西太平洋帕劳砗磲高分辨率氧同位素记录及其指示的气候环境变化

砗磲是海洋中最大的双壳类贝壳,其碳酸盐壳体通常具有年纹层和天纹层,是一种理想的高分辨率古气候研究载体.氧同位素是砗磲古气候研究中最常用的指标之一,但在将其应用于古气候重建之前,通常需要对其现代地球化学过程进行准确的校准.帕劳群岛位于西太平洋暖池西北边缘,其珊瑚礁盘具有丰富的砗磲壳体资源,为开展古气候研究提供了丰富的材料...     

苏北浅滩及长江口海域春季海表面温度长期升温机制分析

在1982—2016年,苏北浅滩及长江口海域春季海表面温度主要呈现出从南至北、从近岸至离岸升温趋势逐渐减小的特征,其中长江口附近海域升温速率最大。研究显示,苏北浅滩及长江口附近海域春季海表面温度的长期升温趋势主要与该海域经向热输送及长江平流热输送的增强有关。进一步的研究发现,春季经向风速的增强导致该海域经向热输送的增加,而春季经向风速的年际及年代际变率又受到太平洋年代际振荡、北极涛动的调控,其中,太平洋年代际振荡指数与经向风速呈负相关,北极涛动指数与经向风速呈正相关,北极涛动指数的年际增加以及太平洋年代际振荡指数的年际降低使得春季南风增强,进而南向的冷平流减弱,北向的热平流增强,使该海域春季海表面温度长期升温。在此过程中,净热通量对其升温过程起到抑制作用,而前冬海温主要是对春季海表面温度的年代际振荡产生重要影响,其主要体现为1982—1999年的升温及2000—2016年的降温过程。     

Decadal variations of the transport and bifurcation of the Pacific North Equatorial Current

Decadal variations of the transport and bifurcation latitude of the North Equatorial Current (NEC) in the northwestern tropical Pacific Ocean over 1959–2011 are investigated using outputs of the Ocean Analysis/Reanalysis System 3 prepared by the European Centre for Medium-Range Weather Forecasts. The results indicate that the NEC transports at different longitudes have different decadal fluctuations, which are strongest around 139°E. The NEC bifurcation latitude (NBL) has its largest decadal variations around 150 m. Extremes of the decadal NEC transport and NBL before 1975 correspond to different circulation anomalies from those after 1975. The regression map against decadal NBL exhibits negative sea surface height (SSH) anomalies and a cyclonic gyre anomaly over the northwestern tropical Pacific Ocean, while that against the decadal NEC transport exhibits a dipole structure, with positive/negative SSH anomalies to the north/south of about 13°N. Furthermore, decadal variations of the NEC transport and NBL over the whole period have different correlations with Pacific Decadal Oscillation (PDO) and Tropical Pacific Decadal Variability (TPDV). Generally, the decadal NEC transport shows higher correlations with PDO than with TPDV, while the NBL has higher correlations with TPDV than with PDO. The high correlation of decadal NEC transport with PDO mainly comes from that of its northern branch with PDO, while its southern branch shows higher correlation with TPDV.     

南黄海牡蛎壳元素组成的原位微区分析及环境指示

碳酸盐生物壳体的周期性生长纹层是记录气候环境变化的天然材料。随着原位微区测试技术的快速发展,高分辨率的同位素和化学元素组成的快速分析显著推动了古气候环境变化及生物地球化学研究。应用激光剥蚀等离子体质谱仪(LAICP-MS)对南黄海现代牡蛎Crassostrea gigas壳体韧带部的元素组成进行原位微区测试,利用内标元素43Ca进行元素比值的校正,探讨了牡蛎壳中化学元素特征及其环境意义。研究的长牡蛎壳体中Mg/Ca、Sr/Ca、Na/Ca比值具有显著的季节性周期变化。环境水体物理化学性质的变化对壳体生长速率影响较大,壳中白垩质方解石和叶片方解石生长层分别对应较高和较低的环境温度,白垩方解石层具有较高的Mg/Ca、Sr/Ca和较低的Na/Ca比值。Mg/Ca比值可指示牡蛎壳体生长环境水体温度,利用前人Mg/Ca比值公式计算可以恢复与器测资料相符的近岸海水温度结果。本研究对应用LA-ICP-MS分析技术开展高分辨率的生物壳体元素组成和环境示踪研究具有借鉴意义。     

Compound response of marine and terrestrial ecosystems to varying climate: pre-anthropogenic perspective from bivalve shell growth increments and tree-rings

Annual growth increments were examined from shells of the ocean quahog (Arctica islandica L.) from northwest Norway and from tree-ring samples of the Scots pine (Pinus sylvestris L.) from nearby coastal areas. The reconstructed annual growth increments were used to compare growth variability in marine and terrestrial ecosystems. Spatiotemporal comparison of the growth records showed statistically significant correlation during the 19th century A.D., indicative of ecosystem-independent response to pre-anthropogenic climate variations. Geographical correlation between marine and terrestrial records was only observed at the local scale. Years with particularly low winter or high summer North Atlantic Oscillation (NAO) indices showed the best synchronization of marine and terrestrial growth. Despite strong correlation during historical time, our palaeoecological evidence suggests that marine and terrestrial ecosystems may show dissimilar growth reaction to recently observed positive winter-NAO phases.     

Sedimentary records of multidecadal-scale variability of diatom productivity in the Bungo Channel, Japan, associated with the Pacific Decadal Oscillation

In order to examine the responses of primary productivity in the southern coastal sea of Japan to the Pacific Decadal Oscillation (PDO) in the 20th century, sedimentary records of diatom productivity (diatom valve fluxes) were reconstructed using core samples from the Bungo Channel (BC) in southwest Japan. The record of the Thalassionema spp. flux—the best index of fall primary productivity in the BC—indicated a multidecadal-scale duration with a low flux (1943–1982) and those with a high flux (1913–1943 and 1982–2001); apparent shifts were recognized in 1943 and 1982. The shift in 1982 was also recognized in the flux records of other early summer to fall predominant genera in the BC and, previously, in the biogenic silica records from a broad region of the southeast BC. This indicates that in our records, this shift reflects a general trend in the primary production in the southeast BC. A comparison among the Thalassionema spp. flux records, meteorological data from an observatory adjacent to the core site, and the PDO index showed that the flux records were more similar to the PDO index than the other meteorological records, which suggests that the multidecadal-scale variability of the BC primary productivity may be associated with some marine-derived forcing. The bottom intrusions of nutrient-rich water that upwelled from the shelf slope into the BC, the axis movement or the transport of the Kuroshio Current off the BC, and a basin-scale wind stress in the North Pacific might play an important role in this forcing and mediate between the BC primary productivity and the PDO.     

太平洋海温场两种不同时间尺度气候模态的分析

利用经验正交函数分解、多元线性回归分析、小波分析和离散功率谱等方法,对太平洋年代际振荡(PDO)和ENSO的关系进行研究,发现太平洋海温场中主要存在着PDO和ENSO两种气候模态.用线性回归分析方法对这两种模态进行分离,结果表明,去除ENSO信息后,太平洋海温变化的关键区出现于北太平洋中纬度地区,PDO的信号很明显;而去除PDO信息后,海温变化的关键区位于赤道中、东太平洋地区,ENSO的信号较明显,此时ENSO循环不具有年代际振荡的特征,表明PDO对ENSO的调制作用是ENSO事件具有年代际变化特征的重要原因.     

Shell growth and oxygen isotopes in the topshell Osilinus turbinatus: resolving past inshore sea surface temperatures

Shells of the rocky shore intertidal gastropod Osilinus turbinatus (von Born), often abundant in archaeological deposits in the Mediterranean region, are a potential source of data on palaeotemperature, palaeoseasonality and archaeological seasonality. To evaluate this species as a climate archive, investigations of annual patterns of shell growth and of monthly variations in oxygen isotopes in shell carbonates were made on different populations in NW Sicily. Mark-recapture experiments at San Vito lo Capo and Mazzaforno show that O. turbinatus grows almost continuously throughout the year but at different rates in different seasons. Around 75% of the yearly shell growth occurs in the autumn and winter. On average, larger/older shells produce narrower annual growth increments than smaller/younger ones. Conspicuous growth lines in larger/older shells show that growth stops during the hottest part of the summer. Oxygen isotope analyses on monthly collected shells of O. turbinatus from three shores (Cala Grande, Monte Cofano and Mazzaforno) show that the isotope values record temperature variations through the year. In all the datasets, surface seawater temperatures (SSTs) calculated from δ¹⁸O_SHELL mostly underestimate measured SSTs, offsets being generally greater in summer. Minimum annual offsets range from 0.0°C to 0.7°C and maximum annual offsets from 3.1°C to 8.7°C. δ¹⁸O_SHELL values fail to record temperatures higher than 25°C. Careful selection of shells to be analysed can reduce offsets between δ¹⁸O_SHELL temperature estimates and measured SSTs for many parts of the year, except the hottest. Allowing for this, shells of O. turbinatus offer good potential as climate archives and for archaeological studies of seasonal patterns of human foraging for shellfish.     

Growth increments and stable isotope variation in shells of the deep-sea hydrothermal vent bivalve mollusk Bathymodiolus brevior from the North Fiji Basin,Pacific Ocean

Bathymodiolus brevior [von Cosel, R., Métivier, B., Hashimoto, J., 1994. Three new species of Bathymodiolus (Bivalvia: Mytilidae) from hydrothermal vents in the Lau Basin and the North Fiji Basin, western Pacific, and the Snake Pit Area, mid-Atlantic ridge. Veliger 37, 374–392] a bivalve mollusk living at deep-sea hydrothermal vents, exhibits daily microgrowth structures in its shell. This interpretation is substantiated by various lines of evidence: (1) similar shell portions of contemporaneous specimens from the same locality contain almost the same number of microincrements; (2) the number of microincrements coincides with the expected number of days in which shell portions of Bathymodiolus spp. form; (3) the width of such microincrements compares well with daily growth rates estimated for the close relative B. thermophilus [Kenk, V.C., Wilson, B.R., 1985. A new mussel (Bivalvia, Mytilidae) from hydrothermal vents in the Galapagos rift-zone. Malacologia 26, 253–271]; (4) different specimens from the same site show similar microgrowth curves. In addition, we found support for tide-controlled shell growth. Daily shell growth rates fluctuate on a fortnightly basis. Some shell portions also revealed the typical tide-controlled microgrowth pattern commonly observed in intertidal bivalves. Based on the analyses of lunar daily growth increments, a growth curve for B. brevior was computed: X_t=14 cm−(14–0.04 cm) e^−0.26t. This curve enables estimation of ontogenetic age from shell length. According to this equation, B. brevior reaches its maximum shell length of 14 cm at about age 18. Shell isotope analyses suggest that some major shell growth interruptions or retardations are related to extremely active hydrothermal venting activity. However, shell growth also stopped during periods of low venting implying physiological controls on shell formation. Results of the present study demonstrate that shells of B. brevior provide calendars and environmental data loggers that can complement or partly substitute for long-term observations of venting systems.     

The Pacific Decadal Oscillation

The Pacific Decadal Oscillation (PDO) has been described by some as a long-lived El Niño-like pattern of Pacific climate variability, and by others as a blend of two sometimes independent modes having distinct spatial and temporal characteristics of North Pacific sea surface temperature (SST) variability. A growing body of evidence highlights a strong tendency for PDO impacts in the Southern Hemisphere, with important surface climate anomalies over the mid-latitude South Pacific Ocean, Australia and South America. Several independent studies find evidence for just two full PDO cycles in the past century: “cool” PDO regimes prevailed from 1890–1924 and again from 1947–1976, while “warm” PDO regimes dominated from 1925–1946 and from 1977 through (at least) the mid-1990's. Interdecadal changes in Pacific climate have widespread impacts on natural systems, including water resources in the Americas and many marine fisheries in the North Pacific. Tree-ring and Pacific coral based climate reconstructions suggest that PDO variations—at a range of varying time scales—can be traced back to at least 1600, although there are important differences between different proxy reconstructions. While 20th Century PDO fluctuations were most energetic in two general periodicities—one from 15-to-25 years, and the other from 50-to-70 years—the mechanisms causing PDO variability remain unclear. To date, there is little in the way of observational evidence to support a mid-latitude coupled air-sea interaction for PDO, though there are several well-understood mechanisms that promote multi-year persistence in North Pacific upper ocean temperature anomalies.     

Long-term diatom fluxes in response to oceanographic conditions at Stations AB and SA in the central subarctic Pacific and the Bering Sea, 1990–1998

Long-term monitoring of diatom fluxes during 1990–1998 was conducted at Station AB in the Bering Sea and Station SA in the central subarctic Pacific in order to decipher the relationships between sinking diatom and the upper water mass environments. The total diatom flux at Station AB was generally twice as high as that at Station SA. The dominant species in the sinking flora was primarily Neodenticula seminae at both stations, which was a significant contributor to organic carbon flux. The flora at Station AB was represented by relatively abundant coastal taxa including Chaetoceros resting spores. These results suggest more favorable conditions for diatom production at Station AB compared with those at Station SA. The possible influences of oligotrophic and temperate water masses were discerned from the positive SST anomaly and the occurrence of a few specimens of temperate species. The cumulative annual fluxes of total diatoms at Stations AB and SA are apparently related to the variation in the mean annual depth of mixed layer. At Station SA, annual mean of total diatom flux showed a negative correlation with the Pacific Decadal Oscillation (PDO) Index, which suggests a significant relationship between surface water turbidity and diatom production. At Station AB, the annual change of coastal diatom flux was correlated with the PDO and the winter value of the Arctic Oscillation, which may suggest a significant influence of Alaskan Stream waters via the Aleutian Islands and intensity of surface water mixing.     

High-resolution isotopic records (δ 18O and δ 13C) and cathodoluminescence study of lucinid shells from methane seeps of the Eastern Mediterranean

We present high-resolution isotopic records and cathodoluminescence studies of recently dead and live bivalve specimens from cold seeps, in an attempt to reconstruct environmental conditions during organism growth, and thereby the possible variability of fluid-venting activity at the seafloor. Shells of the burrowing lucinid Myrtea aff. amorpha were collected at three localities near actively venting methane seeps in the Eastern Mediterranean deep sea, using the Nautile submersible during two French oceanographic cruises: from the Kazan mud volcano, in the vicinity of the Anaximander mounts (MEDINAUT cruise, 1998), and from the central pockmark province and the Amon mud volcano of the Nile deep-sea fan (NAUTINIL cruise, 2003). The oxygen and carbon isotope compositions of 18 shells from the various localities, and also from different sites at the same locality show a rather strong scatter (1.8 < δ ¹⁸O‰ < 3.4; −10.2 < δ ¹³C‰ < 2.2), and values lower than those expected for carbonate precipitated at equilibrium with present-day bottom waters. This means that warm methane-rich fluids were mixed with bottom seawater during precipitation of shell carbonates. We have tried to determine ontogenetic age of two shells by using cathodoluminescence as a sclerochronological proxy, because the direct counting of carbonate increments was not possible in these specimens. There is a relatively good correspondence between cathodoluminescence trends and oxygen isotope profiles that might support the link between manganese incorporation during growth and temperature. Eight specimens of lucinid shells were selected for high-resolution isotopic profiling. A few shells exhibit decreasing δ ¹⁸O and δ ¹³C values from the umbo to the actively growing ventral shell margin, which can be attributed to the commonly observed physiologically controlled deceleration of growth with increasing organism age, this metabolic effect corresponding to the increase of incorporation of respiratory CO₂. A few shells exhibit high-frequency δ ¹⁸O variations with an amplitude of about 1.5‰ that might be related to temperature variations controlled by fluid-venting activity. One shell from the pockmark province of the Nile deep-sea fan records a strong, sharp δ ¹³C decrease of about 9‰, and extending over a 5-mm interval in the shell that can be related to a major methane release event. Another shell from the Kazan mud volcano exhibits a progressive increase of δ ¹³C values from −10‰ to 0‰ with age, which might indicate decreasing methane flow throughout the organism’s life. This study has demonstrated that bivalve shells from deep-sea cold seeps represent good indicators of variability in seepage activity of methane-rich fluids, at various scales in both space and time. Although the precise chronology of the observed events was not established, because shell growth rate is not known in this case, this remains a priority for future studies in such environments.     

A 290-a record of atmospheric circulation over the North Pacific from a Mt.Logan ice core, Yukon Territory

Calibrations between sodium （Na^＋） concentrations from a Mt. Logan ice core and sea level pressure （SLP） series show that Na^＋ concentrations are closely correlated with the autumn-time （September-October-November） Aleutian low （AleuLow）. A deepening of the AleuLow strengthens the transport of sea-salt aerosols from the North Pacific to the Mt. Logan region. The Mt. Logan Na^＋ record is used to develop a 292 a （1688-1979） reconstruction of the AleuLow revealing a dramatic intensification of atmospheric circulation over the North Pacific region since the 20th century. Mean SLP of the AleuLow was about 1 hPa lower during the 20th century than during prior periods. The strongest deepening of the AleuLow appeared in the 1950s. Significant correlations are also found between the Mt. Logan AleuLow proxy series and the Pacific decadal oscillation （PDO） and Pacific circulation （PC） index during the 20th century. Evolutionary spectral analysis of the proxy record shows significant periodicities from 15 to 30 a consistent with PDO fluctuations and the bidecadal oscillation of North Pacific atmosphere-ocean circulation. A period of 11 a in the AleuLow record may be associated with the Schwabe 11-a cycle of sunspot activity. Additional longer ice core records from this region will aid in the efforts to further understand the climatic change over the North Pacific region.     

近50年来长江入海径流量对太平洋年代际震荡变化的响应

太平洋年代际震荡(Pacific Decadal Oscillation)是类似于ENS0型的具有年代际时间尺度变化的太平洋气候变率.PDO既对长期的气候变化趋势产生扰动,又会对年际变化事件(如ENSO)产生重要影响,可使ENSO事件的频率和强度改变,以致影响到ENSO和季风的关系.通过对百年来的PDO数据进行HHT分...     

北太平洋柔鱼不同阶段角质颚微量元素含量差异及洄游路径推测的应用

大洋性鱿鱼的洄游路径能够给我们重要的信息,帮助我们了解其时空分布的变化。标记-重捕和电子标记方法在施行过程中仍存在一些问题。头足类的硬组织,如角质颚,有着稳定的形态特征和类似耳石的连续生长纹,同时包含丰富的生态信息,可以为我们研究物种的时空分布提供相关信息。本研究中,我们以北太平洋柔鱼为研究对象,基于不同角质颚生长阶段进行取样来重建鱿鱼的洄游路径。研究结果认为,通过电感耦合等离子质谱仪（LA-ICP-MS）取样,发现角质颚的喙端矢状平面（RSS）检测到9种微量元素。针对上述几种元素,发现不同生长阶段的磷（P）、铜（Cu）和锌（Zn）存在显著差异。利用钠（Na）、磷和锌与海表面温度（SST）建立线性回归模型。基于贝叶斯模型,计算出不同时期柔鱼出现的较高概率的海域。结合不同时期的高概率分布海域,建立起柔鱼的洄游路径,该结果与前人研究结果一致。本研究也证实了角质颚可以为研究大洋性柔鱼的洄游路径提供有效的信息。     

皱纹盘鲍(Haliotis discus hannai)不同群体贝壳形态和相对生长变异研究

皱纹盘鲍是我国重要的渔业资源,其地理群体也是我国重要的鲍种质资源来源。不同地理群体间形态及相对生长的差异对皱纹盘鲍资源管理和种质资源鉴定等提供重要参考。以我国自然海区采集的7个皱纹盘鲍群体作为研究材料,通过测定9个形态测量指标并定义了这些测量指标间的17个比率变量,分析了群体内和群体间贝壳形态和体重相对生长的变异。除个别变量外,协方差分析揭示形态比率变量在群体间存在显著变异;异速生长研究揭示了壳形态特征与皱纹盘鲍群体中异速生长差异之间的高度线性相关性,异速生长程度呈现一定的群体区别。非度量多维尺度分析(NMDS)和马氏距离聚类分析(CLUSTER)将皱纹盘鲍群体分为2个组,线性判别分析(LDA)与NMDS和CLUSTER结果相符,然而LDA未能较好的将各种群样本分类。研究结果初步表明皱纹盘鲍表现出与我国沿海环境和/或生态条件差异相关的表型可塑性,然而这种表型差异也可能受到人工底播苗种的遗传影响。研究结果将对于皱纹盘鲍渔业资源管理如管理单位的界定,以及为今后全面评价皱纹盘鲍不同地理群体的遗传变异等提供参考。     

西北太平洋柔鱼角质颚微结构及其生长纹周期性研究

本文分析了采集于北太平洋海域的35尾柔鱼(Ommastrephes bartramii)角质颚的微结构,并对其生长纹的周期性进行了验证。研究结果显示:上颚喙部截面由头盖和脊突两部分组成,周期性的生长带明显,每条生长带由明、暗相间的两条生长纹组成。头盖部的生长纹明显比脊突部的清晰,两者交汇于内轴成""形。喙部顶端以及后端常有明显的标记轮,其形成与个体发育期的特殊事件以及外界的突发事件有关。角质颚生长纹数目与耳石日龄相当(P0.05),证明柔鱼角质颚生长纹的沉积为"一日一纹"。根据角质颚生长纹估算柔鱼的生命周期小于1年,样本胴长、体重和角质颚喙长与日龄呈显著的逻辑斯蒂关系。研究结果不仅为柔鱼类年龄鉴定和生长估算提供新方法,而且为我国头足类学者开展相关研究提供重要基础。     

High-resolution trace element profiles in shells of the mangrove bivalve Isognomon ephippium: a record of environmental spatio-temporal variations?

The shell chemistry of Isognomon ephippium from three Kenyan sites (Tudor, Gazi and Mida) has been investigated to determine whether these bivalves record environmental parameters. The Mg, Sr, Ba and Mn distributions in the calcite shell layer were determined by using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). In addition, whole-shell analyses were made to evaluate inter-site differences. While some variability is observed for mean Mg concentrations, the mean Sr concentrations were similar for the three sites. The decreasing mean Ba and Mn concentrations, following the order Tudor > Gazi > Mida, are related to distinct regimes of freshwater and nutrient supply. The Mg profiles, determined by LA-ICP-MS, displayed a close to regular sinusoidal pattern, depending on specimen and sample site. For the Tudor shells, an arbitrary fitting of the Mg profiles to sea-surface temperature (SST) variations emphasised the good relationship between these two parameters and allowed for the calculation of mean annual growth rates. In most of the shells, Sr partly co-varied with Mg and Ba, highlighting the complexity of Sr incorporation. The Ba and Mn profiles of the Tudor shells displayed several sharp maxima. With a time scale deduced from the Mg–SST relationship, the Ba and Mn maxima of the Tudor shells closely followed periods of maximal rainfall associated with the southeast monsoon. These Ba and Mn maxima were tentatively associated with algal bloom events known to succeed these periods of high rainfall. The less clearly marked seasonality of the Ba and Mn maxima for the Gazi and Mida specimens is thought to result from weaker seasonal variations in nutrient supply and reduced nutrients inputs. This study highlights the potential of I. ephippium as a recorder of spatio-temporal environmental variations in tropical coastal ecosystems.     

CCSM3对太平洋年代际振荡的敏感性试验

利用NCAR的CCSM3模式进行控制试验和1870-1999年的130 a模拟试验(敏感性试验),与相应的再分析资料进行对比,分析了太平洋海区的海温变化趋势和北太平洋年代际变率的时空结构,并且讨论了CO2对于北太平洋年代际变率的影响.结果表明:CCSM3模式能够模拟出北太平洋年代际变率的主要特征,其空间分布类似于典型的...     

Local origins of interdecadal Pacific variability in the tropical and North Pacific Ocean: evidence from a comparative study of coral oxygen isotope records

Interdecadal Pacific variability (IPV) is commonly observed in both the tropical and mid-latitude Pacific Ocean, and has a widespread influence on surface climate in the Pan-Pacific Basin. This variability is recorded by climate proxies such as geochemical parameters preserved in corals. However, the origins of IPV remain uncertain. To shed light on this, interdecadal variations in two long coral δ¹⁸O records from Nauru Island and the South China Sea (SCS), respectively located in the tropical Pacific and the mid-latitude North Pacific Ocean, were investigated. The interdecadal fluctuations in the δ¹⁸O series from Nauru Island (tropical Pacific) match those of the NINO3.4 index reasonably well (r=–0.30, n=96, p=0.0015), but are not correlated with those of the Pacific decadal oscillation (PDO) index (r=–0.17, n=96, p=0.05). The δ¹⁸O time series from the SCS (northwestern Pacific), by contrast, co-vary with the PDO index (r=–0.30, n=156, p=0.0007), but are out of phase with the NINO3.4 index at the interdecadal timescale (r=0.04, n=156, p=0.31). The impact on the interdecadal variability of processes occurring outside the growth region of corals is generally weak. The results thus do not support a tropical origin of IPV, but demonstrate that the interdecadal variability in the tropical Pacific and the North Pacific originates predominantly from local coupled ocean–atmosphere processes within these regions. The results also suggest that tropical–extratropical interactions played a role in IPV between 1920 and 1940, which indicates that IPV is a complex climatic phenomenon that involves multiple forcing mechanisms.