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1.
Analysis of the cause and effect relationships between El Niño in the Pacific and its analog in the equatorial Atlantic 总被引：1，自引：0，他引：1
S. S. Kozlenko I. I. Mokhov D. A. Smirnov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(6):704-713
The relations between the processes occurring in the equatorial latitudes of the Pacific and Atlantic oceans were studied on the basis of the Granger causality analysis and a simulation of phase dynamics using the indices of the El Niño-Southern Oscillation (ENSO) and the equatorial Atlantic mode (EAM). Data on the monthly means of the sea-surface temperature over the period 1870–2006 for the Niño 3 (5° S-5° N, 150° W-90° W) and Niño 3.4 (5° S-5° N, 170° W-120° W) regions in the Pacific and the Atlantic 3 region (20° W-0, 3° S-3° N) in the Atlantic Ocean were used as the ENSO and EAM indices. The statistically significant influence of the EAM on the ENSO is noted. The lag time of this influence is estimated at two months. No significant reverse effect is revealed. An increase in the EAM’s influence on the ENSO was observed in the second half of the 20th century. 相似文献
2.
利用最近20 a的大气海洋资料,分析了厄尔尼诺事件与赤道太平洋西风异常以及赤道太平洋次表层海温之间的关系.结果表明,赤道西太平洋(5°S～5°N,120°～160°E)和赤道中东太平洋(5°S～5°N,160°E～160°W)西风异常都存在着与厄尔尼诺周期一致的年际变化,但前者还包含有显著的2～3个月季节内振荡.赤道西太平洋次表层冷暖水东移也呈现年和年际时间尺度的振荡周期.在厄尔尼诺发生前,赤道西太平洋次表层海水出现持续性增暖,赤道西太平洋西风异常频率加快,强度增强.随后赤道中太平洋(160°E～160°W)出现持续性(3个月以上)强西风异常(即西风爆发),并进一步向东扩展,同时次表层暖水沿着赤道波导东移到赤道东太平洋混合层,导致赤道东太平洋海表大面积异常增暖,形成一次厄尔尼诺现象.最后,模式模拟了1980～1984年赤道太平洋海温的变化,进一步证实了赤道纬向西风异常对暖水东移起着重要的作用. 相似文献
3.
The spatiotemporal variability of equatorial Pacific upper ocean heat content (HC) and subsurface heat during two types of El Niño-Southern Oscillation (ENSO), namely eastern and central Pacific (EP and CP) types, is investigated using subsurface ocean heat budget analysis. Results show that HC tendencies during both types of ENSO are mainly controlled by oceanic heat advection beneath the mixed layer to the thermocline, and the role of net surface heat flux can be neglected. The most important three terms are the zonal and vertical advections of anomalous heat by climatological currents (QU 0 T′, QW 0 T′) and zonal advection of climatological heat by anomalous current (QU′T 0). The large contribution of QU 0 T′ extends from west to east along the equatorial Pacific. The considerable contribution of QU′T 0 is confined to the east of 160°W, and that of the QW 0 T′ is observed in the central Pacific between 180°E and 120°W. In particular, a major contribution of QW 0 T′ is also observed in the far eastern Pacific east of 100°W during EP ENSO. There is also a small contribution from meridional advection of climatological heat by anomalous current (QV′T 0). In contrast, the meridional advection of anomalous heat by climatological currents (QV 0 T′) and vertical advection of climatological heat by anomalous current (QW′T 0) are two damping factors in the HC tendency, with the former dominating. Differences in spatial distribution of the heat advection associated with the two types of ENSO are also presented. We define a warm water heat index (WWH) as integrated heat content above 26 kg m?3 potential density (26σ ? ) isopycnal depth within 130°E–80°W and 5°S–5°N. Further examination suggests that the recharge–discharge of WWH is involved in both types of El Niño, though with some differences. First, it takes about 42 (55) months for the evolution of a recharge–discharge cycle during an EP (CP) ENSO. Second, the EP El Niño event peaks during the discharge phase, 7–8 months after the recharge time. The CP El Niño peaks during the recharge phase, 4–5 months before the recharge time. The locations of HC anomalies in the El Niño mature phase relative to those at recharged time explain why the EP and CP El Niño peak in different stages of the recharge–discharge process. 相似文献
4.
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
5.
Positive SST anomalies usually appear in remote ocean such as the China seas during an ENSO event.By analyzing the monthly data of HadISST from 1950 to 2007,it shows that the interannual component of SST anomalies peak approximately 10 months after SST anomalies peak in the eastern equatorial Pacific.As the ENSO event progresses,the positive SST anomalies spread throughout the China seas and eastward along the Kuroshio extension.Atmospheric reanalysis data demonstrate that changes in the net surface heat flux entering into the China seas are responsible for the SST variability.During El Ni o,the western north Pacific anticyclone is generated,with anomalous southwester lies prevailing along the East Asian coast.This anticyclone reduces the mean surface wind speed which decreases the surface heat flux and then increases the SST.The delays between the developing of this anticyclone and the south Indian Ocean anticyclone with approximately 3–6 months cause the 2–3 months lag of the surface heat flux between the China seas and the Indian Ocean.The northwestern Pacific anticyclone is the key process bridging the warming in the eastern equatorial Pacific and that in the China seas. 相似文献
6.
The impact of quasi-decadal (QD: 8 to 18 years) variability in the tropical Pacific on ENSO events is investigated. It is found that there is a significant difference in the behavior of ENSO events between the phases of positive and negative anomalies of the QD Niño-3.4 index. During the period of negative QD-scale Niño-3.4 index, ENSO events, especially La Niña events, occur more frequently, and larger amplitudes of thermal anomalies related to El Niño events appear over the central to eastern equatorial Pacific. Furthermore, propagations of upper ocean heat content anomaly and a phase relationship between upper ocean heat content and Niño-3 index in the equatorial Pacific, which have been pointed out by previous studies, are clearly detected during the period of negative QD Niño-3.4 index. 相似文献
7.
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
8.
《African Journal of Marine Science》2013,35(2):237-246
Changes and fluctuations in sea surface temperature (SST) around the South African coast are analysed at a monthly scale from 1982 to 2009. There is a statistically significant negative trend of up to 0.5 °C per decade in the southern Benguela from January to August, and a cooling trend of lesser magnitude along the South Coast and in the Port Elizabeth/Port Alfred region from May to August. The cooling is due to an increase in upwelling-favourable south-easterly and easterly winds. There is a positive trend in SST of up to 0.55 °C per decade in most parts of the Agulhas Current system during all months of the year, except for KwaZulu-Natal where warming is in summer. The warming was attributed to an intensification of the Agulhas Current in response to a poleward shift of westerly winds and an increase in trade winds in the South Indian Ocean at relevant latitudes. This intensification of the Agulhas Current could also have contributed to the coastal cooling in the Port Alfred dynamic upwelling region. The El Niño Southern Oscillation (ENSO) is significantly positively correlated at a 95% level with the southern Benguela and South Coast from February to May, and negatively correlated with the Agulhas Current system south of 36° S. The correlation with the Antarctic Annular Oscillation is weaker and less coherent. El Niño suppresses upwelling along the coast, whereas La Niña increases it. Although there does not seem to be a linear relationship between the strength of the ENSO and the magnitude of coastal SST perturbation, El Niño and La Niña appear to be linked to major warm and cool events, respectively, at a seasonal scale in summer in the southern Benguela and along the South Coast. However, care must be taken in interpreting low-resolution reanalysed climate data (ERA40 and NCEP) and optimally interpolated Reynolds SST, such as used here. 相似文献
9.
Thirty La Niña events have been selected from monthly mean sea surface temperature (SST) data of the Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) and Centennial Observation-Based Estimates (COBE SST2) datasets from 1870 to 2013 based on a criterion of –0.5°С for a cold anomaly in the Niño 3.4 region (5° N–5° S, 170°–120° W) and its minimum duration of 5 months. The selected events are classified by hierarchical clustering analysis according to two characteristics: geographic coordinates and SST anomalies during the mature phase of La Niña. The objective classification method identifies two types of La Niña differing by the evolution of negative SST anomalies in the equatorial Pacific and by the Southern Oscillation Index. 相似文献
10.
Limitations in sea surface salinity (SSS) observations and timescale separation methods have led to an incomplete picture of the mechanisms of SSS decadal variability in the tropical Pacific Ocean, where the El Niño Southern Oscillation (ENSO) dominates. Little is known regarding the roles of the North Pacific Gyre Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO) in the large-scale SSS variability over the tropical basin. A self-organizing map (SOM) clustering analysis is performed on the intrinsic mode function (IMF) maps, which are decomposed from SSS and other hydrological fields by ensemble empirical mode decomposition (EEMD), to extract their asymmetric features on decadal timescales over the tropical Pacific. For SSS, an anomalous pattern appeared during 1997 to 2004, a period referred to as the anomalous late 1990s, when strong freshening prevailed in large areas over the southwestern basin and moderate salinization occurred in the western equatorial Pacific. During this period, the precipitation and surface currents were simultaneously subjected to anomalous fluctuations: the precipitation dipole and zonal current divergence along the equator coincided with the SSS increase in the far western equatorial Pacific, while the weak zonal current convergence in the southwestern basin and large-scale southward meridional currents tended to induce SSS decreases there. The dominant decadal modes of SSS and sea surface temperature (SST) in the tropical Pacific both resemble the NPGO but occur predominantly during the negative and positive NPGO phases, respectively. The similarities between the NPGO and Central Pacific ENSO (CP-ENSO) in their power spectra and associated spatial patterns in the tropics imply their dynamical links; the correspondence between the NPGO-like patterns during negative (positive) phases and the CP La Niña (CP El Niño) patterns for SSS is also discussed. 相似文献
11.
A time-series sediment trap was deployed from October 2007 to May 2011 in the western subtropical Pacific with the aim of understanding the seasonal and inter-annual variability on particle flux in response to El Niño-Southern Oscillation (ENSO) events. Total mass fluxes varied from 3.04 mg m−2 day−1 to 31.1 mg m−2 day−1, with high fluxes during February–April and low fluxes during other months. This seasonal variation was also characterized by a distinct change in the CaCO3 flux between the two periods. The marked increase in particle flux during February–April may be attributed to enhanced biological productivity in surface waters caused by strong wind-driven mixing in response to the western North Pacific monsoon system. The 2009/10 strong El Niño was accompanied by a significant reduction in particle flux, whereas the La Niña had no recognizable effect on particle flux in the subtropical Pacific. In particular, in the mature phase of the 2009/10 strong El Niño, the fluxes of organic carbon and biogenic silica decreased by 70–80% compared with those during the normal period, implying that the El Niño acted to suppress biological productivity in surface waters. The suppression of biological productivity during the 2009/10 strong El Niño is attributed to the decrease in precipitation due to the shift in the western Pacific warm pool. This finding is opposite that of other studies of the western equatorial Pacific, where El Niño events were observed to result in an increase in biological productivity and particle flux. The difference in particle flux between the western equatorial and subtropical Pacific is attributed to the regional differences in oceanic and atmospheric circulation systems generated by the strong El Niño. 相似文献
12.
热带太平洋第二类El Nio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 Nio事件海温异常的分布特征及其形成机制,讨论了与经典El Nio事件、El Nio Modoki、WP(西太平洋暖池)及CT(冷舌)El Nio事件之间的关系,揭示了第二类El Nio事件对中国降水的影响,得到以下结论。(1)第二类El Nio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 Nio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 Nio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 Nio Modoki与第二类El Nio事件有密切关系,它实质上是第二类El Nio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 Nio事件的主要信息。(3)第二类El Nio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 Nio事件冷期相反。本文结果还指出,WP与CT El Nio事件是由经典El Nio事件第一模态与El Nio Modoki事件组合而成,它们不是独立的El Nio类型。此外,还讨论了夏半年El Nio事件对大气环流影响的物理过程。 相似文献
13.
In this study, El Niño Southern Oscillation (ENSO)-induced interannual variability in the South China Sea (SCS) is documented using outputs from an eddy-resolving data-assimilating model. It is suggested that during an El Niño (La Niña) event, off-equatorial upwelling (downwelling) Rossby waves induced by Pacific equatorial wind anomalies impinge on the Philippine Islands and excite upwelling (downwelling) coastal Kelvin waves that propagate northward along the west coast of the Philippines after entering the SCS through the Mindoro Strait. The coastal Kelvin waves may then induce negative (positive) sea level anomalies in the southeastern SCS and larger (smaller) volume transport through the Mindoro and Luzon Straits during an El Niño (La Niña) event. 相似文献
14.
Kozo Takahashi Jonaotaro Onodera Yoichiro Katsurada 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1298-1318
The water masses of the central and western equatorial Pacific can be divided into two parts: the Western Pacific Warm Pool (WPWP) and the Equatorial Upwelling Region (EUR). The behavior of the WPWP plays a significant role in global climate changes such as the El Niño-Southern Oscillation (ENSO), and it drastically modifies the oceanographic conditions in the area every few years. It is important to evaluate changes in time-series diatom fluxes during both the El Niño and the La Niña events. As a part of the Global Carbon Cycle and Related Mapping based on Satellite Imagery (GCMAPS) Program, time-series sediment trap moorings were deployed and recovered along the Equator at seven stations (Sites MT1–MT7) during five R/V Mirai cruises in the central and western Pacific during January 1999–January 2003. The entire length of this study is divided into two phases depending on the oceanographic conditions: the La Niña event (1999 and 2000); and the El Niño event (2002). Site MT3 was located in the WPWP and Sites MT5–MT7 were in the EUR. Annual means of total diatom fluxes increased towards the east in each year. The fluxes observed at Sites MT4–MT6 decreased from the La Niña event to the El Niño event. However, the fluxes observed at Site MT3 in 2001 and 2002 were higher than those in 2000. Total diatom fluxes showed different seasonal patterns at all sites. The diatom assemblages in the WPWP differed from those of the EUR. Pennate diatoms (e.g., Nitzschia bicapitata, Thalassionema nitzschioides) dominated in the WPWP, while the relative abundances of centric diatoms (e.g., Rhizosolenia bergonii, Azpeitia spp., Thalassiosira spp.) were higher than those of pennate diatoms in the EUR. The diatom fluxes during the La Niña event reflected seasonal oscillation of the WPWP in spatial extent. At Site MT3 during El Niño, terrestrial materials appeared to have been transported by subsurface currents, which might be a secondary influence on total diatom fluxes. The spatial extent of the WPWP reached Site MT7 in 2002, when total diatom fluxes decreased in the sediment traps located in the eastern region including Site MT7. Therefore, we conclude that the relationships between the ENSO and diatoms fluxes in the western and central equatorial Pacific can be explained by the geographic (west–east) expansion or contraction of the WPWP. 相似文献
15.
《Oceanologica Acta》1999,22(3):249-263
Mean conditions, seasonal, and ENSO-related (El Niño Southern Oscillation) variability in the vicinity of Wallis, Futuna, and Samoa islands (13°–15° S, 180°–170° W) over the 1973–1995 period are analysed for wind pseudo-stress, satellite-derived and in situ precipitation, sea surface temperature (SST) and salinity (SSS), sea level, and 0–450 m temperature and geostrophic current. The mean local conditions reflect the presence of the large scale features such as the western Pacific warm pool, the South Pacific Convergence Zone (SPCZ), and the South Pacific anticyclonic gyre. The seasonal changes are closely related to the meridional migrations of the SPCZ, which passes twice a year over the region of study. During the warm phase of ENSO (El Niño), we generally observe saltier-than-average SSS (of the order of 0.4), consistent with a rainfall deficit (0.4 m yr−1), a hint of colder-than-average surface temperature is also identified in subsurface (0.3°C), a weak tendency for westward geostrophic current anomalies (2 cm s−1 at the surface), a sea level decrease (5–10 cm), together with easterly (5 m2s−2) and well marked southerly (10 m2s−2) wind pseudo-stress anomalies. Anomalies of similar magnitude, but of opposite sign, are detected during the cold phase of ENSO (La Niña). While these ENSO-related changes apply prior to the 1990s, they were not observed during the 1991–1994 period, which appears atypical. 相似文献
16.
We investigate an overlooked mechanism—coastal upwelling—for sea surface temperature (SST) cooling in the western side of the mean location of the Pacific warm pool (WSWP: 5°S–5°N, 140°E–150°E) prior to El Niño onset. We analyze various observed data such as the TRIangle Trans-Ocean buoy Network (TRITON) moored buoy data, Conductivity-Temperature-Depth (CTD) data, satellite data and a hindcast experiment output by a high-resolution ocean general circulation model (OGCM). We focus on the precondition of the 2002/03 El Niño event, for which many datasets are available. Relatively cool water upwelled along the north coast of Papua New Guinea (PNG) during December 2001, prior to the onset of the 2002/03 El Niño event, and then spread out over a wider area to the northeast. Simultaneously, strong west-northerly surface winds occur along the north coast. Heat budget analysis of TRITON buoy data in the WSWP reveals that negative zonal heat advection due to eastward current is the main factor for cooling the mixed layer in the WSWP in contrast to the warming effect of the surface heat flux during the period. This cooling requires a source of colder water to the west. Similar analysis of OGCM outputs also suggests that the upwelled relatively cool water along the PNG north coast, and its northeastward extension to the equatorial region, contributes to cooling of the surface water over the WSWP mainly via negative zonal heat advection. Similar mechanisms are confirmed also for the 1982/83 and 1997/98 El Niño events by analyses of OGCM outputs and historical SST data. The low SST in the WSWP generated a positive zonal SST gradient together with high SST east of the WSWP. It may contribute to enhancement of the westerly surface wind in this region, leading to the onset of the 2002/03 El Niño event. 相似文献
17.
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
18.
Having applied the method of discriminant analysis to the TOMS data of satellite sounding of the total ozone content (TOC) in the March months of 1979–2008, the authors could make a new estimate of the TOC field variability in the Northern Hemisphere and interlongitudinal regularities of its changes under the action of climatic variability. The effects of temperature variations in the polar stratosphere, El Niño, and quasi-biennial oscillation (QBO) have proven comparable and reach 80 DU in some regions. The influence of the Arctic Oscillation (AO) reaches 40 DU. The regions of TOC variations and their location and dimensions change depending on the phases of QBO, AO, and El Niño-Southern Oscillation (ENSO). Three regions of increased TOC—over Europe, Eastern Siberia, and the Pacific Ocean—are formed in years with a warm stratosphere. A compensating TOC decrease takes place in the tropics and over Greenland. In the years of El Niño and the easterly QBO phase, the TOC increases over Europe and drops over the central Pacific, as well as to the south from 45° N. The AO controls the ozone growth over most of Eurasia at temperate latitudes and its weak drop over the Atlantic. It was impossible to obtain such quantitative estimates with the use of methods based on an independent analysis of the TOC series at individual points of the coordinate grid. Testing with the Monte Carlo method confirmed that the results obtained are significant with a probability of 95–99.9%. 相似文献
19.
Four year-long time-series sediment trap experiments were conducted along the equatorial Pacific Ocean in order to understand the biogeochemistry of particulate organic matter (POM) on the basis of amino acid (AA) and hexosamine (HA) compositions of the settling particles. Total mass flux in the study area varied over 4 orders of magnitude without a common seasonality among all trap sites. Planktonic blooms were apparent in terms of total mass and AA fluxes at the easternmost end of the Niño-4 region. AA fluxes closely followed the total mass flux profiles, suggesting that increased particle flux delivered a greater amount of labile OM to the deep ocean. A labile OM index (LI)-based classification showed that during the El Niño conditions in 2002, the eastern side of the equatorial Pacific transported relatively more labile OM than the western equatorial Pacific. An overall change in AA and HA composition of settling particles could be revealed with the help of discriminant analysis, suggesting that settling particles during El Niño were compositionally different from those settling during La Niña condition in the equatorial Pacific. 相似文献
20.
Chun-Mao Tseng K.-K. Liu L.-W. Wang G.-C. Gong 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2129-2143
It is demonstrated that weakened wind mixing and strengthened water column stratification resulted in the anomalously low sea surface chlorophyll in the northern South China Sea during the 1997–1998 El Niño event. Remotely sensed sea surface temperature, wind and chlorophyll, which were validated by shipboard observations at the SouthEast Asian Time-series Study (SEATS) station (18°N, 116°E) in the northern South China Sea (SCS) provided the basis for this study. During the 1997–1998 winter at the SEATS station, the sea surface temperature was elevated by about 2 °C above the climatological mean, while the wind speed of the northeast monsoon was reduced from a climatological mean of 9.4 to 6.8 m/s. The concentration of surface chlorophyll-a dropped from 0.2 to 0.1 mg/m3. The monthly area-averaged integrated primary production estimated for the northern SCS area (112–119°E, 15–21°N) was reduced by about 40% of the normal winter value. Under the anomalously high sea surface temperature and weak monsoon, the mixed-layer depth would have been reduced from an average of 65 to 45 m and the nutrients in the mixed layer would have been reduced by half, according to observations at the SEATS station in more recent years. During the 1997–1998 El Niño event, the onset of warming in the northern SCS lagged behind that in the eastern equatorial Pacific by about 5 months and lingered for 11 months. This course of change resembled that of the western Pacific warm pool region. However, contrary to the northern SCS, the sea surface chlorophyll was enhanced in the warm pool region during the event, probably mainly because of the uplifted nutricline. Unlike the eastern equatorial Pacific, the dramatic recovery of biological production did not happen in the SCS in the summer of 1998. These distinctive biogeochemical responses reflect fundamental differences between the SCS and the equatorial Pacific in terms of upper water column dynamics. 相似文献