scholarly journals Spatial distribution of Calanus chilensis off Mejillones Peninsula (northern Chile): ecological consequences upon coastal upwelling

2002 ◽  
Vol 230 ◽  
pp. 225-234 ◽  
Author(s):  
A Giraldo ◽  
R Escribano ◽  
V Marin
Keyword(s):  
Spatial Distribution ◽  
Coastal Upwelling ◽  
Northern Chile ◽  
Ecological Consequences

scholarly journals Controlling factors of the OMZ in the Arabian Sea

2012 ◽  
Vol 9 (5) ◽  
pp. 5509-5550
Author(s):  
L. Resplandy ◽  
M. Lévy ◽  
L. Bopp ◽  
V. Echevin ◽  
S. Pous ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Oxygen Concentration ◽  
Seasonal Cycle ◽  
Arabian Sea ◽  
Coastal Upwelling ◽  
Western Boundary ◽  
Ekman Pumping ◽  
Low Oxygen ◽  
Boundary Current ◽  
Ocean Dynamic

Abstract. In-situ observations indicate that the Arabian Sea oxygen minimum zone (OMZ) is only weakly influenced by the strong seasonal cycle of ocean dynamic and biogeochemistry forced by the asian monsoon system and it is spatially decorrelated from the coastal upwelling systems where the biological production is the strongest. In this study we examine the factors controlling the seasonality and the spatial distribution of the OMZ in the Arabian Sea using a coupled bio-physical model. We find that the oxygen concentration in the OMZ displays a seasonal cycle with an amplitude of 5–15 % of the annual mean oxygen concentration. The OMZ is ventilated by lateral ventilation along the western boundary current and in the coastal undercurrent along India during the summer monsoon and by coastal downwelling and negative Ekman pumping during the fall intermonsoon and winter monsoon. This ventilation is counterbalanced by strong coastal upwelling and positive Ekman pumping of low oxygen waters at the base of the OMZ during the spring intermonsoon. Although the factors controlling the OMZ seasonality are associated with the men circulation, we find that mesoscale dynamics modulates them by limiting the vertical ventilation during winter and enhancing it through lateral advection during the rest of the year. Processes explaining the establishment and spatial distribution of the OMZ were quantified using a perturbation experiment initialised with no OMZ. As expected, the oxygen depletion is triggered by strong biological activity in central Arabian Sea during winter and in western and eastern boundary coastal upwelling systems during summer. We find that the 3-D ocean dynamic largely controls the spatial distribution of the OMZ. The eastward shift ensues from the northward lateral transport of ventilated waters along the western and eastern coasts and the advection offshore of low oxygen waters formed in the upwelling system.

scholarly journals Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (∼  30° S) based on a high-resolution atmospheric regional model (WRF)

Ocean Science ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1049-1065 ◽  
Author(s):  
Luis Bravo ◽  
Marcel Ramos ◽  
Orlando Astudillo ◽  
Boris Dewitte ◽  
Katerina Goubanova
Keyword(s):  
High Resolution ◽  
Wind Stress ◽  
Seasonal Variability ◽  
Coastal Upwelling ◽  
Ekman Transport ◽  
Northern Chile ◽  
Ekman Pumping ◽  
Relative Contribution ◽  
Alongshore Wind Stress ◽  
Alongshore Wind

Abstract. Two physical mechanisms can contribute to coastal upwelling in eastern boundary current systems: offshore Ekman transport due to the predominant alongshore wind stress and Ekman pumping due to the cyclonic wind stress curl, mainly caused by the abrupt decrease in wind stress (drop-off) in a cross-shore band of 100 km. This wind drop-off is thought to be an ubiquitous feature in coastal upwelling systems and to regulate the relative contribution of both mechanisms. It has been poorly studied along the central-northern Chile region because of the lack in wind measurements along the shoreline and of the relatively low resolution of the available atmospheric reanalysis. Here, the seasonal variability in Ekman transport, Ekman pumping and their relative contribution to total upwelling along the central-northern Chile region (∼  30° S) is evaluated from a high-resolution atmospheric model simulation. As a first step, the simulation is validated from satellite observations, which indicates a realistic representation of the spatial and temporal variability of the wind along the coast by the model. The model outputs are then used to document the fine-scale structures in the wind stress and wind curl in relation to the topographic features along the coast (headlands and embayments). Both wind stress and wind curl had a clear seasonal variability with annual and semiannual components. Alongshore wind stress maximum peak occurred in spring, second increase was in fall and minimum in winter. When a threshold of −3  ×  10−5 s−1 for the across-shore gradient of alongshore wind was considered to define the region from which the winds decrease toward the coast, the wind drop-off length scale varied between 8 and 45 km. The relative contribution of the coastal divergence and Ekman pumping to the vertical transport along the coast, considering the estimated wind drop-off length, indicated meridional alternation between both mechanisms, modulated by orography and the intricate coastline. Roughly, coastal divergence predominated in areas with low orography and headlands. Ekman pumping was higher in regions with high orography and the presence of embayments along the coast. In the study region, the vertical transport induced by coastal divergence and Ekman pumping represented 60 and 40 % of the total upwelling transport, respectively. The potential role of Ekman pumping on the spatial structure of sea surface temperature is also discussed.

scholarly journals A Comparison of Marine and Terrestrial Radiocarbon Ages from Northern Chile

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 389-393 ◽  
Author(s):  
John R. Southon ◽  
Amy Oakland Rodman ◽  
Delbert True
Keyword(s):  
20Th Century ◽  
Coastal Upwelling ◽  
Early 20Th Century ◽  
Northern Chile ◽  
Radiocarbon Dates ◽  
Archaeological Artifacts

The calibration of radiocarbon dates on marine materials involves a global marine calibration with regional corrections. Data from well-associated marine and terrestrial materials in archaeological artifacts from northern Chile indicated that the calibration is valid for the period ad 200–900 and suggest that coastal upwelling intensities during that period were similar to those of the early 20th century.

Chlorophyll-a distribution and mesoscale physical processes in upwelling and adjacent oceanic zones off northern Chile (summer–autumn 1994)

2001 ◽  
Vol 81 (2) ◽  
pp. 193-206 ◽  
Author(s):  
Carmen E. Morales ◽  
José L. Blanco ◽  
Mauricio Braun ◽  
Nelson Silva
Keyword(s):  
Coastal Upwelling ◽  
Current System ◽  
Austral Summer ◽  
Nutrient Concentrations ◽  
Northern Chile ◽  
Humboldt Current ◽  
Oxygen Conditions ◽  
Salinity Water ◽  
Humboldt Current System ◽  
Seasonal Signal

Chlorophyll-a (chl-a) distribution and associated physical (temperature, salinity) and chemical (dissolved oxygen) conditions off northern Chile (Humboldt Current System), during the austral summer (February–March) and autumn (May) of 1994, were studied in the region bounded by ∼18–24°S and 70–72°W (out to ∼200 km from the coast; 0–100 m depth); within this region, nutrients were measured in an area of persistent coastal upwelling (∼19–22°S, out to 80 km from the coast). Temperature and salinity distributions, as well as nutrient concentrations, indicated the occurrence of active upwelling during both cruises. Also, and together with maps of geopotential anomaly (0/200 dbar) and depth of the thermocline (15°C isotherm), their distribution suggested the presence of a mainly equatorward flow, anticyclonic eddy-like structures, and intrusions of warm (>19°C), high salinity (>35·0 psu), subtropical water towards the coast. A tongue of cooler and lower salinity water, and of lower flow fields, extended from the coast towards the offshore zone during both sampling periods, in association with higher chl-a concentrations (>1 mg m−3, >20 mg m−2 between 0 and 25 m depth) and predominance of net-phytoplankton (>20 μm). The comparison of these results with those for the winter and spring of 1993 in the same area suggest a relatively weak seasonal signal in chl-a concentration during the 1993–1994 period, with higher water column concentrations during the summer and spring periods in the selected upwelling area, though surface chl-a concentrations for the whole of the area did not vary significantly.

Marine radiocarbon reservoir effect along the northern Chile–southern Peru coast (14–24°S) throughout the Holocene

2011 ◽  
Vol 75 (1) ◽  
pp. 91-103 ◽  
Author(s):  
Luc Ortlieb ◽  
Gabriel Vargas ◽  
Jean-François Saliège
Keyword(s):  
Coastal Upwelling ◽  
Major Influence ◽  
Northern Chile ◽  
Subtropical Anticyclone ◽  
Reservoir Effect ◽  
Subtropical Water ◽  
The Holocene ◽  
Southern Peru ◽  
Subsurface Waters ◽  
Terrestrial Material

AbstractThrough an extensive sampling and dating of pairs of associated shells and charcoal fragments combined with reanalysis of all the available previous data, we reconstruct the evolution throughout the Holocene of the regional marine radiocarbon reservoir effect (ΔR) values along the northern Chile–southern Peru area (14°–24°S). After elimination of the cases in which the terrestrial component yielded older ages than the marine shells to which they were associated, the study is based upon data from 47 pairs of associated marine and terrestrial material.Our results suggest major changes in both the magnitude and variability range of ΔR during the whole Holocene Period: (1) between 10,400 and 6840 cal yr BP, high values (511 ± 278 yr) probably result from a strengthened SE Pacific subtropical anticyclone and shoaling of equatorial subsurface waters during intensified upwelling events; (2) between 5180 and 1160 cal yr BP, lower values (226 ± 98 yr) may reflect a major influence of subtropical water and diminished coastal upwelling processes; (3) during the last ~ thousand years, high values (between 355 ± 105 and 253 ± 207 yr) indicate an increased influence of 14C-depleted water masses and of ENSO. For the early twentieth century a ΔR value of 253 ± 207 yr was calculated.

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