Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period

A precise relative chronology for Greenland and West Antarctic paleotemperature is extended to 90,000 years ago, based on correlation of atmospheric methane records from the Greenland Ice Sheet Project 2 and Byrd ice cores. Over this period, the onset of seven major millennial-scale warmings in Antarctica preceded the onset of Greenland warmings by 1500 to 3000 years. In general, Antarctic temperatures increased gradually while Greenland temperatures were decreasing or constant, and the termination of Antarctic warming was apparently coincident with the onset of rapid warming in Greenland. This pattern provides further evidence for the operation of a "bipolar see-saw" in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales.     

Atmospheric CO2 and climate on millennial time scales during the last glacial period

Reconstructions of ancient atmospheric carbon dioxide (CO2) variations help us better understand how the global carbon cycle and climate are linked. We compared CO2 variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere. CO2 concentration and Antarctic temperature were positively correlated over millennial-scale climate cycles, implying a strong connection to Southern Ocean processes. Evidence from marine sediment proxies indicates that CO2 concentration rose most rapidly when North Atlantic Deep Water shoaled and stratification in the Southern Ocean was reduced. These increases in CO2 concentration occurred during stadial (cold) periods in the Northern Hemisphere, several thousand years before abrupt warming events in Greenland.     

GRIP deuterium excess reveals rapid and orbital-scale changes in Greenland moisture origin

The Northern Hemisphere hydrological cycle is a key factor coupling ice sheets, ocean circulation, and polar amplification of climate change. Here we present a Northern Hemisphere deuterium excess profile covering one climatic cycle, constructed with the use of delta18O and deltaD Greenland Ice Core Project (GRIP) records. Past changes in Greenland source and site temperatures are quantified with precipitation seasonality taken into account. The imprint of obliquity is evidenced in the site-to-source temperature gradient at orbital scale. At the millennial time scale, GRIP source temperature changes reflect southward shifts of the geographical locations of moisture sources during cold events, and these rapid shifts are associated with large-scale changes in atmospheric circulation.     

Synchronous tropical South China Sea SST change and Greenland warming during deglaciation

The tropical ocean plays a major role in global climate. It is therefore crucial to establish the precise phase between tropical and high-latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change. Here we present alkenone sea surface temperature (SST) records from the tropical South China Sea that show an abrupt temperature increase of at least 1 degrees C at the end of the last glacial period. Within the recognized dating uncertainties, this SST increase is synchronous with the B?lling warming observed at 14.6 thousand years ago in the Greenland Ice Sheet Project 2 ice core.     

Natural variability of Greenland climate, vegetation, and ice volume during the past million years

The response of the Greenland ice sheet to global warming is a source of concern notably because of its potential contribution to changes in the sea level. We demonstrated the natural vulnerability of the ice sheet by using pollen records from marine sediment off southwest Greenland that indicate important changes of the vegetation in Greenland over the past million years. The vegetation that developed over southern Greenland during the last interglacial period is consistent with model experiments, suggesting a reduced volume of the Greenland ice sheet. Abundant spruce pollen indicates that boreal coniferous forest developed some 400,000 years ago during the "warm" interval of marine isotope stage 11, providing a time frame for the development and decline of boreal ecosystems over a nearly ice-free Greenland.     

Rapid changes in the hydrologic cycle of the tropical Atlantic during the last glacial

Sedimentary time series of color reflectance and major element chemistry from the anoxic Cariaco Basin off the coast of northern Venezuela record large and abrupt shifts in the hydrologic cycle of the tropical Atlantic during the past 90,000 years. Marine productivity maxima and increased precipitation and riverine discharge from northern South America are closely linked to interstadial (warm) climate events of marine isotope stage 3, as recorded in Greenland ice cores. Increased precipitation at this latitude during interstadials suggests the potential for greater moisture export from the Atlantic to Pacific, which could have affected the salinity balance of the Atlantic and increased thermohaline heat transport to high northern latitudes. This supports the notion that tropical feedbacks played an important role in modulating global climate during the last glacial period.     

Synchronous climate changes in antarctica and the north atlantic

Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.     

Glacial-interglacial changes in moisture sources for greenland: influences on the ice core record of climate

Large, abrupt shifts in the (l8)O/(16)O ratio found in Greenland ice must reflect real features of the climate system variability. These isotopic shifts can be viewed as a result of air temperature fluctuations, but determination of the cause of the changes-the most crucial issue for future climate concerns-requires a detailed understanding of the controls on isotopes in precipitation. Results from general circulation model experiments suggest that the sources of Greenland precipitation varied with different climate states, allowing dynamic atmospheric mechanisms for influencing the ice core isotope shifts.     

Does the trigger for abrupt climate change reside in the ocean or in the atmosphere?

Two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich events. The second has to do with evidence for precursory events associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the abrupt Dansgaard-Oeschger warmings recorded in the Santa Barbara Basin.     

Decadal trends in the north atlantic oscillation: regional temperatures and precipitation

Greenland ice-core data have revealed large decadal climate variations over the North Atlantic that can be related to a major source of low-frequency variability, the North Atlantic Oscillation. Over the past decade, the Oscillation has remained in one extreme phase during the winters, contributing significantly to the recent wintertime warmth across Europe and to cold conditions in the northwest Atlantic. An evaluation of the atmospheric moisture budget reveals coherent large-scale changes since 1980 that are linked to recent dry conditions over southern Europe and the Mediterranean, whereas northern Europe and parts of Scandinavia have generally experienced wetter than normal conditions.     

武汉极端事件重现期计算及变化特征分析

利用武汉站1951~2011年常规气象观测资料,采用GPD方法分别计算了武汉汛期降水、盛夏高低温、冬季低温各重现期下极端事件的重现值,并利用M-K突变检验分析了武汉一年当中关键时期的极端事件变化特征。结果表明,武汉汛期1年一遇指标达92mm,30年一遇指标超过了250 mm特大暴雨量级;汛期极端降水频数从20世纪80年代前期开始出现增长趋势,特别是2005~2008年,增长趋势明显,突变发生在1978年前后。盛夏极端高温1年一遇指标达37.9℃,最低温度1年一遇指标达30.1℃;近10年是极端高温的一个频发时期,平均强度呈线性增长趋势,上升趋势为0.058℃/10a;从80年代末开始,夏季极端低温频数迅速增涨,平均强度也呈线性增长趋势,上升趋势为0.086℃/10a,频数突变发生在1991年,强度突变发生在1993年。冬季极端低温1年一遇指标为-7.5℃,50年一遇指标达-18.3℃;寒冬极端低温集中发生在50~70年代,80年代开始温度逐渐回暖,极端低温强度升高趋势为0.323℃/10a;强度突变发生在1984年,频数突变发生在1987年。     

Rapid Variations in Atmospheric Methane Concentration During the Past 110,000 Years

A methane record from the GISP2 ice core reveals that millennial-scale variations in atmospheric methane concentration characterized much of the past 110,00 years. As previously observed in a shorter record from central Greenland, abrupt concentration shifts of about 50 to 300 parts per billion by volume were coeval with most of the interstadial warming events (better known as Dansgaard-Oeschger events) recorded in the GISP2 ice core throughout the last glacial period. The magnitude of the rapid concentration shifts varied on a longer time scale in a manner consistent with variations in Northern Hemisphere summer insolation, which suggests that insolation may have modulated the effects of interstadial climate change on the terrestrial biosphere.     

800,000 years of abrupt climate variability

We constructed an 800,000-year synthetic record of Greenland climate variability based on the thermal bipolar seesaw model. Our Greenland analog reproduces much of the variability seen in the Greenland ice cores over the past 100,000 years. The synthetic record shows strong similarity with the absolutely dated speleothem record from China, allowing us to place ice core records within an absolute timeframe for the past 400,000 years. Hence, it provides both a stratigraphic reference and a conceptual basis for assessing the long-term evolution of millennial-scale variability and its potential role in climate change at longer time scales. Indeed, we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the Middle to Late Pleistocene.     

Super ENSO and global climate oscillations at millennial time scales

The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (delta18O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite delta18O record into components of temperature and local water delta18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Ni?o-Southern Oscillation (ENSO). El Ni?o conditions correlate with stadials at high latitudes, whereas La Ni?a conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Ni?o.     

近61年来渭河上游陇西段气候变化特征分析

利用陇西县气象站1957—2017年气温和降水观测资料,采用趋势分析、Mann-Kendall检验法和滑动t检验法,分析近61年来渭河上游陇西段气候变化特征。结果表明,近61年来渭河上游陇西段气温呈上升趋势,上升幅度为0.270℃/10 a;春夏秋冬四季气温均呈上升趋势,其中冬季气温上升最为明显,上升幅度为0.312℃/10 a;20世纪50年代—80年代初,气温呈缓慢下降趋势,80年代后期开始,气温逐渐回升,在1997年发生了一次明显增暖的突变。近61年来渭河上游陇西段降水量呈下降趋势,下降幅度为9.535 mm/10 a;其中夏、秋两季降水量呈下降趋势,春、冬两季降水量呈上升趋势,上升幅度较小;降水量在近61年来没有出现明显的突变现象。     

1901 - 2012 年福州市气温变化趋势

采用现代气候统计分析方法并结合Mann-Kendall检验和小波分析法,对1901—2012年福州市年平均气温、年极端最高气温、年极端最低气温等序列数据进行分析研究．结果表明：（1）1901—2012年福州市气温变化呈三峰二谷起伏形态,1981—2010年年平均气温比1901—1930年年平均气温高1．2℃;（2）年极端最高气温演变趋势总体上与年平均气温相似,小波分析结果表明,≥35℃年高温日数和年平均气温均存在较稳定的准50a和准25a的振荡周期;（3）福州市1901—2012年冬季极端最低温度年际分布呈两头高中间低的态势;（4）采用Mann-Kendall检验法分析,结果表明福州地区年平均气温在1990年发生突变,1990年后福州地区显著升温．     

Late Quaternary atmospheric CH4 isotope record suggests marine clathrates are stable

One explanation for the abrupt increases in atmospheric CH4, that occurred repeatedly during the last glacial cycle involves clathrate destabalization events. Because marine clathrates have a distinct deuterium/hydrogen (D/H) isotope ratio, any such destabilization event should cause the D/H ratio of atmospheric CH4 (deltaD(CH4)) to increase. Analyses of air trapped in the ice from the second Greenland ice sheet project show stable and/or decreasing deltaD(CH4) values during the end of the Younger and Older Dryas periods and one stadial period, suggesting that marine clathrates were stable during these abrupt warming episodes. Elevated glacial deltaD(CH4) values may be the result of a lower ratio of net to gross wetland CH4 emissions and an increase in petroleum-based emissions.     

驻马店市高新开发区园林绿地土壤质量现状调查及评价

通过常规的物理化学实验方法分析了驻马店市高新开发区园林绿地土壤质量现状。结果表明：有机质含量处于中等水平,速效磷含量处于中等偏上水平,土壤速效氮含量较低、部分园林绿地土壤速效氮含量极低,土壤速效钾含量处于中等偏下水平,仅有个别绿地土壤缺乏速效钾;土壤以中壤土、重壤土和轻黏土较多,土壤质地较好;然而土壤紧实度偏高（平均为...     

泰安市近58年气候变化特征分析

根据泰安市1951～2008年的气温与降水资料,利用线性拟合、Mann-Kendall、小波分析等方法,研究了泰安市近58年气温与降水的变化倾向、突变和周期等特性。结果表明:近58年来,泰安市年平均气温呈显著上升趋势并且在1993年发生了增温突变。泰安市年降水呈减少趋势,但变化趋势不显著,没有发生明显的突变。年平均气温存在准4、61、4、20、29年的周期性变化,其中准62、9年周期振荡最为强烈。年降水存在准3、5、7、10、16年的周期性变化,其中准5、7年周期振荡最为强烈。     

近45a山西冬季0cm地温时空分布及气候分区

利用1965—2009年山西省59个气象站冬季逐月0 cm地温资料,应用多种统计方法,对近45 a山西冬季0 cm地温时空分布及其次区域特征进行研究。结果表明:(1)近45 a来,山西区域冬季平均0 cm地温为显著升温趋势,升温幅度达0.52℃/10 a;从其年代际变化看,20世纪60年代中期到70年代初略呈下降趋势,70年代中期以后呈现明显上升趋势,并在1993年发生突变,进入温度偏高期。从各站点看,全省大部分地区冬季0 cm地温升温趋势显著。(2)山西冬季0 cm地温的空间分布主要表现为全省一致偏高或偏低,其次是北部和南部盆地偏高、南部山区偏低或相反的分布。(3)山西冬季0 cm地温可分为北部、西南部、东南部3个气候区;近45 a来,各区均为显著升温趋势,东南部、西南部、北部分别在1989,1993,1994年发生突变,突变后各区进入0 cm地温偏高期。