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.     

Abrupt climate change and extinction events in Earth history

Slowly changing boundary conditions can sometimes cause discontinuous responses in climate models and result in relatively rapid transitions between different climate states. Such terrestrially induced abrupt climate transitions could have contributed to biotic crises in earth history. Ancillary events associated with transitions could disperse unstable climate behavior over a longer but still geologically brief interval and account for the stepwise nature of some extinction events. There is a growing body of theoretical and empirical support for the concept of abrupt climate change, and a comparison of paleoclimate data with the Phanerozoic extinction record indicates that climate and biotic transitions often coincide. However, more stratigraphic information is needed to precisely assess phase relations between the two types of transitions. The climate-life comparison also suggests that, if climate change is significantly contributing to biotic turnover, ecosystems may be more sensitive to forcing during the early stages of evolution from an ice-free to a glaciated state. Our analysis suggests that a terrestrially induced climate instability is a viable mechanism for causing rapid environmental change and biotic turnover in earth history, but the relation is not so strong that other sources of variance can be excluded.     

High-resolution Greenland ice core data show abrupt climate change happens in few years

The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.     

银川市极端天气气候事件及其应对措施

近年来,随着全球气候变暖,极端天气也呈现逐渐增多的趋势。从近几年银川的天气个例中总结极端天气气候事件及其危害,从灾害中得到启示,为防灾减灾工作积累经验,并提出应对措施。     

Asynchronous terrestrial and marine signals of climate change during Heinrich events

Tropical regions have been reported to play a key role in climate dynamics. To date, however, there are uncertainties in the timing and the amplitude of the response of tropical ecosystems to millennial-scale climate change. We present evidence of an asynchrony between terrestrial and marine signals of climate change during Heinrich events preserved in marine sediment cores from the Brazilian continental margin. The inferred time lag of about 1000 to 2000 years is much larger than the ecological response to recent climate change and appears to be related to the nature of hydrological changes.     

气候和土地利用变化对松华坝流域水资源的相对作用研究

以云南省滇池松华坝流域为研究对象,利用分布式水文模型(SWAT)探讨了气候和土地利用变化对河道径流和总氮的影响及对水资源变化的相对作用,模拟分析了气候变化背景下两者相对作用程度的变化。结果表明:气候是流域内河道径流变化的主要原因,贡献率为63.1%～96.6%。土地利用对河道径流变化的影响整体上偏小,但是差异较大;在降雨减少或不变时土地利用的贡献率为12.2%～36.9%,在降雨增加时贡献率为3.4%～5.2%。从土地利用类型的变化来看,耕地减少和草地增加可增加河道径流量,反之则减少。气候和土地利用变化都是影响水体总氮变化的主要原因,贡献率分别为68.2%和68.5%,而两者对水体总氮的影响在不同时期差异较大。当总氮数量变化较大,或者减少量超过40%时,土地利用的贡献率比较大,而当总氮负荷增加或者减少幅度较小时,气候的贡献率比较大。土地利用类型和总氮变化量之间的相关性分析表明,耕地面积与总氮变化显著正相关(r=0.814),草地面积与总氮变化显著负相关(r=-0.895),而林地面积与总氮变化相关性不显著。     

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.     

福建省极端温度事件对气候变暖的响应

为探究福建省极端温度事件的变化特征及其未来发展趋势,利用1960—2013年福建省17个气象台站的日平均气温、日最高气温及最低气温等资料,采用趋势分析法、反距离空间插值法、Mann-Kendall突变检验、Morlet小波分析、Pearson相关分析以及Hurst指数等方法,分析了福建省1960—2013年极端温度事件的时空演变规律及其未来发展趋势。结果表明:1)近54年福建省极端高温(低温)事件发生日数呈上升(下降)趋势,而极端温度事件的强度和年极值均呈上升趋势。2)在空间分布上,极端高温(低温)事件各指标值均表现为自东南沿海向西北内陆逐渐递增(递减)的规律,此外,海拔越高极端温度事件各指标值越小。3)年极端温度事件和年平均气温有很好的相关性,其中与极端温度事件发生日数的相关性最高。4)Hurst指数表明,未来极端高温日数、强度、年最高温度、年极端低温强度和年最低温度仍呈增加趋势,而极端低温日数呈现减少趋势,暖冬的趋势将逐渐明显。     

极端气候变化及其对水稻气候产量影响的实证分析——以湖北省为例

为考察湖北极端天气事件的时空变化,采用1980—2014年逐日气候数据,并利用实证分析法研究了极端气候对水稻气候产量的影响。研究表明:1)湖北极端降水量和降水天数均呈下降趋势,极端降水事件由东向西、由南向北递减。2)极端高温呈上升趋势,表现为极端高温天数和强度增加。鄂北、鄂西易发生极端高温事件。3)极端气候类因素对水稻气候产量具有负向影响,其中,最低气温的极小值每增加1%将会使水稻的气候产量降低0.197%。白天极端高温天数对水稻气候产量也具有抑制作用,其每增加1%将会使水稻气候产量降低0.046%。因此,应加强湖北省极端天气事件易发区在水稻生长期内的气候监测和防范。     

Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13

Oxygen-isotope ratios of a stalagmite from Socotra Island in the Indian Ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present. The pattern of precipitation bears a striking resemblance to the oxygen-isotope record from Greenland ice cores, with increased tropical precipitation associated with warm periods in the high northern latitudes. The largest change, at the onset of interstadial 12, occurred very rapidly, in about 25 years. The chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period.     

居住区绿地设计

居住区绿地既是城市绿地系统中重要的部分,又是城市人工造园生态平衡系统中的重要一环。居住区绿化为人们创造了富有生活情趣的生活环境,是居住区环境质量好坏的重要标志,居住区绿化的优劣,对居民的身心健康有很大的影响。     

A 50,000-year record of climate oscillations from Florida and its temporal correlation with the heinrich events

Oscillations of Pinus (pine) pollen in a 50,000-year sequence from Lake Tulane, Florida, indicate that there were major vegetation shifts during the last glacial cycle. Episodes of abundant Pinus populations indicate a climate that was more wet than intervening phases dominated by Quercus (oak) and Ambrosia-type (ragweed and marsh-elder). The Pinus episodes seem to be temporally correlated with the North Atlantic Heinrich events, which were massive, periodic advances of ice streams from the eastern margin of the Laurentide Ice Sheet. Possible links between the Tulane Pinus and Heinrich events include hemispheric cooling, the influences of Mississippi meltwater on sea-surface temperatures in the Gulf of Mexico, and the effects of North Atlantic thermohaline circulation on currents in the Gulf.     

广州市城市园林绿地动态变化

城市园林绿地是城市生态系统的重要组成部分,具有极其重要的社会效益、环境效益和经济效益。以1949年以来广州市城市园林绿地规模为研究对象,分析了其与地区生产总值、第一产业增加值、第二产业增加值、第三产业增加值、常住人口、常住非农业人口、建成区面积、道路总长度等驱动因素之间的相关性,并拟合了一元线性回归方程和二元线性回归方程。结果表明,城市园林绿地规模与各驱动因素之间存在着显著的线性相关,拟合的线性方程拟合优度均较高,其中以建成区面积和常住人口为自变量的二元线性回归方程拟合优度最好。基于研究结果,预测了未来广州市城市园林绿地规模,旨在为相关规划、计划等提供参考依据。     

天山北坡家庭牧场复合系统对极端气候的响应过程

在草原牧区,家庭牧场作为取代游牧制度而产生的新生事物,其对极端气候响应过程的研究尚未见报道。以"极端气候敏感性-影响途径-响应方式"为分析框架,基于问卷调查方法,研究了天山北坡山地草原牧民对极端气候的响应过程。结果表明:1)天山北坡1980-2009年冬季雪灾、秋季旱灾风险趋于增大,家庭牧场草料储备不足、畜种结构经济驱动型增加了对极端气候的敏感性;2)旱灾、雪灾是影响家庭牧场的主要极端气候类型,其作用介质为牲畜和草场;3)自适应与外力适应是牧户响应极端气候的2种主要形式,其中购买草料是最主要的响应策略;4)通过Probit模型估计显示,极端气候认知、家庭特征、资产状况与牧户间适应行为选择有显著的关系。研究认为,家庭牧场对极端气候短期响应的反馈过程主要围绕草、畜2因子展开,基于降水波动的周期性,牧户长期响应形成了家庭牧场生产周期。     

Seasonality and increasing frequency of Greenland glacial earthquakes

Some glaciers and ice streams periodically lurch forward with sufficient force to generate emissions of elastic waves that are recorded on seismometers worldwide. Such glacial earthquakes on Greenland show a strong seasonality as well as a doubling of their rate of occurrence over the past 5 years. These temporal patterns suggest a link to the hydrological cycle and are indicative of a dynamic glacial response to changing climate conditions.     

Recent ice-sheet growth in the interior of Greenland

A continuous data set of Greenland Ice Sheet altimeter height from European Remote Sensing satellites (ERS-1 and ERS-2), 1992 to 2003, has been analyzed. An increase of 6.4 +/- 0.2 centimeters per year (cm/year) is found in the vast interior areas above 1500 meters, in contrast to previous reports of high-elevation balance. Below 1500 meters, the elevation-change rate is -2.0 +/- 0.9 cm/year, in qualitative agreement with reported thinning in the ice-sheet margins. Averaged over the study area, the increase is 5.4 +/- 0.2 cm/year, or approximately 60 cm over 11 years, or approximately 54 cm when corrected for isostatic uplift. Winter elevation changes are shown to be linked to the North Atlantic Oscillation.     

沈阳地区住宅小区绿地病虫害防治措施

园林管理中病虫害的防治是一个大问题,在沈阳市的一些住宅小区,小区内树龄偏大,园区内形成密度较大的林冠,草坪建植时间长,为病虫侵入创造了条件。     

绿地养护成本分析与控制措施

分析了绿地养护工作内容与成本构成,并提出了控制成本的原则和措施,以期节约绿地养护成本开支。     

乌鲁木齐市城市绿地景观结构及其多样性分析

利用乌鲁木齐市2002年QuickBird遥感数据,采用eCognition面向对象的多尺度分割技术提取城市绿地信息,应用景观生态学分析方法,对乌鲁木齐市城市绿地景观结构及其多样性进行系统分析.乌鲁木齐市建成区绿地斑块面积3 612 hm2,斑块数量47 280块,新市区绿地斑块面积最大斑块数量最多,水磨沟区绿地面积较小斑块数量最少.附属绿地斑块面积最大斑块数量最多,生产绿地斑块面积最小斑块数量最少.乌鲁木齐市绿地景观多样性指数为1.98,最大多样性指数2.58,绿地分布不均匀.景观斑块密度为1 308.97块/km2,沙依巴克区绿地斑块破碎,水磨沟区绿地斑块相对较完整.各种绿地类型中,居住绿地景观破碎化程度最高,公共绿地、生产绿地景观较完整.