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We evaluated elevation changes at four sites on debris-covered ablation area of Khumbu Glacier, Nepal Himalaya, since 1978. In 2004, we carried out a ground survey by differential GPS in the upper- and lowermost areas of the ablation area. The amount of surface lowering was calculated by comparing digital elevation models (DEMs) with 30-m grid size, as generated from survey data corrected in 1978, 1995, and in the present study. Because we could not access the middle parts of the debris-covered area due to surface roughness, for this area we used an ASTER-DEM calibrated by the ground survey data. The amount of surface lowering during the period 1978–2004 was insignificant near the terminus. A remarkable acceleration of surface lowering was found in the middle part of the debris-covered ablation area, where the glacier surface is highly undulating. In the uppermost area, surface lowering has continued at a steady rate. Surface flow speeds have decreased since 1956, revealing that the recent decrea...

The mass balance of the Xiao (Lesser) Dongkemadi Glacier located in the Tanggula Mountains, of the central Qinghai-Tibetan Plateau has been monitored since 1989. The results show that the mass balance of the glacier has recently shown a deficit trend, and that the glacial terminus was also retreating. Positive mass balance of the glacier was dominant during the period 1989–1993, and the accumulated mass balance reached 970 mm. However, negative mass balance of the glacier has occurred since 1994, except for the large positive mass balance year 1997. The mass balance was − 701 mm in 1998, an extremely negative glacier mass balance year. The equilibrium line altitude showed a significant increasing trend. The mass balance of the glacier has changed from a significantly positive mass balance to a strongly negative mass balance since 1994. Meteorological data suggest that the rapid decrease in the mass balance is related to summer season warming. Copyright © 2007 John Wiley & Sons, Ltd.

Climatic variabilities on millennial and longer time scales with a bipolar seesaw pattern have been documented in paleoclimatic records, but their frequencies, relationships with mean climatic state, and mechanisms remain unclear. Understanding the processes and sensitivities that underlie these changes will underpin better understanding of the climate system and projections of its future change. We investigate the long-term characteristics of climatic variability using a new ice-core record from Dome Fuji, East Antarctica, combined with an existing long record from the Dome C ice core. Antarctic warming events over the past 720,000 years are most frequent when the Antarctic temperature is slightly below average on orbital time scales, equivalent to an intermediate climate during glacial periods, whereas interglacial and fully glaciated climates are unfavourable for a millennial-scale bipolar seesaw. Numerical experiments using a fully coupled atmosphere-ocean general circulation model with freshwater hosing in the northern North Atlantic showed that climate becomes most unstable in intermediate glacial conditions associated with large changes in sea ice and the Atlantic Meridional Overturning Circulation. Model sensitivity experiments suggest that the prerequisite for the most frequent climate instability with bipolar seesaw pattern during the late Pleistocene era is associated with reduced atmospheric CO2 concentration via global cooling and sea ice formation in the North Atlantic, in addition to extended Northern Hemisphere ice sheets., SCOPUS: ar.j, info:eu-repo/semantics/published

Because the Khumbu Himal of the Nepal Himalayas lacks long-term climate records from weather stations, mountain permafrost degradation serves as an important indicator of climate warming. In 1973, the permafrost lower limit was estimated to be 5200–5300 m above sea level (ASL) on southern-aspect slopes in this region. Using ground-temperature measurements, we examined the mountain permafrost lower limit on slopes with the same aspect in 2004. The results indicate that the permafrost lower limit was 5400–5500 m ASL in 2004. The permafrost lower limit was estimated to be 5400 to 5500 m on slopes with a southern aspect in the Khumbu Himal in 1991 using seismic reflection soundings. Thus, it is possible that the permafrost lower limit has risen 100–300 m between 1973 and 1991, followed by a stable limit of 5400 to 5500 m over the last decade. An increase in mean annual air temperature of approximately 0.2 to 0.4 °C from the 1970s to the 1990s has indicated a rise in the permafrost lower limit of 40 to 80 m at the Tibetan Plateau. The rise in the mountain permafrost lower limit in the Khumbu Himal exceeds that of the Tibetan Plateau, suggesting the possibility of greater climate warming in the Khumbu Himal.

Model calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow–ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter. Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages. Copyright © 2006 John Wiley & Sons, Ltd.

Though solar radiation is important for glacier mass-balance simulation, solar radiation data are not always available. As a result of analyzing meteorological data measured in the Himalaya and the Tibetan Plateau, a favorable correlation between precipitation and atmospheric transmissivity of solar radiation is found in terms of monthly values. Monthly mean solar radiation is derived from the relationship between atmospheric transmissivity of solar radiation and precipitation with input of monthly precipitation, latitude, skyline and time. The differences between estimated and observed monthly mean solar radiation are −2 in most cases. However, the differences at some sites are significantly large. The error in the estimated solar radiation during the monsoon season can be large when the monthly mean precipitation rate is about 5 mm d−1. Though the error in the estimated solar radiation during the non-monsoon season is generally small due to low precipitation in the Himalaya and the Tibetan Plateau during this season, it can exceed 100 W m−2.

Deep ice core drilling was carried out at Dome Fuji, Antarctica in 1995 and 1996 from the bottom of the casing installed in 1993 and reached 2503.52m in December 1996. We used a JARE type electromechanical drill with a core barrel of 2.2m length. Total numbers of ice corings and chip collections were 1369 and 837 respectively. The mean coring depths per run and per day were 1.75m and 8.21m, respectively. Quality of ice cores was perfect throughout the whole depth, even in the brittle zone. We report the outline of the system, coring performance, and troubles encountered.

Post-depositional change of isotope concentration was investigated in a temperate snow pack. Daily snow pit studies were carried out at Moshiri, Hokkaido, for about a week in April 1998. During this time the snow layers were at the melting point. Isotope analysis was conducted on snow particles and the liquid water in between the particles every 5 cm in depth, and on the precipitation and the runoff water (from the bottom of the snow pack) collected during the observation period. It was found that the oxygen isotope concentration in the liquid part was smaller by about 2‰ than the solid part of the wet snow. The difference between the isotope concentrations of the liquid and the solid was low in the surface snow layer, but increased at the bottom. The results suggested that isotope fractionation took place between the liquid and the solid, when liquid water (formed by melting at the snow surface layer) flowed groundwards. Copyright © 2002 John Wiley & Sons, Ltd.

1998年2月から4月にかけて北海道母子里で積雪調査を実施し,そのうち融雪期の湿潤積雪層の同位体比の時間変化過程を調べた.調査では,湿潤積雪から層毎に,固相試料(雪粒子)と液相試料(間隙水)とを別々に採取した.観測期間中の降水と積雪下面からの流出水もあわせて採取した.それぞれの試料についての酸素,水素の同位体比を測定した.その結果,雪粒子の同位体比は間隙水よりも大きい値をとった.その差は表面から下層にいくほど増加する傾向が認められた.また,雪粒子,間隙水ともその同位体比は時間とともに大きくなる結果を得た.これらの結果を解析したところ,積雪表面で融解してできた間隙水の流下が,雪粒子の同位体比の変化に大きな影響をもたらす事が示唆された.

Data on the mass balance of Xiao Dongkemadi glacier in the Tanggula mountains, central Tibetan Plateau, were obtained over 5 5 years from 1989 to 1995. These are the first continuous mass-balance data for a continental-type glacier on the Tibetan Plateau, where the glacier accumulates during the summer monsoon (summer-accumulation-type glacier). Mass-balance vs altitude profiles were steeper in the negative than in the positive mass-balance years. This is considered to have resulted from the effect of summer accumulation. The annual mass balance is compared with air temperature, precipitation, and black-body temperature in the area including the glacier, which is calculated from infrared radiation observations by theJapanese Geostationary Meteorological Satellite. It was found that the interannual variation in the glacier mass balance was not closely related to maximum monthly mean air temperature, while it did have a relatively good correlation with maximum monthly mean black-body temperature.

Basic chemical analyses of a 2503m deep ice core obtained at Dome Fuji Station, Antarctica in 1995-1996 were carried out to determine stable oxygen and hydrogen isotope ratios, major chemical compositions and microparticle concentrations. We here describe the analytical procedure and the results as well as the determination of working time scale. The ice core covers the past 340ka which includes three glacial-interglacial cycles clearly shown by the stable oxygen isotope profile. Major chemical compositions and microparticle concentrations larger than 0.52μm show high concentrations in glacials and low in interglacials.

A mass-balance model based on the energy balance at the snow or ice surface is formulated, with particular attention paid to processes affecting absorption of radiation. The model is applied to a small glacier, Glacier AX010 in the Nepalese Himalaya, and tests of its mass-balance sensitivity to input and climatic parameters are carried out. Calculated and observed area-averaged mass balances of the glacier during summer 1978 (June-September) show good agreement, namely -0.44 and -0.46 m w.e., respectively.Results show the mass balance is strongly sensitive to snow or ice albedo, to the effects of screening by surrounding mountain walls, to areal variations in multiple reflection between clouds and the glacier surface, and to thin snow covers which alter the surface albedo. In tests of the sensitivity of the mass balance to seasonal values of climatic parameters, the mass balance is found to be strongly sensitive to summer air temperature and precipitation but only weakly sensitive to relative humidity.

1991年10月から1993年9月までチベット高原の凍土地帯で気温,降水量の条件が同じと考えられる複数地点の土壌水分量,地温の測定とその他の情報から地表層過程の季節推移を調べた.その結果,測定を行った狭い領域で地温と土壌水分は場所により大きく異なった.冬期間に地表層の土壌水分が減少し,その損失量は5～36mmと推定できた.凍土の融解層の下面が不透水面となるため,融解面の深さの季節変化が融解層内全体の空隙量を変化させた.また同一時期の各地点の融解層の厚さの違いが,それぞれの地点の融解層内全体の空隙量の違いを生じさせ,各地点の土壌水分の差異を生じさせた.この土壌水分の差異によって融解層の形成速度,季節融解層の最大の厚さである活動層の厚さの違いが生じた.特に各地点の融解初期の土壌水分量の場所による違いは,地温と土壌水分の違いを大きくする傾向があった.1992年より1993年は積算暖度が小さいにも係わらず,両年の活動層の厚さの計算値は,それぞれ229,232cmとほぼ等しくなった.

1993年6月から9月まで凍土地帯であるチベット高原タングラ山域の土壌水分条件が異なる2地点(裸地とアースハンモックのある草地)で,融解面の深さに代表される地表層状態の違いが蒸発量に与える影響について観測した.両地点では,草地の方が土壌水分が多く,融解面は浅い.観測期間は,自然蒸発量の飽和蒸発量に対する比(蒸発比)から6月20日前後で区分でき,それぞれプレモンスーン期(乾期)とモンスーン期(雨期)に対応した.両地点では,乾期の蒸発量には土壌水分不足による蒸発抑制が見られた.乾期の平均蒸発量は裸地で2.1mm/d,草地で2.6mm/dとなり,雨期には両地点とも3.3mm/dとほぼ等しくなった.チベット高原でも降水量が多いこの地域は,雨期にはいる前の乾期には地表層状態に依存する場所による蒸発量の違いが見られるが,本格的な雨期に入ると,そのような傾向は見られなくなる.乾期の総蒸発量は雨期の総蒸発量に比べ少ないので両期にわたる暖候期の総蒸発量は場所によって大差ないことがわかった.

This paper focuses on the first year-round observations of surface mass balance, sublimation and snow temperatures at Dome Fuji Station. This station was newly established at the highest point (77°19′01″S, 39°42′12″E; 3810m) in Queen Maud Land, Antarctica by the Japanese Antarctic Research Expedition. It was found that average surface mass balance by the stake method was +2.5g(cm)^ from 25 January 1995 to 30 January 1996 (370 days), of which about 95% of the positive balance was obtained from February to the middle of October (eight and half months). Sublimation from atmosphere to snow surface (mass input : +0.55g(cm)^) was predominant in winter (March to October) and sublimation from snow surface to atmosphere (mass output : -0.39g(cm)^) was predominant in summer (November to February). In the annual balance, sublimation from atmosphere to snow surface (+0.16g(cm)^) prevailed. This corresponds to about 6% of the annual surface mass balance. The snow temperature at 10m depth varied from -57.0 to -57.8℃, and the annual mean 10m snow temperature was -57.3℃.

An ice core from the glacier surface down to 112.59m depth was obtained in 1993 at Dome Fuji Station. The ice core was divided vertically in the home cold laboratory and various analyses were carried out for the solid and liquid phases of core samples. The measurements of numbers of microparticles, electrical conductivity, pH, oxygen isotopic ratio and chemical constituents were carried out for the melted ice core samples. In this report, the procedures and the methods for the measurements are introduced with results obtained. The results open preliminary step on ice core research at Dome Fuji Station, which should be useful to evaluate the environments at the dome in the comparison with core analyses at various sites. The vertical distributions for the some of the values obtained are presented to facilitate further discussion of the past climate and environments.

A 112.59m-deep ice core was drilled at Dome Fuji Station by a JARE-34 party in 1993 when a pilot hole was prepared for a deep core drilling operation. A preliminary examination was made for ice core chronology by two signals : one electric conductivity peaks measured in the home laboratory and the other field observation results obtained by JARE-36 party on the deeper part of the core. The electric conductivity peak analyses suggest the same 5 volcanic eruptions, in 1464 AD, 1259 AD, 865 AD, 639 AD and 346 BC, reported for the ice core of Byrd Camp, Antarctica. Field observations for ECM and crystal size distributions suggest that the period 374m depth level corresponds to the end of Wisconsin ice period. The results suggest that accumulation rate at Dome Fuji Station is between 2.5 and 3.0cm of water equivalent/year, and the end of Wisconsin-Holocene Transition will be found between depths of 340 and 400m. The depth-age curves for the core at Dome Fuji Station are obtained from the surface (at present) to 400m (at 12000years BP).

In the Himalayas-Tibet, glaciers varied much due to uplift of the area and variation of the monsoon as well as general climatic change since Quaternary ice ages. The variation of glacier mass balance is described qualitatively on the basis of present characteristics of summer-accumulation type glaciers. Variation of such glaciers is sensitive to that of summer temperature. Transition of annual variation patterns of the glacier mass balance is shown for the period from the last ice age to the present. Increase of ablation due to decrease of the surface albedo is considered to be effective in shrinking of the glaciers during this period. It is pointed out that development of methods to reconstruct the paleo-water-cycle under changing influence of the monsoon is important to clarify the history of areal characteristics of glacier accumulation.

In 1978, the first detailed glaciological studies were carried out on the small glacier AX010 in a glacier inventory of Dudh Kosi region, in the Nepal Himalaya. Its length, area and highest and lowest elevations in 1978 were 1.7 km, 0.57 km2, 5360 and 4950 m a.s.l., respectively. Two resurveys of its terminus position and/or surface elevations were carried out in 1989 and 1991. The glacier retreated by about 30 and 28 m during the periods 1978–89 and 1989–91, respectively. In 1995, annual monitoring of this glacier by means of ground survey, stake method and topographical mapping began, in order to obtain its mass balance, surface flow velocity and extent, and link them with climatic conditions. The results obtained in 1995 are summarized as follows: (1) During the period 1991–95, the glacier retreated by 12 m. (2) Associated with the ice-thickness loss in the lower part of the glacier, the horizontal surface velocities along the center line in 1995 (June–October) showed a remarkable decrease on the glacier tongue, to about 50% of those in 1978. Shrinkage of the glacier in the near future is predicted from a simple model calculation for the case that climatic conditions remain unchanged from 1995. The results show that the present shrinkage should continue and accelerate.

The relations between mass balance and meltwater refreezing were examined on the basis of glaciological observations carried out in summer 1993 on Xiao Dongkemadi Glacier, Tanggula Mountains, central Tibetan Plateau. On this glacier, a part of meltwaler refreezes at the snow/ice interface as superimposed ice. The amount of superimposed ice formation was determined by both meltwater supply and temperature condition of the glacier. Snow-layer thickness on the glacier ice body is less than 2 m, even in the higher accumulation zone. About 60% of meltwaler generated in the accumulation zone for the period May–September was trapped at the snow/ice interface by refreezing, and was not discharged out of the glacier. About 26% of accumulated snow to the glacier surface was replaced on the snow/ice interface by refreezing in the accumulation zone. These facts indicate that superimposed ice formation is quite significant for water retention in glaciers under low-precipitation conditions.

The 36th Japanese Antarctic Research Expedition (JARE-36) consisted of 40 wintering members and 16 summer members with one atmospheric chemist from Germany. The icebreaker SHIRASE left Tokyo on November 14,1994,and arrived at Syowa Station on December 24 via Fremantle. All cargo of about 1070t was unloaded by January 12,1995. Constructions to replace old buildings and facilities at Syowa Station and for a large HF radar system and others were carried out by February 14. For the Deep Ice Coring Project at Dome Fuji, an oversnow traverse to/from the Dome Fuji Station (77°19′S, 39°42′E, 3810m a.s.l.) was performed; the first wintering at the new station was started by 9 members from January 29. Observations on geology, geodesy, biology and others were carried out around Syowa Station, Lutzow-Holm Bay and Riiser-Larsen Massif. Observations on physical, chemical and biological oceanography, geomagnetism and others were made through the voyage of the SHIRASE from Tokyo via Antarctica to Sydney. The summer party of JARE-36 returned together with the JARE-35 wintering party to Tokyo from Sydney by air on March 28 with satisfactory results.

第36次南極地域観測隊夏隊16名(上田観測隊長), ドイツの交換科学者1名および越冬隊40名(召田隊長, 石沢副隊長)は, 1994年11月14日「しらせ」にて東京港を出発し, フリーマントル寄港後, 12月24日昭和基地に接岸した。翌年1月12日までに, 約1070トンの物資輸送を終え, 2月14日まで昭和基地施設更新建設工事, 大型短波レーダー設置ほかの作業を行った。氷床ドーム深層掘削計画では, ドーム往復内陸旅行を実施し, ドームふじ観測拠点で第35次拠点建設班と合流, 完成した新拠点で1月29日から9名による初越冬を開始した。昭和基地とその近辺では潮汐・海潮流, 生物, 測地, 気球回収予備実験, リュツォ・ホルム湾周辺露岸域とリーセルラルセン山域では地殼形成過程に関する地質調査, 測地, 生物などの観測を実施した。また往路に引き続き帰路の船上で, 海洋物理・化学・生物, 地磁気ほかの観測をしつつシドニーに到着した。第36次夏隊は順調な成果をあげ, 第35次越冬隊とともに3月28日空路帰国した。, The 36th Japanese Antarctic Research Expedition (JARE-36) consisted of 40 wintering members and 16 summer members with one atmospheric chemist from Germany. The icebreaker SHIRASE left Tokyo on November 14,1994,and arrived at Syowa Station on December 24 via Fremantle. All cargo of about 1070t was unloaded by January 12,1995. Constructions to replace old buildings and facilities at Syowa Station and for a large HF radar system and others were carried out by February 14. For the Deep Ice Coring Project at Dome Fuji, an oversnow traverse to/from the Dome Fuji Station (77°19′S, 39°42′E, 3810m a.s.l.) was performed; the first wintering at the new station was started by 9 members from January 29. Observations on geology, geodesy, biology and others were carried out around Syowa Station, Lutzow-Holm Bay and Riiser-Larsen Massif. Observations on physical, chemical and biological oceanography, geomagnetism and others were made through the voyage of the SHIRASE from Tokyo via Antarctica to Sydney. The summer party of JARE-36 returned together with the JARE-35 wintering party to Tokyo from Sydney by air on March 28 with satisfactory results.

アジアでは比較的情報の多い中国西部と旧ソ連の氷河変動資料をまとめた.1960年代から80年代初期にかけて,コンロン山域以外は後退氷河が多く,アルタイ,天山,パミール,チーレン山域の順に北方ほどその傾向が強い.しかし,この間に中国西部やパミールでは1960-70年代に後退から前進に転じる氷河が増え,一方,旧ソ連天山やコーカサスでは後退傾向が優勢なまま,大きな変化はない.また,約30年＆sim;60年間程度の氷河変動データのある乾燥域(大陸性)の3氷河(2＆sim;4km長)と湿潤域(海洋性)の3氷河(10＆sim;13km長)について,年間末端変動距離の氷河長に対する割合の年による変化をみた.1980年代はいずれの氷河も5m/km程度までの後退範囲にあったが,毎年観測されているTs.Tyuksu氷河(西部天山)とウルムチ1号氷河(東部天山)では,この間に後退量が増えつつある.この2氷河について,氷河変動と夏気温や年降水量との関係を紹介した.

The surface mass balance in east Dronning Maud Land has been observed mainlvbv means of the snow-stake method. The surface mass balance generallv decreased with distance from the coast; from more than 250 mm a−1 in the coastal region to less than 50 mm a−1 in the inland region higher than 3500 m in altitude. At Mizuho Station (2230 m a.s.l.). the sublimation was about 50 mm a−1. precipitation was between 140 and 260 mm a−1, and the loss from the surface by theredistribution was estimated to be about 100 mm a−1, which agrees with the surface mass balance estimated as 70 mm a−1 from the grain-growth rate. Around the mountainous area, the balance was small or in some cases negative, where a bare-ice field has developed. In the inland area, 3000– 3200 m a.s.l..the surface mass balance was less than 50 mm a−1, i.e. lower than in the surrounding areas. This low mass-balance area can be explained bv redistribution by the drifting snow. The whole mass input in five drainage basins with a total area of 620 × 103 km2 is 61.2Gton a−1 and the mean surface mass balance is 99 mm a−1.

南極の斜面下降風域で, 積雪層を形成する前段階の新しいドリフトの試料をほぼ1年間にわたって採取し, それらの酸素同位体組成を測定した。また, 同地点の積雪層の同位体プロファイルも得られた。ドリフトのδ^O値は, 夏に高く(-30～-40‰), 冬は-50‰近くまで下がる場合があるが, 時々夏なみに高かった。δ^O値と試料採取時の気温との関係はばらつき, 試料の起源の相違のためか, 採取時の気象状態によってずれた。もしこれらのドリフトが連続的に堆積すれば, 積雪層のδ^O値の鉛直プロファイルも広い幅で複雑な変化をするはずだが, 実際は-35～-45‰の範囲で単調に変化する。このプロファイルの極大・極小位置は, 堆積中断で形成された氷板の分布と良い相関がある。これらの結果は, 雪の同位体組成の堆積後の変化が, 積雪の同位体プロファイルの理解に重要なことを示している。, Oxygen isotopic contents of fresh snow drifts in the katabatic wind zone were measured. The samples were collected at a stage before forming deposited snow layers throughout the year. Besides, the oxygen isotope profiles of deposited snow layers at the same place were obtained. The δ^O contents of the snow drifts had high values in summer (-30～-40‰); in winter, values were generally low (above -50‰) but sometimes there were high values similar to those in summer. Deviation of relations between air temperature at sampling time and δ^O contents of the snow drifts under different weather conditions is discussed. Vertical profiles of δ^O contents of deposited snow are supposed to show a wide annual range and complicated annual variation, if such snow drifts accumulated continuously. However, those of deposited snow actually seen in the surface layers usually show a narrow range (-35～-45‰) and simplified pattern. Positions of maxima and minima in δ^O profiles of deposited snow have good correlations with layering of ice crusts which were formed during hiatus periods of snow deposition. These results indicate the importance of change of the isotopic contents after snow deposition for understanding the isotope profiles of deposited snow.

Oxygen isotopic contents of fresh snow drifts in the katabatic wind zone were measured. The samples were collected at a stage before forming deposited snow layers throughout the year. Besides, the oxygen isotope profiles of deposited snow layers at the same place were obtained. The δ^O contents of the snow drifts had high values in summer (-30～-40‰); in winter, values were generally low (above -50‰) but sometimes there were high values similar to those in summer. Deviation of relations between air temperature at sampling time and δ^O contents of the snow drifts under different weather conditions is discussed. Vertical profiles of δ^O contents of deposited snow are supposed to show a wide annual range and complicated annual variation, if such snow drifts accumulated continuously. However, those of deposited snow actually seen in the surface layers usually show a narrow range (-35～-45‰) and simplified pattern. Positions of maxima and minima in δ^O profiles of deposited snow have good correlations with layering of ice crusts which were formed during hiatus periods of snow deposition. These results indicate the importance of change of the isotopic contents after snow deposition for understanding the isotope profiles of deposited snow.

[1] We describe four decades of temporal fluctuations in the ablation of the Hamaguri-yuki snow patch in the northern Japan Alps. Annual ablation depth through the melting season shows a significant correlation with the initial depth (at the beginning of the melting season), whereas a less significant correlation is found with a temperature index that is generally believed to correlate well with ablation. The scale effect of the snow patch, which appears to modify the wind speed over the patch, has a more significant effect on snow ablation than does the radiation shadowing effect of surrounding mountains. In the case of a thinner and therefore smaller initial springtime snow patch, the speed of the local wind may be reduced over the snow surface, thereby suppressing ablation, whereas wind speed is not reduced (and ablation is not suppressed) in the case of a thicker snow patch. This self-regulating feedback means that over the past four decades, the thickness of the snow patch has fluctuated in a manner that is largely independent of summertime temperature. Our findings also suggest that the self-regulating feedback, which influences ablation, allows some small wind-drifted glaciers to survive, whereas previous studies reported enhanced accumulation at such glaciers via a similar topographic effect on wind speed and suppressed ablation via the shading effect of surrounding mountains on solar radiation.

Annual mass exchange differs between maritime and continental glaciers. A common characteristic of these glaciers in Asian high-mountain areas is that most of the annual accumulation occurs in summer. Since variations in mass balance of a summer-accumulation type of glacier are quite sensitive to variations in summer air temperature, shrinkages of such glaciers due to climate warming are predicted by the use of simplified experimental relations between air temperature and mass balance, disregarding variation of other climatic variables such as cloudiness and precipitation. The results predict that both small and large maritime glaciers are more sensitive to warming than a continental ice cap. A small glacier would disappear in a few decades if the air temperature persisted a few degrees above that of an equilibrium state of mass balance.

Vertical profiles of oxygen isotopic contents in deposited snow were obtained in the region where katabatic winds prevail (Mizuho Station : 70.7°S, 44.3°E, 2230m), the inland dome-like plateau (Dome Camp : 77.0°S, 35.0°E, 3761m) and the transitional zone between them (Advance Camp : 74.2°S, 35.0°E, 3198m). At Mizuho Station, the δ^O contents have high values around the hiatus layers. However, synchronous relations cannot be found between the neighboring profiles, since snow was exchanged due to deposition and erosion by strong winds. Inter-annual variations of oxygen isotopic contents in snow have been preserved better in the inner parts of the ice sheet between the three zones observed in this study. The profile at Dome Camp has good correlation with the inter-annual variation of summer temperature at 5000gpm above the South Pole. This result suggests that the temperature at this level above the South Pole is representable for air temperature condition over the inland ice sheet, and the meteorological conditions in summer have a strong effect on the transition of the oxygen isotopic content of snow after deposition due to evaporation-sublimation.

斜面下降風の卓越した地域と内陸高原ドーム域および両者の遷移帯における積雪の酸素同位体組成の垂直プロファイルを比較し, それぞれのプロファイルと各地域の堆積環境の特性をのべる。試料は, みずほ基地(高度2230m)の101本雪尺列にそった幅10m, 深さ1mのトレンチ, 前進拠点(3198m)の3m深雪穴, ドームキャンプ(3761m)の5m深雪穴から得た。試料の年代は, みずほ基地では雪尺測定値, 前進拠点とドームキャンプとではトリチウム濃度と総ベータ線量のピーク位置から求めた。斜面下降風域では雪の削はく・再堆積が起こりやすいため, 積雪の酸素同位体組成の経年変化は内陸ドーム頂部に近いほど良く保存される。ドームキャンプのプロファイルは, 南極点上空5000gpmにおける夏の気温の経年変化とよい相関にある。これは夏の気象状態が, 堆積後の蒸発・昇華による積雪表層の同位体組成の遷移に強く影響した結果と考えられる。, Vertical profiles of oxygen isotopic contents in deposited snow were obtained in the region where katabatic winds prevail (Mizuho Station : 70.7°S, 44.3°E, 2230m), the inland dome-like plateau (Dome Camp : 77.0°S, 35.0°E, 3761m) and the transitional zone between them (Advance Camp : 74.2°S, 35.0°E, 3198m). At Mizuho Station, the δ^O contents have high values around the hiatus layers. However, synchronous relations cannot be found between the neighboring profiles, since snow was exchanged due to deposition and erosion by strong winds. Inter-annual variations of oxygen isotopic contents in snow have been preserved better in the inner parts of the ice sheet between the three zones observed in this study. The profile at Dome Camp has good correlation with the inter-annual variation of summer temperature at 5000gpm above the South Pole. This result suggests that the temperature at this level above the South Pole is representable for air temperature condition over the inland ice sheet, and the meteorological conditions in summer have a strong effect on the transition of the oxygen isotopic content of snow after deposition due to evaporation-sublimation.

Shallow corings and pit studies were carried out in 1987 on the Chongce Ice Cap in the West Kunlun Mountains which lie along the southern edge of the Taklamakan Desert. Stratigraphic observations, as well as measurements of insoluble particles, chemical constituents and liquid conductivity, on the core and pit samples allowed identification of annual layers, although visible dirt layers are not always annual signals. A vertical profile of stable isotope content showed a periodic variation near the surface, strongly attenuated with depth.

[1] Two net balance records of neighboring glaciers under different conditions are analyzed to extract temporal variations in glacier melting in the Himalayas. Significant melt was observed every year at one site (wet site), whereas no melt occurred at the second site because of its high elevation (dry site). Accumulation at the wet site of a glacier is estimated from the dry site neighboring another glacier through a measured precipitation record for a short time period. The difference between the estimated accumulation and the net balances at the wet site is obtained as the “melt index,” which represents the glacier melting conditions. The melt index with an interannual timescale is significant as a climatic proxy at high elevation since no relationship between stable isotopes and temperature is established and few long-term temperature records are available at high elevations in the Himalayas. The melt index showed a decadal fluctuation with a major amplitude never reported in previous studies with respect to temperature and ice cores analyses in the Himalayas. Ice cores from a site where significant melt occurs every year have not been considered available in reconstructing past climates since climatic signals in ice were disturbed by meltwater infiltration. However, we suggest a new approach to glean temperature information by a combination of wet and dry cores, not obtainable from a good-quality ice core alone.

Information on paleoenvironmental changes on the earth is preserved in the form of physical and chemical stratigraphic features in large polar ice sheets. Extraction of ice core signals makes it possible to evaluate and reconstruct past global variations of climate and stmospheric circulation. A deep ice coring and analysis effort was started at Dome Fuji Station (77°19′01″S, 39°42′12″E). Antarctica by the 32nd Japanese Antarctic Research Expedition (JARE-32) in 1991 and will be completed with continuous deep core retrieval in 1997. JARE-32,-33 and -34 parties set up a traverse route from Syowa Station to Dome Fuji Station, selected the coring site considering the results from radar soundings and GPS positions, and conducted shallow ice coring to a depth of 112.6m at the site. JARE-35 party completed construction of a camping/drilling facility for JARE-36 and -37 wintering parties to perform deep ice coring through the ice sheet with a thickness of approximately 3km. JARE-36 parties also conducted glaciological, meteorological and medical observations during the periods of cargo transportation and camp-construction activities both along the traverse route and at the Dome Fuji Station drilling site.

For ice core analysis, it is important to understand how chemical substances are preserved in glaciers. We have tried to make clear how the record of chemical substances (main anions : NO^-_3,SO^_4 and Cl^-) is preserved during the surface snow to firn transition in high altitude, East Antarctica. Chemical analyses and the measurement of density and size of snow crystals at every 1cm interval in depth have been carried out with a shallow pit sample in the Dome Fuji area (77.7°S, 39.1°E), East Antarctica, where a deep ice core will be retrieved in the near future. This sample was taken by the 33th Japanese Antarctic Research Expedition in 1992. We have estimated the mass of sublimated parts of snow crystals at every 1cm interval in depth from snow crystal size during the growth of snow crystals in the surface layer at shallow depths. And we have compared NO^-_3,SO^_4 and Cl^- concentrations with the mass, density, Na^+ concentration, δ^ O and so on. The concentration of NO^-_3 was found to have decreased rapidly with depth in the surface layer at shallow depths. It seems that NO^-_3 contained in the sublimated parts of snow crystals is emitted to the atmosphere as gas (e.g. as HNO_3) during the growth of snow crystals. Seasonal variations in the concentration of SO^_4 were found at all depths we have analyzed (0-1.4m, 8-10m). And the average concentration of SO^_4 in the shallow part (0-1.4m) is almost equal to that in the deep part (8-10m). SO^_4 seems to be preserved during the surface snow to firn transition. The average concentration of Cl^- in the shallow part is almost equal to that in the deep part too. Seasonal variations in the concentration of Cl^- in the shallow part is almost equal to that in the deep part too. Seasonal variations in the concentration of Cl^- were found in the shallow part too, but those were not found in the deep part. We cannot now judge weather Cl^- is preserved during the surface snow to firn transition or not. We expect new results about Cl^- from new samples.

For dating an ice core, identification of annual layers is of great importance. Dating is usually examined by detecting seasonal cycles of concentration of chemical components along the core. Chemical analyses have been carried out with a 10m-long shallow core of Dome Camp (77.0°S, 35.0°E) sampled by JARE-26 in December 1985,to see the potential use of this method for a deep ice core to be retrieved in the near future near the camp, East Antarctica. We have analyzed, with an ion chromatograph, Cl^-, NO_3^- and SO_4^ concentrations for small "disk" samples cut horizontally at every 1cm interval in depth so that 8 or 9 successive samples will cover an annual layer, because the accumulation rate has been estimated to be 9.2cm/year (snow) as an average for the last few decades at Dome Camp. Periodic variations were found in the concentration profiles of both Cl^- and SO_4^. The period of the latter was found to be close to 9cm. Hence SO_4^ could be a good indicator of annual layers for core samples near the dome, although care has to be taken for volcanic events which would have an enormous effect on SO_4^ concentration. The period of the variation of Cl^- concentration, however, was much longer than the thickness of an annual layer. The concentration of NO_3^- was found to have decreased rapidly with depth, which seems to indicate a discernible loss of NO_3^- during the growth of snow crystals in the surface layer at shallow depths.

Vertical profiles of oxygen isotopic contents in deposited snow were obtained in the region where katabatic winds prevail (Mizuho Station : 70.7°S, 44.3°E, 2230m), the inland dome-like plateau (Dome Camp : 77.0°S, 35.0°E, 3761m) and the transitional zone between them (Advance Camp : 74.2°S, 35.0°E, 3198m). Ten profiles from a snow trench 10m wide and 1m deep, a profile from a snow pit 3m deep and that from a snow pit 5m deep were obtained at Mizuho Station, Advance Camp and Dome Camp, respectively. Snow layers were dated on the basis of stake measurements at Mizuho Station, a peak of tritium content (in 1966) at Advance Camp and peaks of tritium and gross β activities (in 1965,1955) at Dome Camp. At Mizuho Station, δ^O contents have high values around the hiatus layers. However, synchronous relations cannot be found between neighboring profiles, since snow was exchanged due to deposition and erosion by strong winds. Inter-annual variations of oxygen isotopic contents in snow have been preserved better in the inner parts of the ice sheet between the three zones observed in this study. The profile at Dome Camp has good correlation with the inter-annual variation of summer temperature at 5000gpm above the South Pole. This result suggests that the temperature at this level above the South Pole is representative for air temperature condition over the inland ice sheet, and the meteorological conditions in summer have a strong effect on the transition of the oxygen isotopic content of snow after deposition due to evaporation-sublimation.

Glacier fluctuations during the Holocene in the Himalayas are compared with those in the world. Characteristics of glacier mass balance in the Nepal Himalaya, which belongs to the summer-accumulation type, are described. And the glacier fluctuations after the Little Ice Age in the Nepal Himalaya are discussed on the basis of variation of summer air temperature, which is the controling factor of glacier mass balance in this area.

A thermal drilling was carried cut in August of 1974 on the Khumbu Glacier flowing from Mt. Sagarmatha (English name Everest) in the East Nepal Himalayas. The drilling site was set at 5, 360 m above sea-level in the upper part of the ablation area of the glacier.The drilling was continued to a depth of 20.3 m where the drilling stopped due to the freezing of the drilled hole. Down to the depth, the relationship between the depth and the time of drilling was obtained, and the analysis of the results obtained showed that there were 7 layers down to a depth of 20 m. Three layers of them were ordinary glacier ice layers, three layers were blue ice layers or ice layers contaminated with dirt, and one layer corresponded to a vertically distributed ice layer containing air bubbles or a horizontally distributed ice layer containing water.A simple calculation of the freezing rate of the drilled hole showed that the ice temperature at a depth of 2 m was below -2°C at the time of drilling. The measurement of the resistance of a thermister put into the hole showed the ice temperature at a depth of 2.7 m was -5.3°C on 23rd November. Therefore, it was concluded that the distribution of ice temperature in the ablation area of the glacier might be of the polar type.

Glaciological observations on the high plateau in the East Queen Maud Land, Antarctica, were carried out along a route of the oversnow traverse, by the 25th and 26th Japanese Antarctic Research Expeditions in 1984 and 1985. The surface topography of the dome-like plateau (Valkyrjedomen, which is the second highest in Antarctica) and the positions of ice divides were determined clearly. The position and altitude of the highest place of the dome are 77°22′S, 39°37′E and 3807m a.s.l. Snow drift samples were collected along the route from Mizuho Station to Valkyrjedomen and were melted carefully in a snow vehicle. The value of electric conductivity of the melted snow samples at 0℃ was obtained before storing in the pre-cleaned bottles. In a home laboratory, pH measurements of the samples were carried out. It was revealed that the high electric conductivity and low pH values were found among the snow samples collected in the dome area, especially around the region higher than 3600m a.s.l. The region has the different glaciological characteristics from those in the katabatic wind region, that is, the lower degree of the surface inclinations, the lower net accumulation, the more smooth surface morphology, the lower ram hardness of surface snow layer and the higher lapse rate of snow temperature at 10m depth. Taking the comparatively higher concentration of artificial radio nuclides reported in the other Antarctic inland area into consideration too, the glacio-chemical environments in the Antarctic inland region are thought to be characterized by the transportation of the stratospheric aerosols or gases.

Observations of water discharge from a drainage area of 142.5 km2 including glacier zones were made at Dingboche (4330 m) in east Nepal. The annual discharge of this drainage was estimated as 1.7 × 108m3. The annual variation of the discharge showed a tendency to increase in summer and decrease in winter. It is assumed that precipitation during the monsoon season strongly contributes to high discharge in summer. On the basis of the data of ablation of glaciers and precipitation in this region, preliminary estimates of water balance in the drainage during a year were made. Since the variation of daily mean air temperature at Lhajung near Dingboche had a good correlation with the vatiation of daily discharge in summer but not in winter, the contribution of melt water from glaciers to the variation of the discharge was also discussed on the basis of the air temperature over glaciers estimated from the monthly mean temperature at Lhajung. Diurnal variations of the discharge in different months showed periodic tendencies which might be due to the diurnal variations of discharge of melt water from glaciers. The seasonal change of this tendency can be explained by the change of air temperature. Monthly discharge in depth of runoff from this drainage was compared with that at a point 460 m in altitude, in the lower part of this drainage. The latter was nearly twice as much as the former during the monsoon season, since precipitation in the upper drainage during the monsson season is less than below.