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1.
We describe a new tree-ring width data set of 14 white spruce chronologies for the Seward Peninsula (SP), Alaska, based on living and subfossil wood dating from 1358 to 2001 AD. A composite chronology derived from these data correlates positively and significantly with summer temperatures at Nome from 1910 to 1970, after which there is some loss of positive temperature response. There is inferred cooling during periods within the Little Ice Age (LIA) from the early to middle 1600s and late 1700s to middle 1800s; and warming from the middle 1600s to early 1700s. We also present a larger composite data set covering 978–2001 AD, utilizing the SP ring-width data in combination with archaeological wood measurements and other recent collections from northwestern Alaska. The Regional Curve Standardization (RCS) method was employed to maximize potential low-frequency information in this data set. The RCS chronology shows intervals of persistent above-average growth around the time of the Medieval Warm Period (MWP) early in the millennium, which are comparable to growth levels in recent centuries. There is a more sustained cold interval during the LIA inferred from the RCS record as compared to the SP ring-width series. The chronologies correlate significantly with Bering and Chukchi Sea sea surface temperatures and with the Pacific Decadal Oscillation index. These atmosphere–ocean linkages probably account for the differences between these records and large-scale reconstructions of Arctic and Northern Hemisphere temperatures based largely on continental interior proxy data.  相似文献   

2.
We review here proxy records of temperature and precipitation in China during the Holocene, especially the last two millennia. The quality of proxy data, methodology of reconstruction, and uncertainties in reconstruction were emphasized in comparing different temperature and precipitation reconstruction and clarifying temporal and spatial patterns of temperature and precipitation during the Holocene. The Holocene climate was generally warm and wet. The warmest period occurred in 9.6-6.2 cal ka BP, whereas a period of maximum monsoon precipitation started at about 11.0 cal ka BP and lasted until about 8.0-5.0 cal ka BP. There were a series of millennial-scale cold or dry events superimposed on the general trend of climate changes. During past two millennia, a warming trend in the 20th century was clearly detected, but the warming magnitude was smaller than the maximum level of the Medieval Warm Period and the Middle Holocene. Cold conditions occurred over the whole of China during the Little Ice Age （AD 1400-AD 1900）, but the warming of the Medieval Warm Period （AD 900-AD 1300） was not distinct in China, especially west China. The spatial pattern of precipitation showed significant regional differences in China, especially east China. The modern warm period has lasted 20 years from 1987 to 2006. Bi-decadal oscillation in precipitation variability was apparent over China during the 20th century. Solar activity and volcanic eruptions both were major forcings governing the climate variability during the last millennium.  相似文献   

3.
We review here proxy records of temperatare and precipitation in China during the Holocene,especially the last two millennia.The quality of proxy data,methodology of reconstruction,and uncertainties in reconstruction were emphasized in comparing different temperatare and precipitation reconstruction and clarilying temporal and spatial patterns of temperature and precipitation during the Holocene.The Holocene climate was generally warm and wet.The warmest period occurred in 9.6-6.2 cal ka BP,whereas a period of maximum monsoon precipitation started at about 11.0 cal ka BP and lasted until about 8.O-5.0 cal ka BP.There were a series of millennial-scale cold or dry events superimposed on the general trend of climate changes.During past two millennia,a warming trend in the 20th century was clearly detected,but the warming magnitude was smaller than the maximum level of the Medieval Warm Period and the Middle Holocene.Cold conditions occurred over the whole of China during the Little Ice Age (AD 1400-AD 1900),but the warming of the Medieval Warm Period(AD 900-AD 1300)was not distinct in China,especially west China.The spatial pattern of precipitation showed significant regional differences in China,especially east China.The modern warm period has lasted 20、years from 1987 to 2006.Bi-decadal oscillation in precipitation variability was apparent over China during the 20th century. Solar activity and volcanic eruptions both were major forcings governing the climate variability during the last millennium.  相似文献   

4.
Two concepts are introduced for detecting abrupt climate changes. In the first case, the sampling frequency of climate data is high as compared to the frequency of climate events examined. The method is based on a separation of trend and noise in the data and is applicable to any dataset that satisfies some mild smoothness and statistical dependence conditions for the trend and the noise, respectively. We say that an abrupt change occurs when the first derivative of the trend function has a discontinuity and the task is to identify such points. The technique is applied to Northern Hemisphere temperature data from 1850 to 2009, Northern Hemisphere temperature data from proxy data, a.d. 200?C1995 and Holocene ??18O values going back to 11,700 years BP. Several abrupt changes are detected that are, among other things, beneficial for determining the Medieval Warm Period, Little Ice Age and Holocene Climate Optimum. In the second case, the sampling frequency is low relative to the frequency of climate events studied. A typical example includes Dansgaard?COeschger events. The methodology used here is based on a refinement of autoregressive conditional heteroscedastic models. The key element of this approach is the volatility that characterises the time-varying variance, and abrupt changes are defined by high volatilities. The technique applied to ??18O values going back to 122,950 years BP is suitable for identifying DO events. These two approaches for the two cases are closely related despite the fact that at first glance, they seem quite different.  相似文献   

5.
A tree-ring 14C record and a simple box model of the global 14C cycle are combined using a method of optimal estimation theory (Rauch-Tung-Striebel smoother). The combination is used to infer information about the time evolution of 14C production in the atmosphere for the period 9400 year BC to AD 1900 year. Unlike previous attempts to infer changes from the tree-ring record, the errors in both the 14C data and the model, which are assumed to be purely random (not systematic), are formally considered. The optimal time evolution of is compared to independent evidence of changes in cosmogenic nuclide production over the Holocene from a variety of records on their original chronology, e.g., a record of the virtual axial dipole moment (VADM) based on a compilation of archeomagnetic data, the record of 10Be concentration from the GISP2 ice core (Central Greenland), and the record of 10Be concentration from the PS1 ice core (South Pole). The rank correlations between and are highly significant (p < 0.01), indicating that geomagnetic field intensity and 10Be concentration in GISP2 and PS1 changed monotonically with 14C production. The linear correlation coefficients between are also highly significant (p<0.01) but relatively small (–0.76, 0.48, and 0.60, respectively). Thus, an important fraction (42–77%) of the variance in the geomagnetic and 10Be data is not accounted for by linear regression on the 14C productions implied by the tree-ring record. The variance near the 1500 yr period, which previous authors interpreted as solar variability, represents a small fraction of the total variance in the time series (<15% for the band 1200–1800 yr) and does not correspond to a spectral peak. Hence, the hypothesis of a direct solar forcing mechanism for the postulated millennial climate variability during the Holocene is not supported.  相似文献   

6.
Sediment cores from Lake Titicaca contain proxy records of past lake level and hydrologic change on the South American Altiplano. Large downcore shifts in the isotopic composition of organic carbon, C/N, wt.%Corg, %CaCO3, and % biogenicsilica illustrate the dynamic changes in lake level that occurred during the past 20,000 years. The first cores taken from water depths greater than 50 meters in the northern subbasin of the lake are used to develop and extend the paleolake-level record back to the Last Glacial Maximum (LGM). Quantitative estimates of lake level are developed using transfer functions based on the 13C of modern lacustrine organic sources and the 13C of modern sedimented organic matter from core-tops. Lake level was slightly higher than modern during much of the post-LGM (20,000–13,500 yr BP) and lake water was freshunder the associated outflow conditions. The Pleistocene/Holocene transition (13,500–7,500 yr BP) was a period of gradual regression, punctuated by minor trangressions. Following a brief highstand at about 7250 yr BP, lake level dropped rapidly to 85 m below the modern level, reaching maximum lowstand conditions by 6250 yr BP. Lake level increased rapidly between 5000yr BP and 4000 yr BP, and less rapidly between 4000 yr BP and 1500 yr BP.Lake level remained relatively high throughout the latest Holocene with only minor fluctuations (<12 meters). Orbitally induced changes in solar insolation, coupled with long-term changes in El Niño-Southern Oscillation variability, are the most likely driving forces behind millennial-scale shifts in lake level that reflect regional-scale changes in the moisture balance of the Atlantic-Amazon-Altiplano hydrologic system.  相似文献   

7.
Summary ¶An Objective 500-hPa cyclone detection and analysis is performed during the warm-dry period (16 April to 15 October) of the year for the Central and Eastern Mediterranean Region (30°N–50°N, 5°E–35°E). The 40-year NCEP/NCAR reanalyzes gridded data of geopotential height and temperature employed in the study, enable a climatic approach with a spatial (2.5°×2.5°) and a 6-hour temporal (00, 06, 12, 18 UTC) resolution. The occurrence frequency for the entire region shows a high interannual variability without significant trends. The frequency maximization over land in the middle of the warm period indicates a possible relationship with land-air temperature difference. Three primary activity centers (Turkey, Black Sea and Genoa) are objectively determined in the frequency domain as local maxima and their intensity is assessed in terms of average geopotential height and temperature values. The Turkey center, though the most frequent, consists of shallow lows in contrast to the Black Sea center, which is second in frequency, but on average, contains the deepest lows amongst the three. The Genoa center, which comes third in frequency, shows the highest variability in the intensity of the lows. Frequency distributions in the area, during the three sub periods (Early, Middle and Late Warm Period) and during the four synoptic hours, provide insight in to the origins of these systems at the three locations and reveal secondary centers, such as the centers in the Adriatic (at 18 UTC), Northern Greece (during Middle Warm Period) and the South Aegean Sea (during Late Warm Period).Received February 20, 2002; revised November 4, 2002; accepted January 16, 2003 Published online July 30, 2003  相似文献   

8.
An increasing number of proxy records, which are related to changes in the hydrological cycle, have been collected for climate reconstructions of the last millennium. There has been, however, little attempt to test climate models with such proxy records or to interpret proxy records using climate model simulations. In the present study, we analyze the hydrological changes between three different types of experiments: a present-day control, a perpetual AD 1640, and an ensemble of six transient Maunder Minimum (AD 1640–1715) simulations. Atmospheric moisture transport is investigated in terms of contributions of specific humidity and circulation changes. The study points out the importance of the specific humidity contribution to changes in moisture transport reflected in hydrological proxy records. The moisture budget of the western tropical Pacific is also investigated to aid the interpretation of a proxy record in this specific region. The present-day freshening of the western tropical Pacific, compared to the Maunder Minimum, is explained by the increased zonal moisture transport via trade winds, mainly due to the increased amount of atmospheric water vapor content in the warming world. Due to the existence of several uncertainty factors, such as forcing reconstructions, the link between the model simulations and proxy records is, however, not definitive, but the thermal contribution to hydrological proxy records is important and not limited to the Maunder Minimum period.  相似文献   

9.
Owen K. Davis 《Climatic change》1994,26(2-3):271-287
Decreased solar activity correlates with positive cosmogenic isotope anomalies, and with cool, wet climate in temperate regions of the world. The relationship of isotope anomalies to climate may be the opposite for areas influenced by monsoonal precipitation, i.e., negative anomalies may be wet and warm. Petersen (1988) has found evidence for increased summer precipitation in the American Southwest that can be shown to be coincident with negative14C anomalies during the Medieval Warm Period. The present study compares palynological indicators of lake level for the Southwest with Petersen's data and with the14C isotope chronology. Percentages of aquatic pollen and algae from three sites within the Arizona Monsoon record greater lake depth or fresher water from A.D. 700–1350, between the Roman IV and Wolf positive isotope anomalies, thereby supporting Petersens's findings. Maximum summer moisture coincides with maximum population density of prehistoric people of the Southwest. However, water depth at a more northern site was low at this time, suggesting a climateisotope relationship similar to that of other temperate regions. Further analysis of latitudinal patterns is hampered by inadequate14C dating.  相似文献   

10.
We inferred the Holocene paleoclimate history of the northeastern Yucatan Peninsula, Mexico, by studying stratigraphic variations in stable isotopes (δ 18O and δ 13C) and lithologic properties (organic matter and carbonate content) in sediment cores taken in 6.3 and 16.2 m of water from Lake Punta Laguna. We present a simple model to explain the lithologic and isotopic variations, and discuss the inferred paleoclimate history in terms of its relation to ancient Maya cultural development. We find evidence for lower lake level and drier climate at about the same time as each major discontinuity in Maya cultural history: Preclassic Abandonment (150–250 A.D.), Maya Hiatus (534 to 593 A.D.), Terminal Classic Collapse (750–1050 A.D.), and Postclassic Abandonment (mid-fifteenth century). Although these broad temporal correlations suggest climate played a role in Maya cultural evolution, chronological uncertainties preclude a detailed analysis of climate changes and archaeologically documented cultural transformations.  相似文献   

11.
Two Holocene ice core records from East Antarctica (Vostok and EPICA-Dome C) were analysed for dust concentration and size distribution at a temporal resolution of 1 sample per ~50 years. A series of volcanic markers randomly distributed over the common part of the ice cores (from 9.8 to 3.5 kyear BP) ensures accurate relative dating (±33 years). Dust-size records from the two sites display oscillations structured in cycles with sub-millennial and secular scale frequencies that are apparently asynchronous. The power spectra of the composite sum (Σ) of the two dust-size records display spectral energy mostly for 150- to 500-year periodicities. On the other hand, the 200-year band is common to both records and the 200 year components of the two sites are out-of-phase (100-year lead or lag) over ~5.5 kyear, a phenomenon also reflected by a significant (>99% conf. lev.) band in the power spectra of the composite difference (Δ) of the two size records. During long-range transport, mineral dust originating from the Southern Hemisphere continents is graded to a variable extent depending on the altitude and duration of atmospheric transport. Relatively coarse dust is associated with air mass penetration from the middle–lower troposphere and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the Antarctic plateau, a hypothesis already proposed for the changes that occurred during the Last Glacial Maximum to Holocene transition (Delmonte et al. 2004b). Moreover, we assume that the overall fluctuation of air mass advection over Antarctica depends on the meridional pressure gradient with respect to low latitudes, i.e. the Antarctic Oscillation (AAO). We therefore suggest a regional variability in atmospheric circulation over East Antarctica. The 150–500 year power spectrum of the composite (Σ) parameter represents the long term variability of the AAO, imprinted by secular internal oscillations probably related to the southern ocean-climatic system. On the other hand, the Δ dust composite parameter suggests a persistent atmospheric dipole over East Antarctica delivering coarser (finer) dust particles alternatively to Vostok and Dome C regions with a bi-centennial periodicity. Indeed, a seesaw phenomenon in dust size distribution was already observed at three East Antarctic sites during the last deglaciation (Delmonte et al. 2004b) and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south pole. Interestingly, the Δ parameter shows a pronounced 200-year oscillation mode, throwing new light on the unresolved question of a possible relationship between climate and solar activity.  相似文献   

12.
Climatic change evidence and lacustrine varves from maar lakes,Germany   总被引：2，自引：0，他引：2  
Annually laminated, non-glacial lake sediments from Lake Holzmaar (Eifel, western Germany) were investigated using large Merkt thin sections. The absolute age of varve intervals with variations in thickness and composition were correlated to climatic changes recorded by glacier fluctuations in the Alps. Back to 8800 years VT (varve time = varve years before 1950) glacier advances coincide with sedimentation rate minima; prior to 8800 years VT they coincide with sedimentation rate maxima. The early and middle Holocene sediments suggest a periodicity of about 1000 years for cold/warm cycles. A sequence of 512 varve-thickness measurements was subjected to spectral analysis. These provide apparent evidence for a 11-year sun-spot cycle.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program.  相似文献   

13.
A quantitative measure of the rate at which fossil-pollen abundances changed over the last 18 000 years at 18 sites spread across eastern North America distinguishes local from regionally synchronous changes. Abrupt regional changes occurred at most sites in late-glacial time (at 13700, 12 300, and 10000 radiocarbon yr BP) and during the last 1000 years. The record of abrupt late-glacial vegetation changes in eastern North America correlates well with abrupt global changes in ice-sheet volume, mountain snow-lines, North Atlantic deep-water production, atmospheric CO2, and atmospheric dust, although the palynological signal varies from site to site. Changes in vegetation during most of the Holocene, although locally significant, were not regionally synchronous. The analysis reveals non-alpine evidence for Neoglacial/Little Ice Age climate change during the last 1000 years, which was the only time during the Holocene when climate change was of sufficient magnitude to cause a synchronous vegetational response throughout the subcontinent. During the two millennia preceding this widespread synchronous change, the rate of change at all sites was low and the average rate of change was the lowest of the Holocene.Contribution to Clima Locarno Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program  相似文献   

14.
Annual precipitation for the last 2,500 years was reconstructed for northeastern Qinghai from living and archaeological juniper trees. A dominant feature of the precipitation of this area is a high degree of variability in mean rainfall at annual, decadal, and centennial scales, with many wet and dry periods that are corroborated by other paleoclimatic indicators. Reconstructed values of annual precipitation vary mostly from 100 to 300 mm and thus are no different from the modern instrumental record in Dulan. However, relatively dry years with below-average precipitation occurred more frequently in the past than in the present. Periods of relatively dry years occurred during 74–25 BC, AD 51–375, 426–500, 526–575, 626–700, 1100–1225, 1251–1325, 1451–1525, 1651–1750 and 1801–1825. Periods with a relatively wet climate occurred during AD 376–425, 576–625, 951–1050, 1351–1375, 1551–1600 and the present. This variability is probably related to latitudinal positions of winter frontal storms. Another key feature of precipitation in this area is an apparently direct relationship between interannual variability in rainfall with temperature, whereby increased warming in the future might lead to increased flooding and droughts. Such increased climatic variability might then impact human societies of the area, much as the climate has done for the past 2,500 years.  相似文献   

15.
Summary The response of Lake Victoria basin climate to changes in the lake surface temperatures (LST) has been examined using NCAR-Regional climate model (RegCM2). In the control run uniform lake surface temperature of 24°C was prescribed and the model integrated for four months, starting at the beginning of September, 1988. In the anomaly experiments the LST was perturbed by ±1.5°C, and kept constant during the entire period of the integrations.Simulation results show significant relationship between basin-wide spatial distribution of rainfall and changes in LST. In general during the short rains at warmer/cooler LSTs, significant increase/decrease in the simulated rainfall occurs over the lake surface and surrounding areas. Rainfall exceeding the amount in the control run by more than 50%, particularly over the western, south/southwestern and central parts of the lake is simulated in the run in which the LST is 1.5°C warmer than the control. It is also evident from our results that different parts of the lake basin respond differently to LST changes which is in contrast to the common characterization of the lake basin as a single homogeneous climate regime in many previous studies.In general the results show that regions with largest response to LST anomalies during the short rains are collocated with the ITCZ. In October when the ITCZ is directly located over the lake, the largest response (maximum rainfall) is also located over the same region. As the season progresses and the ITCZ shifts out of the lake into northern Tanzania, the regions of rainfall maxima also shift with it. This appears to explain the unexpected reduction in over-lake rainfall in December in spite of the LST being warmer than control by 1.5°C. We believe this is a direct consequence of the enhanced convection to the south of the lake (over ITCZ) and the tendency of the system to conserve local moisture budget over the lake.  相似文献   

16.
Abrupt temperature changes during the last 1,500 years   总被引：1，自引：1，他引：0  
We investigate the occurrence of abrupt changes in a total of 35 different proxy records from the extra-tropical Northern Hemisphere for the last ~1,500 years. The proxy records include ice-core δ18O, speleothem, tree ring width/density, marine sediment and lake sediment records with annual, sub-decadal or decadal resolutions. The aim is to explore the spatio–temporal distribution of abrupt climate changes using a kink point analysis technique. A clustering of warm kink points (the kink points with the highest temperatures) around AD 1000 appears corresponding to the Medieval Warm Period and indicates a geographically widespread temperature peak at that time. Kink points around AD 1000 are somewhat more numerous on higher latitudes than on lower latitudes. There are some tendencies for the coldest kink points (the kink points with the lowest temperatures) to be clustered in the ninetenth century, but they are generally more unevenly spaced in time than the warm peaks around AD 1000. The relative lack of kink points detected during the 1500 s–1700 s, likely the coldest part of the Little Ice Age, implies that this cold period was relatively stable and without abrupt events. A possible cluster of kink points on lower latitudes in the early ninth century is also found. No clear difference in the timing of kink points between the different proxy types can be observed.  相似文献   

17.
Jinwon Kim 《Climatic change》2005,68(1-2):153-168
The effects of increased atmospheric CO2 on the frequency of extreme hydrologic events in the Western United States (WUS) for the 10-yr period of 2040–2049 are examined using dynamically downscaled regional climate change signals. For assessing the changes in the occurrence of hydrologic extremes, downscaled climate change signals in daily precipitation and runoff that are likely to indicate the occurrence of extreme events are examined. Downscaled climate change signals in the selected indicators suggest that the global warming induced by increased CO2 is likely to increase extreme hydrologic events in the WUS. The indicators for heavy precipitation events show largest increases in the mountainous regions of the northern California Coastal Range and the Sierra Nevada. Increased cold season precipitation and increased rainfall-portion of precipitation at the expense of snowfall in the projected warmer climate result in large increases in high runoff events in the Sierra Nevada river basins that are already prone to cold season flooding in todays climate. The projected changes in the hydrologic characteristics in the WUS are mainly associated with higher freezing levels in the warmer climate and increases in the cold season water vapor influx from the Pacific Ocean.  相似文献   

18.
The Medieval Warm Period is an interval of purportedly warm climate during the early part of the past millennium. The duration, areal extent, and even existence of the Medieval Warm Period have been debated; in some areas the climate of this interval appears to have been affected more by changes in precipitation than in temperature. Here, we provide new evidence showing that several glaciers in western North America advanced during Medieval time and that some glaciers achieved extents similar to those at the peak of the Little Ice Age, many hundred years later. The advances cannot be reconciled with a climate similar to that of the twentieth century, which has been argued to be an analog, and likely were the result of increased winter precipitation due to prolonged La Niña-like conditions that, in turn, may be linked to elevated solar activity. Changes in solar output may initiate a response in the tropical Pacific that directly impacts the El Niño/Southern Oscillation and associated North Pacific teleconnections.  相似文献   

19.
An integrated use of independent palaeoclimatological proxy techniques that reflect different components of the climate system provides a potential key for functional analysis of past climate changes. Here we report a 10,000 year quantitative record of annual mean temperature (T ann), based on pollen-climate transfer functions and pollen-stratigraphical data from Lake Flarken, south-central Sweden. The pollen-based temperature reconstruction is compared with a reconstruction of effective humidity, as reflected by a δ18O record obtained on stratigraphy of lacustrine carbonates from Lake Igelsjön, c. 10 km from Lake Flarken, which gives evidence of pronounced changes in effective humidity. The relatively low T ann, and high effective humidity as reflected by a low evaporation/inflow ratio suggest a maritime early Holocene climate (10,000–8,300 cal year BP), seemingly incompatible with the highly seasonal solar insolation configuration. We argue that the maritime climate was due to the stronger-than-present zonal flow, enhanced by the high early Holocene sea-surface temperatures in the North Atlantic. The maritime climate mode was disrupted by the abrupt cold event at 8,200 cal year BP, followed at 8,000 cal year BP by a stable Holocene Thermal Maximum. The latter was characterized by T ann values about 2.5°C higher than at present and markedly dry conditions, indicative of stable summer-time anti-cyclonic circulation, possibly corresponding with modern blocking anticyclonic conditions. The last 4,300 year period is characterized by an increasingly cold, moist, and unstable climate. The results demonstrate the value of combining two independent palaeoclimatic proxies in enhancing the reliability, generality, and interpretability of the palaeoclimatic results. Further methodological refinements especially in resolving past seasonal climatic contrasts are needed to better understand the role of different forcing factors in driving millennial-scale climate dynamics.  相似文献   

20.
Here we present a multi-proxy paleolimnological record from a closed-basin lake (Ebinur Lake) in northwestern China to investigate climate change in this arid region during the last 1,500 years. The 120-cm long sediment core was dated by AMS radiocarbon and 210Pb methods. The fine-grained clay sediments contain 3–17% organic matter (OM) and 9–31% carbonate, and are interrupted by multiple sand and silt layers. These sand/silt layers, having consistently low OM, were found at 700–800, 1000–1100, 1300–1400, and 1700–1750 a.d., with a time spacing of 300–400 years. We interpret that the low OM sand/silt layers were deposited during higher lake levels caused by increased river inflow from the surrounding mountains during wet climate intervals. This interpretation is supported by concurrent decreases in δ 18O and δ 13C of bulk carbonate and in carbonate content. Wet climate intervals at 700–800 a.d. and at 1700–1750 a.d. also correlate with elevated snow accumulation and low δ 18O from Guliya ice core on the NW Tibetan Plateau, both regions strongly influenced by the westerlies. This approximate 400-year periodicity of wet–dry climate oscillations appear to correlate with solar activity as shown by atmosphere 14C concentration and with paleo-moisture records in interior North America. Our results suggest that solar activities might have played a significant role in driving wet–dry climate oscillations at centennial scales in the interior of Eurasian continent.  相似文献   

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