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1.
The coastal waters of Peru and Chile are among the most productive of the world's oceans. A striking source of interannual variability in this upwelling ecosystem, El Niño, results in large population and community variations. During El Niño the seasonal upwelling ceases and warm, clear oceanic waters occur close inshore, setting a unique oceanographic scenario in which the performance of populations and communities can be studied. While most attention has been focused on the pelagic components of such systems, numerous changes occur in inshore, benthic populations. Likewise, little attention has been paid to the critical role of humans as predators or active users of inshore, benthic resources. Humans as components of the ecosystem can impose significant alterations on population and community structure. In this paper the fishery statistics of three economically important inshore, benthic resources (the gastropod Concholepas concholepas, the cephalopod Octopus vulgaris and the kelp Lessonia nigrescens) are analysed in relation to the strong 1982/83 El Niño event. In particular, trends are described for landings in the far northern regions of Chile, where the marked effect of El Niño was concurrent with high levels of exploitation of C. concholepas and L. nigrescens.  相似文献   

2.
During the past 30 years, 42 molecular studies have been undertaken in New Zealand to examine the phylogeography of coastal benthic invertebrates and plants. Here, we identify generalities and/or patterns that have emerged from this research and consider the processes implicated in generating genetic structure within populations. Studies have used various molecular markers and examined taxonomic groups with a range of life histories and dispersal strategies. Genetic disjunctions have been identified at multiple locations, with the most frequently observed division occurring between northern and southern populations at the top of the South Island. Although upwelling has been implicated as a cause of this disjunction, oceanographic evidence is lacking and alternative hypotheses exist. A significant negative correlation between larval duration and genetic differentiation (r2 = 0.39, P < 0.001, n = 29) across all studies suggests that larval duration might be used as a proxy for dispersal potential. However, among taxa with short larval durations (<10 days) there was greater variability in genetic differentiation than among taxa with longer pelagic periods. This variability implies that when larval duration is short, other factors may determine dispersal and connectivity among populations. Although there has been little congruence between the phylogeographic data and recognised biogeographic regions, recent research has resolved population subdivision at finer spatial scales corresponding more closely with existing biogeographic classifications. The use of fast‐evolving and ecologically significant molecular markers in hypothesis‐driven research could further improve our ability to detect population subdivision and identify the processes structuring marine ecosystems.  相似文献   

3.
Many infaunal sandy-bottom communities in shallow waters of the Peruvian upwelling system are inhabited by large coexisting populations of the surf clams Mesodesma donacium and Donax peruvianus as well as by the anomuran mole crab Emerita analoga. Under normal conditions, equilibrium states are possible with any one of these species dominating. A Mesodesma community south of Lima in Peru was investigated over 2,5 years, covering periods prior to, during and after the El Niño (EN) of 1982–83. It was revisited several times later. Growth, recruitment and mortality and, therefore, production of Mesodesma and Donax varied to some extent before EN. However, during the event Mesodesma became locally extinct and had not recolonized the area by July 1986, three years after the return of normal temperatures. Donax, which took over immediately after EN, never reached the densities of the former dominant Mesodesma. Emerita remained a rare species as well, whereas spionid polychaetes increased in importance. The medium-term effect of the exceptionally strong EN of 1982–83 appears to have been very marked on Peruvian sandy beaches. A comparison is made with other shallow-water communities of the upwelling system, and the importance of EN in terms of oscillations of clam stocks off Peru and Chile is discussed.  相似文献   

4.
利用1958—2019年的观测和再分析数据集,对冷、暖两类厄尔尼诺-南方涛动（El Niño-Southern Oscillation,ENSO）事件与后期华东地区春季降水之间的关系进行了分析。结果表明：（1）在暖ENSO事件中,华东春季降水量与前冬季ENSO海面温度异常存在较强的正相关关系。在冷ENSO事件中,这种强正相关向内陆地区西移,主要集中在江西和湖南。（2）暖ENSO事件通常会导致浙江、江苏和福建等沿海省份春季降水量过剩,而冷ENSO事件往往导致江西和湖南降水偏少。这归因于ENSO对大气环流的非线性影响。（3）与暖ENSO事件相比,冷ENSO事件引起的海面温度异常中心明显西移,造成异常低层大气环流的西移,最终导致华东降水的西移效应。（4）通过分析和发现,强调了华东春季降水对ENSO的非线性响应,这对华东地区的季节性气候预测具有重要意义。  相似文献   

5.
ENSO indices from sea surface salinity observed by Aquarius and Argo   总被引：1，自引：0，他引：1  
Analysis of the first 26 months of data from the Aquarius satellite confirms the existence of a sharp sea surface salinity (SSS) front along the equator in the western equatorial Pacific. Following several earlier studies, we use the longitudinal location of the 34.8-psu isohaline as an index, termed Niño-S34.8, to measure the zonal displacement of the SSS front and consequently the eastern edge of the western Pacific warm pool. The on-going collection of the Array for Real-time Geostrophic Oceanography (ARGO) program data shows high correlations between Niño-S34.8 and the existing indices of El Niño, suggesting its potential important role in ENSO evolution. Further analysis of the ARGO data reveals that SSS variability in the southeastern tropical Pacific is crucial to identify the type of El Niño. A new SSS index, termed the southeastern Pacific SSS index (SEPSI), is defined based on the SSS variability in the region (0°–10°S, 150°–90°W). The SEPSI is highly correlated with the El Niño Modoki index, as well as the Trans-Niño index, introduced by previous studies. It has large positive anomalies during central Pacific El Niño or El Niño Modoki events, as a result of enhanced zonal sea surface temperature gradients between the central and eastern tropical Pacific, and can be used to characterize the type of El Niño. The processes that possibly control these SSS indices are also discussed.  相似文献   

6.
气候模式FIO-ESM对2015/16年厄尔尼诺的预测   总被引：1，自引：0，他引：1  
Recently atmospheric and oceanic observations indicate the tropical Pacific is at the El Ni?o condition. However,it's not clear whether this El Ni?o event of this year is comparable to the very strong one of 1997/98 which brought huge influence on the whole world. In this study, based on the Ensemble Adjusted Kalman Filter(EAKF)assimilation scheme and First Institute of Oceanography-Earth System Model(FIO-ESM), the assimilation system is setup, which can provide reasonable initial conditions for prediction. And the hindcast results suggest the skill of El Ni?o-Southern Oscillation(ENSO) prediction is comparable to other dynamical coupled models. Then the prediction for 2015/16 El Ni?o by using FIO-ESM is started from 1 November 2015. The ensemble results indicate that the 2015/16 El Ni?o will continue to be strong. By the end of 2015, the strongest strength is very like more than 2.0°C and the ensemble mean strength is 2.34°C, which indicates 2015/16 El Ni?o event will be very strong but slightly less than that of 1997/98 El Ni?o event(2.40°C) calculated relative a climatology based on the years1992–2014. The prediction results also suggest 2015/16 El Ni?o event will be a transition to ENSO-neutral level in the early spring(FMA) 2016, and then may transfer to La Ni?a in summer 2016.  相似文献   

7.
热带太平洋第二类El Nio事件及其对中国气候的影响   总被引：1，自引：0，他引：1  
基于热带太平洋次表层海温资料,分析了热带太平洋第二类El Nio事件海温异常的分布特征及其形成机制,讨论了与经典El Nio事件、El Nio Modoki、WP(西太平洋暖池)及CT(冷舌)El Nio事件之间的关系,揭示了第二类El Nio事件对中国降水的影响,得到以下结论。(1)第二类El Nio事件表征为热带太平洋次表层海温异常第三模态,占总方差贡献的4.7%。在海洋表面层,第二类El Nio事件暖期赤道东太平洋为沿赤道西伸的冷舌,热带中西太平洋为环绕冷舌的马蹄型大范围暖区。该型具11a和30~40a年代际振荡及3~4a年际变率,峰值多出现在春季。第二类El Nio事件是热带太平洋异常海面风应力场和赤道两侧的风应力旋度共同作用的结果,在赤道东印度洋-中西太平洋与赤道东太平洋-南美洲上空出现以反号垂直运动为特征的异常Walker环流。(2)El Nio Modoki与第二类El Nio事件有密切关系,它实质上是第二类El Nio事件次表层海温与近海面大气相互作用的结果,捕捉了第二类El Nio事件的主要信息。(3)第二类El Nio事件对中国春季及夏初降水有一定影响。在事件暖期,东海地区存在一个显著的异常反气旋性环流,其南侧的中国南方地区盛行异常东北气流,水汽来源减少,导致该地区少雨,其西侧的异常偏南气流北上直达华北地区,异常多水汽向北输送,并与北方的偏北流场相遇,导致该地区降水偏多。在第二类El Nio事件冷期相反。本文结果还指出,WP与CT El Nio事件是由经典El Nio事件第一模态与El Nio Modoki事件组合而成,它们不是独立的El Nio类型。此外,还讨论了夏半年El Nio事件对大气环流影响的物理过程。  相似文献   

8.
Two onboard observation campaigns were carried out in the western boundary region of the Philippine Sea in December 2006 and January 2008 during the 2006/07 El Niño and the 2007/08 La Niña to observe the North Equatorial Current (NEC), Mindanao Current (MC), and Kuroshio current system. The NEC and MC measured in late 2006 under El Niño conditions were stronger than those measured during early 2008 under La Niña conditions. The opposite was true for the current speed of the Kuroshio, which was stronger in early 2008 than in late 2006. The increase in dynamic height around 8°N, 130°E from December 2006 to January 2008 resulted in a weakening of the NEC and MC. Local wind variability in this region did not appear to contribute to changes in the current system.  相似文献   

9.
Physical factors affecting El Niño events are subdivided into two categories. The first category includes those physical factors that have been demonstrated by modern science to have an effect on El Niño events. The second category comprises those physical factors that are only a hypothesis based on correlations that have yet to be corroborated to have affected El Niño events. This paper proposes the concept of a cause chain for an El Niño, pointing out that physical factors are linked and interdependent. The feedback effect and decrease-increase effect upon physical factors within the cause chain provide results superior to any single theory. We can only further explore the feedback effect and decrease-increase effect together with comprehensive analysis on the contributive ratio of these physical factors so as to improve the forecast accuracy of El Niño events. This represents a new way of thinking in the explanation of the cause of El Niño events.  相似文献   

10.
Larval dispersal is critical for the maintenance of species populations in patchy and ephemeral hydrothermal vent habitats. On fast‐spreading ridges, such as the East Pacific Rise, rates of habitat turnover are comparable to estimated lifespans of many of the inhabiting species. Traditionally, dispersal questions have been addressed with two very different approaches, larval studies and population genetics. Population genetic studies of vent‐endemic species have been informative for determining whether patterns of dispersal are suggestive of stepping stone or island models and estimating rates of gene flow (effective migrants per generation) over broad geographic ranges. However, these studies leave fundamental questions unanswered about the specific mechanisms by which larvae disperse and species maintain their populations and biogeographic ranges. With the goal of examining genetic structure and elucidating alternative larval dispersal mechanisms, we employed a genomic DNA fingerprinting technique, amplified fragment length polymorphisms (AFLPs). To assess the potential utility of AFLPs, and genetic structure of the hydrothermal vent tubeworm Riftia pachyptila, genomic ‘fingerprints’ were recovered from 29 individuals from five vent fields spanning a distance of up to c. 5000 km along the East Pacific Rise. In contrast to previous population genetic studies that found little to no genetic structure using allozymes and mitochondrial DNA, genetic analyses of 630 polymorphic AFLP loci identified distinct subclades within R. pachyptila populations. Significant levels of differentiation were observed among populations from all vent regions as well as within each region. Discrete assemblages of tubeworms separated by as little as c. 400 m within a given vent region were genetically distinguishable and cohorts (based on size‐frequency distribution) within an aggregation were found to be most closely related. These results suggest that mechanisms of larval dispersal act to retain cohort fidelity in R. pachyptila.  相似文献   

11.
Market squid (Doryteuthis opalescens) are ecologically and economically important to the California Current Ecosystem, but populations undergo dramatic fluctuations that greatly affect food web dynamics and fishing communities. These population fluctuations are broadly attributed to 5–7‐years trends that can affect the oceanography across 1,000 km areas; however, monthly patterns over kilometer scales remain elusive. To investigate the population dynamics of market squid, we analysed the density and distribution of paralarvae in coastal waters from San Diego to Half Moon Bay, California, from 2011 to 2016. Warming local ocean conditions and a strong El Niño event drove a dramatic decline in relative paralarval abundance during the study period. Paralarval abundance was high during cool and productive La Niña conditions from 2011 to 2013, and extraordinarily low during warm and eutrophic El Niño conditions from 2015 to 2016 over the traditional spawning grounds in Southern and Central California. Market squid spawned earlier in the season and shifted northward during the transition from cool to warm ocean conditions. We used a general additive model to assess the variability in paralarval density and found that sea surface temperature (SST), zooplankton displacement volume, the log of surface chlorophyll‐a, and spatial and temporal predictor variables explained >40% of the deviance (adjusted r2 of .29). Greatest paralarval densities were associated with cool SST, moderate zooplankton concentrations and low chlorophyll‐a concentrations. In this paper we explore yearly and monthly trends in nearshore spawning for an economically important squid species and identify the major environmental influences that control their population variability.  相似文献   

12.
Previously published estimates of the area of the Peru upwelling ecosystem vary by more than an order of magnitude. In an effort to improve this situation, we used a 24-month sequence of SeaWiFS satellite images of chlorophyll in the surface water off Peru from 5°S to 18.5°S during September 1997–August 1999 to estimate the size of the nutrient enhanced productive habitat associated with the upwelling. The first 12-month period was marked by El Niño conditions, the second by strong upwelling. Using a chlorophyll threshold of >1.0 mg m−3 to define the limit of the productive habitat resulted in maximum area estimates of 120×103 km2 during September 1997–August 1998, and 220×103 km2 during September 1998–August 1999. The latter result is consistent with an area estimate we calculated using total fishery landings and a regression relating fishery yields per unit area to annual primary production per unit area. Although year-to-year variation in the annual mean size of the upwelling ecosystem must be significant, even discounting El Niño events, our analysis has shown that at least five of the extreme earlier values are not good estimates of the size of the productive habitat. We may now be close to knowing the average size of the ecosystem to within a factor of about two.  相似文献   

13.
利用1950—2020年冬季HadISST逐月海面温度（sea surface temperature,SST）资料、SODAv2.2.4逐月SST和三维海洋流速同化资料以及NCEP/NCAR 2 m高度上的逐月气温（surface air temperature,SAT）资料,使用非对称合成差分析方法、海洋混合层热量收支诊断方法等,探究El Niño事件和La Niña事件下造成赤道东太平洋（E区：110°W~80°W,10°S~10°N）、赤道中太平洋（C区：160°E~170°W,10°S~10°N）SST异常场显著不同非对称性特征的可能海洋动力过程,分析ENSO事件非对称强迫下2 m高度上SAT异常场的非对称空间响应。结果表明：E区El Niño事件的强度显著强于La Niña事件,C区则相反。非线性动力学加热作用对E区和C区El Niño年和La Niña 年SST异常场的非对称分量都起到了正反馈作用,是造成这两个区域SST异常场产生正、负非对称分量的主导动力因子。埃克曼输送作用不利于E区SST异常场正非对称分量的形成,但有利于C区SST异常场负非对称分量的形成。平均流、纬向平流和温跃层的非对称正反馈作用阻碍了C区SST异常场负非对称分量的形成。2 m高度上SAT异常场的非对称分布与SST异常场的非对称分布较为一致,但SAT异常场正、负非对称分量的显著范围明显减小,部分区域的非对称结果不显著。  相似文献   

14.
The statistical significance of Global Atmospheric Oscillation (GAO), whose main element is the well-known El Niño–Southern Oscillation in the equatorial Pacific, was assessed from monthly mean atmospheric pressure data at sea level at the nodes of a regular 5° × 5° grid covering the entire surface of the Earth. The data were collected in 1920–2012. It was found that statistically reliable GAO signals cover almost the entire tropical zone and they also appear at mid- and high latitudes of both hemispheres.  相似文献   

15.
Characteristics of the Arctic Oscillation and El Niño-Southern Oscillation effects manifested on interannual scales in the equatorial stratosphere are determined. Wavelet analysis of local phase shifts, coherence, and correlation is used to obtain correlation portraits of the largest factors of climate variability against the background of coherent variations in the equatorial stratospheric wind speed at the 50- and 15-hPa pressure levels. It is shown that the Arctic Oscillation and El Niño-Southern Oscillation signals may reach the tropical stratosphere. The signals are easily identified in a wide range of scales, including quasi-biennial, 3-to 5-year, and 10-to 11-year periods. The results obtained reflect a coherent pattern of the manifestation of these signals at the selected stratospheric levels. It is found that the El Niño-Southern Oscillation effect at periods close to 10–11 years reaches the stratospheric level rather rapidly, in the same or next month, while the effects of the Arctic Oscillation index are delayed by nine months. The estimates obtained show that a phase shift of almost 180° in the Arctic Oscillation index relative to the equatorial stratospheric wind occurred in almost all of the range of interannual periods in 1978 and 1992. For the El Niño-Southern Oscillation, an increase in local correlations on a scale of 3-to 5-year variations was observed in 1980–1990, a 180° phase shift occurred in 1992, and the correlation with stratospheric wind increased in 1992–2004. The estimates obtained are indicative of a change in the atmospheric circulation pattern that took place in the Northern Hemisphere in 1978–1991.  相似文献   

16.
The Pacific interior subtropical?tropical cells (STCs) and their relation to the two types of El Niño-Southern Oscillation (ENSO) are investigated by using GODAS reanalysis ocean data for the period of 1980–2017. The results show that the interior STC transport into the equatorial region across 9°S and 9°N has a close relationship with the eastern Pacific (EP) ENSO, while it is much weaker with the central Pacific (CP) ENSO. It is suggested that the effect of interior STCs on the tropical Pacific climate is reflected in its relation with the western Pacific thermocline depth or SSHA. During the EP El Niño, the anomalous interior STCs at 9°S and 9°N converge to the equatorial region from the lag months of ? 25 to ? 8, leading to an accumulation of heat content in the equatorial Pacific; from the lag months of ? 8 to 10, they diverge poleward, inducing a discharge of equatorial heat content. The peak poleward interior STC anomaly first appears at 9°N at a zero-lag time, while that at 9°S is observed 4–5 months later. But there is also no appearance of a time lag between the interior STCs at 9°N and 9°S in recharging the period during the EP La Niña mature phase. However, during CP El Niño, only the conspicuous anomalous interior STC divergence appears during the mature and decay phases for the lag months of ? 2 to 10, with being symmetric at 9°N and 9°S.  相似文献   

17.
系统地分析了137°E断面温、盐度的多年变化,主要结果为:(1)137°E断面100m层温度,在低纬度海域于某些年份出现异常低温,此现象可能与厄尔尼诺事件有关;指出棉兰老冷涡的存在是造成该断面于6°～8°N附近出现低温的主要原因。(2)厄尔尼诺期间,冬季137°E断面上28℃等温线所在纬度小于其多年平均值。(3)冬季137°E断面上次表层高盐水可划分为强型、次强型、中等型和弱型4种类型。  相似文献   

18.
On the basis of the statistical analysis of the global fields of outgoing long-wave radiation, surface temperature of the ocean, and components of the wind velocity, we analyze five El Niño events observed in 1963–1983. We study the dependence of the global circulation in the lower atmosphere on the behaviour of the temperature of the surface waters and outgoing long-wave radiation in the west part of the tropical zone of the Pacific Ocean. General regularities and specific features of different El Niño events are also analyzed.  相似文献   

19.
In this paper a methodology is applied to generate synthetic wave series during mean and extreme conditions. An analysis is carried out that describes mean and extreme wave behavior for several climatic conditions along the Colombian Caribbean Coast. During mean conditions, the most energetic ocean waves are observed during the DJF season for both ENSO phases (El Niño and La Niña) for most of the Caribbean Sea. During the Niño years, there is a reduction in the speed of the north-east trade winds and their associated waves, but only in the DJF and MAM seasons. However, during the JJA season, this situation is reversed with the highest values occurring during El Niño and low values appearing during La Niña. Toward the east around the Guajira region, this general pattern is shown to change significantly. For extreme conditions, the results show a significant influence of extreme events toward the northwest, around La Guajira and the insular zones of San Andres and Providence when compared with other regions along the coast. All of these results (including the synthetic wave series) provide a design and management tool for the successful implementation of any coastal project (scientific or consulting) in Colombia.  相似文献   

20.
Time-series data from sediment trap moorings intermittently deployed during 1991–1999 show that the fluxes of biogenic material (carbonate, opal and organic matter, including amino acids) and other related parameters are temporally and spatially distinct across the Western Pacific Warm Pool (WPWP). These variations resulted from the El Niño and La Niña conditions, which alternately prevailed over the equatorial Pacific Ocean during the mooring deployments. The westernmost WPWP (a hemipelagic region) recorded relatively high average total mass and amino acid fluxes during the El Niño event. This was in sharp contrast to the eastern part of the WPWP (oligotrophic and weak upwelling regions) which recorded higher flux values during the La Niña event. Settling particulate organic matter was rich in labile components (amino acids) during La Niña throughout the study area. Relative molar ratios of aspartic acid to β-alanine together with relative molar content of non-protein amino acids β-alanine and γ-aminobutyric acid) suggested that organic matter degradation was more intense during La Niña relative to that during El Niño in the WPWP. This study clearly shows that during an El Niño event the well documented decrease in export flux in the easternmost equatorial Pacific is accompanied by a significant increase in export flux in the westernmost equatorial Pacific Ocean.  相似文献   

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