scholarly journals Seasonal Variability of SST Fronts in the Inner Sea of Chiloé and Its Adjacent Coastal Ocean, Northern Patagonia

2021 ◽  
Vol 13 (2) ◽  
pp. 181
Author(s):  
Gonzalo S. Saldías ◽  
Wilber Hernández ◽  
Carlos Lara ◽  
Richard Muñoz ◽  
Cristian Rojas ◽  
...  
Keyword(s):  
Coastal Upwelling ◽  
Environmental Variability ◽  
Function Analysis ◽  
Coastal Ocean ◽  
Dominant Mode ◽  
Early Summer ◽  
High Biological Activity ◽  
Northern Patagonia ◽  
Sst Gradient ◽  
Sst Fronts

Surface oceanic fronts are regions characterized by high biological activity. Here, Sea Surface Temperature (SST) fronts are analyzed for the period 2003–2019 using the Multi-scale Ultra-high Resolution (MUR) SST product in northern Patagonia, a coastal region with high environmental variability through river discharges and coastal upwelling events. SST gradient magnitudes were maximum off Chiloé Island in summer and fall, coherent with the highest frontal probability in the coastal oceanic area, which would correspond to the formation of a coastal upwelling front in the meridional direction. Increased gradient magnitudes in the Inner Sea of Chiloé (ISC) were found primarily in spring and summer. The frontal probability analysis revealed the highest occurrences were confined to the northern area (north of Desertores Islands) and around the southern border of Boca del Guafo. An Empirical Orthogonal Function analysis was performed to clarify the dominant modes of variability in SST gradient magnitudes. The meridional coastal fronts explained the dominant mode (78% of the variance) off Chiloé Island, which dominates in summer, whereas the SST fronts inside the ISC (second mode; 15.8%) were found to dominate in spring and early summer (October–January). Future efforts are suggested focusing on high frontal probability areas to study the vertical structure and variability of the coastal fronts in the ISC and its adjacent coastal ocean.

scholarly journals Volume and Nutrient Transports Disturbed by the Typhoon Chebi (2013) in the Upwelling Zone East of Hainan Island, China

2021 ◽  
Vol 9 (3) ◽  
pp. 324
Author(s):  
Manli Zheng ◽  
Lingling Xie ◽  
Quanan Zheng ◽  
Mingming Li ◽  
Fajin Chen ◽  
...  
Keyword(s):  
South China Sea ◽  
Coastal Upwelling ◽  
Unit Area ◽  
Hainan Island ◽  
Volume Transport ◽  
Coastal Ocean ◽  
Offshore Water ◽  
Nutrient Distribution ◽  
Before And After ◽  
Ekman Flow

Using cruise observations before and after the typhoon Chebi in August 2013 and those without the typhoon in July 2012, this study investigates variations in current structure, nutrient distribution, and transports disturbed by a typhoon in a typical coastal upwelling zone east of Hainan Island in the northwestern South China Sea. The results show that along-shore northeastward flow dominates the coastal ocean with a volume transport of 0.64 × 106 m3/s in the case without the typhoon. The flow reversed southwestward, with its volume transport halved before the typhoon passage. After the typhoon passage, the flow returned back northeastward except the upper layer in waters deeper than 50 m and the total volume transport decreased to 0.10 × 106 m3/s. For the cross-shelf component, the flow kept shoreward, while transports crossing the 50 m isobath decreased from 0.25, 0.12 to 0.06 × 106 m3/s in the case without the typhoon as well as before and after typhoon passage, respectively. For the along-shore/cross-shelf nutrient transports, SiO32− has the largest value of 866.13/632.74 μmol/s per unit area, NO3− half of that, and PO43− and NO2− one order smaller in the offshore water without the typhoon. The values dramatically decreased to about one-third for SiO32−, NO3−, and PO43− after the typhoon, but changed little for NO2−. The disturbed wind field and associated Ekman flow and upwelling process may explain the variations in the current and nutrient transports after the typhoon.

scholarly journals Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)

2017 ◽  
Vol 14 (5) ◽  
pp. 1165-1179 ◽  
Author(s):  
Diana Zúñiga ◽  
Celia Santos ◽  
María Froján ◽  
Emilia Salgueiro ◽  
Marta M. Rufino ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediment ◽  
Sediment Trap ◽  
Coastal Upwelling ◽  
Late Summer ◽  
Early Summer ◽  
Marine Diatom ◽  
Photic Zone ◽  
Upwelling System ◽  
Water Column Stratification

Abstract. The objective of the current work is to improve our understanding of how water column diatom's abundance and assemblage composition is seasonally transferred from the photic zone to seafloor sediments. To address this, we used a dataset derived from water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system. Diatom fluxes (2.2 (±5.6) 106 valves m−2 d−1) represented the majority of the siliceous microorganisms sinking out from the photic zone during all studied years and showed seasonal variability. Contrasting results between water column and sediment trap diatom abundances were found during downwelling periods, as shown by the unexpectedly high diatom export signals when diatom-derived primary production achieved their minimum levels. They were principally related to surface sediment remobilization and intense Minho and Douro river discharge that constitute an additional source of particulate matter to the inner continental shelf. In fact, contributions of allochthonous particles to the sinking material were confirmed by the significant increase of both benthic and freshwater diatoms in the sediment trap assemblage. In contrast, we found that most of the living diatom species blooming during highly productive upwelling periods were dissolved during sinking, and only those resistant to dissolution and the Chaetoceros and Leptocylindrus spp. resting spores were susceptible to being exported and buried. Furthermore, Chaetoceros spp. dominate during spring–early summer, when persistent northerly winds lead to the upwelling of nutrient-rich waters on the shelf, while Leptocylindrus spp. appear associated with late-summer upwelling relaxation, characterized by water column stratification and nutrient depletion. These findings evidence that the contributions of these diatom genera to the sediment's total marine diatom assemblage should allow for the reconstruction of different past upwelling regimes.

Reproductive cycle of purple clam, Amiantis purpurata (Bivalvia: Veneridae) in northern Patagonia (Argentina)

2005 ◽  
Vol 85 (2) ◽  
pp. 367-373 ◽  
Author(s):  
Enrique M. Morsan ◽  
Marina A. Kroeck
Keyword(s):  
Reproductive Cycle ◽  
Continuous Process ◽  
Early Summer ◽  
Maturation Stage ◽  
Reproductive Pattern ◽  
Oocyte Diameter ◽  
Histological Techniques ◽  
Northern Patagonia ◽  
History Of ◽  
Quantitative Indicators

The reproductive cycle of the purple clam (Amiantis purpurata) northern Patagonian population was studied throughout a 19-month period (September 1993–March 1995) using standard histological techniques and quantitative indicators (oocyte diameter distributions, oocytes per ocular field and relative oocyte area). In this species gametogenesis is a continuous process involving a complete gonadal restitution after the end of the reproductive season (no resting period). The proliferation phase occurs during the coldest half of the year (April to September) and maturation takes place during spring (September to December). Several partial emissions of gametes, with subsequent restitution of the gametogenic series, occur during the summer months. During the total maturation stage, oocytes never filled the whole alveolar area: maximum per cent of alveolar sections occupied by oocytes (46%) was observed in late spring–early summer. Implications of the reproductive pattern in the context of palaeogeographic history of northern Patagonia, and the isolation of this population are discussed.

Environment: the key to understanding the South African chokka squid (Loligo vulgaris reynaudii) life cycle and fishery?

1994 ◽  
Vol 6 (2) ◽  
pp. 249-258 ◽  
Author(s):  
M.J. Roberts ◽  
W.H.H. Sauer
Keyword(s):  
Life Cycle ◽  
Coastal Upwelling ◽  
Environmental Variability ◽  
Southern Oscillation ◽  
The South ◽  
Enso Events ◽  
Loligo Vulgaris ◽  
Large Fluctuations ◽  
High Turbidity ◽  
Physical And Chemical

This paper explores effects of environmental variability on the life cycle of the chokka squid, Loligo vulgaris reynaudii in South Africa, particularly the effect of physical and chemical influences on adult distribution, and the availability of spawning aggregations to the local jig fishery. The following hypotheses are presented: 1) temperature, dissolved oxygen and currents have a direct effect on the demersal distribution of adult chokka on the feeding grounds, but this is restricted to the west coast where environmental conditions are more extreme relative to the south coast, 2) chokka catches increase in proportion to the extent of coastal upwelling, 3) spawning behavior along the inshore regions (<50m) is strongly influenced by turbidity near the seabed. High turbidity forces the spawning popuation to lay their eggs in deeper waters, and are thus not available to the jig fishery. 4) El Niño – Southern Oscillation (ENSO) events are linked with large fluctuations in the availability of spawning squid aggregations to the inshore jig fishery.

The Influence of an SST Front on a Heavy Rainfall Event over Coastal Taiwan during TiMREX

2014 ◽  
Vol 71 (9) ◽  
pp. 3223-3249 ◽  
Author(s):  
Michael D. Toy ◽  
Richard H. Johnson
Keyword(s):  
Northern South China Sea ◽  
Wrf Model ◽  
Early Summer ◽  
Rainfall Event ◽  
Precipitation Event ◽  
Heavy Rainfall Event ◽  
Low Level ◽  
Sst Front ◽  
Southwest Coast ◽  
Sst Gradient

Abstract A long-lived heavy precipitation area was observed along the southwest coast of Taiwan from 13 to 18 June 2008 during the Terrain-Influenced Monsoon Rainfall Experiment (TiMREX). Rainfall amounts exceeded 500 mm along portions of the coast, and the coastal plains experienced severe flooding. The precipitation systems were influenced by blocking effects, as the southerly moist monsoon flow impinged on the island. A relatively strong gradient in the sea surface temperature (SST) off the southwest coast of Taiwan existed during the rainfall event. Mesoscale SST fronts are known to influence the planetary boundary layer (PBL) such that low-level convergence and precipitation are enhanced under certain circumstances. In this study, the authors investigate the role of the SST front in enhancing the 13–18 June 2008 precipitation event over Taiwan using the Weather Research and Forecasting (WRF) Model. In control simulations with the observed SST, there is a transition from a well-mixed to a stable PBL across the front, causing the low-level flow to decelerate, resulting in an enhancement of horizontal convergence. Such a transition in the PBL and the associated convergence is greatly reduced in smoothed SST gradient model simulations, which produce over 20% less precipitation over southwest Taiwan. Sensitivity tests show that, qualitatively, the results are independent of the existence of the island of Taiwan. These findings indicate that the SST gradient over the northern South China Sea during the early summer monsoon can have a significant impact on the intensity of rainfall over Taiwan.

Wind-induced upwelling along the west coast of North America, 1899–1988

1995 ◽  
Vol 52 (2) ◽  
pp. 325-334 ◽  
Author(s):  
William W. Hsieh ◽  
Daniel M. Ware ◽  
Richard E. Thomson
Keyword(s):  
British Columbia ◽  
Baja California ◽  
Coastal Upwelling ◽  
Function Analysis ◽  
Geostrophic Wind ◽  
Second Mode ◽  
Coastal Sea ◽  
Coastal Downwelling ◽  
Alongshore Wind Stress ◽  
Alongshore Wind

Alongshore geostrophic wind stresses (AWS) were used as an "index" of wind-induced coastal upwelling/downwelling for eight coastal stations from Baja California to Alaska for 1899–1988. For winters since around 1940, downwelling has intensified along Alaska and northern British Columbia, while upwelling has increased along Baja California. El Niño events induced strong winter coastal downwelling poleward of 40°N. During summer, upwelling has increased since around 1940 along southern British Columbia to Baja California, while from 1899 to 1940, upwelling declined along southern California to Baja California. Empirical orthogonal function analysis of the AWS showed that the first mode consisted of the AWS at the eight stations all varying in-phase, while the second mode had the northern four stations out-of-phase with the southern four stations. Off southern British Columbia, correlations between coastal sea level and AWS and between sea surface temperature and AWS were both strong during winter but insignificant during summer. In contrast, correlation between salinity and alongshore wind stress was insignificant during fall and winter, but strong during spring and moderate during summer. Summer AWS was positively correlated with both the fatness of sardine and the condition factor of herring off British Columbia.

scholarly journals Modulation of hydroxyl variability by ENSO in the absence of external forcing

2018 ◽  
Vol 115 (36) ◽  
pp. 8931-8936 ◽  
Author(s):  
Alexander J. Turner ◽  
Inez Fung ◽  
Vaishali Naik ◽  
Larry W. Horowitz ◽  
Ronald C. Cohen
Keyword(s):  
Climate Model ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Oxidative Capacity ◽  
Dominant Mode ◽  
External Forcing ◽  
External Forcings ◽  
Methane Budget ◽  
Interannual Fluctuations ◽  
The Impact

The hydroxyl radical (OH) is the primary oxidant in the troposphere, and the impact of its fluctuations on the methane budget has been disputed in recent years, however measurements of OH are insufficient to characterize global interannual fluctuations relevant for methane. Here, we use a 6,000-y control simulation of preindustrial conditions with a chemistry-climate model to quantify the natural variability in OH and internal feedbacks governing that variability. We find that, even in the absence of external forcing, maximum OH changes are 3.8 ± 0.8% over a decade, which is large in the context of the recent methane growth from 2007–2017. We show that the OH variability is not a white-noise process. A wavelet analysis indicates that OH variability exhibits significant feedbacks with the same periodicity as the El Niño–Southern Oscillation (ENSO). We find intrinsically generated modulation of the OH variability, suggesting that OH may show periods of rapid or no change in future decades that are solely due to the internal climate dynamics (as opposed to external forcings). An empirical orthogonal function analysis further indicates that ENSO is the dominant mode of OH variability, with the modulation of OH occurring primarily through lightningNOx. La Niña is associated with an increase in convection in the Tropical Pacific, which increases the simulated occurrence of lightning and allows for more OH production. Understanding this link between OH and ENSO may improve the predictability of the oxidative capacity of the troposphere and assist in elucidating the causes of current and historical trends in methane.

Physiological responses of juvenile Chilean scallops (Argopecten purpuratus) to isolated and combined environmental drivers of coastal upwelling

2019 ◽  
Vol 76 (6) ◽  
pp. 1836-1849 ◽  
Author(s):  
Laura Ramajo ◽  
Carolina Fernández ◽  
Yolanda Núñez ◽  
Paz Caballero ◽  
Marco A Lardies ◽  
...  
Keyword(s):  
Coastal Upwelling ◽  
Environmental Variability ◽  
Physiological Responses ◽  
Environmental Drivers ◽  
Hypoxic Conditions ◽  
Argopecten Purpuratus ◽  
Physiological Adaptations ◽  
Metabolic Performance ◽  
Increasing Temperature ◽  
The Impact

Abstract Coastal biota is exposed to continuous environmental variability as a consequence of natural and anthropogenic processes. Responding to heterogeneous conditions requires the presence of physiological strategies to cope with the environment. Ecosystems influenced by upwelling endure naturally cold, acidic and hypoxic conditions, nevertheless they sustain major fisheries worldwide. This suggests that species inhabiting upwelling habitats possess physiological adaptations to handle high environmental variability. Here, we assessed the impact of the main upwelling drivers (temperature, pH and oxygen) in isolation and combined on eco-physiological responses of Chilean scallop Argopecten purpuratus. A. purpuratus responded to hypoxia by increasing their metabolic performance to maintain growth and calcification. Calcification was only affected by pH and increased under acidic conditions. Further, A. purpuratus juveniles prioritized calcification at the expense of growth under upwelling conditions. Increasing temperature had a significant impact by enhancing the physiological performance of A. purpuratus juveniles independently of oxygen and pH conditions, but this was associated with earlier and higher mortalities. Our results suggest that A. purpuratus is acclimated to short-term colder, acidic and hypoxic conditions, and provide important information of how this species responds to the heterogeneous environment of upwelling, which is significantly relevant in the climatic context of upwelling intensification.

Growth of Juvenile Coho Salmon (Oncorhynchus kisutch) off Oregon and Washington, USA, in Years of Differing Coastal Upwelling

1988 ◽  
Vol 45 (6) ◽  
pp. 1036-1044 ◽  
Author(s):  
J. P. Fisher ◽  
W. G. Pearcy
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Coastal Upwelling ◽  
Coho Salmon ◽  
Slow Growth ◽  
Oncorhynchus Kisutch ◽  
Early Summer ◽  
Alternative Prey ◽  
Stomach Fullness ◽  
Poor Condition

Estimated growth rates, condition, and stomach fullness of juvenile coho salmon (Oncorhynchus kisutch) caught in the ocean in early summer, when mortality was most variable, were as high in 1983 and 1984, years of very low survival and low early upwelling, as in 1981, 1982, and 1985, years of higher survival and higher early upwelling. Chronic food shortage leading to starvation, poor condition, or slow growth apparently was not the cause of the increased mortality of juvenile coho salmon in 1983 and 1984. Survival of juvenile coho salmon was positively correlated with purse seine catches of fish in June and with early summer upwelling, 1981–85. Hence, year-class success probably was determined early in the summer, soon after most juvenile coho salmon entered the ocean. Spacing of the first five ocean circuli, which was positively correlated with growth rate, was not significantly different for fish caught early in the summer and those caught late in the summer, suggesting that growth rate selective mortality in the ocean was not strong. The increase in mortality in 1983 and 1984 may have been caused by increased predation on juvenile coho salmon due to decreased numbers of alternative prey for predators.

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