冰川零平衡线处的物质平衡及其应用

论证了在稳定状态时的冰川平衡线即零平衡线ＥＬＡ０）处的比净平衡大致等于整个冰川的平均净平衡。提出了ＥＬＡ０的直接测定方法、误差范围以及利用冰川中值高度计算ＥＬＡ０的公式。认为可以利用ＥＬＡ０的特征简化冰川物质平衡的观测及计算，以及利用冰川编目资料大面积估算冰川物质平衡状况的可能性。     

Modern glacier characteristics as a basis for inferring former climates with particular reference to the Loch Lomond Stadial

Studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude (ELA) is the most critical parameter in the link between glaciers and climate. Average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind-drifting and avalanching of snow, and approximates closely to accumulation at the equilibrium line. Ablation is most usefully predicted by mean summer temperature and there is a close, non-linear relationship between accumulation and mean summer temperature at the equilibrium line. Following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes, the application of the above relationships to the Loch Lomond Readvance glaciers of Highland Britain is considered and an outline of the precipitation pattern and the mean summer temperature of the Loch Lomond Stadial is given.     

Significance of snowblow in the generation of Loch Lomond Stadial (Younger Dryas) glaciers in the western Pennines,northern England

Geomorphological mapping has identified the former existence of five cirque glaciers that formed during the Loch Lomond Stadial in the western Pennines, northern England. Landforms in Mallerstang, which previously have been interpreted as moraine ridges, are shown to be better explained as large complex landslides. Reconstruction of these former glaciers has allowed the calculation of the former equilibrium line altitudes (ELA) by a number of different methods. Values for the ELA show a range across the area from 311 m to 608 m OD, but with low values (311 m and 428 m) for the two western glaciers. These are explained by the existence of large plateau areas adjacent to the former glaciers, which contributed additional mass to the glaciers by snowblow on to the glacier surfaces. Delimitation of the potential snowblow area for each glacier shows that it has a distinct orientation, with the western sector (225–315°) being statistically significant with the ELA indicating the importance of winds from this direction in determining the existence of these palaeoglaciers. The significance of snowblow for the generation of small glaciers in marginal areas means that such local factors must be investigated before regional firn line trends are determined in former glaciated areas.     

Palaeoclimatic reconstruction from Loch Lomond Readvance glaciers in the West Drumochter Hills,Scotland

Geomorphological mapping in the West Drumochter Hills provides evidence of a readvance of locally nourished glaciers during the Loch Lomond (Younger Dryas) Stade, in the form of an icefield 67.7 km² in area drained by outlet glaciers. The icefield limits accord broadly with those proposed by Sissons (1980) but all geomorphic, stratigraphic and sedimentological evidence conflicts with a recent proposal that the landforms in the area reflect southwestwards retreat of the last ice sheet. Up‐valley continuity of recessional moraines indicates that the ice remained active and close to climatic equilibrium during the earlier stages of glacier retreat, consistent with slow warming following the coldest part of the stade. The pattern of equilibrium line altitudes (ELAs) across the icefield is consistent with transfer of snow by westerly and southerly winds. The ELA of the reconstructed icefield as a whole is 622–629 m, although this figure is likely to be lower than the regional (climatic) ELA because the icefield probably received additional snow blown from adjacent plateau surfaces and slopes. Inclusion of potential snow‐blow areas in the ELA calculation yields a value of 648–656 m; the climatic ELA is therefore likely to have lain between 622 and 656 m. Mean June to August temperature at the ELA, based on chironomid assemblages at two sites, falls within the range 4.0 ± 0.7°C. Empirical relationships between temperature and precipitation at modern glacier ELAs indicate that mean annual precipitation (MAP) at the ELA was 1977 ± 464 mm, statistically indistinguishable from modern values. Comparison with precipitation values calculated for the Isle of Mull on the west coast suggest that the precipitation gradient across the Central Highlands of Scotland was steeper during the Loch Lomond Stade than at present, probably as the result of efficient scavenging of precipitation from westerly airflows by the West Highland Icefield. Copyright © 2005 John Wiley & Sons, Ltd.     

尼泊尔冰川1980-2010年的变化特征

利用尼泊尔已发布的冰川编目数据、遥感数据及DEM数字高程模型,利用GIS和Excel对尼泊尔境内冰川的结构特征及1980-2010年的冰川变化特征进行了分析,并运用冰川系统功能模型模拟了同期尼泊尔冰川的变化趋势。结果表明：（1）尼泊尔境内冰川平均规模较小,且冰川分布的海拔差异大。（2）尼泊尔冰川平衡线高度分布受地形影响明显,呈现出反纬向性变化特征,存在若干以高峰为中心的高值区域。（3）1980-2010年尼泊尔冰川整体呈现退缩状态,冰川数量增加了378条,冰川面积和体积均减少,分别减少了24%和29%;小规模冰川或冰川系统退缩更快,1980-1990年冰川变化速率最快。（4）采用历史时期的气温变化率,冰川系统功能模型可以较好地模拟冰川历史时期的变化特征。     

冰川物质平衡线的估算方法

冰川物质平衡线高度(ELA)与气候变化, 特别是与气温和降水的变化关系密切, 是重建古气候和反映冰川积累和消融变化的重要代用指标.直接观测方法可以获得较为精准的ELA, 但不能大范围展开.因此, ELA的间接估算方法, 如赫斯法(Hess)、 积累区面积比率法(AAR)、 面积–高程平衡率法(AABR)、 末端至冰斗后壁比率法(THAR)、 终碛到最高峰高差比率法(TSAM)、 侧碛最大高度法(MELM)、 冰斗底部高程法(CF)、 冰川作用阈值法(GT)等, 得到了广泛的发展与应用.然而, 由于受到雪崩或风吹雪补给、 表碛覆盖、 冰川类型和形态等因素的影响, 单一使用某种方法易受到算法本身的限制, 误差较大, 需综合考虑各种算法的适用性和选取参数的差异, 以提高计算的精度, 同时也要考虑到后期构造抬升等的影响.     

Application of a degree-day model to reconstruct Pleistocene glacial climates

There is empirical evidence of a nonlinear relation between annual precipitation, or accumulation, and summer mean temperature at the equilibrium line altitude (ELA) on glaciers around the world. The degree-day model gives a similar relation between accumulation and summer temperature, although instead of a single universal curve there is a family of curves depending upon the annual temperature range. Furthermore, the degree-day model also gives nonlinear relations between accumulation and annual mean temperature. Thus, estimations of accumulation can be made from both summer and annual temperatures at the ELA of former reconstructed glaciers, such as those in Greece. This is particularly useful since these climatic variables have major implications for biological proxies, such as vegetation history indicated in the pollen record, and for periglacial proxies, such as permafrost distributions indicated in the geomorphological record. The close relationship between glaciers and climate provides one of the most precise methods for reconstructing former climates and offers considerable potential for resolving our understanding of Pleistocene cold-stage climates.     

北极Svalbard地区冰川物质平衡研究进展

回顾了Svalbard地区冰川物质平衡观测研究的历史,总结了该区域自1950年代以来冰川物质平衡的主要特征.结果表明:1)冰川净平衡、冬季积累和夏季消融没有明显长期变化趋势,净平衡一般为负值,导致冰体不断地缩减;2)冰川冬季积累年际波动较小,基本保持稳定状态;夏季消融年际波动较大,但没有融化增加的迹象;3)面积/海拔高度分布的不同导致了各冰川物质平衡的差异,面积较小(<10 km²)、海拔较低(<500 m)的冰川持续退缩;而具有更高海拔高度、更大面积的冰川则处于平衡或略微增长状态;4)净平衡与冰川平衡线高度(ELA)具有良好的负相关性,平均物质平衡梯度无明显变化,物质平衡对平衡线高度变化(气候变化)的敏感性保持稳定;5)Svalbard地区冰川物质平衡与该区夏季各月正积温和冬季降水具有密切的相关性.最后提出了加强Svalbard地区冰川物质平衡内补给过程研究以及与我国天山冰川物质平衡的对比研究,以求更加准确地认识Svalbard地区冰川物质平衡特征.     

我国大陆型山地冰川对气候变化的响应

以乌鲁木齐河源１号冰川、唐古拉山冬克玛底冰川和祁连山“七一”冰川为例,着重探讨青藏高原冰川变化的能量机制．得到了在不同气候变化情景下,冰川平衡线对气候因子波动的响应值,并预测未来气候变化对青藏高原冰川物质平衡过程的影响．文中所选取的３条冰川中,以１号冰川对气候变化的响应最为强烈,而“七一”冰川以其独特的能量交换特征,对气候因子波动的响应相当迟缓,从而在全球山地冰川普遍缩小规模的背景下,该冰川处于相对较为稳定的状态．     

1984—2019年念青唐古拉山中段冰川ELA变化估算及特征分析

平衡线高度（equilibrium line altitude,ELA）是冰川响应气候变化的直接反映,分析其变化特征对于了解现在和过去的气候具有重要意义。念青唐古拉山中段作为西南季风通道以及怒江与雅鲁藏布江的分水岭,ELA变化及特征研究可为不同流域冰川变化与气候相互关系提供参考。基于遥感影像及气候数据,结合模型计算的冰川ELA数据作为输入参数,建立多元线性回归方程,重建并分析了1984—2019年间念青唐古拉山中段冰川ELA变化。结果表明：研究时段内平均ELA为5 360 m a.s.l.,总体呈上升趋势,上升速率为1.57 m?a^-1。ELA年变化量显示出波动变化特征,波动范围为5 360~5 420 m a.s.l.,上升幅度为60 m。受印度季风、流域位置及冰川朝向等因素影响,各流域ELA变化具有差异性,霞曲流域、易贡藏布流域和麦曲流域多年平均ELA高程分别为5 335 m a.s.l.、4 987 m a.s.l.和5 317 m a.s.l.,平均上升幅度分别为265 m、314 m和335 m,上升速率分别7.57 m?a^-1、8.97 m?a^-1和9.57 m?a^-1。对冰川区多年ELA变化的气候响应分析显示,ELA变化主要受气温控制,随气温变化1 ℃,冰川ELA总体波动幅度为126.02 m。     

北半球冰川物质平衡变化的若干特征及其气候意义

根据北半球连续观测的４０多条冰川物质平衡资料，分析了目前冰川物质平衡状态及影响它们的地形因互。冰川物质平衡的变化在区域间存在着一定的联系：斯堪的纳维亚、落基山和天山地 区冰川物质平衡的变化在大多数时间内存在着对应联 系，而与阿尔卑斯山冰川物质平衡的变化具有不同程度的反向波动特征。     

The Loch Lomond Readvance on north Arran,Scotland: glacier reconstruction and palaeoclimatic implications

Geomorphological mapping of northern Arran provides evidence for two advances of locally nourished glaciers, the younger being attributable to the Loch Lomond Stade (LLS) of ca. 12.9–11.5 k yr BP, primarily through the mutually exclusive relationship between glacial limits and Lateglacial periglacial features. The age of the earlier advance is unknown. Inferred LLS glacier cover comprised two small icefields and eight small corrie or valley glaciers and totalled 11.1 km². ELAs reconstructed using area–altitude balance ratio methods range from 268 m to 631 m for individual glaciers, with an area‐weighted mean ELA of 371 m. ELAs of individual glaciers are strongly related to snow‐contributing areas. The area‐weighted mean ELA is consistent with a north–south decline in LLS ELAs along the west coast of Great Britain. This decline has an average latitudinal gradient of 70 m 100 km^?1, equivalent to a mean southwards ablation‐season temperature increase of ca. 0.42°C 100 km^?1. Mean June–August temperatures at the regional climatic ELA, estimated from chironomid assemblages in SE Scotland, lay between 5.7 ± 0.1°C and 4.1 ± 0.2°C. Empirical relationships between temperature and precipitation at modern glacier ELAs indicate equivalent mean annual precipitation at the ELA lay between 2002 ± 490 mm and 2615 ± 449 mm. These figures suggest that stadial precipitation on Arran fell within a range between +8% and ?33% of present mean annual precipitation. Copyright © 2006 John Wiley & Sons, Ltd.     

长江源区冰川对气候变化的响应

长江源区是青藏高原冰川分布集中的地区之一,冰川总面积达1276.02km².研究表明,该区属于青藏高原升温幅度最大的地区之一,到2050年气温将比1961—1990年平均气温高出2.3~2.7℃,降水增加1%~33%.基于冰川编目资料,采用有关对长江源区未来50a内的气温和降水预测数据,应用冰川系统对气候响应的模型,对该区未来50a内冰川变化趋势进行预测.结果表明:到2010年、2030年、2050年该区冰川面积平均将减少3.2%、6.9%和11.6%;冰川径流平均将增加20.4%、26%和28.5%;零平衡线上升值为14m、30m和50m左右.最后,针对气候变化的不确定性,对预测结果的不确定性进行了探讨.     

青藏高原东南巴松措流域和派山谷末次冰盛期冰川与气候重建

末次冰盛期(LGM)时全球大范围降温,青藏高原冰川大规模扩张,重建LGM时期古冰川规模对认识高原冰川水资源演化及古气候条件有重要的科学意义。根据青藏高原东南巴松措流域及派山谷两地的冰川地貌及其10Be暴露年代数据,本文应用冰川纵剖面模型定量重建了两地冰川在LGM时期的范围、冰储量和平衡线高度(ELA)等参数,并通过冰川气候模型恢复了LGM时的气候条件。结果表明：巴松措流域LGM时期的冰川面积约为982.3km²,是现代冰川面积的4.5倍,冰储量约为274.4km³;派山谷无现代冰川分布,LGM时期的冰川面积达5.76km²,冰储量约为0.51km³;LGM时期两冰川的平衡线高度分别为4 460～4 547m和3 569～3 694m,与现代冰川相比分别降低了535m和1 034～1 184m。在降水减少60%的情况下,考虑LGM以来的构造剥蚀对平衡线高度变化的影响,LGM时期巴松措流域和派山谷冰川的夏季平均气温分别比现在低约2.96～4.89℃和5.09～6.99℃。     

Multivariate models for predicting glacier termini

Concerns over the rapid retreat rates of mountain glaciers have been rising as global temperatures have continued to increase. The extent of variation in the retreat of mountain glaciers can provide information about changes to different climatic conditions. Assessing the retreat rates of glaciers is crucial to assess the continuing existence of mountain glaciers and the ramifications of those retreats on water security for human societies. Therefore, mathematical and statistical models for the quantification of glacier dynamics in response to climate change are in high demand. In this research, we propose a multivariate regression model that estimates glacier change and predicts the location of glacier terminus over time, based on observed climate factors. The proposed method is applied to temporal sequences of ground observations for a number of glaciers around the globe. This model can potentially be used for monitoring glacier systems using climatic factors.     

Terminal environment, topographic control and fluctuations of West Greenland glaciers

Glaciers are commonly regarded as sensitive indicators of climatic change, but iceberg calving can partially decouple glacier oscillations from climatic forcing. Recent fluctuations (1942–85) of 72 West Greenland outlet glaciers were studied using aerial photographs, and nine of them examined in the field. Despite similar climatic forcing, variable glacier behaviour is apparent. Eighty-four percent of the land terminating glaciers have been retreating or stable during the period, whereas more than half the tidewater and lake terminating glaciers have been advancing. The calving glaciers exhibit much greater variability in frontal behaviour. Patterns of change suggest that the land-terminating glaciers are controlled dominantly by variations in summer temperature, but that calving dynamics have caused the tidewater and lake-calving glaciers to respond to climatic change in non-linear ways. Dynamic and response contrasts are apparent between freshwater and tidewater glaciers. Trough geometry is of great significance in controlling the nature and magnitude of frontal change of calving glaciers; in particular, topographic 'pinning points' represent potentially stable locations within the fjord at which stillstands almost invariably occur, irrespective of climatic change or regional trends.     

Loch Lomond Stadial glaciers in the Aran and Arenig Mountains,North Wales,Great Britain

Geomorphological evidence for four former local glaciers has been mapped in the Aran and Arenig Mountains, North Wales. Former glacial extent was deduced from the distribution and assemblage of end and lateral moraines, hummocky moraine, boulder limits, drift limits and periglacial trimlines. Comparison of infilled lake sediment stratigraphies inside and outside of the former glacier limits suggests a Loch Lomond Stadial (Late Devensian) age of the former glaciers (c. 12.9–11.5 cal. ka BP ). This finding is also supported by periglacial–landform contrasts between the land inside and outside of the glacier limits. Reconstruction of the four glaciers illustrates a mean equilibrium line altitude (ELA) of c. 504 m. From the reconstructed ELAs and the combination of precipitation and snowblow input for total accumulation, by analogy with Norwegian glaciers, a mean sea‐level July temperature is calculated at 8.4°C. Copyright © 2002 John Wiley & Sons, Ltd.     

Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.     

Late Quaternary glaciation and equilibrium line altitude variations of the McKinley River region,central Alaska Range

Dortch, J. M., Owen, L. A., Caffee, M. W. & Brease, P. 2009: Late Quaternary glaciation and equilibrium line altitude variations of the McKinley River region, central Alaska Range. Boreas, 10.1111/j.1502‐3885.2009.00121.x. ISSN 0300‐9483 Glacial deposits and landforms produced by the Muldrow and Peters glaciers in the McKinley River region of Alaska were examined using geomorphic and ¹⁰Be terrestrial cosmogenic nuclide (TCN) surface exposure dating (SED) methods to assess the timing and nature of late Quaternary glaciation and moraine stabilization. In addition to the oldest glacial deposits (McLeod Creek Drift), a group of four late Pleistocene moraines (MP‐I, II, III and IV) and three late Holocene till deposits (‘X’, ‘Y’ and ‘Z’ drifts) are present in the region, representing at least eight glacial advances. The ¹⁰Be TCN ages for the MP‐I moraine ranged from 2.5 kyr to 146 kyr, which highlights the problems of defining the ages of late Quaternary moraines using SED methods in central Alaska. The Muldrow ‘X’ drift has a ¹⁰Be TCN age of ～0.54 kyr, which is ～1.3 kyr younger than the independent minimum lichen age of ～1.8 kyr. This age difference probably represents the minimum time between formation and early stabilization of the moraine. Contemporary and former equilibrium line altitudes (ELAs) were determined. The ELA depressions for the Muldrow glacial system were 560, 400, 350 and 190 m and for the Peters glacial system 560, 360, 150 and 10 m, based on MP‐I through MP‐IV moraines, respectively. The difference between ELA depressions for the Muldrow and Peters glaciers likely reflects differences in supraglacial debris‐cover, glacier hypsometry and topographic controls on glacier mass balance.     

Holocene climate inferred from glacier extent,lake sediment and tree rings at Goat Lake,Kenai Mountains,Alaska, USA

Lake sediment, glacier extent and tree rings were used to reconstruct Holocene climate changes from Goat Lake at 550 m asl in the Kenai Mountains, south‐central Alaska. Radiocarbon‐dated sediment cores taken at 55 m water depth show glacial‐lacustrine conditions until about 9500 cal. yr BP, followed by organic‐rich sedimentation with an overall increasing trend in organic matter and biogenic silica content leading up to the Little Ice Age (LIA). Through most of the Holocene, the northern outlet of the Harding Icefield remained below the drainage divide that currently separates it from Goat Lake. A sharp transition from gyttja to inorganic mud about AD 1660 signifies the reappearance of glacier meltwater into Goat Lake during the LIA, marking the maximum Holocene (postglacial) extent. Meltwater continued to discharge into the lake until about AD 1900. A 207 yr tree‐ring series from 25 mountain hemlocks growing in the Goat Lake watershed correlates with other regional tree‐ring series that indicate an average summer temperature reduction of about 1°C during the 19th century compared with the early–mid 20th century. Cirque glaciers around Goat Lake reached their maximum LIA extent in the late 19th century. Assuming that glacier equilibrium‐line altitudes (ELA) are controlled solely by summer temperature, then the cooling of 1°C combined with the local environmental lapse rate would indicate an ELA lowering of 170 m. In contrast, reconstructed ELAs of 12 cirque glaciers near Goat Lake average only 34 ± 18 m lower during the LIA. The restricted ELA lowering can be explained by a reduction in accumulation‐season precipitation caused by a weakening of the Aleutian low‐pressure system during the late LIA. Copyright © 2008 John Wiley & Sons, Ltd.