热带太平洋第二类El Nio事件及其对中国气候的影响

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。     

Anomalous eastward displacement of the tropical western Pacific warm pool and warming of the tropical eastern Pacific

INTRODUCTIONSincetheTOGA-COARElOP(October1992--March1993),usingthelOPdatamanyscientistshaveanalyzedthedifferenttimescaleair-seainteractionduringoccurringanddevelopingperiodof1992/1993EINifio,andespeciallyemphasizedtheintraseasonalvariation(Wuetal.,1993;Liu,1993;WuandSheng,1993).ThishasgottenanewunderstandingoftheEINino*ThisworkissupportedbytheNationalKeyProjectStudiesonShort-rangeClimatePredictionSysteminChinaundercontractNo.96--908-04-02--2.1.FirstinstituteofOceanography,S…     

Spatio-temporal variability of chlorophyll a and its responses to sea surface temperature, winds and height anomaly in the western South China Sea

To understand the response of marine ecosystem to environmental factors, the oceanographic (physical and biochemical) data are analyzed to examine the spatio-temporal distributions of chlorophyll a (Chl a) associated with surface temperature, winds and height anomaly for long periods (1997-2008) in the western South China Sea (SCS). The results indicate that seasonal and spatial distributions of Chl a are primarily influenced by monsoon winds and hydrography. A preliminary Empirical Orthogonal Function (EOF) analysis of remotely sensed data is used to assess basic characteristics of the response process of Chl a to physical changes, which reveals interannual variability of anomalous low Chl a values corresponding to strong El Ni o (1997-1998), high values corresponding to strong La Ni a (1999-2000), low Chl a corresponding to moderate El Ni o (2001-2003), upward Chl a after warm event in 2005 off the east coast of Vietnam. The variability of Chl a in nearshore and the Mekong River Estuary (MER) waters also suggests its response to these warm or cold processes. Considering the evidence for covariabilities between Chl a and sea surface temperature, winds, height anomaly (upwelling or downwelling), cold waters input and strong winds mixing may play important roles in the spatial and temporal variability of high Chl a. Such research activities could be very important to gain a mechanistic understanding of ecosystem responses to the climate change in the SCS.     

ENSO-induced interannual variability in the southeastern South China Sea

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.     

Coupled seasonal variability in the South China Sea

The present study documents the relationship between seasonal variations in sea surface temperature (SST) and precipitation in the South China Sea (SCS) region. There are strong interactions between the atmosphere and ocean in the seasonal variations of SST and precipitation. During the transition to warm and cold seasons, the SST tendency is primarily contributed by net heat flux dominated by shortwave radiation and latent heat flux with a complementary contribution from ocean advection and upwelling. The contribution of wind-driven oceanic processes depends on the region and is more important in the northern SCS than in the southern SCS. During warm and cold seasons, local SST forcing contributes to regional precipitation by modulating the atmospheric stability and lower-level moisture convergence. The SST difference between the SCS and the western North Pacific influences the convection over the SCS through its modulation of the circulation pattern.     

Climatic variability in the vicinity of Wallis,Futuna, and Samoa islands (13°–15° S, 180°–170° W)

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.     

Heat budget of the western Pacific warm pool and the contribution of eddy heat transport diagnosed from HYCOM assimilation

Using the high-resolution Hybrid Coordinate Ocean Model and the Navy Coupled Ocean Data Assimilation Global 1/12° Analysis (GLBa0.08), and the Objectively Analyzed Air–Sea Fluxes and the International Satellite Climatology Cloud Project products, we investigated the seasonal and interannual evolutions of heat budget, including the pseudo-heat content change, the net air–sea heat flux and the eddy heat transport (EHT), based on the time-dependent heat budget analysis in the western Pacific warm pool (WPWP). The results show that the pseudo-heat content change has significant semi-annual variation, which peaks in April–May and September. There is strong positive feedback between EHT and the net air–sea heat flux. EHT is important in balancing the sea surface heat flux into the WPWP. The seasonal EHT variability is dominated by its meridional component. On the interannual time scale, the zonal and vertical components of EHT show comparable amplitudes with the meridional one. The observed net air–sea heat flux in the WPWP is highly correlated with EHT and the pseudo-heat content change on the interannual time scale. The net air–sea heat flux leads the pseudo-heat content change by about half a month and leads EHT by about one month. The variations of the air–sea heat flux and EHT are connected to the El Niño Southern Oscillation events: during the development of El Niño (La Niña) events, the warm pool expanded eastward (retreated westward), the net air–sea surface flux into the WPWP increased (decreased) and EHT enhanced (weakened) significantly.     

ENSO indices from sea surface salinity observed by Aquarius and Argo

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.     

Anomalous hydrographic and biological conditions in the northern South China Sea during the 1997–1998 El Niño and comparisons with the equatorial Pacific

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.     

Coastal upwelling along the north coast of Papua New Guinea and SST cooling over the pacific warm pool: A case study for the 2002/03 El Niño event

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.     

20世纪90年代后期南海上层海温变化趋势的转折

In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea(SCS) is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS sea surface temperature(SST) have changed from warming to cooling since the late 1990 s. A heat budget analysis suggests that the warming of the surface mixed layer during 1984–1999 is primarily attributed to the horizontal heat advection and the decrease of upward long wave radiation, with the net surface heat flux playing a damping role due to the increase of upward latent and sensible heat fluxes. On the other hand, the cooling of the surface mixed layer during 2000–2009 is broadly controlled by net surface heat flux, with the radiation flux playing the dominant role. A possible mechanism is explored that the variation of a sea level pressure(SLP) over the North Pacific Ocean may change the prevailing winds over the SCS, which contributes to the change of the SST in the SCS through the horizontal heat advection and heat fluxes.     

Influence of Asian monsoon and ENSO events on particle fluxes in the western subtropical Pacific

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.     

中国科学院气候系统模式模拟的ENSO循环

On the basis of more than 200-year control run, the performance of the climate system model of Chinese Academy of Sciences(CAS-ESM-C) in simulating the El Ni?o-Southern Oscillation(ENSO) cycle is evaluated, including the onset, development and decay of the ENSO. It is shown that, the model can reasonably simulate the annual cycle and interannual variability of sea surface temperature(SST) in the tropical Pacific, as well as the seasonal phase-locking of the ENSO. The model also captures two prerequisites for the El Ni?o onset, i.e., a westerly anomaly and a warm SST anomaly in the equatorial western Pacific. Owing to too strong forcing from an extratropical meridional wind, however, the westerly anomaly in this region is largely overestimated. Moreover, the simulated thermocline is much shallower with a weaker slope. As a result, the warm SST anomaly from the western Pacific propagates eastward more quickly, leading to a faster development of an El Ni?o. During the decay stage, owing to a stronger El Ni?o in the model, the secondary Gill-type response of the tropical atmosphere to the eastern Pacific warming is much stronger, thereby resulting in a persistent easterly anomaly in the western Pacific. Meanwhile, a cold anomaly in the warm pool appears as a result of a lifted thermocline via Ekman pumping. Finally, an El Ni?o decays into a La Ni?a through their interactions. In addition, the shorter period and larger amplitude of the ENSO in the model can be attributed to a shallower thermocline in the equatorial Pacific, which speeds up the zonal redistribution of a heat content in the upper ocean.     

西沙周边海域海平面异常变化特征及成因分析

Based on the analysis of wind,ocean currents,sea surface temperature(SST) and remote sensing satellite altimeter data,the characteristics and possible causes of sea level anomalies in the Xisha sea area are investigated.The main results are shown as follows:(1) Since 1993,the sea level in the Xisha sea area was obviously higher than normal in 1998,2001,2008,2010 and 2013.Especially,the sea level in 1998 and 2010 was abnormally high,and the sea level in 2010 was 13.2 cm higher than the muti-year mean,which was the highest in the history.In 2010,the sea level in the Xisha sea area had risen 43 cm from June to August,with the strength twice the annual variation range.(2) The sea level in the Xisha sea area was not only affected by the tidal force of the celestial bodies,but also closely related to the quasi 2 a periodic oscillation of tropical western Pacific monsoon and ENSO events.(3)There was a significant negative correlation between sea level in the Xisha sea area and ENSO events.The high sea level anomaly all happened during the developing phase of La Ni?a.They also show significant negative correlations with Ni?o 4 and Ni?o 3.4 indices,and the lag correlation coefficients for 2 months and 3 months are–0.46 and –0.45,respectively.(4) During the early La Ni?a event form June to November in 2010,the anomalous wind field was cyclonic.A strong clockwise vortex was formed for the current in 25 m layer in the Xisha sea area,and the velocity of the current is close to the speed of the Kuroshio near the Luzon Strait.In normal years,there is a "cool eddy".While in 2010,from July to August,the SST in the area was 2–3°C higher than that of the same period in the history.     

热带太平洋海平面低频变化

本文选取ECMWF ORAS4再分析数据对1959-2015年热带太平洋海平面的低频变化进行了分析。热带太平洋海平面年际变化第一模态反映了ENSO爆发阶段的海平面变化,热带东、西太平洋变化反相,其时间序列与Niño3.4指数高度相关。海平面第二模态则体现了El Niño爆发前后热带太平洋暖水的输运过程。El Niño爆发前热带西太平洋暖水聚集的位置,以及爆发后暖水向赤道外输运的位置在两类El Niño事件中均有所不同。此外,ENSO的周期在近半个世纪发生了显著的年代际变化,这一变化与热带太平洋的年代际变化有关。热带太平洋的年代际变化对海平面趋势变化也有着显著的影响。卫星高度计观测到的近20年海平面的快速上升（下降）正是由20世纪90年代后热带太平洋频繁的位相转换引起的。     

热带西太平洋暖池异常东伸与热带东太平洋增温

本文利用“Climate Diagnostics Bulletin”、“Oceanographic Monthly Summary”、美国夏威夷水位中心提供的资料以及TOGA-COAREIOP资料,分析了1992～1993厄尔尼诺事件中西太平洋暖池、东太平洋SST对异常风场的响应,结果指出:由于西风暴发而引起的西太平洋暖水向东输送,不仅导致西太平详水位降低,而且导致温跃层显着升高,进而引起上层海水热含量显着减少,这种减少在温跃层更为明显.东太平洋与此相反,热含量与温跃层深度出现正距平,正距平中心出现时间比西太平洋的负距平均晚两个月;暖池28℃等温线的异常东伸是海流对低空西风异常直接响应的结果,定量估算表明,纬向流异常所引起的温度平流是暖池28℃等温线异常东伸的主要动力,是热带东太平洋异常增温的主要原因之一.     

Oceanic processes of upper ocean heat content associated with two types of ENSO

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.     

热带太平洋海温异常对北极海冰的可能影响

本文利用1950-2015年间Hadley环流中心海冰和海温资料及NCEP/NCAR再分析资料,研究了热带太平洋海温异常对北极海冰的可能影响,并从大气环流和净表面热通量两个角度探讨了可能的物理机制。结果表明,在ENSO事件发展年的夏、秋季节,EP型与CP型El Niño事件与北极海冰异常的联系无明显信号。而La Niña事件期间北极海冰出现显著异常,并且EP型与CP型La Niña之间存在明显差异。EP型La Niña发生时,北极地区巴伦支海、喀拉海关键区海冰异常减少,CP型La Niña事件则对应着东西伯利亚海、楚科奇海地区海冰异常增加。在EP型La Niña发展年的夏、秋季节,热带太平洋海温异常通过遥相关波列,使得巴伦支海、喀拉海海平面气压为负异常并与中纬度气压正异常共同构成类似AO正位相的结构,形成的风场异常有利于北大西洋暖水的输入,同时造成暖平流,偏高的水汽含量进一步加强了净表面热通量收入,使得巴伦支海、喀拉海海冰异常减少。而在CP型La Niña发展年的夏季,东西伯利亚海、楚科奇海关键区受其东侧气旋式环流的影响,以异常北风分量占主导,将海冰从极点附近由北向南输送到关键区,海冰异常增加,而净表面热通量的作用较小。     

Seasonal variability of the surface chlorophyll in the western tropical Pacific from SeaWiFS data

We used Sea-viewing Wide Field-of-view Sensor (SeaWiFS) to document the seasonal cycle of surface chlorophyll in the western tropical Pacific. Surface waters in this region can be divided into two ecosystems. The western end of the cold, salty waters of the cold tongue with high nutrient low chlorophyll (HNLC) characteristics occupies most of the eastern part of the region, while warm, fresh, and oligotrophic waters of the warm pool stand in the western part. Nevertheless, disruption of the oligotrophy may show up at different locations. We reconstructed the seasonal cycle of chlorophyll, sea surface temperature (SST), winds, and surface currents from satellite data and satellite-derived products by extracting the annual and semi-annual harmonics of the time series at each grid point. The calculation was done for the 1999–2004 years in order to exclude the consequences of the major 1997–1998 El Niño Southern Oscillation event. The variance explained by the seasonal cycle for this period highlights three regions with high seasonality: (1) The oligotrophy/HNLC transition zone undergoes meridional seasonal displacements. The cold tongue is at its northernmost (southernmost) position during boreal spring (fall). These displacements can be explained in terms of meridional advection of chlorophyll-rich waters and are consistent with the seasonal cycle of the north and south equatorial countercurrents that transport phytoplankton-poor waters. (2) Ocean-color images show seasonal enrichments in the far western north equatorial countercurrent (NECC) area, especially during boreal spring. The chlorophyll maximum coincides with the maximum NECC velocity, follows a SST minimum, and occurs during the upwelling-favorable phase of the wind stress curl. We attribute these enrichments to local upwelling associated with current meandering, horizontal advection from further west, and transport of nutrient-rich waters by the New Guinea coastal undercurrent. (3) Near the Solomon Archipelago, we observe enhancements of chlorophyll concentration southwest of the islands in austral winter, when both the southwestward surface currents and the southeasterly wind stress are strongest. This may be a combination of an island-mass effect and wind-driven upwelling. Horizontal advection from the Solomon area leads to an almost concurrent seasonal chlorophyll enrichment in the northern Coral Sea. In the Gulf of Papua, high chlorophyll concentrations at the same time can be explained by the presence of a strong cyclonic circulation. This study highlights the richness of the response of surface chlorophyll to physical processes at the seasonal time scale in a region usually acknowledged as oligotrophic.