基于CryoSat-2雷达高度计数据的南极内陆冰盖高程变化与物质平衡

南极冰盖对海平面影响巨大,高程变化测量是南极物质平衡监测的重要手段。采用欧空局CryoSat-2雷达高度计数据,通过提取卫星升降轨的地面交叉点,监测了南极内陆冰盖的高程变化（物质平衡）。结果表明,后向散射能量对Ku波段的CryoSat-2雷达高度计的高程数据具有一定的影响,经后向散射能量校正后,时间序列上的高程变化变得平缓,高程变化与已有的降雪数据相比,更加符合实际情况。2010年11月至2017年11月南极内陆冰盖高程变化趋势为（-1.1±0.2）cm·a^-1。西南极的Kamb冰流高程变化率为（38.7±1.1）cm·a^-1,Moeller冰流高程变化率为（-10.3±1.2）cm·a^-1,部分Thwaites冰川区域高程变化率为（-13.4±1.8）cm·a^-1,东南极的Wilkes Land出现高下降区,最高达-20 cm·a^-1。Dronning Maud Land虽然出现变化异常的点,但整体并没有显著的高程变化。南极内陆冰盖质量变化为（-10.6±6.2）Gt·a^-1,整体上南极内陆冰盖质量变化平缓,部分区域变化较大,Kamb冰流达到（17.9±0.5）Gt·a^-1,Moeller冰流达到（-3.4±0.4）Gt·a^-1,部分Thwaites冰川区达到（-3.7±0.5）Gt·a^-1。     

基于浅层探冰雷达的东南极内陆地区冰盖内部等时层提取

中国第32次南极考察内陆队首次使用雪地车载浅层探冰雷达取得了中山站至昆仑站全程1 300 km 的浅层冰盖数据,通过MATLAB对数据进行FFT转换、背景滤波、改变叠加次数去噪和基于曲波变换的图像处理,使用Reflexw对MATLAB处理后数据进行地形校正、二次背景滤波和平滑滤波等处理,成功提取了冰盖浅层等时层并得出了等时层的平均深度、最大深度和波动情况。最后进行了数据的连接,展示了LGB69冰芯处等时层的分布并与冰芯数据结合大体对应了相应等时层的年代和事件。给出了Dome A附近的等时层分布情况。为东南极中山站至昆仑站沿途的物质积累率计算提供重要的数据支撑。     

The Mid‐Brunhes Event and West Antarctic ice sheet stability

The complex cyclical nature of Pleistocene climate, driven by the evolving orbital configuration of the Earth, is well known but not well understood. A major climatic transition took place at the Mid‐Brunhes Event (MBE), ca. 430 ka ago after which the amplitude of the ca.100 ka climate oscillations increased, with substantially warmer interglacials, including periods warmer than present. Recent modelling has indicated that while the timing of these warmer‐than‐present transient (WPT) events is consistent with southern warming due to a deglaciation‐forced slowdown of the Atlantic Meridional Overturning Circulation, the magnitude of warming requires a local amplification, for which a candidate is the feedback of significant West Antarctic Ice Sheet (WAIS) retreat. We here extend this argument, based on the absence of WPTs in the early ice core record (450–800 ka ago), to hypothesize that the MBE could be a manifestation of decreased WAIS stability, triggered by ongoing subglacial erosion. Copyright © 2011 John Wiley & Sons, Ltd.     

基于InSAR和ICESat的南极冰盖地区DEM提取和精度分析

结合InSAR和ICESat测高数据,以东南极PANDA断面4个实验区为例,进行DEM生成研究.在干涉相位转换成高程前,引入ICESat测高数据作为控制点优化干涉对基线,消除基线线性误差趋势的影响.利用控制点之外的ICESat测高数据分析4个实验区的DEM精度及其差异,并探讨了引起DEM误差的原因.冰流和地貌特征是影响InSAR生成冰盖DEM精度的重要因素.针对冰流的影响,从理论上进行了分析并结合冰流速数据进行了分析验证.最后利用克里金插值法改正InSAR DEM残余误差,并利用GPS实测控制点对改正效果进行验证.结果表明:对于高纬区流速较小且分布一致的区域,改正效果很好,DEM精度可达3 m;而对于冰流速较大且复杂的地区,需采用多基线等算法进一步消弱冰流引入的误差.     

A new ice sheet model validated by remote sensing of the Greenland ice sheet

Accurate prediction of future sea level rise requires models that accurately reproduce and explain the recent observed dramatic ice sheet behaviours. This study presents a new multi-phase, multiple-rheology, scalable and extensible geofluid model of the Greenland ice sheet that shows the credential of successfully reproducing the mass loss rate derived from the Gravity Recovery and Climate Experiment (GRACE), and the microwave remote sensed surface melt area over the past decade. Model simulated early 21st century surface ice flow compares satisfactorily with InSAR measurements. Accurate simulation of the three metrics simultaneously cannot be explained by fortunate model tuning and give us confidence in using this modelling system for projection of the future fate of Greenland Ice Sheet (GrIS). Based on this fully adaptable three dimensional, thermo-mechanically coupled prognostic ice model, we examined the flow sensitivity to granular basal sliding, and further identified that this leads to a positive feedback contributing to enhanced mass loss in a future warming climate. The rheological properties of ice depend sensitively on its temperature, thus we further verified modelâ?s temperature solver against in situ observations. Driven by the NCEP/NCAR reanalysis atmospheric parameters, the ice model simulated GrIS mass loss rate compares favourably with that derived from the GRACE measurements, or about ?147 km³/yr over the 2002–2008 period. Increase of the summer maximum melt area extent (SME) is indicative of expansion of the ablation zone. The modeled SME from year 1979 to 2006 compares well with the cross-polarized gradient ratio method (XPGR) observed melt area in terms of annual variabilities. A high correlation of 0.88 is found between the two time series. In the 30-year model simulation series, the surface melt exhibited large inter-annual and decadal variability, years 2002, 2005 and 2007 being three significant recent melt episodes.     

Oxygen isotopic and chemical compositions of cosmic spherules collected from the Antarctic ice sheet: Implications for their precursor materials

Bulk chemical compositions and oxygen isotopic compositions were analyzed for 48 stony cosmic spherules (melted micrometeorites) collected from the Antarctic ice sheet using electron- and ion-microprobes. No clear correlation was found between their isotopic compositions and textures. The oxygen isotopic compositions showed an extremely wide range from −28‰ to +93‰ in δ¹⁸O and from −21‰ to +13‰ in Δ¹⁷O. In δ¹⁸O-δ¹⁷O space, most samples (38 out of 48) plot close to the terrestrial fractionation line, but 7 samples plot along the carbonaceous chondrite anhydrous mineral (CCAM) line. Three samples plot well above the terrestrial fractionation line. One of these has a Δ¹⁷O of +13‰, the largest value ever found in solar system materials. One possible precursor for this spherule could be ¹⁶O-poor planetary material that is still unknown as a meteorite. The majority of the remaining spherules are thought to be related to carbonaceous chondrites.     

Deluge II and the continent of doom: rising sea level and collapsing Antarctic ice

Hughes, Terence J. 1987 06 01: Deluge II and the continent of doom: rising sea level and collapsing Antarctic ice. Boreas , Vol. 16, pp. 89–100. Oslo. ISSN 0300–9483.
Many cultures in both the Old and New Worlds have preserved legends of a Great Flood. In the Biblical deluge, 'the springs of the great deep broke through and the sluices of heaven opened' (Genesis 7: 11). The rise in sea level, as opposed to prolonged rainfall, is a conceivable cause of global flooding because the last stages in collapse of late Wisconsin/Weichselian ice sheets occurred in the late prehistorical period, from 8,000 to 6,000 B.C. A possible mechanism that might collapse large parts of ice sheets in a short time is found in Jakobshavns Isbrae, which drains the west-central part of the Greenland Ice Sheet. This mechanism, called the Jakobshavns Effect, is described and its possible role in Holocene collapse of former Northern Hemisphere ice sheets (Deluge I) and future collapse of parts of the Antarctic Ice Sheet (Deluge II) is examined. Rapid global flooding by this mechanism is extremely unlikely; however, we lack the information needed to eliminate the possibility.     

Late Holocene relative sea level rise and the Neoglacial history of the Greenland ice sheet

In West Greenland, early and mid Holocene relative sea level (RSL) fall was replaced by late Holocene RSL rise during the Neoglacial, after 4–3 cal. ka BP (thousand calibrated years before present). Here we present the results of an isolation basin RSL study completed near to the coastal town of Sisimiut, in central West Greenland. RSL fell from 14 m above sea level at 5.7 cal. ka BP to reach a lowstand of ?4.0 m at 2.3–1.2 cal. ka BP, before rising by an equivalent amount to present. Differences in the timing and magnitude of the RSL lowstand between this and other sites in West and South Greenland record the varied interplay of local and non‐Greenland RSL processes, notably the reloading of the Earth's crust caused by a Neoglacial expansion of the Greenland Ice Sheet (GIS) and the subsidence associated with the collapse of the Laurentide Ice Sheet forebulge. This means that the timing of the sea level lowstand cannot be used to infer directly when the GIS advanced during the Neoglacial. The rise in Late Holocene RSL is contrary to recently reported bedrock uplift in the Sisimiut area, based on repeat GPS surveys. This indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late Holocene, and that there has been a switch from subsidence to uplift at some point in the last thousand years or so. Copyright © 2008 John Wiley & Sons, Ltd.     

基于同位素示踪降水在两极海冰质量平衡中的贡献

极地海冰在全球气候系统中扮演着重要角色。在全球变暖背景下,两极海冰范围呈现相反的变化趋势,即北极海冰显著减少,南极海冰则略有增加,然而目前对两极海冰不对称变化的驱动机制还存在争议。已有研究集中在海冰变化与温度的相互作用上,而对降水在海冰生消过程中所起作用则知之甚少。两极海冰的这种不对称变化可能与降水在海冰生消中起到的不同作用有关：降水在北极主要起到促进海冰消融的作用,而在南极主要起到促使海冰加积生长的作用。降水在两极海冰质量平衡中的贡献可以通过同位素示踪加以厘定,本文详细对比了同位素判别法、线性混合模型和贝叶斯混合模型等研究方法的不同特点及应用上的优劣。利用氧同位素（δ¹⁸O）和氘盈余（d-excess）建立的海冰同位素混合模型,可量化融池在北极海冰质量平衡中的贡献和雪冰在南极海冰质量平衡中的贡献。罗斯海是南极海冰增大最明显的区域,且各种起源的海冰类型齐全（冰针冰、雪冰、附加冰和小板冰）,通过三氧同位素（¹⁷O-excess）作为新的示踪同位素,可进一步量化罗斯海海冰质量平衡中四组分的贡献比,探究罗斯海海冰异常变化的生长机制。

     

基于ICESat数据的南极冰盖DEM插值方法比较及精度分析

南极数字高程模型(DEM)是从事南极地学和环境变化研究的基础. 内插是建立数字高程模型的重要技术点, 插值方法有多种, 根据不同的适用情况, 不同的插值方法各有优劣. 利用克里格、 距离反权、 三角网剖分、 最小曲率以及移动平均5种插值方法分别建立南极冰盖小范围区域的DEM, 通过抽取部分观测数据作为验证值对各插值方法进行了比较. 结果表明: 克里格插值方法的可靠性最好, 稳定性最高. 然后, 利用克里格插值方法, 基于ICESat测高卫星的GLA12数据建立了南极冰盖的DEM. 由于南极大陆实测数据有限, 缺乏对DEM的检核. 为了分析所建DEM的可靠性, 利用中国南极内陆冰盖考察所采集的GPS实测数据, 对所建立的DEM进行了验证分析. 结果显示, DEM在坡度较缓的南极内陆冰盖区域精度较高, 符合度在3 m以内; 距离卫星轨道越近的区域精度越高, 可达到1 m 以内. 在坡度较大, 高程变化较为显著的区域如沿海地区, 精度较低, 差距最大的点超过40 m.     

The ice lobes of the Scandinavian ice sheet during the deglaciation in Finland.

On the basis of glacial landforms interpreted by means of Landsat satellite imagery and ice-flow data obtained by other methods, the Scandinavian ice sheet has been observed to have divided at the deglaciation stage into several ice lobes. The ice lobes were more active parts of the uniform ice sheet. They represent parts that had bordered on each other in different directions or on more passive portions of the ice. The reasons for the appearance of separate ice lobes were evidently the Fennoscandian topography, the location of accumulation areas, and regional differences in the amounts of ice generated. In the boundary zones of the different ice lobes, there occur exceptionally large glaciofluvial forms and moraines (interlobate complexes). An area of passive ice was often between ice lobes, and in such areas there occur no noteworthy eskers, marginal formations or streamlined forms. In the part of Finland located on the southern side of the Arctic Circle, six different ice lobes and four major areas of passive ice are interpreted to have existed.     

Debris structures in basal ice exposed at the margin of the Greenland ice sheet

The basal ice of many glaciers contains debris structures that reflect subglacial processes. Presented here is an unusually clear photograph of ice and debris in the lowest 2 m of the basal layer at the margin of the Greenland ice sheet. The photograph shows ice-debris relationships and deformation structures that reflect entrainment processes and flow history.     

Greenland ice sheet history since the last glaciation

The position of the Inland Ice margin during the late Wisconsin-Würm glaciation (ca. 15,000 yr BP) is probably marked by offshore banks (submarine moraines?) in the Davis Strait. The history of the Inland Ice since the late Wisconsin-Würm can be divided into four principal phases: (1) Relatively slow retreat from the offshore banks occurred at an average rate of approximately 1 km/100 yr until ca. 10,000 yr BP (Younger Dryas?) when the Taserqat moraine system was formed by a readvance. (2) At ca. 9500 yr BP, the rate of retreat increased markedly to about 3 km/100 yr, and although nearly 100 km of retreat occurred by ca. 6500 yr BP, it was punctuated by frequent regional reexpansions of the Inland Ice that formed extensive moraine systems at ca. 8800-8700 yr BP (Avatdleq-Sarfartôq moraines), 8400-8100 yr BP (Angujârtorfik-Fjord moraines), 7300 yr BP (Umîvît moraines), and 7200-6500 yr BP (Keglen-Mt, Keglen moraines). (3) Between 6500 and 700 yr BP, discontinous ice-margin deposits and ice-disintegration features were formed during retreat, which may have continued until the ice margin was near or behind its present position by ca. 6000 yr BP. Most of the discontinuous ice-margin deposits occur within 5–10 km of the present ice margin, and may have been formed by two main phases of readvance at ca. 4800-4000 yr BP and 2500-2000 yr BP. (4) Since a readvance at ca. 700 yr BP, the Inland Ice margin has undergone several minor retreats and readvances resulting in deposition of numerous closely spaced moraines within about 3 km of the present ice margin. The young moraines are diffieulto to correlate regionally, but several individual moraines have the following approximate ages: A.D. 1650, 1750, and 1880–1920.Inland Ice fluctuations in West Greenland were very closely paralleled by Holocene glacial events in East Greenland and the eastern Canadian Aretic. Such similarity of glacier behavior over a large area strongly suggests that widespread climatic change was the direct cause of Holocene glacial fluctuations. Moreover, historical advances of the Inland Ice margin followed slight temperature decreases by no more than a few decades, and ¹⁸O data from Greenland ice cores show that slight temperature decreases occurred frequently throughout the Holocene. Therefore, we conclude that construction of the major Holocene moraine systems in West Greenland was caused by slight temperature decreases, which decreased rates of ablation and thereby produced practically immediate advances of the ice sheet margin, but did not necessarily affect the long-term equilibrium of the ice sheet.     

Nunataks of the last ice sheet in northwest Scotland

High-level weathering limits separating ice-scoured topography from an upper zone of frost-weathered detritus were identified on 17 mountains in NW Scotland at altitudes of <600 m to< 900 m, and a further 6 peaks were found to support evidence of ice scouring to summit level. Weathering limits are most clearly defined on Torridon Sandstone, which is resistant to frost shattering, but can also be mapped on Cambrian Quartzite, Lewisian Gneiss and Moine Schist. Contrasts in degree of rock surface weathering above and below the weathering limits were evaluated using measurements of joint depth and rock surface hardness, and through X-ray diffraction analyses of clay mineral assemblages. The results indicate significantly more advanced rock and soil weathering above the weathering limits. Widespread persistence of gibbsite above the weathering limits suggests that they represent the upper limit of Late Devensian glacial erosion, and the regularity of the decline in weathering limit altitude along former flowlines eliminates the possibility that it represents a former thermal boundary between protective cold-based and erosive warm-based ice. The weathering limits are therefore interpreted as periglacial trimlines defining the maximum surface altitude of the last ice sheet around former nunataks. Calculated basal shear stresses of 50–78 kPa are consistent with this interpretation. The altitude of the trimlines implies that the former ice shed lay at 900–930 m in the Fannich Mountains and descended gently northwards, and that the ice surface descended NW from the ice shed to >500 m over the extreme NW tip of Scotland and to 700–730 m at the head of Little Loch Broom.     

Supposed area-wasting of the Weichselian ice sheet in Denmark

The deglaciation at the end of the Weichselian in the Danish area has previously been considered to occur as a frontal wastage. Since the glacier ice was assumed to be debris-free, the wasting should be characterized by outwash plains and successions of end-moraines. The almost complete lack of sandur plains in the eastern part of the area and indications from recent investigations of widespread occurrence of flow till justify a re-evaluation of the mentioned deglaciation model.
Two morphological features have a general occurrence: the plains and the 'tunnel' valleys. The plains appear stepwise in the landscapes, and are frequently limited by steep slopes. Topmost is a subcircular kame-like hill. Sedimentologically, the plains mainly consist of melt water deposits, and the scattered occurrences of till are interpreted as flow till. The plains continue from the open landscape into the 'tunnel' valleys where they appear as terraces.
These features are considered to have been formed during the deglaciation. The almost horizontal surface of the ice sheet over large areas caused a sensitivity to changes in the climate. The wasting of the ice may therefore be expected to affect large areas almost simultaneously. On the assumption that the ice contained debris, an increasing amount of clastic matter was released on the ice surface. This material was concentrated in the depressions. If such a depression perforated the ice, the content of sediments settled on the substratum and a plain was established. During continued wasting the thickness of the ice decreased and the depressions were enlarged. They assumed the character of sandur plains. As still larger areas of these supraglacial sandurs rested on the basement the successive lower situated plains were formed. The latest ice was preserved where the 'tunnel' valleys are situated to-day.     

Isotopic and related studies of Antarctic ice samples

The ice samples obtained from Dakshin Gangotri, Antarctica show the presence of nuclear debris, attributed mainly to French nuclear explosions. Cosmogenic⁷Be occurs at levels of 30 dpm/L. The vertical profile ofδD in 6 m long drill core ranges between ?130 and ?180‰ compared to Standard Mean Ocean Water (SMOW). No systematic change with depth is seen. Small amounts of dust obtained by filtering melt water show presence of metallic spherules. Absence of elements characteristic of meteoritic or cometary debris suggests that most of them are of volcanic or industrial origin.     

A review of changes monitoring in the Antarctic ice shelves北大核心CSCD

冰架是南极冰盖物质损失的主要出口。南极冰架动态变化和物质平衡的研究对揭示南极地区的气候变化具有重要的参考价值。本文从表面融化、冰流速、前缘崩解、底部融化和物质平衡五个方面入手,对近些年来南极冰架变化监测的研究进展进行梳理和归纳总结,综述了它们的观测方法、观测结果、机制分析及当前面临的问题。极地观测卫星和现场观测网络的发展、冰架多维度综合分析及数值模拟研究的推进,将有助于进一步揭示冰架变化因子之间的耦合作用及其演变机制,为全球增温影响南极冰盖/冰架的物理机制研究及其变化预测提供重要依据。     

Calibrating a glaciological model of the Greenland ice sheet from the Last Glacial Maximum to present-day using field observations of relative sea level and ice extent

We constrain a three-dimensional thermomechanical model of Greenland ice sheet (GrIS) evolution from the Last Glacial Maximum (LGM, 21 ka BP) to the present-day using, primarily, observations of relative sea level (RSL) as well as field data on past ice extent. Our new model (Huy2) fits a majority of the observations and is characterised by a number of key features: (i) the ice sheet had an excess volume (relative to present) of 4.1 m ice-equivalent sea level at the LGM, which increased to reach a maximum value of 4.6 m at 16.5 ka BP; (ii) retreat from the continental shelf was not continuous around the entire margin, as there was a Younger Dryas readvance in some areas. The final episode of marine retreat was rapid and relatively late (c. 12 ka BP), leaving the ice sheet land based by 10 ka BP; (iii) in response to the Holocene Thermal Maximum (HTM) the ice margin retreated behind its present-day position by up to 80 km in the southwest, 20 km in the south and 80 km in a small area of the northeast. As a result of this retreat the modelled ice sheet reaches a minimum extent between 5 and 4 ka BP, which corresponds to a deficit volume (relative to present) of 0.17 m ice-equivalent sea level. Our results suggest that remaining discrepancies between the model and the observations are likely associated with non-Greenland ice load, differences between modelled and observed present-day ice elevation around the margin, lateral variations in Earth structure and/or the pattern of ice margin retreat.     

High-resolution reconstruction of the last ice sheet in NW Scotland

Reconstructions of the last (late Devensian) British ice sheet have hitherto been based on assumptions regarding its extent and form. Here we employ observational evidence for the maximum altitude of glacial erosion (trimlines) on mountains that protruded through the ice (palaeonunataks) to reconstruct the form of the ice sheet over ≈ 10 000 km² of NW Scotland. Contrasts in the clay mineralogy of soils and exposure ages of rock surfaces above and below these trimlines confirm that they represent the upper limit of late Devensian glacial erosion. The reconstruction yields realistic values of basal shear stress and is consistent with independent evidence of ice movement directions. The ice sheet reached ≈ 950 m altitude over the present N–S watershed, descended northwards and north-westwards, was deflected around an ice dome on Skye and an independent Outer Hebrides ice cap, and probably extended across the adjacent shelf on a bed of deforming sediments.