On calculating glacial isostatic adjustment

Modeling the earth's fluid and elastic response to the melting of the glaciers of the last ice age is the most direct way to infer the earth's radial viscosity profile.Here,we compare two methods for calculating the viscoelastic response to surface loading.In one,the elastic equation of motion is converted to a viscoelastic equation using the Correspondence Principle.In the other,elastic deformation is added to the viscous flow as isostatic adjustment proceeds.The two modeling methods predict adjustment histories that are different enough to potentially impact the interpretation of the observed glacial isostatic adjustment(GIA).The differences arise from buoyancy and whether fluid displacements are subjected to hydrostatic pre-stress.The methods agree if they use the same equations and boundary conditions.The origin of the differences is determined by varying the boundary conditions and pre-stress application.

Paleoenvironmental changes recorded by grain size of loess/paleosol sequence from the Chifeng City,Northeastern China since the Last Glacial

The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China.Results showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the region.The EM1 represents atmospheric dust as the background.The EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),respectively.Results of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.

Flooding(or breaching)of inter-connected proglacial lakes by cascading overflow in the arid region of Western Mongolia(Mt.Tsambagarav,Mongolian Altai)

This study investigates the glacial lake outburst flood(GLOF)hazards in the Tsambagarav mountain range in Western Mongolia,focusing on the Khukhnuruu Valley and its interconnected proglacial lakes.Over the last 30 years,significant glacier retreats,driven by rising temperatures and changing precipitation patterns,have led to the formation and expansion of several proglacial lakes.Fieldwork combined with satellite data and meteorological analysis was used to assess the dynamics of glacier and lake area changes,with particular focus on the flood events of July 2021.The research reveals a substantial reduction in glacier area,particularly in the Khukhnuruu E complex,where glacier area decreased by 19.3%.The study highlights the influence of increasing temperatures and summer precipitation,which have accelerated ice melt,contributing to the expansion and eventual breaching of lakes.Additionally,lake area changes were influenced by the steepness of the terrain,with steeper slopes exacerbating peak discharge during floods.Of the studied seven lakes(Lake 1 to Lake 7),Lake 1 experienced the most dramatic reduction,with a decrease in area by 73.51%and volume by 84.84%,followed by Lake 7.This study underscores the region's vulnerability to climate-induced hazards and stresses the need for a comprehensive early warning system and disaster preparedness measures to mitigate future risks.

Glacial debris flow susceptibility mapping based on combined models in the Parlung Tsangpo Basin,China

Machine learning(ML)-based prediction models for mapping hazard(e.g.,landslide and debris flow)susceptibility have been widely developed in recent research.However,in some specific areas,ML models have limited application because of the uncertainties in identifying negative samples.The Parlung Tsangpo Basin exemplifies a region prone to recurrent glacial debris flows(GDFs)and is characterized by a prominent landform featuring deep gullies.Considering the limitations of the ML model,we developed and compared two combined statistical models(FA-WE and FA-IC)based on factor analysis(FA),weight of evidence(WE),and the information content(IC)method.The final GDF susceptibility maps were generated by selecting 8 most important static factors and considering the influence of precipitation.The results show that the FA-IC model has the best performance.The areas with a very high susceptibility to GDFs are primarily located in the narrow valley section upstream,on both sides of the valley in the middle and downstream of the Parlung Tsangpo River,and in the narrow valley section of each tributary.These areas encompass 86 gullies and are characterized as"narrow and steep".

Glacial lakes under climate change: the imperative for comparative studies of microbial carbon metabolism in the Qinghai-Xizang Plateau and the Arctic

Glacial lakes,intimately linked to glacier termini,are crucial landscape features of the Qinghai-Xizang Plateau(QXP,Qinghai-Tibet Plateau)and the Arctic.Climate warming has accelerated glacier retreat and the rapid expansion of glacial lakes in both regions.Despite being typically considered harsh environments,these lakes serve as vital reservoirs for microbial biodiversity and carbon metabolism.In the face of climate change,glacial lake ecosystems over the QXP and the Arctic are undergoing unprecedentedtransformations.Thisopinioneditorial highlights the significance of conducting research and establishing long-term monitoring programs focused on microbial carbon metabolism in these glacial lakes.

Revisiting East Asian monsoon change during the Last Glacial Maximum using PMIP4 simulations

利用PMIP4多模式试验数据,本文重新检查了末次冰盛期(距今约21000年)东亚季风变化.结果表明:相对于工业革命前期,所有5个模式一致模拟显示末次冰盛期东亚季风减弱,冬季和夏季减幅分别为1%-18%和2-32%;不同模式中东亚季风环流变化的空间分布存在差异,这主要源于该时期大尺度变冷和海平面气压梯度变化的空间分布不同;由于模式之间的差异和重建记录之间的不确定性,未来有待开展更多模拟和重建工作以更好地理解冰期东亚季风变化.

Evolution and bathymetry of glacial lake at the lowest elevation in Nepal Himalaya

One of the prominent impacts of climate change induced glacier retreat in the Himalayas is the formation and expansion of glacial lakes. The newly formed glacial lakes are mostly located in higher altitudinal regions(4200-5800 m) of Himalaya,however, a new glacial lake(Kapuche, 28.446° N and 84.116° E) have been reported to be emerged in the relatively low elevation area of ~2450 m above sea level(masl) in the Nepal Himalaya. This short communication presents the remote sensing-based evolution and field-based bathymetry of Kapuche lake, and further discusses its formation process and lake type for being a glacial lake at the lowest elevation in Nepal Himalaya.

Glacial reconstruction and periglacial dynamics at the end of Late Pleistocene on the surface of Cofre de Perote volcano,México:a climatological retrospective

Despite being within the intertropical region of the planet,the Mexican territory still has glacier-covered mountains.In recent decades,important advances have been made in studies on glaciology and periglacial environment in Mexico both for current and past conditions.However,in spite of Cofre de Perote volcano(4200 m a.s.l.)being a strategically located mountain,it has not yet been studied in regards to the glacial and periglacial processes;in fact,those dynamics have modified the mountain massifs in the past.To complement the series of studies on glacial history in the high mountain environment of México,this study reconstructs the glacial cover and the periglacial environment of the volcano surface during the final stage of the Late Pleistocene based on climatic retrospective and through the identification of geomorphological features.The findings indicate the existence of a large glacier(ice cap)that covered the northern,western,and southern slopes of the mountain;while in the eastern sector there were two small glaciers,one being of cirque type,and the other of valley type.The current temperature conditions prevent the occurrence of permanent ice bodies;at the same time,it was found that the periglacial blockfields of the slopes is a legacy of the climatic conditions that prevailed at the end of Late Pleistocene.

Ecological and hydrologic evolution history in the sensitive zone of both East Asian summer monsoon and Westerly since the Last Glacial Maximum

The Qilian Mountains,located in the northeastern Qinghai-Tibet Plateau,is a sensitive zone of both East Asian summer monsoon(EASM)and westerly winds(WW).The evolution history and driving mechanism of the ecosystem and hydrologic cycle in this region on long-term timescales have not yet been clarified.In this study,we comprehensively study the hydrologic and ecological evolution history in the sensitive zone since the Last Glacial Maximum(LGM)by integrating surface sediments,paleoclimate records,TraCE-21ka transient simulations,and PMIP3-CMIP5 multi-model simulation.Results show that hydrologic and ecological proxies from surface sediments are significantly different from west to east and mainly divided into three sections:the monsoonaffected region in the eastern Qilian Mountains,the intersection region in the central Qilian Mountains,and the westerly-affected region in the western Qilian Mountains.Meanwhile,paleo-ecological and paleohydrologic reconstructions from the surroundings uncover a synchronous climate evolution that the EASM mainly controls the eastern Qilian Mountains and penetrates the central Qilian Mountains in monsoon intensity maximum,while the WW dominates the central and western Qilian Mountains on both glacial-interglacial and millennial timescales.The simulation results further bear out the glacial humid climate in the central and western Qilian Mountains caused by the enhanced WW,and the humidity maximum in the eastern Qilian Mountains controlled by the strong mid-Holocene monsoon.In general,east-west differences in climate pattern and response for the EASM and the WW are integrally stable on both short-term and long-term timescales.

CO2 Air-Water Exchanges during Seasonal and Glacial Cycles

Based on the photosynthesis-respiration reversible reaction and the available statistics, we attempted to quantify the planetary seasonal exchanges of CO2 between air and water from 1970 and compared them to the glacial ACC cycles as reported from ice cores archives. In 2020, the overall continental absorption (AW) was 8.0 giga tonnes of carbon per year (GtC/y). Emissions into the atmosphere (EW) resulting from mineral degradation by respiration and combustion of biomass and fossil hydrocarbons were 14.7 GtC/y, an increase of 2.4% per year since 1970. The continental surplus balance (-AW+EW) of 6.7 GtC/y was shared between the atmosphere, which received 5.1 GtC/y (GATM), and the ocean which absorbed 1.6 GtC/y. This ocean contribution (OC) corresponded to 17% of the 9.2 GtC/y emissions by combustion of fossil hydrocarbons (EFOS). Analysis of the ACC oscillations during 2020 in the northern hemisphere showed that the ocean absorbed 11.1 GtC during the warm season and outgassed 9.5 GtC during the cold season. Assuming proportionality to world population, the ACC, 414 parts per million (ppm) in 2021, would reach 584 ppm in 2080, still growing at a rate of 0.6% per year. The gain of atmospheric CO2 (GATM) and its absorption by the ocean (OC) were expected to peak at 7.0 and 2.2 GtC/y, respectively, in 2080. This increase in the availability of atmospheric CO2 resulted in improved yields of agriculture which more than compensated for the reduction by half of food-producing areas per capita from 1970.

末次冰期东海嵊山岛黄土粒度端元分析及其环境意义

【目的】东海岛屿晚更新世风尘黄土堆积是我国黄土在东部长三角及外延海域重要的拓展,深化这一区域风尘黄土沉积的物源特征和后期演化问题研究,对于认识晚更新世区域古环境变化尤为重要。【方法】在OSL测年和磁化率测试基础上,基于东海岛屿典型风尘黄土剖面(嵊山岛黄土)的粒度分析,开展了粒度组成的端元分析,探讨了其蕴含的古环境信息。【结果与结论】嵊山岛黄土沉积可提取出3个粒度端元(EM1~EM3),进一步分析发现EM1可能代表通过高空西风气流传输的远源黏粒组分,EM2可能代表以浮尘形式远距离悬浮搬运并随风力减弱而沉降堆积的细粉砂组分,EM3可能代表冬季风驱动下的近地表短距离搬运堆积的粗粉砂组分。粒度端元分析结果表明,高空西风输送的黏粒端元组分和远距离悬浮运移的浮尘端元组分可能是沉积剖面主要粉尘来源;综合年代学结果、百分频率磁化率和颗粒中值粒径等参数分析,认为东海嵊山岛黄土沉积过程在MIS3阶段先后经历暖湿—冷干—暖湿的旋回波动;并且,所记录的MIS3阶段气候波动以及MIS2阶段末次冰盛期和冰消期的古环境变化同深海氧同位素和古海平面变化趋势相对应,说明东海陆架区域该时期环境演变与全球性气候波动相协同。

四川盆地及周缘前震旦系裂谷特征与油气地质意义

四川盆地及周缘已被证实发育较大规模的前震旦系裂谷,但其在盆地内部的展布及发育特征尚不明确,因此在一定程度上制约了对盆地深部构造格局的认识。为此,在前人研究的基础上,利用最新的重磁电资料,通过联合解译和小子域滤波等新技术对新元古界构造形态进行了研究,同时结合区域地震大剖面的精细解释并辅以航磁资料进行验证,分析了新元古代裂谷的特征及其对上覆地层的沉积控制作用。研究结果表明:①盆地内部自西北至东南共发育3条近乎平行的前震旦系裂谷,其中以川中裂谷规模最大;②裂谷内部发育一系列与裂谷走向近平行的次级正断层,将裂谷内部结构复杂化,形成一系列断陷;③裂谷内断层在平面上呈平行/斜列式、相向/相背平行式及同向平行式组合,对应在剖面上呈阶梯式、垒堑式、地堑式及铲式半地堑式等组合特征;④盆地东北部盆缘露头揭示南华系—陡山沱组在裂谷内发育冰期—间冰期交互沉积,主要为三角洲、陆棚与斜坡盆地相碎屑岩和冰碛岩。结论认为,应用重磁联合解译+井震资料修订+露头剖面验证的新方法,证实四川盆地前震旦系裂谷的存在,且南华纪裂谷边界(主干)断裂控制了上覆地层沉积古地理格局和坡折带的发育,部分裂谷控制了寒武系或早古生界沉积中心的分布,并对后期沉降中心、构造圈闭的形成以及含油气系统有着极为重要的影响。

张掖盆地晚更新世至中全新世气候变化:孢粉学和重矿物学证据

为确定张掖盆地晚第四纪沉积地层时代和探讨其蕴含的古气候信息,笔者利用孢粉分析、重矿物分析、光释光测年等方法对研究区晚更新世以来气候变化特征进行了重建,并确认了当地全新世和晚更新世地层界限。结果表明:地层自下而上划分为4个孢粉组合带和植被类型及气候特征:①深度为56.8~26.4 m,年龄为112.7~63.3 ka,属末次间冰期,粉组合为松–板栗–藜–菊–蒿,针阔叶混交林草原植被,为晚更新世温暖较湿润气候。②深度为26.4~2.6 m,年龄为63.3~11.8 ka,与末次冰期相当,孢粉组合为松–麻黄–藜–蒿,植被类型为针阔叶混交林草原植被,为晚更新世干燥寒冷气候。③深度为2.6~0.8 m,年龄为11.8~8.9 ka,全新世早期,孢粉组合为松–藜–蒿,稀树针阔叶混交林草原植被,较凉较干气候。④深度为0.8~0.15 m,年龄为8.9~7.8 ka,全新世早期向中期过渡期,孢粉组合为松–藜–菊–蒿,稀树针阔叶混交林草原植被,为温暖较干气候。孢粉组合所揭示的晚更新世—中全新世气候变化特征,对于揭示张掖盆地甚至西北干旱区的古气候变化具有重要意义。

基于Sentinel-1时序数据的山地冰川表面消融变化研究--以老虎沟12号冰川为例

冰川是影响气候变化的主要因素,合成孔径雷达(SAR)不仅具有较高空间分辨率和多极化等特点,而且对冰雪融化引起的介电常数变化较为敏感,已成为山地冰川表面消融变化监测的重要数据源。基于Sentinel-1时序数据,提出了一种综合应用多时相多极化SAR变化检测算法和Sigmoid函数的冰川表面消融监测方法。以祁连山老虎沟12号冰川为研究区,利用“中心线-圆”方法获得的冰川东、西支64个样区,通过各点2019-2020年124个时相的SAR后向散射系数变化特征确定了7个典型样区及2019和2020年冰川消融期;基于同轨道参考影像与多时相融雪影像对比,分别获得变化监测影像VV和VH极化后向散射系数,对其进行权重组合后提取湿雪像元;通过Sigmoid函数并结合湿雪平均海拔高度提取干雪,从而得到2年冰川消融期内16个时相的冰川表面干湿雪分布。利用2019年09月01日无人机数字正射影像(DOM)以及与Sentinel-1邻近日期5景Sentinel-2影像对提取结果进行精度验证,并结合冰川上气象站点气温和降水数据对误差结果进行深入分析。实验结果表明,该方法能够有效提取冰川表面干、湿雪分布,总体分类精度OA高达96%,Kappa系数高达0.84。老虎沟12号冰川消融期及覆盖各类型消融变化规律存在年际变化:2019年冰川的消融期为5月初至9月中下旬,2020年的消融期为6月中下旬至9月初;2019年从消融季开始,冰川表面干雪面积迅速减小,而湿雪与冰川冰面积在整个消融期均较大,但随着强降雪出现,干雪面积骤然上升,2020年冰川冰和湿雪面积变化明显,冰川冰面积持续增加,湿雪面积持续减小,而干雪面积在高海拔区趋于稳定。

东北地区末次盛冰期以来孢粉数据库构建技术与应用

孢粉数据库是研究区域尺度的古环境演变历史、古气候变化规律等重要的基础数据。对东北地区末次盛冰期以来71条孢粉序列进行数据处理。首先,重新计算各种属的百分比;其次,校正年代并建立年代序列;最后,以1000年的分辨率插值孢粉序列。由此,构建了标准统一的孢粉数据库,结合GIS技术展示了数据库信息,并重建了东北地区古植被演化的特征。该数据库可有效应用于东北地区古环境演化等研究。

乙酸正丁酯的实验室合成条件优化研究

以冰醋酸和正丁醇为原料,浓H_(2)SO_(4)作催化剂,无水Mg SO4为干燥剂合成乙酸正丁酯,研究了投料比、反应时间、反应温度、浓H_(2)SO_(4)用量等对产率和纯度的影响。得出最佳反应条件为:冰醋酸与正丁醇的物质的量之比为1∶1.05,冰醋酸的用量为14.00g,浓H_(2)SO_(4)用量为1.00m L,回流反应时间为40min。在该条件下合成乙酸正丁酯,纯度超过98%,产率可达80%以上。

芩蓟凉血合剂对痔病相近动物模型的影响

目的探讨芩蓟凉血合剂(Qinji Liangxue mixture,QLM)对抗痔作用的机制。方法分别使用巴豆油制剂(croton oil preparation,COP)、冰醋酸制备大鼠急性痔病动物模型,将80只SD雌性大鼠,随机分为COP组与冰醋酸组两组,每组40只。COP组,随机分为对照组1(CA组),模型组1(CB组),QLM低剂量组1-1(CC组),QLM高剂量组1-2(CD组),地奥司明组1(CE组),每组8只;冰醋酸组,随机分为对照组2(GA组),模型组2(GB组),QLM低剂量组2-1(GC组),QLM高剂量组2-2(GD组),地奥司明组2(GE组),每组8只。除对照组,其余组均使用COP或冰醋酸处理,随后使用不同药物治疗7 d。使用苏木精-伊红(HE)染色观察COP及冰醋酸诱导的肛门直肠组织形态学,使用ELISA检测COP诱导的大鼠血清IL-6、TNF-α水平,记录冰醋酸诱导的大鼠肛周溃疡面积。将24只C57BL/6小鼠随机分为对照组(A组),QLM低剂量组(B组),QLM高剂量组(C组),肾上腺色腙片组(D组),每组6只,连续治疗7 d,使用毛细管法及断尾法评价QLM的止血疗效。结果QLM能够显著改善痔病相近动物模型的病理损伤,减轻COP诱导的病变程度评分(P<0.05),降低血清IL-6、TNF-α水平(P<0.05),减少冰醋酸诱导的肛周溃疡面积(P<0.05),缩短凝血及出血时间(P<0.05)。结论QLM具有良好的抗痔活性,其作用可能是通过抗炎、止血、减少组织损伤实现的。

昆仑山北坡冰川湖变化及其溃决风险评估

探究昆仑山北坡冰川湖时空变化及冰川湖溃决洪水(Glacier lake outburst flood,GLOF)风险评估对区域水资源安全和生态发展具有重要意义。基于Google Earth Engine(GEE)遥感计算平台分析昆仑山北坡冰川湖近30 a的变化特征和GLOF风险评估模型对当前的冰碛湖进行灾害与风险评估。结果表明:(1)1990—2023年昆仑山北坡冰川湖呈显著增长趋势,冰川湖的数量从1990年的248个增加到2023年的925个(增加了2.73倍),面积从1990年的14.99 km^(2)增加到2023年的54.83 km^(2)(增加了2.66倍),冰川湖在昆仑山北坡西部高海拔山区增加显著。(2)通过对2023年GLOF风险评估分析得出,灾害水平在叶尔羌河流域最高(约占47.2%),其次是和田河流域(约占15.7%)。风险水平较高是叶尔羌河流域(约占50.8%),叶尔羌河流域高风险冰川湖占整个昆仑山北坡高风险冰川湖的60.7%。(3)1990—2023年冰川湖的增长趋势与区域气候变化相关,山区降水增加和冰川积雪消融是冰川湖扩张的主要原因。开展冰川湖溃决洪水风险评估可为干旱区水资源可持续利用,为下游地区防灾预警提供科学依据和支撑。

贡嘎山玉龙西高寒钙华地貌对冰川活动的记录

文章选取贡嘎山西侧玉龙西断裂带附近的钙华及周边冰碛物为研究对象,在野外调查的基础上,通过卫星高光谱遥感数据进行钙华识别,对钙华进行航空摄影测量,并构建主要钙华体精细化DEM及三维模型,分析钙华分布规律及地貌特征。结果表明:研究区钙华集中分布于玉龙西区域南北向断裂带两侧,沟谷由高向低处延伸,部分残留钙华体长宽比及表面擦痕等形态特征符合鲸背石、羊背石的外观特点。根据XRD半定量测试结果,结合地形特征,推测覆盖于钙华体之上的堆积物可能是冰川活动的产物,冰川活动时期,上部杂谷脑组风化剥蚀的物质随着冰川作用搬运至钙华体之上,活跃的冰川活动导致早期钙华遭受强烈的冰川侵蚀作用,形成冰川侵蚀地貌。

青藏高原冰前湖与冰川相互作用研究进展

基于已有研究,对青藏高原地区冰川与冰湖(主要为冰前湖)相互作用的机理研究进行梳理,以理解青藏高原冰川后退与冰湖扩张的过程和模式,加深对冰川与冰湖相互作用过程和机理的认识。青藏高原地区冰前湖主要分布于藏东南喜马拉雅山和念青唐古拉山,有记录和查明冰湖溃决成因的事件中,冰川动态引起冰前湖溃决事件占到冰湖溃决总事件的55%,且多分布于喜马拉雅山和念青唐古拉山等藏东南地区。冰川与冰前湖的相互作用模式表现为:冰川对冰前湖的作用和冰前湖对冰川的反作用。其中,冰川对冰湖的作用主要包括冰川退缩为冰湖发育提供了空间、冰川融水为冰湖形成和扩张提供了充足水源、冰川极端事件(冰面/内水系溃决、冰川前进/运动、冰崩等)引起冰湖溃决;冰前湖对冰川的反馈机制体现在冰前湖对冰川的热力融冰、冰前湖动力过程导致末端冰川崩解等物质亏损、冰前湖的演变对母冰川的气候效应。需要说明的是,二者之间的相互作用不是孤立的,是彼此依存、同时发生。未来冰川与冰前湖研究中,应致力于:(1)建立统一的冰川观测规范和冰湖-冰川数据集;(2)集成“气候-冰川-冰湖-灾害”为一体的综合观测体系,实现数据共享;(3)耦合冰川与冰湖模型,模拟相互作用过程与机制;(4)统一冰湖溃决灾害的评价体系和完善预警机制。此外,冰川与冰湖变化的理论相对成熟,但冰川与冰前湖相互作用的理论研究依然不够,亟需不断完善。