Snow,runoff, and mass balance modeling for the entire Mittivakkat Glacier (1998–2006), Ammassalik Island,SE Greenland

Geografisk Tidsskrift, Danish Journal of Geography 108(1):121–136, 2008

SnowModel, a physically-based snow evolution modeling system that includes four submodels—MicroMet, EnBal, SnowPack, and SnowTran-3D—was used to simulate eight full-year (1998/99 through 2005/06) evolutions of snow accumulation, blowing snow sublimation, evaporation, snow and ice surface melt, runoff, and mass changes on the entire Mittivakkat Glacier (31 km²) in southeast Greenland. Meteorological observations from two meteorological stations inside the glacier catchment were used as model input, and glaciological mass balance observations were used for model calibration (1998/99 through 2001/02) and validation (2002/03 through 2005/06) of winter snow simulations. As confirmed by observations, the spatially modeled end-of-winter snow water equivalent (SWE) accumulation increased with elevation up to 700–800 m a.s.l. in response to elevation, topography, and dominating wind direction, and maximum snow deposition occurred on the lee side of the ridge east and south of the glacier. Simulated end-of-summer cumulative runoff decreased with elevation and minimum runoff occurred on the shadowed side of the ridge east and south of the glacier. The modeled test period averaged annual mass balance was 65 mm w. eq. y^?1 or ～8% more than the observed. For the simulation period, the glacier net mass balance varies from -199 to -1,834 mm w.eq. y^?1, averaging -900 (±470) mm w.eq.y^?1. The glacier averaged annual modeled precipitation ranged from 1,299 to 1,613 mm w.eq. y^?1, evaporation and sublimation from 206 to 289 mm w.eq., and runoff from 1,531 to 2,869 mm w.eq. y^?1. The model simulated Mittivakkat Glacier net loss of900 mm w.eq. y^?1 contributes approximately 42% to the average simulated runoff of 2,140 mm w.eq. y^?1, indicating a mean specific runoff of 67.8 l s^?1 km^?2.     

ANNUAL ACCUMULATION OVER THE GREENLAND ICE SHEET INTERPOLATED FROM HISTORICAL AND NEWLY COMPILED OBSERVATION DATA

The estimation of ice/snow accumulation is of great significance in quantifying the mass balance of ice sheets and variation in water resources. Improving the accuracy and reducing uncertainty has been a challenge for the estimation of annual accumulation over the Greenland ice sheet. In this study, we kriged and analyzed the spatial pattern of accumulation based on an observation data series including 315 points used in a recent research, plus 101 ice cores and snow pits and newly compiled 23 coastal weather station data. The estimated annual accumulation over the Greenland ice sheet is 31.2 g cm^?2 yr^?1, with a standard error of 0.9 g cm^?2 yr^?1. The main differences between the improved map developed in this study and the recently published accumulation maps are in the coastal areas, especially southeast and southwest regions. The analysis of accumulations versus elevation reveals the distribution patterns of accumulation over the Greenland ice sheet.     

Snow accumulation, melt, mass loss, and the near-surface ice temperature structure of Irenebreen, Svalbard

This study examines the mass balance, accumulation, melt, and near-surface ice thermal structure of Irenebreen, a 4.1 km² glacier located in northwest Spitsbergen, Svalbard. Traditional glaciological mass balance measurements by stake readings and snow surveying have been conducted annually at the glacier since 2002, yielding a mean annual net mass balance of −65 cm w.e. for the period 2002–2009. In 2009, the annual mass balance of Irenebreen was −63 cm w.e. despite above-average snow accumulation in winter. The near-surface ice temperature in the accumulation area was investigated with automatic borehole thermistors. The mean annual surface ice temperatures (September–August) of the accumulation area were −3.7 °C at 1 m depth and −3.3 °C at 10 m depth. Irenebreen is potentially polythermal, with cold ice and a temperate surface layer during summer. This temperate surface layer is influenced by seasonal changes in temperature. In winter, the temperature of all the ice is below the melting point and temperate layers are probably present in basal sections of the glacier. This supposition is supported by the presence of icings in the forefield of Irenebreen.     

Glaciers in Svalbard: mass balance, runoff and freshwater flux

Gain or loss of the freshwater stored in Svalbard glaciers has both global implications for sea level and, on a more local scale, impacts upon the hydrology of rivers and the freshwater flux to fjords. This paper gives an overview of the potential runoff from the Svalbard glaciers. The freshwater flux from basins of different scales is quantified. In small basins (A < 10 km²), the extra runoff due to the negative mass balance of the glaciers is related to the proportion of glacier cover and can at present yield more than 20% higher runoff than if the glaciers were in equilibrium with the present climate. This does not apply generally to the ice masses of Svalbard, which are mostly much closer to being in balance. The total surface runoff from Svalbard glaciers due to melting of snow and ice is roughly 25 ± 5 km³ a⁻¹, which corresponds to a specific runoff of 680 ± 140 mm a⁻¹, only slightly more than the annual snow accumulation. Calving of icebergs from Svalbard glaciers currently contributes significantly to the freshwater flux and is estimated to be 4 ± 1 km³ a⁻¹ or about 110 mm a⁻¹.     

南极普里兹湾临近海域夏季纽鳃樽对浮游植物的摄食研究

于 1 998年 1 2月至 1 999年 1月南极夏季 ,对南大洋普里兹湾临近海域主要被囊类纽鳃樽的数量密度分布进行了现场调查 ,同时于 - 3站对纽鳃樽对浮游植物的摄食率利用肠道色索法和颗粒递减法进行了现场研究。调查结果表明 ,纽鳃樽主要分布于调查海区的浮冰区北部边缘及其以北的开阔水域。在密集区其数量密度高达 2 795ind..1 0 0 0 m- 3,浮冰区几乎没有发现。 - 3站现场摄食实验结果显示 ,纽鳃樽个体肠道色素含量变化范围为 0 .1 4～ 1 .2 7μg.ind.- 1,平均为0 .98μg.ind.- 1。肠道色素法测得的纽鳃樽对浮游植物的摄食率为 7.9μg.ind.- 1d- 1,滤水率为2 81 ind.- 1d- 1。颗粒递减法测得纽鳃樽滤水率为 1 5.3± 4.61 ind.- 1d- 1,比肠道色素法所得结果偏低。虽然由此推算纽鳃樽群体的日摄食量只占浮游植物现存量的 0 .8% ,但是对于初级生产力却有一定的摄食压力 ( 72 .2 % )。     

中山站至内陆330公里冰川学剖面考察

１９９６～１９９７年南极夏季期间，中国组织实施了首次南极内陆冰盖冰川学考察，深入冰盖内陆３３０ｋｍ，作为中山站至南极内陆最高点ＤｏｍｅＡ大剖面研究计划的开始。计划将对冰盖物质平衡、２００年以来环境演化过程、冰雪／气交换过程等科学问题开展观测研究。本次考察进行了物质平衡、地貌、气象、雪坑地层观测，采集了表层、雪坑、冰雪芯样品。     

Snow accumulation distribution on Spitsbergen, Svalbard, in 1997

A survey of the regional snow accumulation variability on Spitsbergen, Svalbard, was carried out during three field campaigns in May 1997. The survey was carried out along three transects from west-to-east approcimately at the following latitudes: 77°30', 78° and 78°50'degrees north. The altitudes span from sea level to 1000 metres elevation. Snow depth was measured with two different ground-penetrating radar systems, PulsEKKO (450 MHz) and GSSI SIR System-2 (500 MHz), pulled behind snow machines. Snow characteristics such as snow temperature, snow density and stratigraphy were measured in snow pits in nine areas, three along each transect. Our data suggest the following: (1)the accumulation-elevation gradients vary from 3 mm/100 m in the northeast to 237 mm/100 min the central-south with an average value of 104 mm/100m for all measurements: (2)snow accumulation was 38 to 49% higher at the eastern coast than at the western coast; (3) a clear minimum in accumulation (or continental climate) is seen for the central (inland) locations in the middle and northern transects while no such minimum exists along the southern transect; (4) a south-to-north gradient produces 55% and 40% less snow accumulation at the northern locations compared to the southern locations at the western and eastern coasts, respectively. These drops in winter snow accumulation occur over a distance of less than 200 km.     

Variation of Stable Isotopes in Surface Snow along a Traverse from Coast to Plateau’s interior in East Antarctica and Its Climatic Significance

The variations of stable water isotopes of surface snow in east Antarctic Ice Sheet, are discussed by a total of 251 samples, which were taken along a 330 km traverse from Zhongshan Station to the outer edge of the Antarctic plateau and from four snow pits excavated along the route. Analyzing results of the samples showed the expected linear relationship between the parameters ?D and ?18O with slope S1 and intercept d1. When the data set was examined using a sliding window with a width of 5 samples, it was found that there were two areas with different ratios of S1 and d1. The boundary between these two areas occurred at an elevation of about 2,000 m, suggesting two different sources of water vapour. Nearly half (47%) of the fresh-snow samples had negative deuterium excess (d=?D? 8?18O) values, but few of the snow pit samples did, suggesting that variations of ? are quickly smoothed by isotopic diffusion in the near-surface firn. Analysis of the phase relationship between ?D and deuterium excess in the snow pit stratigraphies showed that they were mostly in phase from Jan. 1994 to Sept. 1995, but mostly out of phase from Sept. 1995 to Jan. 1997.     

Accumulation Rate Measurements at Taylor Dome, East Antarctica: Techniques and Strategies for Mass Balance Measurements in Polar Environments

Accumulation rate measurements on the East Antarctic plateau are challenging due to both spatial and temporal variability. Annual stratigraphy is often not reliably or consistently preserved in the firn, and so accumulation cannot be determined from snow pit stratigraphy. We present a suite of accumulation rate measurements collected over several seasons at Taylor Dome, East Antarctica. We compare net accumulation results from direct burial rate measurements and β -activity firn cores along a 35 km traverse. The two methods are consistent and show that the net accumulation varies from greater than 10 cm a⁻¹ to about 1 cm a⁻¹ (ice equivalent) southwest to northeast across the dome. We map the depth of shallow radar layering to interpolate and extrapolate these point-location measurements and show that considerable variations occur over kilometer scales resulting from subtle surface topography. We also present accumulation rates estimated from concentration of the cosmogenic isotope ¹⁰Be and from activity profiles of ²¹⁰Pb. Finally, satellite passive microwave data are used to estimate spatially averaged accumulation rates on the regional to continental scale to provide a context for these local observations. We show that robust mass balance measurements in this environment must rely on spatial and/or temporal averaging.     

STRATIGRAPHY, DENSITY AND CRYSTAL STRUCTURE OF FIRN-ICE AT DE08-A VERY HIGH ACCUMULATION SITE ON LAW DOME, ANTARCTICA

An approximately 195 mm diameter firn/ice core, 234 m long, was thermally drilled in 1987 austral summer at DE08 (66°43′S, 113°12′E) on Law Dome, East Antarctica, where the accumulation rate is about 1200kg/(m~2. a); 10m ice temperature is about-18.8℃. Analysis was mainly made at the site immediately after drilling. The snow stratigraphy at DE08 is characterised by the lack of coarse-grained snow and other distinct visible feature normally corresponding to annual layers. There is a smooth transformation from fine-grained snow at shallow depth to ice at about 80-90m which is greater than that at most other polar locations due to its abnormally high accumulation rate. According to the marked change in the trend of density with depth and in the crystal properties four stages of the transformation of snow to ice and development of crystal structure can be distinguished; settling stage (0-10m); sintering stage (10-90m); rapid crystal growth stage (90-170m); and dynamic metamorphism stage (170-234m). The     

南极冰盖表面物质平衡实测技术综述

研究南极冰盖的物质平衡状况是研究冰盖与全球海平面变化关系的基础性工作,也对重建冰芯古气候记录有重要意义。积累率是冰盖物质平衡计算中最重要的收入项。大空间尺度上的表面物质平衡信息只能通过遥感技术来获取。但因存在多源误差,仅靠遥感手段,冰盖物质平衡的信息难以准确获取,这是南极冰川学面临的最大挑战之一。因此实测数据不可或缺。表面物质平衡的实地测量有多种方法,如花杆、超声高度计(雪深仪)、雪层物理／化学层位法(比如雪坑、冰芯／雪芯积累率恢复,探冰雷达连续测量冰内等时层结构等)。本文对南极冰盖表面物质平衡的实地测量技术做一概述,对每种方法的特点进行了比较和讨论。     

SURFACE MASS BALANCE AND ITS VARIATION ON THE MIZUHO PLATEAU, ANTARCTICA IN 1987-1988

From the surface mass accumulation data in year of 1987/88, the distribution and variation of annual mass balance on Mizuho Plateau are discussed. The authors also analyze the effects of shortterm climatic and topographical variations on the mass balance. It is found that there are some differences in spatial distribution and annual average state in the year of 1987/88 and other years. Ia the area at elevation lower than 550 m near the coast, the mass balance appears to be negative. The annual mass balance over 80 km distance from S_(16) to inland is 0.84m snow depth. A low mass balance zone from 80 km site to Mizuho Station, is considered to be only 0.14 m snow depth. It is found from the comparison of mass balances that the mass-balance level on the glaciers in West China is 9 times higher than that on Mizuho Plateau, where the massbalance level appears to be low accumulative and low expensive, but inverse in middle and low latitude regions, such as on glaciers in West China. The effects of short-term     

A Mass Balance Model that Uses Low-altitude Meteorological Observations and the Area–Altitude Distribution of a Glacier

A glacier mass balance model that requires only low-altitude precipitation and temperature observations and the glacier's areaaltitude distribution is presented as an alternative to direct field measurements. Input to the model for South Cascade Glacier are daily weather observations at stations 30–60 km from the glacier and at altitudes 1300 to 1500 m lower than the glacier. The model relies on the internal consistency of mass balance variables that are generated by simulation using the low-altitude weather data. The daily values of such balance variables as snowline altitude, zero balance altitude, glacier balance, balance flux and the accumulation area ratio are correlated throughout the ablation season using two-degree polynomial regressions to obtain the lowest fitting error. When the minimum average error (or maximum R ²) is attained, the generated balances and other variables are considered to be real. A simplex optimization technique is used to determine the optimal coefficient values that are used in algorithms to convert meteorological observations to snow accumulation and snow and ice ablation. The independently produced simulation results for the 1959–1996 period are compared with balances measured at the glacier. The agreement between annual balances for individual years is fair and between long-term volume changes measured by the geodetic method is excellent.     

南极洲乔治王岛柯林斯冰帽冰芯层位和密度变化的一般特征

柯林斯冰帽两支冰芯层位记录证实了该冰帽主冰穹顶部（海拔约７００ｍ）属暖渗浸带，小冰穹顶部（海拔约２５０ｍ）属渗浸带。雪、冰的层位分布和密度变化包含了一定的测年信息。主冰穹顶冰芯密度－深度曲线在表层呈现韵律性变化，与层位记录中的融化冻结现象相对应，据此粗略划分年层，断定当地年积累雪层厚度为３－３．５ｍ，折合水当量１６５０－１９２５ｋｇ／ｍ２ａ，年平均积累速率约为２．０ｍ／ａ（冰当量）。主冰穹顶成冰深度为３８－３９ｍ，此深度以上密度自上而下缓慢增加，但以下由于含水层的出现，密度迅速升高，在５－６ｍ区间达到９００ｋｇ／ｍ３。小冰穹冰芯除表层外，密度基本在８００－９００ｋｇ／ｍ３之间，冰芯中雪冰互层，存在污化面，４０ｍ以下发现很厚的火山灰沉积物。小冰穹平均年积累率约为０．７ｍ／ａ（冰当量），成冰深度７－８ｍ，成冰年限为１０年左右     

Measurements and Models of the Mass Balance of Hintereisferner

This paper summarizes the methods applied to determine the mass balance of Hintereisferner and several other glaciers in the Tyrolean Alps since 1952. On an annual basis the direct glaciological method was applied with fixed date measurements on 10–15 accumulation pits and 30–90 ablation stakes on 9 km².
Indirect mass balance determination from equilibrium line altitude, accumulation area ratios or representative stakes, yield fair results and some exceptions could be related to anomalous meteorological conditions.
Monthly or more frequent stake readings supplied time series of ablation at various altitudes and slope aspects that served as basis for the calibration of energy and mass balance models. Of various models developed, two are presented in this paper. Both are based on degree days, one using daily values from a valley station to predict the mean annual balance of the entire glacier, while the other calculates day-to-day changes at 50-m grid points on the glacier.
The geodetic method has been applied for longer periods and yields results consistent with those of the glaciological method. The balance velocity calculated from recent ice thickness soundings and accumulation measurements is significantly less than observed velocity.     

Mass Balance Measurements on the Lemon Creek Glacier, Juneau Icefield, Alaska 1953–1998

Annual balance measurements on the Lemon Creek Glacier, Alaska conducted by the Juneau Icefield Research Program (JIRP) from 1953 through 1998 provide a continuous 46 year record. This is one of the nine American glaciers selected in a global monitoring network during the International Geophysical year, 1957/58. These data have been acquired primarily by employing consistent ground methods, conducted on similar annual dates and calculated using comparable methodology. The results have been until now fairly precise, but of uncertain accuracy. An adjunct comparison of topographic surface maps of the glacier made in 1957 and 32 years later in 1989 provides a rough determination of glacier surface elevation changes which are clearly of less precision than the compilation of annual ground data. Airborne surface profiling in 1995, and global positioning system leveling transects in 1996–1998 update the record of surface elevation changes over the past decade. The mean glacier ice thickness reductions suggested by these methods from 1957–1989, from 1957–1995 and from 1957–1998 are ?13.2 m, ?16.4 m, and ?21.7 m, respectively. It is of interest that the geodetic interpretations agree fairly well with the trend of sequential balances from ground-level stratigraphic measurements. To date, however, the infrequent mapping methods in this study have yielded specific balances averaging between 5 and 11% less than those resulting from our annual on-site glaciological monitoring. For future studies this can be an important factor. The ground data are, therefore, the ones in which we have most confidence. These show cumulative ice losses of ?13.9 m (12.7 m water equivalent w.e.) from 1957–1989, of ?19.0 m (?17.1 m w.e.) from 1957–1995, of ?24.4 m (22 m w.e.) from 1957–1998, and ?24.7 m (22.2 m w.e.) for the total cumulative loss over the full 46 years between 1953 and 1998. Although the balance trend has been increasingly negative it averages ?0.48 m/a in w.e. or 0.52 m of ice loss per year. To refine the reliability of density determinations in this data set the effects of internal accumulation from refrozen meltwater producing diagenetic ice structures in the annual firnpack have been taken into account. An unusual dearth of such structures within the 1997/98 firnpack provided a unique opportunity to facilitate application of the probing technique over broad areas of the nv. This added to our ground truth and verified accuracy of the test-pit measurements used in these long-term mass balance computations. The glacier's continuing negative mass balance has fueled a terminal retreat of 800 m during the 1953–1998 period. The annual balance trend indicates that despite a higher mean elevation and a higher elevation terminus from thinning and retreat, mean annual balance has been strongly negative since 1977 (?0.78 m/a w.e.). Dramatically increased negative mass balances have occurred in the 1990s, with 1996 and 1997 being the only years on record with no retained accumulation since field observations were initiated in the glacier source areas in 1948.     

Monoclinal flexure of an orogenic plateau margin during subduction,south Turkey

Geologic evidence across orogenic plateau margins enables the discrimination of the relative contributions of orogenic, epeirogenic and/or climatic processes that lead to growth and maintenance of those plateaus and their margins. Here, we discuss the mode of formation of the southern margin of the Central Anatolian Plateau (SCAP) and evaluate its time of formation using fieldwork in the onshore and seismic reflection data in the offshore. In the onshore, uplifted Miocene rocks in a dip‐slope topography show monocline flexure over >100 km, km‐scale asymmetric folds verging south, and outcrop‐scale syn‐sedimentary reverse faults. On the Turkish shelf, vertical faults transect the basal latest Messinian of a 10 km fold where on‐structure syntectonic wedges and synsedimentary unconformities indicate pre‐Pliocene uplift and erosion, followed by Pliocene and younger deformation. Collectively, Miocene rocks delineate a flexural monocline at plateau margin scale that is expressed along our on‐offshore sections as a kink‐band fold with a steep flank 20–25 km long. In these reconstructed sections, we estimate a relative vertical displacement of 3.8 km at rates of ca. 0.5 mm/y, and horizontal shortening values <1 %. We use this evidence together with our observations of shortening at outcrop, basin, plateau‐margin and forearc‐system scales to infer that the SCAP forms as a monoclinal flexure to accommodate deep‐seated thickening and shortening since >5 Ma, and to contextualize the plateau margin as the forearc high of the Cyprus subduction system.     

南极瑞穗高原1987—1988年度表面物质平衡及其变化

根据1987/1988年度表面物质积累资料,对Mizuho(瑞穗)高原该年度物质平衡的分布规律及其变化进行了讨论,同时还对年内短期天气过程及地形变化对物质平衡的影响进行了分析。研究发现1987/1988年度物质平衡的空间分布与多年平均状况存在较大区别:海拔550m以下的沿海地带表现为负物质平衡状态。从S_16点向内陆80km范围内为高值物质平衡区。年平均净物质平衡量达0.84m雪层深;80km到瑞穗高原内陆的瑞穗站之间为低值物质平衡区,年平均物质平衡量仅0.14m雪层深。在瑞穗高原,表面物质平衡水平表现为低积累,低支出的特征。此外,年内短期气候和地形变化对物质平衡的影响均大于多年平均状态,在高值物质平衡区,气候变化对物质平衡的影响大于地形变化的影响;而在低值物质平衡区,地形变化对物质平衡的影响则大于气候变化对物质平衡的影响。     

Amery ice shelf DEM and its marine ice distribution

The Amery Ice Shelf is the largest ice shelf in East Antarctica.A new DEM was generated for this ice shelf,using kriging to interpolate the data from ICESat altimetry and the AIS-DEM.The ice thickness distribution map is conver ted from the new DEM,assuming hydrostatic equilibrium.The Amery Ice Shelf mari ne ice,up to 230 m thick,is concentrated in the northwest of the ice shelf.Th e volume of the marine ice is 2.38×10～3 km～3 and accounts for about 5.6% of t he shelf volume.     

基于CloudSat资料分析北疆强降雪天气的云结构特征

利用NASA发布的2008—2015年CloudSat卫星的2B-CWC-RO、2B-CLDCLASS、2C-SNOW-PROFILE和地面气象站的观测资料,对北疆沿天山及其周边区域内21次强降雪天气降雪前和降雪期间卫星过境时云宏微观特征进行了对比分析。本文将研究区域分为了北疆沿天山西部和中部地区,分析结果表明：（1）降雪前和降雪期间的云类型以层云、积云、高层云和深对流云为主。（2）降雪前冰粒子等效半径均值分布在58.65~67.29 μm之间,冰粒子数浓度的均值在41.2~76.5 L-1之间,冰水含量的均值在25.4~135.1 mg·m^-3之间,雪水含量均值在28.0~88.0 mg·m^-3之间,降雪强度均值在0.08~0.36 mm·h^-1之间。（3）降雪前冰粒子等效半径、冰粒子数浓度、冰水含量、雪水含量和降雪强度均值分别比降雪期间大2.9 %、6.2 %、34.4 %、36.4 %和18.7 %,且高值区主要集中在北疆沿天山西部地区。