scholarly journals Climate Variability of the Northern Argentinean Shelf Circulation: Impact on Engraulis Anchoita

2021 ◽  
Author(s):  
Guillermo Auad ◽  
Patricia Martos
Keyword(s):  
Climatic Variability ◽  
Surface Velocity ◽  
Spatial And Temporal Variability ◽  
Shelf Area ◽  
Local Circulation ◽  
Coupled Modes ◽  
Climatic Fluctuations ◽  
Shelf Circulation ◽  
Biological Variables ◽  
Argentinean Shelf

A high-resolution ocean model and hydrographic observations are used to characterize the shelf circulation of the northern Argentinean shelf during the study period (1993–2008) and ultimately to explore possible linkages among atmospheric, oceanic, and biological climatic variability. Abundance of larvae and eggs of the local anchovy species, Engraulis anchoita, exhibit a spatial and temporal variability similar to those stocks found in other parts of the world and that we interpret in the context of the particularities of the local circulation and hydrography. Two (statistically) coupled modes of wind stress-surface velocity are described and interpreted in terms of historical and new information. A complex picture emerges in which the intensity of both a thermal shelf front, the alongshore flow, and larvae abundance would be connected and forced by local wind stresses. For all areas examined on the shelf, the larvae/egg abundance would not be very sensitive to short-lived climatic fluctuations (e.g., year-to-year) but they would be indeed to regime shifts. The shallow shelf area bounded by the 39°S and 41°S parallels would expose a clearer linkage between physical and biological variables than that north of 39°S. We attribute this fact to the particular physical conditions found in the southernmost area, which would favor an increased habitat quality for Engraulis anchoita.

scholarly journals Climate Variability of the Northern Argentinean Shelf Circulation: Impact on Engraulis Anchoita

2012 ◽  
Vol 3 (1) ◽  
pp. 17-43 ◽  
Author(s):  
Guillermo Auad ◽  
Patricia Martos
Keyword(s):  
Climatic Variability ◽  
Surface Velocity ◽  
Spatial And Temporal Variability ◽  
Shelf Area ◽  
Local Circulation ◽  
Coupled Modes ◽  
Climatic Fluctuations ◽  
Shelf Circulation ◽  
Biological Variables ◽  
Argentinean Shelf

A high-resolution ocean model and hydrographic observations are used to characterize the shelf circulation of the northern Argentinean shelf during the study period (1993–2008) and ultimately to explore possible linkages among atmospheric, oceanic, and biological climatic variability. Abundance of larvae and eggs of the local anchovy species, Engraulis anchoita, exhibit a spatial and temporal variability similar to those stocks found in other parts of the world and that we interpret in the context of the particularities of the local circulation and hydrography. Two (statistically) coupled modes of wind stress-surface velocity are described and interpreted in terms of historical and new information. A complex picture emerges in which the intensity of both a thermal shelf front, the alongshore flow, and larvae abundance would be connected and forced by local wind stresses. For all areas examined on the shelf, the larvae/egg abundance would not be very sensitive to short-lived climatic fluctuations (e.g., year-to-year) but they would be indeed to regime shifts. The shallow shelf area bounded by the 39°S and 41°S parallels would expose a clearer linkage between physical and biological variables than that north of 39°S. We attribute this fact to the particular physical conditions found in the southernmost area, which would favor an increased habitat quality for Engraulis anchoita.

scholarly journals Demographic effects of interacting species: exploring stable coexistence under increased climatic variability in a semiarid shrub community

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ana I. García-Cervigón ◽  
Pedro F. Quintana-Ascencio ◽  
Adrián Escudero ◽  
Merari E. Ferrer-Cervantes ◽  
Ana M. Sánchez ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Species Coexistence ◽  
Climatic Factors ◽  
Demographic Data ◽  
Climatic Variability ◽  
Biotic Interactions ◽  
Vital Rates ◽  
Climatic Fluctuations ◽  
Demographic Models ◽  
Shrub Community

AbstractPopulation persistence is strongly determined by climatic variability. Changes in the patterns of climatic events linked to global warming may alter population dynamics, but their effects may be strongly modulated by biotic interactions. Plant populations interact with each other in such a way that responses to climate of a single population may impact the dynamics of the whole community. In this study, we assess how climate variability affects persistence and coexistence of two dominant plant species in a semiarid shrub community on gypsum soils. We use 9 years of demographic data to parameterize demographic models and to simulate population dynamics under different climatic and ecological scenarios. We observe that populations of both coexisting species may respond to common climatic fluctuations both similarly and in idiosyncratic ways, depending on the yearly combination of climatic factors. Biotic interactions (both within and among species) modulate some of their vital rates, but their effects on population dynamics highly depend on climatic fluctuations. Our results indicate that increased levels of climatic variability may alter interspecific relationships. These alterations might potentially affect species coexistence, disrupting competitive hierarchies and ultimately leading to abrupt changes in community composition.

scholarly journals Nutrient water quality of the Wye catchment, UK: exploring patterns and fluxes using the Environment Agency data archives

2003 ◽  
Vol 7 (5) ◽  
pp. 722-743 ◽  
Author(s):  
H. P. Jarvie ◽  
C. Neal ◽  
P. J. A. Withers ◽  
A. Robinson ◽  
N. Salter
Keyword(s):  
Water Quality ◽  
Sewage Treatment ◽  
Quality Data ◽  
Agricultural Activity ◽  
Spatial And Temporal Variability ◽  
Water Quality Data ◽  
Climatic Fluctuations ◽  
Mass Load ◽  
Environment Agency

Abstract. Water quality data, collected by the Environment Agency in England and Wales over 10 years (1991 – 2000) were used to examine the spatial distribution of nutrient pollution risk and for assessing broad-scale spatial and temporal variability in nutrient fluxes across the Wye catchment. Nutrient water quality across the upper and middle Wye catchment, and along the main River Wye, is generally very good. However, the main areas of concern lie in the small tributaries in the south and east of the catchment, which have lower dilution capacity and high agricultural and effluent inputs, and where mean Total Reactive Phosphorus (TRP) in some cases exceed 1 mg-P l-1. Indeed, mass load calculations have demonstrated that the lowland south and east portion of the catchment contributes more than 85% of the whole-catchment TRP and more than 78% of nitrate (NO3‾) loads. Ratios of NO3‾:Ca were used to fingerprint different water-types across the catchment, linked to weathering and agricultural activity. The Wye catchment has been subject to two major sets of perturbations during the study period: (i) climatic fluctuations, with a drought during 1995-6, followed by a subsequent drought-break in 1997/8, and extreme high river flows in the autumn/winter of 2000/2001, and (ii) introduction of tertiary P-treatment at major sewage treatment works in the catchment. The implications of these perturbations for the nutrient water quality of the Wye catchment are discussed. Recommendations are made for more targeted monitoring to directly assess diffuse source nutrient contributions. Keywords: nutrients, phosphate, phosphorus, nitrate, nitrogen, river, Wye, PSYCHIC, Defra

scholarly journals Testing Farmers’ Perception of Climate Variability: A Case Study from Kirtipur of Kathmandu Valley

2012 ◽  
pp. 30-34
Author(s):  
Jiban Mani Poudel
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Global Climate ◽  
Climatic Variability ◽  
Global Perspective ◽  
Kathmandu Valley ◽  
Climatic Fluctuations ◽  
Climate Fluctuations ◽  
Global And Local

In the 21st century, global climate change has become a public and political discourse. However, there is still a wide gap between global and local perspectives. The global perspective focuses on climate fluctuations that affect the larger region; and their analysis is based on long-term records over centuries and millennium. By comparison, local peoples’ perspectives vary locally, and local analyses are limited to a few days, years, decades and generations only. This paper examines how farmers in Kirtipur of Kathmandu Valley, Nepal, understand climate variability in their surroundings. The researcher has used a cognized model to understand farmers’ perception on weather fluctuations and climate change. The researcher has documented several eyewitness accounts of farmers about weather fluctuations which they have been observing in a lifetime. The researcher has also used rainfall data from 1970-2009 to test the accuracy of perceptions. Unlike meteorological analyses, farmers recall and their understanding of climatic variability by weather-crop interaction, and events associating with climatic fluctuations and perceptions are shaped by both physical visibility and cultural frame or belief system.DOI: http://dx.doi.org/10.3126/hn.v11i1.7200 Hydro Nepal Special Issue: Conference Proceedings 2012 pp.30-34

scholarly journals Marine late Saalian to Eemian environments and climatic variability in the Danish shelf area

2000 ◽  
Vol 79 (2-3) ◽  
pp. 335-343 ◽  
Author(s):  
Marit-Solveig Seidenkrantz ◽  
Karen Luise Knudsen ◽  
Peter Kristensen
Keyword(s):  
Climate Variability ◽  
Shallow Water ◽  
Oxygen Isotope ◽  
Deep Water ◽  
Climatic Variability ◽  
Shelf Area ◽  
North East ◽  
The North ◽  
Mis 5E

AbstractThe marine Eemian (marine oxygen-isotope substage 5e: MIS 5e) is represented by shallow-water deposits in southern and western Denmark, while relatively deep-water environments occurred to the north and north-east, where complete interglacial successions seem to be present. We present an overview of the marine Eemian deposits in Denmark, and discuss in more detail indications of climate variability, both for the late Saalian and within the Eemian.

scholarly journals Analysis of long-term climatic changes at Hodeidah-Yemen during the period between 1984 and 2019

2021 ◽  
Author(s):  
Abkar Ali Iraqi ◽  
AbdAlla Mohammed AbdAlla
Keyword(s):  
Climatic Variability ◽  
Arab Country ◽  
Climatic Fluctuations ◽  
Sen’S Slope Estimator ◽  
Sen’S Slope ◽  
Mk Test ◽  
Slope Estimator ◽  
Annual Means ◽  
C 50 ◽  
Increasing Trends

Abstract Yemen is one of the Arab country that is vulnerable to climate changes, and this is clear from the indicators of impact on water resources, coastal zone environments, etc. This work focuses on studying the climatic variability at Hodeidah city-Yemen during the period between 1984 and 2019. This study aimed to characterize trends in mean monthly, seasonal and annual temperature. To attain these objectives the collected data were analyzed using both parametric (linear regression) and non-parametric (Mann–Kendall, Spearman and Sen's slope estimator tests) methods to detect the trend and the magnitudes of rates of changes of temperature over time. Analysis of data indicates clear climatic fluctuations of temperature. The annual means of temperature during the period of study were varied between 26.9°C and 30.1°C. The warmest years were observed during the more recent years of the study period ( 2005 to 2018). The increasing rate of annual temperature is about + 0.075°C /year, + 0.37°C/5year, + 0.75°C/decade ,+2.53°C, over the whole period of study(1985 to 2019), + 3.7°C/50 year and increase to + 4.85°C in 2050. On a monthly timescale, there are similar magnitudes of rates of change from December to September with highest rates in October and November. The results also showed that most months and seasons have significant positive trends in temperature and (Z-α/2) values of the MK Test > 1.96 and positive value of Sen’s slope estimator indicates significant an increasing trend towards warmer years. Anomalies of temperature confirm significant increasing trends towards warmer years (2000s to 2019).

scholarly journals Simulation of Atmospheric Circulation over Tahiti and of Local Effects on the Transport of 210Pb

2009 ◽  
Vol 137 (6) ◽  
pp. 1863-1880 ◽  
Author(s):  
P. Heinrich ◽  
X. Blanchard
Keyword(s):  
Atmospheric Circulation ◽  
General Circulation ◽  
Transport Model ◽  
Mesoscale Model ◽  
Natural Radionuclide ◽  
Circulation Model ◽  
Spatial And Temporal Variability ◽  
Local Circulation ◽  
Meteorological Model ◽  
The Impact

Abstract Atmospheric transport of the natural radionuclide 210Pb is simulated by a general circulation model (GCM) and calculated surface concentrations are compared with those recorded at the Tahiti station on a daily scale. Numerical results for 2006 show the underestimation of concentrations for most recorded peaks. The purpose of this paper is to explain the observed discrepancies, to evaluate the GCM physical parameterizations, and to determine by numerical means the concentrations at Tahiti for a pollutant circulating across the South Pacific Ocean. Three meteorological situations in 2006 are further analyzed. Circulation over Tahiti for these periods is simulated by a mesoscale meteorological model using four nested grids with resolutions ranging from 27 to 1 km. The calculated wind fields are validated by those observed at two stations on the northwest coast of Tahiti, which is exposed both to topography-induced vortices and to thermally driven local breezes. Atmospheric dispersion of an offshore plume is then calculated by a particle Lagrangian transport model, driven by the mesoscale model at 1- and 81-km resolutions, representing local and global circulations, respectively. Simulations at 1-km resolution show the complex atmospheric circulation over Tahiti, which results in a large spatial and temporal variability of 210Pb surface concentrations on an hourly scale. The impact of local circulation is, however, limited when daily averaged concentrations at the station are considered. Under the studied regimes, transport simulations at the two resolutions lead to similar daily averaged concentrations. The deficiencies of the GCM in simulating daily averaged 210Pb concentrations could be attributable to the deep convection parameterization.

Records of climate changes and anthropogenic actions over dune fields in historical times

2020 ◽  
Author(s):  
Mihaela Tudor ◽  
Ana Ramos-Pereira ◽  
Joana Gaspar de Freitas
Keyword(s):  
Climatic Variability ◽  
Coastal Dunes ◽  
Coastal Dune ◽  
Environmental Data ◽  
Dune System ◽  
Climatic Fluctuations ◽  
Dune Systems ◽  
Sand Drift ◽  
Aeolian Activity ◽  
Historical Times

<p>Coastal dunes are very complex systems and very sensitive to climatic variability and human actions. In Portugal, coastal dune fields have undergone major changes over historical times. The aim of the paper is focused on the coastal dune systems evolution over the last five centuries, natural and man induced (namely by deforestation and afforestation) and their transformation under the present global changes (sea level rise and coastal storms). The analysis of historical records and environmental data using a set of proxies recorded over the last 1,000 yrs, show intense aeolian activity and sand drift episodes during Little Age Period, causing serious problems for human settlements and agriculture. Coastal society have responded to the wind-blown sands fixing the dunes through afforestation. The process is well documented in the historical sources and many management measures, including abundant legislation, projects and reports were carried out by Portuguese authorities to avoid sand incursion inland.  According to the main report of the General Forest Administration, in the final of 18th century, was estimated an area of about 72 000 ha of free aeolian sands in need of afforestation. Thus, along Portuguese coastline, the dunes experienced a period of stability during the 20th century, due to planting of grasses and pine forest. This paper examines the pathways of the transgressive dune fields of the Central Western Portuguese coast, over various stages of coastal evolution. Mapping the morphological features between Mondego river mouth and Nazaré, using a combination of satellite images, aerial photographs and Lidar data we identified distinct phases of aeolian activity and landforms modification that were associated to climatic fluctuations. This coastal dune system is composed by a succession of different aeolian phases, including a littoral foredune, which lies inland with a complexity of morphologies with transverse and crescentic ridges, and also parabolic dunes. The results show that the dunes building and sand migration inland appears to be linked to the conditions of predominantly negative winter North Atlantic Oscillation index (NAOi), driven by climatic variability during Holocene/Antrhopocene. The consistency of intense sand drift episodes with abrupt cold events during Little Age Period, drastically reduced the area occupied by vegetation, causing changes in aeolian sedimentary processes. Thus, it seems that coastal dunes evolution over the past centuries have been controlled by the two-way interactions between natural conditions and human activities, shaping the Portuguese coastline. Placing historical evidence in a geographical perspective, we hope to fill the gaps in coastal zone dynamics, providing new insights of the human-landscape relationships to predict the future response of the coastal dune systems to human pressure and climate change.<br>Key-words: coastal dunes evolution, geomorphological features, sand drift, anthropogenic impacts, climatic fluctuation, Western Portugal.</p>

scholarly journals Climatic Variability of Near-Surface Turbulent Kinetic Energy over the United States: Implications for Fire-Weather Predictions

2013 ◽  
Vol 52 (4) ◽  
pp. 753-772 ◽  
Author(s):  
Warren E. Heilman ◽  
Xindi Bian
Keyword(s):  
United States ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Atmospheric Turbulence ◽  
Climatic Variability ◽  
Fire Behavior ◽  
The United States ◽  
Spatial And Temporal Variability ◽  
Fire Weather ◽  
Near Surface

AbstractRecent research suggests that high levels of ambient near-surface atmospheric turbulence are often associated with rapid and sometimes erratic wildland fire spread that may eventually lead to large burn areas. Previous research has also examined the feasibility of using near-surface atmospheric turbulent kinetic energy (TKEs) alone or in combination with the Haines index (HI) as an additional indicator of anomalous atmospheric conditions conducive to erratic or extreme fire behavior. However, the application of TKEs-based indices for operational fire-weather predictions in the United States on a regional or national basis first requires a climatic assessment of the spatial and temporal patterns of the indices that can then be used for testing their operational effectiveness. This study provides an initial examination of some of the spatial and temporal variability patterns across the United States of TKEs and the product of HI and TKEs (HITKEs) using data from the North American Regional Reanalysis dataset covering the 1979–2008 period. The analyses suggest that there are regional differences in the behavior of these indices and that regionally dependent threshold values for TKEs and HITKEs may be needed for their potential use as operational indicators of anomalous atmospheric turbulence conditions conducive to erratic fire behavior. The analyses also indicate that broad areas within the northeastern, southeastern, and southwestern regions of the United States have experienced statistically significant positive trends in TKEs and HITKEs values over the 1979–2008 period, with the most substantial increases in values occurring over the 1994–2008 period.

scholarly journals Simulating long-term past changes in the balance between water demand and availability and assessing their main drivers at the river basin management scale

2014 ◽  
Vol 11 (11) ◽  
pp. 12315-12364 ◽  
Author(s):  
J. Fabre ◽  
D. Ruelland ◽  
A. Dezetter ◽  
B. Grouillet
Keyword(s):  
Water Stress ◽  
Water Resources ◽  
Water Demand ◽  
River Flow ◽  
Climatic Variability ◽  
Spatial And Temporal Variability ◽  
Ebro Basin ◽  
Anthropogenic Pressures ◽  
Modeling Framework ◽  
Time Step

Abstract. The aim of this study was to assess the balance between water demand and availability and its spatial and temporal variability from 1971 to 2009 in the Herault (2500 km2, France) and the Ebro (85 000 km2, Spain) catchments. Natural streamflow was evaluated using a conceptual hydrological model. The regulation of river flow was accounted for through a widely applicable demand-driven reservoir management model applied to the largest dam in the Herault basin and to 11 major dams in the Ebro basin. Urban water demand was estimated from population and monthly unit water consumption data. Water demand for irrigation was computed from irrigated area, crop and soil data, and climatic forcing. Finally, a series of indicators comparing water supply and water demand at strategic resource and demand nodes were computed at a 10 day time step. Variations in water stress in each catchment over the past 40 years were successfully modeled, taking into account climatic and anthropogenic pressures and changes in water management strategies over time. Observed changes in discharge were explained by separating human and hydro-climatic pressures on water resources: respectively 20 and 3% of the decrease in the Ebro and the Herault discharges were linked to human-induced changes. Although key areas of the Herault basin were shown to be highly sensitive to hydro-climatic variability, the balance between water uses and availability in the Ebro basin appears to be more critical, owing to high agricultural pressure on water resources. The proposed modeling framework is currently being used to assess water stress under climatic and socio-economic prospective scenarios. Further research will investigate the effectiveness of adaptation policies aimed at maintaining the balance between water use and availability.

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