scholarly journals High-Frequency Variability of the Surface Ocean Properties Off Central Chile During the Upwelling Season

2021 ◽  
Vol 8 ◽  
Author(s):  
Catalina Aguirre ◽  
René Garreaud ◽  
Lucy Belmar ◽  
Laura Farías ◽  
Laura Ramajo ◽  
...  
Keyword(s):  
High Frequency ◽  
Coastal Upwelling ◽  
Quantitative Description ◽  
Mean Flow ◽  
Austral Spring ◽  
Subtropical Anticyclone ◽  
Near Surface ◽  
Central Chile ◽  
South Central ◽  
High Frequency Variability

The ocean off south-central Chile is subject to seasonal upwelling whose intensity is mainly controlled by the latitudinal migration of the southeast Pacific subtropical anticyclone. During austral spring and summer, the mean flow is equatorward favoring coastal upwelling, but periods of strong southerly winds are intermixed with periods of relaxed southerlies or weak northerly winds (downwelling favorable). This sub-seasonal, high-frequency variability of the coastal winds results in pronounced changes in oceanographic conditions and air-sea heat and gas exchanges, whose quantitative description has been limited by the lack of in-situ monitoring. In this study, high frequency fluctuations of meteorological, oceanographic and biogeochemical near surface variables were analyzed during two consecutive upwelling seasons (2016–17 and 2017–18) using observations from a coastal buoy located in the continental shelf off south-central Chile (36.4°S, 73°W), ∼10 km off the coast. The radiative-driven diel cycle is noticeable in meteorological variables but less pronounced for oceanographic and biogeochemical variables [ocean temperature, nitrate (NO3−), partial pressure of carbon dioxide (pCO2sea), pH, dissolved oxygen (DO)]. Fluorescence, as a proxy of chlorophyll-a, showed diel variations more controlled by biological processes. In the synoptic scale, 23 active upwelling events (strong southerlies, lasting between 2 and 15 days, 6 days in average) were identified, alternated with periods of relaxed southerlies of shorter duration (4.5 days in average). Upwelling events were related to the development of an atmospheric low-level coastal jet in response to an intense along-shore pressure gradient. Physical and biogeochemical surface seawater properties responded to upwelling favorable wind stress with approximately a 12-h lag. During upwelling events, SST, DO and pH decrease, while NO3−, pCO2sea, and air-sea fluxes increases. During the relaxed southerly wind periods, opposite tendencies were observed. The fluorescence response to wind variations is complex and diverse, but in many cases there was a reduction in the phytoplankton biomass during the upwelling events followed by higher values during wind relaxations. The sub-seasonal variability of the coastal ocean characterized here is important for biogeochemical and productivity studies.

scholarly journals High-frequency variability of CO<sub>2</sub> in Grand Passage, Bay of Fundy, Nova Scotia

2019 ◽  
Vol 16 (2) ◽  
pp. 605-616 ◽  
Author(s):  
Rachel M. Horwitz ◽  
Alex E. Hay ◽  
William J. Burt ◽  
Richard A. Cheel ◽  
Joseph Salisbury ◽  
...  
Keyword(s):  
Nova Scotia ◽  
High Frequency ◽  
Dissolved Inorganic Carbon ◽  
Diel Cycle ◽  
Global Ocean ◽  
Bay Of Fundy ◽  
Mean Flow ◽  
Carbonate System ◽  
Tidal Pumping ◽  
High Frequency Variability

Abstract. Assessing changes in the marine carbon cycle arising from anthropogenic CO2 emissions requires a detailed understanding of the carbonate system's natural variability. Coastal ecosystems vary over short spatial and temporal scales, so their dynamics are not well described by long-term and broad regional averages. A year-long time series of pCO2, temperature, salinity, and currents is used to quantify the high-frequency variability of the carbonate system at the mouth of the Bay of Fundy, Nova Scotia. The seasonal cycle of pCO2 is modulated by a diel cycle that is larger in summer than in winter and a tidal contribution that is primarily M2, with amplitude roughly half that of the diel cycle throughout the year. The interaction between tidal currents and carbonate system variables leads to lateral transport by tidal pumping, which moves alkalinity and dissolved inorganic carbon (DIC) out of the bay, opposite to the mean flow in the region, and constitutes a new feature of how this strongly tidal region connects to the larger Gulf of Maine and northwest Atlantic carbon system. These results suggest that tidal pumping could substantially modulate the coastal ocean's response to global ocean acidification in any region with large tides and spatial variation in biological activity, requiring that high-frequency variability be accounted for in assessments of carbon budgets of coastal regions.

Spatial distribution of copepods in the north of the Humboldt Current region off Chile during coastal upwelling

2000 ◽  
Vol 80 (2) ◽  
pp. 283-290 ◽  
Author(s):  
Ruben Escribano ◽  
Pamela Hidalgo
Keyword(s):  
Coastal Upwelling ◽  
Species Abundance ◽  
Stepwise Multiple Regression ◽  
Turnover Rates ◽  
Austral Spring ◽  
Strong Negative Correlation ◽  
Humboldt Current ◽  
Near Surface ◽  
The North ◽  
Numerical Abundance

During the austral spring (December 1996), numerical abundance of copepod species (Crustacea: Copepoda) was estimated from 53 sampling stations scattered over the coastal waters off Mejillones Peninsula, northern Chile. Samples were obtained from two depth strata; 0-50 m and 50-200 m depth. Oceanographic data over the three-day cruise indicated that coastal upwelling was actively occurring during the survey.A total of 19 species was identified, of which four of them, Paracalanus parvus, Oncaea conifera, Oithona similis and Calanus chilensis, accounted for more than 80% of the whole copepod assemblage in terms of numerical abundance. Using the K-means exploratory analysis the 53 locations were grouped into two clusters: an upwelling type and a non-upwelling type. The former characterized by locations nearshore, with low temperature (<17°C) and high chorophyll-a (>13.4 mg m−3), while the latter had warmer waters (>18°C) and low chlorophyll-a (<4.8 mg m−3). Chlorophyll-a (chl-a), distance to shoreline and temperature at 10 m depth (T10) were all significant variables ( P<0.05) for clustering analysis. There was a strong negative correlation between T10 and chl-a ( P<0.01). The same clustering technique, based on species abundance, suggested the presence of a unique cluster, whose composition was dominated by P. parvus, O. similis, Acartia tonsa and Centropages brachiatus. Stepwise multiple regression showed that these species were also strongly correlated to chl-a and T10. Together these analyses suggest that water mass circulation during upwelling is the driving force for structuring spatial patterns of copepod distribution. In addition, a vertical distribution parameter suggested that copepods, independently of time of the day, tended to remain in a large proportion in near surface waters, possibly constrained by a shallow oxygen minimum layer. This implies that advection during active upwelling may cause large fractions of populations being transported offshore, allowing zooplankton export to more oceanic waters. Rapid turnover rates of copepods growing continuously year-round, may act as a mechanism to compensate population losses during persistent coastal upwelling.

scholarly journals Seasonal Variability of Upwelling off Central-Southern Chile

2019 ◽  
Vol 11 (15) ◽  
pp. 1737 ◽  
Author(s):  
Andre Pinochet ◽  
José Garcés-Vargas ◽  
Carlos Lara ◽  
Francisco Olguín
Keyword(s):  
Seasonal Variability ◽  
Coastal Upwelling ◽  
Current System ◽  
Surface Wind ◽  
Sea Surface ◽  
Southern Chile ◽  
Austral Spring ◽  
Humboldt Current ◽  
Subtropical Anticyclone ◽  
Cross Correlation Analysis

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.

scholarly journals High-frequency variability of CO<sub>2</sub> in Grand Passage, Bay of Fundy, Nova Scotia

2018 ◽  
Author(s):  
Rachel M. Horwitz ◽  
Alex E. Hay ◽  
William Burt ◽  
Richard Cheel ◽  
Joseph Salisbury ◽  
...  
Keyword(s):  
Nova Scotia ◽  
High Frequency ◽  
Gulf Of Maine ◽  
Diel Cycle ◽  
Global Ocean ◽  
Bay Of Fundy ◽  
Mean Flow ◽  
Carbonate System ◽  
Tidal Pumping ◽  
High Frequency Variability

Abstract. Assessing changes in the marine carbon cycle arising from anthropogenic CO2 emissions requires a detailed understanding of the carbonate system's natural variability. Coastal ecosystems vary over short spatial and temporal scales, so their dynamics are not well-described by long-term and broad regional averages. A year-long time series of pCO2, temperature, salinity, and currents is used to quantify the high-frequency variability of the carbonate system at the mouth of the Bay of Fundy, Nova Scotia. The seasonal cycle of pCO2 is modulated by a diel cycle that is larger in summer than in winter, and a tidal contribution that is primarily M2, with amplitude roughly half that of the diel cycle throughout the year. The interaction between tidal currents and carbonate system variables leads to lateral transport by tidal pumping, which moves alkalinity and DIC out of the bay, opposite to the mean flow in the region, and constitutes a new feature of how this strongly tidal region connects to the larger Gulf of Maine and Northwest Atlantic carbon system. These results suggest that tidal pumping could substantially modulate the coastal ocean's response to global ocean acidification in any region with large tides and spatial variation in biological activity, requiring that high-frequency variability be accounted for in assessments of carbon budgets of coastal regions.

scholarly journals Uncovering the Composition and Diversity of Pelagic Copepods in the Oligotrophic Blue Water of the South Pacific Subtropical Gyre

2021 ◽  
Vol 8 ◽  
Author(s):  
Johanna Medellín-Mora ◽  
Rubén Escribano ◽  
Andrea Corredor-Acosta ◽  
Pamela Hidalgo ◽  
Wolfgang Schneider
Keyword(s):  
Coastal Upwelling ◽  
Mesoscale Eddies ◽  
South Pacific ◽  
Subtropical Gyre ◽  
The South ◽  
Austral Spring ◽  
Near Surface ◽  
Shallow Habitat ◽  
Basin Scale ◽  
Pelagic Copepods

The subtropical gyres occupy approximately 40% of the surface of the Earth and are widely recognized as oligotrophic zones. Among them, the South Pacific subtropical gyre (SPSG) shows the lowest chlorophyll-a levels (0.02–0.04 μgL–1), the deepest nutricline (&gt;200 m) and euphotic zone (∼160 m), and the lowest rates of nitrogen fixation. The zooplankton community is poorly known in the SPSG. We report a study focused on the composition and distribution of pelagic copepods within the gyre so as to uncover the diversity and habitat conditions of this special community. Therefore, during the austral spring of 2015, an oceanographic cruise was conducted across the eastern side of the SPSG. Physical and chemical variables were measured in the upper 1000 m, while zooplankton samples were collected by means of vertically stratified hauls using a multiple net sampler for five layers (0–800 m). Satellite data were also used to assess near-surface phytoplankton biomass (Chl-a) and physical-dynamics conditions during the cruise, and 121 species of copepods were identified, which belonged to five taxonomic orders, 24 families, and 50 genera. Calanoida and Cyclopoida were the most frequent orders, containing 57% and 38% of species, respectively, whereas Harpacticoida and Mormonilloida contained 2% of species each, and Siphonostomatoida contained 1% of species. The vertical distribution of copepods revealed an ecological zonation linked to a strongly stratified water column, such that three different vertical habitats were defined: shallow (0–200 m), intermediate (200–400 m), and deep (400–800 m). Both the abundance and diversity of copepods were greater in the shallow habitat and were strongly associated with water temperature, whereas copepods in the subsurface layers subsisted with relatively low oxygen waters (2–3 mL O2 L–1) and presumably originated at the Chilean upwelling zone, being transported offshore by mesoscale eddies. Furthermore, the analysis of species composition revealed a marked dominance of small-sized copepods, which may play a key role in nutrient recycling under an oligotrophic condition, as inferred from their mostly omnivorous feeding behavior. Our findings also suggested a potentially high endemism within the gyre, although basin-scale circulation and mesoscale eddies, traveling from the coastal upwelling zone and transporting plankton, can also influence the epipelagic fauna.

ИССЛЕДОВАНИЯ АКУСТИЧЕСКИХ ХАРАКТЕРИСТИК ВЕРХНЕГО СЛОЯ МОРЯ МЕТОДОМ МНОГОЧАСТОТНОГО АКУСТИЧЕСКОГО ЗОНДИРОВАНИЯ

2020 ◽  
Author(s):  
V.A. Bulanov ◽  
I.V. Korskov ◽  
A.V. Storozhenko ◽  
S.N. Sosedko
Keyword(s):  
High Frequency ◽  
Wave Motion ◽  
High Spatial Resolution ◽  
Wind Waves ◽  
Acoustic Parameter ◽  
Sea Surface ◽  
Near Surface ◽  
Acoustical Properties ◽  
Acoustic Spectroscopy ◽  
Sea Bottom

Описано применение акустического зондирования для исследования акустических характеристик верхнего слоя моря с использованием широкополосных остронаправленных инвертированных излучателей,устанавливаемых на дно. В основу метода положен принцип регистрации обратного рассеяния и отраженияот поверхности моря акустических импульсов с различной частотой, позволяющий одновременно измерятьрассеяние и поглощение звука и нелинейный акустический параметр морской воды. Многочастотное зондирование позволяет реализовать акустическую спектроскопию пузырьков в приповерхностных слоях моря,проводить оценку газосодержания и получать данные о спектре поверхностного волнения при различных состояниях моря вплоть до штормовых. Применение остронаправленных высокочастотных пучков ультразвукапозволяет разделить информацию о планктоне и пузырьках и определить с высоким пространственным разрешением структуру пузырьковых облаков, образующихся при обрушении ветровых волн, и структуру планктонных сообществ. Участие планктона в волновом движении в толще морской воды позволяет определитьпараметры внутренних волн спектр и распределение по амплитудам в различное время.This paper represents the application of acoustic probingfor the investigation of acoustical properties of the upperlayer of the sea using broadband narrow-beam invertedtransducers that are mounted on the sea bottom. Thismethod is based on the principle of the recording of thebackscattering and reflections of acoustic pulses of differentfrequencies from the sea surface. That simultaneouslyallows measuring scattering and absorption of the soundand non-linear acoustic parameter of seawater. Multifrequencyprobing allows performing acoustic spectroscopy ofbubbles in the near-surface layer of the sea, estimating gascontent, and obtaining data on the spectrum of the surfacewaves in various states of the sea up to a storm. Utilizationof the high-frequency narrow ultrasound beams allows us toseparate the information about plankton and bubbles and todetermine the structure of bubble clouds, created during thebreaking of wind waves, along with the structure of planktoncommunities with high spatial resolution. The participationof plankton in the wave motion in the seawater columnallows determining parameters of internal waves, such asspectrum and distribution of amplitudes at different times.

scholarly journals Cyclonic and anticyclonic contributions to atmospheric energetics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Satoru Okajima ◽  
Hisashi Nakamura ◽  
Yohai Kaspi
Keyword(s):  
Storm Track ◽  
Mean Flow ◽  
Weather Variability ◽  
Jet Streams ◽  
Near Surface ◽  
Westerly Jet ◽  
Track Dynamics ◽  
New Findings ◽  
Atmospheric Energetics ◽  
Thermally Driven

AbstractMigratory cyclones and anticyclones account for most of the day-to-day weather variability in the extratropics. These transient eddies act to maintain the midlatitude jet streams by systematically transporting westerly momentum and heat. Yet, little is known about the separate contributions of cyclones and anticyclones to their interaction with the westerlies. Here, using a novel methodology for identifying cyclonic and anticyclonic vortices based on curvature, we quantify their separate contributions to atmospheric energetics and their feedback on the westerly jet streams as represented in Eulerian statistics. We show that climatological westerly acceleration by cyclonic vortices acts to dominantly reinforce the wintertime eddy-driven near-surface westerlies and associated cyclonic shear. Though less baroclinic and energetic, anticyclones still play an important role in transporting westerly momentum toward midlatitudes from the upper-tropospheric thermally driven jet core and carrying eddy energy downstream. These new findings have uncovered essential characteristics of atmospheric energetics, storm track dynamics and eddy-mean flow interaction.

scholarly journals Cardiorespiratory Fitness: Reference on the Six-Minute Walk Test and Oxygen Consumption in Adolescents from South-Central Chile

2021 ◽  
Vol 18 (5) ◽  
pp. 2474
Author(s):  
Jaime Vásquez-Gómez ◽  
Nelson Gatica Salas ◽  
Pedro Jiménez Villarroel ◽  
Luis Rojas-Araya ◽  
Cesar Faundez-Casanova ◽  
...  
Keyword(s):  
Cardiorespiratory Fitness ◽  
Reference Values ◽  
Estimation Error ◽  
Walk Test ◽  
Central Chile ◽  
Six Minute Walk Test ◽  
Body Adiposity ◽  
South Central ◽  
Males And Females ◽  
Minute Walk

Cardiorespiratory fitness (CRF) provides oxygen to the exercising muscles and is related to body adiposity, with cardiometabolic variables. The aim was to develop reference values and a predictive model of CRF in Chilean adolescents. A total of 741 adolescents of both genders (15.7 years old) participated in a basic anthropometry, performance in the six-minute walk test (SMWT), and in Course Navette was measured. Percentiles were determined for the SMWT, for the V̇O2max, and an equation was developed to estimate it. The validity of the equation was checked using distribution assumptions and the Bland–Altman diagram. The STATA v.14 program was used (p < 0.05). The 50th percentile values for males and females in the SMWT and in the V̇O2max of Course Navette were, respectively, from 607 to 690 and from 630 to 641 m, and from 43.9 to 45 and from 37.5 to 31.5 mlO2·kg·min−1, for the range of 13 to 17 years. For its part, the model to predict V̇O2max incorporated gender, heart rate, height, waist-to-height ratio (WHR), and distance in the SMWT (R2 = 0.62; estimation error = 0.38 LO2·min−1; p <0.001). Reference values can guide physical fitness in Chilean adolescents, and V̇O2max was possible to predict from morphofunctional variables.

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