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641.
I.INTKODUCTIONTheArcticOcean,withanareaofapproximately9.5X106krnZ,ispredominantlysea--icecoveredthroughouttheyearinitscentralarea,whilethesouthedgeofmarginalicezone(MIZ)variesseasonally.ThemaxinltlmofIcecoverextentoccursbetweenFebruaryandMarch,whilethemininlunlisbetweenAugustandseptember.Placingtheiceedgeto8%iceconcentration(percentarealcoveragesofseaice)isopleths,variationofextentofsea--icecoveroftheArcticOceanisI)etween9X106--16X106kmZIbytheobservationofasatellite--bornescanningm… 相似文献
642.
The climatic signal in varved sediments from Lake C2, northern Ellesmere Island, Canada 总被引:1,自引:0,他引:1
Annually-laminated clastic sediments preserve a high resolution proxy record of paleoclimate, provided that allochthonous sedimentation represents a response to meteorological forcing of watershed sediment transfer. Here, we demonstrate this linkage, and illustrate a calibration process using the most recent 40 years of a varve record from Lake C2 (82°50 N; 78°00 W), three years of field measurements, and meteorological data for 1951–92 from nearby AES weather station Alert. Field measurements were used to correlate proxies of the energy available for snowmelt (e.g. air temperature) and daily suspended sediment discharge (SSQ). Our calibration was extended through use of weather data from Alert. Both mean daily air temperature at Echo, and daily SSQ, were well correlated with air temperature at 600 m above Alert, as obtained from the 1200 Z (0800 LST) rawinsonde sounding. Accordingly, we used pooled 1990 and 1992 Alert 600 m data to predict the lagged daily sediment discharge into Lake C2 (adj. r
2=0.43). Daily values were summed each year in order to produce an annual series of predicted sediment transfer to the lake. The original varve chronology was based on eight sediment cores recovered from the deep basin of the lake (>80 m). Although low-frequency fluctuations of the varve and predicted SSQ series agree, slight tuning of the varve record optimizes the correlation between them. Adjustments were based on examination of weather data for specific years, reexamination of sediment core thin sections, and by aligning fluctuations in the two series which closely matched. Although the original chronology is reasonably well correlated with 600 m temperatures at Alert (for JJA mean, r=0.41, significant at 0.01), the adjusted chronology is both better correlated and contains a more precise climate signal (r=0.54 for July mean, significant at 0.01). This is the first calibrated varve record produced from Arctic lake sediments, and demonstrates that varves from Lake C2 contain a paleoclimatic record. We believe the post-facto manipulations required to produce the adjusted varve chronology are reasonable given the uncertainties inherent in varve counting, and the lack of any independent corroborating chronostratigraphic markers.This is the ninth in a series of papers published in this issue on the Taconite Inlet Lakes Project. These papers were collected by Dr R. S. Bradley. 相似文献
643.
L. Genoni P. Iacumin V. Nikolaev Yu. Gribchenko A. Longinelli 《Earth and Planetary Science Letters》1998,160(3-4):587-592
58 samples of fossil mammoth and reindeer teeth and bones of various ages and coming from different locations were studied for the oxygen isotopic composition of their phosphate. Samples from Siberia have interstadial (Marine Isotope Stage 3), stadial (MIS 2), late-glacial and post-glacial ages. Russian and Ukrainian samples refer to the late-glacial and transitional (between the interstadial and glacial stages) time. The δ18O of palaeoenvironmental waters were calculated from the δ18Op obtained from fossil samples by means of the isotope equations calibrated on modern specimens of elephants and deer respectively. The δ18Ow obtained are generally lighter than those measured nowadays in the same areas and not far from those measured on ice cores of Holocene age, the isotopic differences being not greater than a few δ units. The calculated values are also in fairly good agreement with some isotopic values obtained from Siberian permafrost samples. According to the results obtained it seems that the elephant and deer equations can be reasonably used respectively in the case of fossil mammoth and deer skeletons to evaluate environmental palaeowaters. 相似文献
644.
The flux of sensible heat (SH) and momentum (FM), drag coefficient of momentum (Cm), roughness length of momentum (Zom) and Richardson number (Ri) on the icefloe in Arctic(80°10. 8' N, 30°0. 5' E) were calculated by means of the gradient method of turbulent diffusion theory fromthe data of air/ice exchange on the icefloe with different area and different locations on a same ice floe in August, 1991, which were performed by the scientists from Institute of Geophysics, University of Bergen, Norway and Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China.The results show that firstly the quantity of icefloes area is associated with the sensible heat flux and the roughness length of momentum, which seems the smaller area of icefloes, the bigger sensible heat flux and roughness length of momentum ; secondly, the location of measuring stations is also in relation to be exchange of air/ice on a same icefloe, which seems the nearer the boundary between sea water and icefloes, the stronger exchange of air/ice.As our measuring period was only one week and two different area icefloes were only selected, the above results can not be the final conclusions. However, while these results can be the final conclusions from longer period data on the more different area icefloes, they should provide some effective parameters for modeling experiment on the air-sea-ice exchange. 相似文献
645.
应用地球化学元素、地球化学淋溶系数及环境温度指标,研究了北极阿拉斯加巴罗热融湖Ikroavik钻孔岩芯AB-32连续的高分辨环境记录。结合210Pb测年数据,指出巴罗地区气候、环境变化的历史状况是:1600~1735年为寒冷、干燥时期;1750~1830年,气候变暖、变湿;1830年出现明显的地球化学转折界限,1830~1994年,气候较湿润温暖。1969~1970年前后,巴罗地区有一变冷阶段。AB-32钻孔岩芯1830年左右表现的古地球化学特征与现代Ikroavik湖泊环境地球化学特征相吻合,并且和Elson泻湖AB-67沉积岩芯反映的气候环境变化基本一致。 相似文献
646.
To meet the low warming targets proposed in the 2015 Paris Agreement,substantial reduction in carbon emissions is needed in the future.It is important to know how surface climates respond under low warming targets.The present study investigates the surface temperature changes under the low-forcing scenario of Representative Concentration Pathways(RCP2.6)and its updated version(Shared Socioeconomic Pathways,SSP1-2.6)by the Flexible Global Ocean-Atmosphere-Land System(FGOALS)models participating in phases 5 and 6 of the Coupled Model Intercomparison Project(CMIP5 and CMIP6,respectively).In both scenarios,radiative forcing(RF)first increases to a peak of 3 W m^?2 around 2045 and then decreases to 2.6 W m^?2 by 2100.Global mean surface air temperature rises in all FGOALS models when RF increases(RF increasing stage)and declines or holds nearly constant when RF decreases(RF decreasing stage).The surface temperature change is distinct in its sign and magnitude between the RF increasing and decreasing stages over the land,Arctic,North Atlantic subpolar region,and Southern Ocean.Besides,the regional surface temperature change pattern displays pronounced model-to-model spread during both the RF increasing and decreasing stages,mainly due to large intermodel differences in climatological surface temperature,ice-albedo feedback,natural variability,and Atlantic Meridional Overturning Circulation change.The pattern of tropical precipitation change is generally anchored by the spatial variations of relative surface temperature change(deviations from the tropical mean value)in the FGOALS models.Moreover,the projected changes in the updated FGOALS models are closer to the multi-model ensemble mean results than their predecessors,suggesting that there are noticeable improvements in the future projections of FGOALS models from CMIP5 to CMIP6. 相似文献
647.
A fair and equitable low carbon future depends on a just transition which, in turn, requires leadership. Where the Arctic is concerned, this leadership is currently lacking. To gauge which states are most likely to provide leadership in the global energy transition, a quantitative rank-percentile assessment of 21 Arctic Council members and Observer states was conducted, using measures relevant to the just transition. Data from multiple open-access sources were combined, creating a model to ‘evaluate energy and equity aspects of Distributional, Procedural and Restorative’ justice (DeePeR). Results suggest normative leadership on a just transition for the Arctic comprises international climate contributions in line with carbon emission records and a commitment to both fair and green jobs. Reflections are made on the positive and negative effects of a more involved EU for the just transition agenda in the Arctic. 相似文献
648.
WU Bingyi ZHANG Renhe & WANG Jia . Chinese Academy of Meteorological Sciences Beijing China . International Arctic Research Center University of Alaska Fairbanks AK USA 《中国科学D辑(英文版)》2005,48(9):1529-1536
Arctic sea ice, an important component of the cli- mate system, has received significant attention re- cently. Arctic sea ice variation is an important indica- tor of changes in the climate system, such as global change and polar amplification, and observation and climate modeling suggests that sea ice can itself be an agent of climate change[1―4]. Previous studies[3,5] have shown that sea ice influences the surface and atmos- pheric boundary layer temperature. Potentially more important is t… 相似文献
649.
Characteristics of the pCO2 distribution in surface water of the Bering Abyssal Plain and their relationships with the ambient hydrological conditions
were discussed using variations of the partial pressure of CO2 in surface water of the Bering Abyssal Plain and the Chukchi Sea. Data in this study are from a field investigation during
the First Chinese National Arctic Research Expedition in 1999. Compared to the high productivity in the Bering Continental
Shelf, much lower levels of chlorophyll a were observed in the Bering Abyssal Plain. The effect of hydrological factors on
the pCO2 distribution in surface seawater of the Plain in summer has become a major driving force and dominated over biological factors.
The Plain also presents a High Nutrient Low Chlorophyll (HNLC). In addition, the pCO2 distribution in the Bering Abyssal Plain has also been found to be influenced from the Bering Slope Current which would transform
to the Anadyr Current when it inflows northwestward over the Plain. The Anadyr Current would bring a high nutrient water to
the western Arctic Ocean where local nutrients are almost depleted in the surface water during the summer time. Resupplying
nutrients would stimulate the growth of phytoplankton and enhance capacity of absorbing atmospheric CO2 in the surface water. Otherwise, in the Bering Sea the dissolved inorganic carbon brought from freshwater are not deposited
down to the deep sea water but most of them would be transported into the western Arctic Ocean by the Alaska Coastal Current
to form a carbon sink there. Therefore, the two carbon sinks in the western Arctic Ocean, one carried by the Anadyr Current
and another by the Alaska Costal Current, will implicate the western Arctic Ocean in global change. 相似文献
650.
A 1.93 m long sediment core was obtained from Fish Lake, Truelove Lowland, Devon Island, Nunavut, Canada. Multivariate statistical techniques using a wide range of chemical variables successfully reconstructed the late Holocene history of the Fish Lake watershed. Factor analysis identified six geomorphic mechanisms controlling the formation of sediments. Cluster analysis produced a grouping of core segments and discriminant analysis confirmed that 100% of the samples were correctly classified. The results indicated that the environmental history of the Fish Lake watershed in the past 6500 years can be divided into five phases. These are 6500-5700 years BP, 5700-1700 years BP, 1700-1000 years BP, 1000-600 years BP and 600 years BP to the present. In the Fish Lake watershed, during its time as a terrestrial system, the interactions of erosion, weathering, leaching, soil development, vegetation succession and climatic change have shaped the surrounding landscape as well as determined the evolution of the lake. 相似文献