCP) observations at two strategic sites, providing valuable insights into the currents at the gulf's connections with the open ocean. Measurements were conducted from July to September 2016 and May to July 2018. Additionally, the main modes of subtidal current variability were compared with the local wind through coherence wavelets, revealing a direct influence of cyclones on the modulation of the gulf's currents. Our findings suggest that intense northerly wind events, associated with the passage of extratropical cyclones, can cause surface water transport into the gulf, accumulating at the gulf's head. This would result in a pronounced pressure gradient, driving a water outflow through both connections with the open ocean, thereby altering the coastal circulation patterns. As the northerly wind decreases, the surface inflow in the northwest region attenuates, allowing the water to exit at shallower depths. This mechanism suggests cyclones play a vital role in renewing the waters of semi-enclosed bays such as the Gulf of Arauco, potentially reducing the water residence times. Consequently, these insights provide a broader understanding of wind-driven coastal dynamics, highlighting their significant impacts on marine ecosystems and coastal management in similar semi-enclosed bays globally. By contributing to the broader knowledge of the interaction between atmospheric and oceanic processes in coastal regions, this research offers a comparative perspective applicable to other regions affected by similar atmospheric phenomena.

El golfo de Arauco, situado en Chile centro-sur, es una de las zonas con las tasas más altas de producción biológica en el Sistema de Corrientes de Humboldt Sur. En este golfo, donde la actividad urbano-industrial convive con comunidades pesqueras y concesiones acuícolas, son múltiples los forzantes físicos que influyen en la variabilidad espacio-temporal de las propiedades hidrográficas. En este contexto, el viento es uno de los forzantes más relevantes, el cual muestra un marcado ciclo estacional. Así, durante primavera- verano, predominan los vientos hacia el norte favorables a surgencia costera, promoviendo la incursión de aguas con alta concentración de nutrientes, bajo oxígeno, alta salinidad y baja temperatura que sustentan las altas tasas de producción primaria reportadas para esta zona. Durante otoño e invierno, el aumento de las descargas de agua dulce provenientes de ríos adyacentes y el predominio de los vientos favorables a hundimiento (hacia el sur), gobiernan la hidrodinámica del golfo. En esta investigación, caracterizamos la variabilidad estacional de la hidrografía en el golfo de Arauco con datos de tres campañas realizadas en primavera 2021, verano e invierno 2022. Adicionalmente, datos satelitales provenientes del sensor MODIS-aqua de temperatura superficial del mar, clorofila-a y Rrs645 fueron utilizados para complementar la información in situ. Nuestros resultados muestran una marcada estacionalidad en la hidrografía del golfo de Arauco, principalmente en la temperatura superficial del mar. En primavera, bajos valores térmicos (<13°C) abarcaron una extensa área del golfo, desde la desembocadura del río Biobío hasta Punta Lavapié. Por otra parte, en verano, altas temperaturas (>15°C) se observaron al interior del golfo de Arauco, caracterizando una sombra de surgencia. Bajas temperaturas (<12°C) fueron detectadas en invierno con una distribución espacial homogénea. La clorofila superficial fue alta (>20 mg m-3) en gran parte del golfo durante primavera y verano, lo cual obedece al aumento en la radiación solar y a los vientos favorables a surgencia. Destacamos la baja salinidad (<20 psu) presente durante invierno, donde la pluma del río Biobío se extendió desde la desembocadura hacia el sur del golfo de Arauco, abarcando toda la zona costera. La distribución del oxígeno disuelto en la columna de agua mostró variaciones similares en primavera y verano, donde concentraciones >5 ml L-1 se presentaron en los 10 m superiores. No obstante, la hipoxia cubrió todo el fondo de la zona de estudio, desde el norte del golfo hasta la última estación en Boca Chica durante verano. A través de estos análisis, detectamos que el golfo de Arauco presenta diferentes patrones espaciales hidrográficos estacionales que evidencian la alta variabilidad a la cual está expuesto, donde el viento, la descarga del río Biobío y la radiación solar gobiernan la estructura de la columna de agua.

Coastal upwelling is the dominant physical process triggering high biological productivity in Eastern Boundary Upwelling Systems (EBUS). These regions are characterized by intense upwelling events driven by Equatorward alongshore winds. In the Humboldt current system off central-southern Chile (30–40°S) the coastal upwelling process has been studied from several approaches including biogeochemical, fisheries and physical studies. Yet, the phenology of wind-driven upwelling along the meridional gradient has been poorly inspected. Using reanalysis data from the ERA5 product (1966–2020), we calculated the Cumulative Upwelling Index (CUI, m2 s−1 × 1000 m) to characterize the phenology of coastal upwelling off central-southern Chile, identifying the beginning (STI), the maximum (MAX) and the end (END) of the upwelling season. In addition, we quantified the duration (LUSI) and the total magnitude (TUMI) of the upwelling season. The response of the water column to cumulative wind stress was determined using in situ hydrographic data (2002–2020) from a middle shelf station off Concepción, which showed marked seasonal and interannual variability. In general, the onset, duration, and intensity of Ekman transport were highly variable. At 36.5°S (off Concepción), the STI occurred on August 6 ± 25.4 days and the duration of the upwelling season (LUSI) was ∼9 months ± 32.5 days. On the other hand, the TUMI at this latitude was −1.97 × 108 ± 4.88 × 107. The CUI climatology during El Niño years showed weak and late upwelling (STI = August 29 ± 16.2 days) while upwelling was strong and early (STI = July 13 ± 30.6 days) during La Niña compared to the mean climatology. The water column showed a direct response to cumulative wind-driven upwelling conditions during El Niño 2015-2016 and La Niña 2007-2008. The rise of cold (≤11 °C), saline (34.5 isohaline), dense (>25.8 kg m−3), and oxygen-poor (≤ 1 ml L−1) subsurface waters corresponded to stronger upwelling winds during La Niña 2007–2008. In contrast, coastal upwelling was substantially weak, with a warmer water column and the isotherm of 11.5 °C located below 30 m depth during El Niño 2015–2016.

The Gulf of Arauco, located in central Chile, is one of the most productive areas in the Southern Humboldt Current System. Here, urban-industrial activities coexist with fishing communities and aquaculture concessions. In this context, the seasonal variability of the wind forcing is one of the main factors impacting its hydrographicvariability. Upwelling favorable winds predominate in summer, promoting the incursion of subsurface waters with high nutrients that sustain the high primary production of the gulf. During autumn and winter, the increased freshwater discharges and downwelling-favorable winds drive to a large extent the gulf's hydrodynamics. We present the seasonal hydrographic variability of the Gulf of Arauco during three contrasting periods (spring 2021, summer, and winter 2022) through in situ and satellite data. Our results show a marked hydrographic seasonality, mainly in the sea surface temperature. Low thermal values (<13 degrees C) covered most of the gulf in spring, from the Biobio River mouth to Punta Lavapie. High temperatures (>15 degrees C) featuring an upwelling shadow characterized the gulf in summer. Low temperatures (<12 degrees C) were detected in winter with a homogeneous spatial distribution. Surface chlorophyll was high (>20 mg m-3) during spring and summer because of increased solar radiation and upwelling favorable winds predominance. Low salinity (<20 psu) waters, associated with spreading the Biobio River plume, dominated in winter. The dissolved oxygen distribution showed similar variations in spring and summer, where waters with concentrations >5 ml L-1 were found in the upper 10 m. However, hypoxic waters covered the bottom along the entire nearshore coastal band during summer. We conclude that the Gulf of Arauco exhibits contrasting seasonal hydrographic patterns where the wind, the Biobio River discharge, and solar radiation modulate the water column structure.

Off the central-southern Chilean coast (35°–38°S), the Gulf of Arauco is one of Chile's largest semi-enclosed coastal areas. It hosts industrialized activities within a highly productive zone of the Southern Humboldt Current System. One of the principal hydrodynamical forcings of the region is the Biobio River, whose discharge significantly influences coastal dynamics in the Gulf. The present work aims to study the impact of the Biobio River freshwater discharge on the circulation patterns in the Gulf of Arauco, using a high-resolution interannual simulation of the period 2013–2018. The simulation includes monthly interannual discharge from the significant four rivers for the study zone (Mataquito, Maule, Biobío, and Itata). The focus is primarily on wintertime (June–September), the highest freshwater discharges period. The modeled temperature and salinity fields were consistent with in-situ observations, presenting a moderate bias. The water masses highlighted in the TS diagrams, the temperature time series, and especially the currents near the Biobio River mouth were well represented in the simulation. It was found that the Biobio River strongly impacted the circulation in the Gulf of Arauco, intensifying the currents and causing a notable salinity decrease. Offshore zonal currents were intensified west of the Biobio River mouth, whereas southward alongshore currents were enhanced, especially during August. The influence of the Biobio River in the Gulf of Arauco was closely related to discharge strength. A strong relation between predominant southward downwelling-favorable wind stress and meridional currents was found, probably due to the formation of a buoyant coastal current strengthened by the wind-driven current during winter. Finally, surface buoyant waters associated with the river discharge generated a strong baroclinic zonal pressure gradient equilibrating the sheared meridional flow and enhancing the meridional ageostrophic pressure gradient, Reynolds stress, and near-surface vertical mixing of momentum.

GENERAL INFORMATION Title of Dataset: Replication data for: - Sea Surface Temperature (SST, daily) MODIS-Aqua (2016-2019)

We predicted small-scale hydrodynamics, including the effect of the aquaculture farming infrastructure, for a region within the group of salmon farm concessions identified in the Chilean regulation as ACS-7. The geographical region corresponds to the Caucahue Channel, composed of two branches connected by a constriction on Caucahue Island, Inland Sea of Chiloe, Chilean Patagonia. The prediction methodology considers the interaction of a regional ocean model and a high-resolution local CFD model. The model prediction was validated using available data from ADCP. We find that the Caucahue Channel is characterized by a complex circulation and hydrodynamics, including an unstable shear flow, with meanders and turbulent structures, and retention zones. Results show the aquaculture infrastructure has a non-local hydrodynamic effect. Differences in horizontal and vertical velocity can be quite significant even far from aquaculture centers, reaching up to 300% and 170%, respectively, in simulations without taking its effects into account. The useful characteristics of this predictive approach and its potential use in particle tracking and species diffusion prediction allow for the use of projecting as a tool for strengthening the environmental and productive management of this industry.

The response of inner shelf circulation and bottom temperature variability to synoptic wind forcing and freshwater outflow is evaluated in an area with a wide continental shelf off central Chile. This forced circulation, with a strong seasonal evolution from upwelling- to downwelling-favorable conditions, is a key process modulating the exchange of water properties in a coastal zone characterized by multiple river outflows and high biological productivity. Ocean currents on the inner shelf (34 m depth) off the Itata River mouth were obtained and analyzed for a nine-month record (December 2008 to September 2009). The synoptic wind and current variability was defined between 2 and 16 days (0.02 to 0.0026 cph). The subinertial coastal circulation within the inner shelf off Itata River was dominated by the along-shelf flow, while cross-shelf flows driven by along-shelf winds were substantially reduced. The alongshore synoptic currents showed two distinct modal structures: (i) A mean two-layer flow field during upwelling-favorable wind stress with northward (southward) flow at the surface (bottom), and (ii) a mean southward flow through the entire water column during downwelling-favorable wind stress periods, which were intensified during peak river discharge events in winter. Calculations of the wind index clarified the relative importance of wind versus buoyancy forcing on the alongshore flow. The wind forcing dominated during summer when the river discharge was minimum, whereas the relative importance of the freshwater outflow from the Itata River became dominant in winter (May-August) when the buoyancy forcing, in conjunction with southward wind events, modulated strong barotropic southward flows. The change in the long-term regime of coastal winds and river discharges, with a dominance of upwelling winds and reduced river outflows in the last decade, is discussed in the context of observations of thinner river plumes under frequent upwelling conditions off central Chile.

Some semienclosed bays in the eastern boundary upwelling systems worldwide display a strong surface temperature gradient between cold water upwelled outside and warmer water inside these bays. This anomalous coastal temperature pattern is known as upwelling shadow (US). Research on this topic has mainly focused on identifying spatiotemporal patterns of US events, but the influence of the atmospheric synoptic variability on the temporal evolution of US events remains less well documented. This study uses observational, satellite-derived, and reanalysis data to propose a mechanism that relates synoptic-scale atmospheric phenomena with the development of US events in the Gulf of Arauco (GA), a highly productive and the largest semienclosed bay in central Chile (around 37 degrees S). The mechanism associates the passage of migratory anticyclones over the study area with two key processes. The first process is the formation of a coastal low-level wind jet, which intensifies the upwelling of cold subsurface waters outside the GA. We strongly suggest that the second one is the development of a coastal low pressure, which usually implies clear skies (increasing the solar radiation input) and weak downwelling favorable winds along the coast, factors that could largely explain the observed surface warming inside this embayment during these events. The presence of cold water upwelled offshore and the enhanced surface warming inside the GA, possibly also modulated by a weakened circulation, results in a strong thermal gradient with average temperature differences of more than 3 degrees C, generating the US.

The biogeochemical dynamics of fjords in the southeastern Pacific Ocean are strongly influenced by hydrological and oceanographic processes occurring at a seasonal scale. In this study, we describe the role of hydrographic forcing on the seasonal variability of the carbonate system of the Sub-Antarctic glacial fjord, Seno Ballena, in the Strait of Magellan (53°S). Biogeochemical variables were measured in 2018 during three seasonal hydrographic cruises (fall, winter and spring) and from a high-frequency p CO 2 -pH mooring for 10 months at 10 ± 1 m depth in the fjord. The hydrographic data showed that freshwater input from the glacier influenced the adjacent surface layer of the fjord and forced the development of undersaturated CO 2 (< 400 μatm) and low aragonite saturation state (Ω Ar < 1) water. During spring, the surface water had relatively low p CO 2 (mean = 365, range: 167 - 471 μatm), high pH (mean = 8.1 on the total proton concentration scale, range: 8.0 - 8.3), and high Ω Ar (mean = 1.6, range: 1.3 - 4.0). Concurrent measurements of phytoplankton biomass and nutrient conditions during spring indicated that the periods of lower p CO 2 values corresponded to higher phytoplankton photosynthesis rates, resulting from autochthonous nutrient input and vertical mixing. In contrast, higher values of p CO 2 (range: 365 – 433 μatm) and relatively lower values of pH T (range: 8.0 – 8.1) and Ω Ar (range: 0.9 – 2.0) were recorded in cold surface waters during winter and fall. The naturally low freshwater carbonate ion concentrations diluted the carbonate ion concentrations in seawater and decreased the calcium carbonate saturation of the fjord. In spring, at 10 m depth, higher primary productivity caused a relative increase in Ω Ar and pH T . Assuming global climate change will bring further glacier retreat and ocean acidification, this study represents important advances in our understanding of glacier meltwater processes on CO 2 dynamics in glacier–fjord systems.

Background Marine aquaculture is a very important economic and food production activity in Patagonian channels. The biophysical mechanisms through which farms interact with surrounding areas is poorly understood. A better understanding of the relationship between zooplankton distribution, hydrodynamics and aquaculture farms in Patagonian channels can contribute to the environmental sustainability of this activity. Methods The study was conducted in winter in the Caucahué Channel (Chiloé Island, southern Chile), which is composed of two asymmetric northern and southern sections separated by a geomorphological constriction (a narrows) and hosts 55 aquaculture farms. Intensive zooplankton and water column sampling (time scale: 12 h) was carried out, together with current measurements as a background of the channel hydrodynamics (time scale: 30 days). Results Spatial dissimilarities in composition and abundances of zooplankton communities and in water column variables were identified between the two sections of the channel in this short-term time scale. In the southern section we found higher abundances of holo- and meroplankton and higher species richness. No differences in zooplankton community were found between sampling sites near and far from aquaculture farms. Southward asymmetrical residual flow and semidiurnal tidal excursion were verified in the central part of the channel during two tidal fortnightly time periods. Conclusions (i) Clear dissimilarity in zooplankton composition were found between the two sections of Caucahué Channel in the time scale studied; and (ii) Quemchi geomorphological constriction and the asymmetrical southward residual flow could act as a physical barrier favoring the spatial dissimilarities found in biotic and abiotic variables between the two sections of the channel.

The upwelling shadow in the Gulf of Arauco (GA) is studied using 15 years of daily satellite images of Sea Surface Temperature (SST) from Geostationary Operational Environmental Satellites (GOES), as well as heat flux and wind data from the ERA5 reanalysis product. An Upwelling Shadow Index (USI) is developed based on the SST differences between the GA and the region off Punta Lavapie (PL) farther offshore, characterized by active upwelling. USI values greater than 0.91 degrees C and SST differences less than 1.1 degrees C, correspond to an upwelling shadow event. These cases occurred 10.29% of the time and were more frequent in spring/summer during events of upwelling-favorable winds with strong cyclonic wind stress curl, interspersed with wind relaxations. Multiple correlations between USI and wind stress curl and solar radiation showed an r(2) = 40%-80% for some summer months. Most events persisted for only 1 day (53%), whereas 34% of upwelling shadow events lasted between 2 and 4 days and 9% of events were longer than 4 days. Water residence times as long as 15 days were observed in the GA during upwelling shadow events. During southerly wind relaxation (less than 2 days), cold surface waters flowing north from PL curved onshore and entered the GA from the north, weakening the thermal gradient between PL and GA and the upwelling shadow. Long periods of wind relaxation (at least 1 week) resulted in the dissipation of the thermal gradient due to the warming of offshore waters.

10 months (2018) time series data of pCO2, pH, temperature, salinity, and dissolved oxygen at Seno Ballena fjord in the Chilean Patagonia.The sensors (SAMI-CO2, SAMI-pH, SBE37, Aanderaa 5331A) recorded data every 4 hour from March to December. Lat 53.67461 S, Long 72.56061 W.