Relict glacial landscape in the Sierra Baguales Mountain Range(50°-51° S): evidence of glaciation dynamics and types in the eastern foothills of the southern Patagonian Andes

The glacial morphology of southern South American presents invaluable evidence to reconstruct former glacier behaviour and its relation to climate and environmental changes. However, there are still spatial and temporal gaps in the reconstruction of the Holocene Patagonian glacial landscape. Here we present the first geomorphological record for the Sierra Baguales Mountain Range(SBMR), forming the eastern foothills of the Southern Patagonian Andes 200 km from the Pacific coast. This area is topographically isolated from the Southern Patagonian Ice Field(SPIF), and is affected by the Westerly Winds. The study area shows evidence of ice sheet and alpine glaciations related to Andean uplift,which caused a marked climatic contrast between its western and eastern flanks since the Last Glacial Maximum(LGM). The regional rock mass strength and precipitation gradient acted as a controlling factor in the glacial cirque distribution and sizes, as well as in the development of glaciation types. We report new radiocarbon dates associated with warm/dry to cold/wet climatic changes during the middle Holocene, when former small alpine glaciers were located in the uppermost section of the SBMR basins, and eventually converged to form a small ice field or a composite valley glacier at lower elevations.This can be explained by an estimated regional temperature drop of 3.8°C±0.8°C, based on a 585±26m Equilibrium Line Altitude(ELA) descent, inferred by geomorphological evidence and the Accumulation Area Ratio(AAR), in addition to a free-air adiabatic lapse rate. Subsequently, the glaciers receded due to climatic factors including a rise in temperature, as well as non-climatic factors, mainly the glacier bedrock topography.     

Relationship between flow speed variability of three tidewater glaciers and surface melt intensity in Greenland between 1979 and 2006

The margin of the Greenland ice sheet has undergone rapid changes over the past decade as a result of the thinning, acceleration, and retreat of many fast-flowing tidewater outlet glaciers. Satellite observations show that three major tidewater outlet glaciers in Greenland retreated between 2000 and 2005, with synchronous increases in flow speed, causing a deficit in ice sheet mass budget and the potential for sea level rise. In this study, we investigated whether this acceleration was related to surface melt processes, and found that both flow speed and positive degree day (PDD) anomalies of the three glaciers varied together, indicating a causal relationship. Jakobshavn Isbræ had lower flow speeds before 2000, during which PDD anomalies were negative, except for modest warming in 1993 and 1995. From 1999–2000, during which it is thought a threshold was passed, the flow speed of the glacier started to increase. However, the two glaciers in east Greenland showed a delayed response. Abrupt warming occurred in the vicinity of the two glaciers around 2001, but flow speed did not increase until 2003 for the Helheim Glacier, and until 2004 for the Kangerdlugssuaq Glacier. Furthermore, the two eastern glaciers switched to a deceleration mode more quickly than Jakobshavn Isbræ. The observed differences in both acceleration and deceleration among the glaciers suggest that the relationship between surface melt and outlet glacier dynamics is not simple but complex.     

Last glaciation and maximum glaciation in the Qinghai-Xizang (Tibet) Plateau: A controversy to M. Kuhle’s ice sheet hypothesis

Since the late 1950’s, many Chinese scientists have explored the remains of the Quaternary glaciation in the Qinghai-Xizang (Tibet) Plateau and its surrounding mountains. In the main, 3–4 glaciations have been recognized. The largest one occurred in the Late Middle Pleistocene with piedmont glaciers, ice caps and trellis valley glaciers in many high peak regions. But here is no evidence of a unified ice sheet covering the whole plateau as described by M. Kuhle. Due to the further uplifting of the Himalayas and Qinghai-Xizang Plateau the climate became progressively driver, diminishing the extension of glaciers during the Late Pleistocene. The elevation of the snow line during the Last Glaciation was about 4,000 m on the south, east and northeast edges of the plateau and ascended to 5500 m on the hinder northwest of the plateau. The thermal effect of the big plateau massif, the sharp increase of aridity from the southeast rim to the northwest inland area and the abrupt decrease of precipitation during the Ice Age largely account for the distribution of the Quaternary glaciers in the Qinghai-Xizang Plateau. The neglect of Chinese literature may be one of the causes accounting for M. Kuhle’s misinterpretation on the environment of the Quaternary glaciations in the Qinghai-Xizang Plateau.     

Effect of compressive strength on the performance of the NEMO-LIM model in Arctic Sea ice simulation

Satellite records show that the extent and thickness of sea ice in the Arctic Ocean have significantly decreased since the early 1970s. The prediction of sea ice is highly important, but accurate simulation of sea ice variations remains highly challenging. For improving model performance, sensitivity experiments were conducted using the coupled ocean and sea ice model (NEMO-LIM), and the simulation results were compared against satellite observations. Moreover, the contribution ratios of dynamic and thermodynamic processes to sea ice variations were analyzed. The results show that the performance of the model in reconstructing the spatial distribution of Arctic sea ice is highly sensitive to ice strength decay constant (C^rhg). By reducing the C^rhg constant, the sea ice compressive strength increases, leading to improved simulated sea ice states. The contribution of thermodynamic processes to sea ice melting was reduced due to less deformation and fracture of sea ice with increased compressive strength. Meanwhile, dynamic processes constrained more sea ice to the central Arctic Ocean and contributed to the increases in ice concentration, reducing the simulation bias in the central Arctic Ocean in summer. The root mean square error (RMSE) between modeled and the CryoSat-2/SMOS satellite observed ice thickness was reduced in the compressive strength-enhanced model solution. The ice thickness, especially of multiyear thick ice, was also reduced and matched with the satellite observation better in the freezing season. These provide an essential foundation on exploring the response of the marine ecosystem and biogeochemical cycling to sea ice changes.

     

Evidence for Accelerating Glacier Ice Loss in the Takht＇ e Solaiman Mountains of Iran from 1955 to 2010

This study reports on the clean ice area and surface elevation changes of the Khersan and Merjikesh glaciers in the north of Iran between 1955 and 2010 based on several high to medium spatial resolution remote sensing data.The object-oriented classification technique has been applied to nine remote sensing images to estimate the debris-free areas.The satellite-based analysis revealed that the clean ice areas of Khersan and Merjikesh glaciers shrank since 2010 with an overall area decrease of about 45% and 60% respectively.It means that the dramatic proportions of 1955 glaciers surface area are covered with debris during the last five decades.Although the general trend is a clean ice area decrease,some advancement is observed over the period of 1997-2004.During 1987-1991 the maximum decrease in the clean ice area was observed.However,the clean ice area had steadily increased between 1997 and 2010.To quantify the elevation changes besides the debris-free change analysis,several Digital Elevation Models(DEMs) were extracted from aerial photo(1955),topographic map(1997),ASTER image(2002) and Worldview-2 image(2010) and after it a 3-D Coregistration and a linear relationship adjustments techniques were used to remove the systematic shifts and elevation dependent biases.Unlike the sinusoidal variation of our case studies which was inferred from planimetric analysis,the elevation change results revealed that the glacier surface lowering has occurred during 1955-2010 continuously without any thickening with the mean annual thinning of about 0.4 ± 0.04 m per year and 0.3 ± 0.026 m per year for Khersan and Merjikesh glaciers,respectively.The maximum thinning rate has been observed during 1997-2002(about 1.1 ± 0.09 per year and 0.96 ± 0.01 mper year,respectively),which was compatible partially with debris-free change analysis.The present result demonstrates that although in debris-covered glaciers clean ice area change analysis can illustrate the direction of changes(retreat or advance),due to the high uncertainty in glacier area delineation in such glaciers,it cannot reveal the actual glacier changes.Thus,both planimetric and volumetric change analyses are very critical to obtain accurate glacier variation results.     

Sea ice thickness measurement in spring season in Bothnian Bay using an electromagnetic induction instrument

As an important component of the cryosphere,sea ice is very sensitive to the climate change.The study of the sea ice physics needs accurate sea ice thickness.This paper presents an electromagnetic-induction(EM) technique which can be used to measure the sea ice thickness distribution efficiently,and the successful application in Bothnian Bay.Based on the electromagnetic field theory and the electrical properties of sea ice and seawater,EM technique can detect the distance between the instrument and the ice/water interface accurately,than the sea ice thickness is obtained.Contrastive analysis of the apparent conductivity data obtained by EM and the value of drill-hole at same positions allows a construction of a transformable formula of the apparent conductivity to sea ice thickness.The verification of the sea ice thickness calculated by this formula indicates that EM technique is able to get reliable sea ice thickness with average relative error of only 12%.The statistic of all ice thickness profiles shows that the level ice distribution in Bothnian Bay was 0.4-0.6 m.     

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????????GPS??GRACE??????????????????????????????????????е????????ICE-5G and ICE-3G???????????????????????????????????????????е??????????????????????????????????????????????????仯????????????GRACE?????????????????ICE-5G????????????????????????????????????????????С~20%??????????????????????~40%?????????????????????α???????仯??GPS??GRACE???????????????????????????????????????????????????????Ч??? (~150 km??80%?????) ?????????????????????????~90 km); ????μ?????Ч??????????3.7 × 10²⁰?? Pas ??1.9 × 10²¹?? Pas (90%?????)???????????????????????????С~20%??     

Practical Model of Sea Ice Thickness of Bohai Sea Based on MODIS Data

Sea ice thickness is one of the most important input parameters in the studies on sea ice disaster prevention and mitigation. It is also the most important content in remote sensing monitoring of sea ice. In this study, a practical model of sea ice thickness (PMSIT) was proposed based on the Moderate Resolution Imaging Spectroradiometer (MODIS) data. In the proposed model, the MODIS data of the first band were used to estimate sea ice thickness and the difference between the second-band reflectance and the fifth-band reflectance in the MODIS data was calculated to obtain the difference attenuation index (DAI) of each pixel. The obtained DAI was used to estimate the integrated attenuation coefficient of the first band of the MODIS at the pixel level. Then the model was used to estimate sea ice thickness in the Bohai Sea with the MODIS data and then validated with the actual sea ice survey data. The validation results showed that the proposed model and corresponding parameterization scheme could largely avoid the estimation error of sea ice thickness caused by the spatial and temporal heterogeneity of sea ice extinction and allowed the error of 18.7% compared with the measured sea ice thickness.     

Distribution of borehole temperature at four high-altitude alpine glaciers in Central Asia

The distribution of borehole temperature at four high-altitude alpine glaciers was investigated. The result shows that the temperature ranges from -13.4℃ to -1.84℃, indicating the glaciers are cold throughout the boreholes. The negative gradient （i.e., the temperature decreasing with the increasing of depth） due to the advection of ice and climate warming, and the negative gradient moving downwards relates to climate warming, are probably responsible for the observed minimum temperature moving to lower depth in boreholes of the Gyabrag glacier and Miaoergou glacier compared to the previously investigated continental ice core borehole temperature in West China. The borehole temperature at 10m depth ranges from -8.0℃ in the Gyabrag glacier in the central Himalayas to -12.9℃ in the Tsabagarav glacier in the Altai range. The borehole temperature at 10 m depth is 3-4 degrees higher than the calculated mean annual air temperature on the surface of the glaciers and the higher 10 m depth temperature is mainly caused by the production of latent heat due to melt-water percolation and refreezing. The basal temperature is far below the melting point, indicating that the glaciers are frozen to bedrock. The very low temperature gradients near the bedrock suggest that the influence of geothermal flux and ice flow on basal temperature is very weak. The low temperature and small velocity of ice flow of glaciers are beneficial for preservation of the chemical and isotopic information in ice cores.     

Decadal cimatic variations indicated by dulan tree-ring and comparison with other proxy data in China of the last 2000 years

Based on high-resolution tree-ring data from Dulan area of Qinghai Province, five spells have been divided: the warm period before 230’s A. D., the cold period between 240’s A. D. and 800’s A. D., the significantly warm period between 810’s A. D. and 1070’s, i. e. “Medieval Warm Period”, the cold period including the “Little Ice Age” 1420’ – 1870’s and the warming period since 1880’s. All the eleven coldest or warmest decades and several great abrupt changes took place before the Middle Ages, indicating that climatic system operated in great instability during the period 150’s – 1100’s A. D., Comparison of the tree-ring data with other temperature proxy data from East China, Guliya ice core as well as the south of Qinghai-Xizang Plateau shows that such great climatic events as Eastern Han warm period between the beginning of the 1st century and the previous fifty years of the third century, the cold period covering the span of the Wei, the Jin, and the Southern and Northern dynasties, the well-known “Medieval Warm Period” as well as the “Little Ice Age” appeared in these series such as East China and Dulan area. Only the first two climatic events were recorded conspicuously in Guliya ice core while the “Medieval Warm Period” and “Little Ice Age” is far weaker. Also, the well-defined “Medieval Warm Period” didn’t occurred in the south of Qinghai-Xizang Plateau. The warming since the 20th century is the warmest in the last 2000 years Guliya ice core, the second in Dulan area and East China, but it scarcely seems pronounced in the eastern part of Qinghai-Xizang Plateau. Foundation item: Under the auspices of the projects of the Chinese Academy of Sciences (KZ951-A1-204-02 and KZ951-A1 402-03). Biography: YANG Bao(1971–), male, a native of Yanggao County, Shanxi Province, Ph. D. His research interestinclude global change.     

Summer fast ice evolution off Zhongshan Station,Antarctica

Based on the field data acquired in the program of fast ice observation off Zhongshan Station, Prydz Bay, East Antarctica during the austral summer 2005/ 2006, physical properties evolution of fast ice during the ice ablation season is analyzed in detail. Results show that the annual maximum ice thickness in 2005 occurred in later November, and then ice started to reek, and the ablation duration was 62 days; sea water under the ice became warmer synchronously; corresponding to the warming sea ice temperature, a ＂relative cold mid-layer＂ appeared in sea ice; the fast ice marginal line recoiled back to the shore observably, and the recoil distance was 20.9 km from 18 December 2005 through 14 January 2006. In addition, based on the data of sea ice thickness survey along the investigation course of MV Xuelong on December 18 of 2005, the ice thickness distribution paten in the marginal ice zone have been described ： sea ice thickness increased, but the diversity of floe ice thick-ness decreased from open water to fast ice zone distinctly.     

Mechanism of sea ice formation based on comprehensive observation data in Liaodong Bay,China

Sea ice disaster is one of the principal natural hazards that affect some coastal areas of China, and the formation of ice cover in a wave field has important characteristics. However, analysis of the mechanism in which waves affect the thermodynamic process of sea ice is lacking, and the influence of waves is not taken into consideration in numerical models of sea ice, largely because of a lack of simultaneous observations of waves and sea ice. Using observational data of the sea ice cycle in the coastal waters of Liaodong Bay(China), we analyzed the characteristics of hydrology, meteorology, and sea ice thickness during the formation of sea ice, and explored the changes in the interrelationships among heat fluxes, waves, and sea ice under actual sea conditions. The results could provide a decision-making support as a reference to the establishment and improvement of China's early warning system to sea ice disasters, and the protection of ice drilling operations and production platform safety.     

基于CryoSat-2数据反演2011～2017年波弗特海海冰厚度变化

利用CryoSat-2卫星测高数据反演波弗特海的海冰厚度,并利用2010~2013年10月份仰视声呐(ULS)和2011年冰桥计划（IceBridge）数据对结果进行精度评估。结果表明,测高反演的海冰吃水深度与ULS吃水深度差值的最大值和标准差分别为14 cm和4 cm;测高反演的海冰厚度与冰桥计划海冰厚度差值的平均值和标准差分别为2.7 cm和65.7 cm,优于Laxon(2013)研究结果（分别优化2.1 cm和6.6 cm）。在此基础上,研究2011~2017年波弗特海夏冬两季的海冰厚度变化,发现二者具有类似的分布特征,且冬季3月海冰覆盖范围更广,厚度更大;进一步分析2011~2017年3月份冬季海冰厚度年际变化,发现其呈整体下降趋势,且2012年最小,2014年最大。     

北极熊栖息地稳定性的遥感评估方法

北极熊是北极最重要的哺乳动物之一,近年来数量却在减少。海冰作为北极熊狩猎、活动和繁殖的平台,是其栖息地的重要组成部分。因此其种群栖息地变化主要依赖于海冰变化。本文基于美国雪冰中心的海冰密集度和NOAA提供的ETOPO1基岩数据,分析了北极海冰密集度、开阔水域面积、海冰消退时间、海冰出现时间、开阔水域季节长度的年际变化,进而评价北极熊栖息地的稳定性。结果表明,海冰密集度呈现降低的趋势,开阔水域面积增大,多年冰数量减少,大多变为一年冰。海冰消退时间提前,海冰出现时间延后,开阔水域季节长度大幅增加,与1992年相比增加了72 d。19个栖息地中,巴伦支海是开阔水域面积和季节长度变化贡献最大的海域,增加速度分别为9.71×10³ km²/a和71.69 d/10a。以开阔水域季节长度变化率为依据,将北极熊栖息地划分为稳定、次稳定和不稳定3个等级。总共有3个稳定栖息地,包括分布在相对其他栖息地而言纬度较低的楚科奇海、西哈得孙湾和南哈得孙湾。13个次稳定栖息地,包括拉普捷夫海、喀拉海、东格陵兰、巴芬湾、戴维斯海峡、福克斯湾、布西亚湾、麦克林托克海峡、梅尔维尔子爵海峡、挪威湾、北波弗特、南波弗特和兰开斯特海峡。3个不稳定栖息地,均位于70°N以北,包括北极盆地、巴伦支海和凯恩盆地。稳定区主要位于低纬度,不稳定区全部位于高纬度。该分级结果表明高纬度地区虽然海冰覆盖多,但是年际变化十分显著,不稳定的3个区域内北极熊对海冰变化适应时间更少,年际迁移变化大,对北极熊的生存发展更为不利。     

Increasing Winter Conductive Heat Transfer in the Arctic Sea-ice-covered Areas:1979–2014

Sea ice is a quite sensitive indicator in response to regional and global climate changes. Based on monthly mean PanArctic Ice Ocean Modeling and Assimilation System(PIOMAS) sea ice thickness fields, we computed the conductive heat flux(CHF) in the Arctic Ocean in the four winter months(November–February) for a long period of 36 years(1979–2014). The calculated results for each month manifest the increasing extension of the domain with high CHF values since 1979 till 2014. In 2014, regions of roughly 90% of the central Arctic Ocean have been dominated by the CHF values larger than 18 Wm~(-2)(November–December) and 12 Wm~(-2)(January–February), especially significant in the shelf seas around the Arctic Ocean. Moreover, the population distribution frequency(PDF) patterns of the CHF with time show gradually peak shifting toward increased CHF values. The spatiotemporal patterns in terms of the trends in sea ice thickness and other three geophysical parameters, surface air temperature(SAT), sea ice thickness(SIT), and CHF, are well coupled. This suggests that the thinner sea ice cover preconditions for the more oceanic heat loss into atmosphere(as suggested by increased CHF values), which probably contributes to warmer atmosphere which in turn in the long run will cause thinner ice cover. This represents a positive feedback mechanism of which the overall effects would amplify the Arctic climate changes.     

The research of Polar sea ice and its role in climate change

As an important part of global climate system, the Polar sea ice is effccting on global climate changes through ocean surface radiation balance, mass balance, energy balance as well as the circulating of sea water temperature and salinity. Sea ice research has a centuries - old history. The many correlative sea ice projects were established through the extensive international cooperation during the period from the primary research of intensity and the boaring capacity of sea ice to the development of sea/ice/air coupled model. Based on these reseamhes, the sea ice variety was combined with the global climate change. All research about sea ice includes： the physical properties and processes of sea ice and its snow cover, the ecosystem of sea ice regions, sea ice and upper snow albedo, mass balance of sea ice regions, sea ice and climate coupled model. The simulation suggests that the both of the area and volume of polar sea ice would be reduced in next century. With the developing of the sea ice research, more scientific issues are mentioned. Such as the interaction between sea ice and the other factors of global climate system, the seasonal and regional distribution of polar sea ice thickness, polar sea ice boundary and area variety trends, the growth and melt as well as their influencing factors, the role of the polynya and the sea/air interactions. We should give the best solutions to all of the issues in future sea ice studying.     

Analysis of multi-dimensional SAR for determining the thickness of thin sea ice in the Bohai Sea

Flat thin ice (<30 cm thick) is a common ice type in the Bohai Sea, China. Ice thickness detection is important to offshore exploration and marine transport in winter. Synthetic aperture radar (SAR) can be used to acquire sea ice data in all weather conditions, and it is a useful tool for monitoring sea ice conditions. In this paper, we combine a multi-layered sea ice electromagnetic (EM) scattering model with a sea ice thermodynamic model to assess the determination of the thickness of flat thin ice in the Bohai Sea using SAR at different frequencies, polarization, and incidence angles. Our modeling studies suggest that co-polarization backscattering coefficients and the co-polarized ratio can be used to retrieve the thickness of flat thin ice from C- and X-band SAR, while the co-polarized correlation coefficient can be used to retrieve flat thin ice thickness from L-, C-, and X-band SAR. Importantly, small or moderate incidence angles should be chosen to avoid the effect of speckle noise.     

Relative sea level rise and its effects on environment and resources in China’s coastal areas

Due to global climate warming and natural and man-made land subsidence etc., relative sea level rise in the coastal plains of China will exceed 2–3 times over the golbal mean value during the first half part of the 21st century. It will result in a series of adverse impacts on evolution of natural environment and socioeconomic development of the coastal area. This paper analyses environmental and resource effects induced by relative sea level rise in China’s coastal areas on the basis of rough estimate of future relative sea level rise. These effects include inundating tidal flat and wetlands and increase in inundated risk of coastal habitable land, exacerbating storm surge. coastal erosion, flooding and salt water intrusion hazards, as well as endangering land, water, tourism and living resources and their utilization.     

Snow and sea ice thermodynamics in the Arctic： Model validation and sensitivity study against SHEBA data

Evolution of the Arctic sea ice and its snow cover during the SHEBA year were simulated by applying a high-resolution thermodynamic snow/ice model （HIGHTSI）. Attention was paid to the impact of albedo on snow and sea ice mass balance, effect of snow on total ice mass balance, and the model vertical resolution. The SHEBA annual simulation was made applying the best possible external forcing data set created by the Sea Ice Model Intercomparison Project. The HIGHTSI control run reasonably reproduced the observed snow and ice thickness. A number of albedo schemes were incorporated into HIGHTSI to study the feedback processes between the albedo and snow and ice thickness. The snow thickness turned out to be an essential variable in the albedo parameterization. Albedo schemes dependent on the surface temperature were liable to excessive positive feedback effects generated by errors in the modelled surface temperature. The superimposed ice formation should be taken into account for the annual Arctic sea ice mass balance.     

Clean and safe supply of fish and shellfish to clear the HACCP regulation by use of clean and cold deep ocean water in Rausu, Hokkaido, Japan

For the supply of fish and shellfish to consumers in fresh condition, clean handling after catch from the sea is essential. According to HACCP （Hazard Analysis and Critical Control Points）, it is important to meet such requirement by keeping fish and shellfish under a certain low temperature and clean conditions after catching. The deep ocean water （DOW） characterized by low temperature and cleanliness has been chosen for fish and shellfish handlings, particularly for salmon, cod, and sea urchin in Town ＇Rausu＇ in Hokkaido, Japan. DOW below 2.9℃ of an amount of nearly 5 000 m^3 is planned to be pumped up every day from a depth of about 350 m, and temporarily stored in a large simulated tank on land. DOW is then supplied to fish boats through hydrants distributed throughout the harbor and used for keeping salmon in clean and cold conditions. Ice made from DOW is also used for lowering temperature if necessary. DOW and ice made from DOW are also used during the transportation of fish and shellfish. The entire system is scheduled to be completed by the summer of 2005.