研究者詳細 - 藤田　耕史

論文 - 藤田　耕史

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Effect of dust event timing on glacier runoff: sensitivity analysis for a Tibetan glacier. 査読有り

Fujita K

Hydrological Processes 21 巻 ( 21 ) 頁： 2892-2896 2007年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The impact of the timing of dust deposition on glacier runoff was evaluated using a glacier mass-balance model with a newly improved scheme to track a dusted layer in a snow layer of a glacier. The lowering of surface albedo due to the dusted layer appearing leads to a drastic increase of glacier runoff even under the same meteorological conditions. Calculations of seasonal sensitivity, the relationship between dusted date and resulting runoff, have shown that dust deposition during a melting season might cause a drastic mass outflow from a glacier through changing the surface albedo during the melting season.

http://www3.interscience.wiley.com/journal/113509005/abstract

Topographical survey of end-moraine and dead ice area at the Imja Glacial Lake in 2001 and 2002. 査読有り

Sakai A, Saito M, Nishimura K, Yamada T, Iizuka Y, Harada K, Kobayashi S, Fujita K, Gurung CB

Bulletin of Glaciological Research 24 巻頁： 29-36 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

A survey was carried out at the end moraine and the dead ice area of the Imja Glacial Lake in October 2001 and in April 2002 using a digital theodolite with a laser distance meter and differential Global Positioning System (d-GPS). The survey points covered the whole dead ice area and end moraine of the Imja Glacier, and map contours were produced at 5 m intervals. This topographical map will be a significant means to analyze the time variation of the dead ice area and end moraine in future re-mapping. Changes in the lake level and the spillway on the dead ice area since 1994 were also analyzed in comparison with the measurements in 1994 by Watanabe et al. (1995).

Meteorological observations during 2002-2004 in Lunana region, Bhutan Himalayas. 査読有り

Suzuki R, Fujita K, Ageta Y, Naito N, Matsuda Y, Karma

Bulletin of Glaciological Research 24 巻頁： 71-78 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

Meteorological observations were carried out in the Lunana region, Bhutan Himalayas, from September 2002 to October 2004. An automatic weather station (Lugge AWS) was installed at 4524 m a.s.l. on the end moraine of Lugge Glacier. In addition, air temperatures, ground temperatures and relative humidity were observed simultaneously around the AWS from late September to early October in 2003 and 2004 to investigate spatial variation of these components. Characteristics of seasonal and diurnal variations of meteorological elements are shown using the data observed by the AWS. Relatively large spatial variability of surface temperature is shown by the data observed at different sites compared to that of air temperature and relative humidity.

Worldwide shrinkage of glaciers. 招待有り

Fujita K

Japanese Alpine News 8 巻頁： 90-96 2007年

Glaciological data collected by the 44th Japanese Antarctic Research Expedition during 2003-2004.

Kameda T, Fujita K, Sugita O, Hashida G

JARE Data Reports, National Institute of Polar Research 298 (Glaciology 32) 巻頁： 92pp 2007年

Climatic and atmospheric circulation pattern variability from ice-core isotope/geochemistry records (Altai, Tien Shan and Tibet). 査読有り

Aizen VB, Aizen EM, Joswiak DR, Fujita K, Takeuchi N, Nikitin SA

Annals of Glaciology 43 巻頁： 49-60 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Several firn/ice cores were recovered from the Siberian Altai (Belukha plateau), central Tien Shan (Inilchek glacier) and the Tibetan Plateau (Zuoqiupu glacier, Bomi) from 1998 to 2003. The comparison analyses of stable-isotope/geochemistry records obtained from these firn/ice cores identified the physical links controlling the climate-related signals at the seasonal-scale variability. The core data related to physical stratigraphy, meteorology and synoptic atmospheric dynamics were the basis for calibration, validation and clustering of the relationships between the firn-/ice-core isotope/geochemistry and snow accumulation, air temperature and precipitation origin. The mean annual accumulation (in water equivalent) was 106 g cm-2 a-1 at Inilchek glacier, 69 g cm-2 a-1 at Belukha and 196 g cm-2 a-1 at Zuoqiupu. The slopes in regression lines between the δ18O ice-core records and air temperature were found to be positive for the Tien Shan and Altai glaciers and negative for southeastern Tibet, where heavy amounts of isotopically depleted precipitation occur during summer monsoons. The technique of coupling synoptic climatology and meteorological data with δ18O and d-excess in firn-core records was developed to determine climate-related signals and to identify the origin of moisture. In Altai, two-thirds of accumulation from 1984 to 2001 was formed from oceanic precipitation, and the rest of the precipitation was recycled over Aral-Caspian sources. In the Tien Shan, 87% of snow accumulation forms by precipitation originating from the Aral-Caspian closed basin, the eastern Mediterranean and Black Seas, and 13% from the North Atlantic.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00009

Concentrations and source variations of n-alkanes in a 21 m-ice core and snow samples at Belukha Glacier, Russian Altai Mountains. 査読有り

Miyake T, Nakazawa F, Sukugawa H, Takeuchi N, Fujita K, Ohta K, Nakawo M

Annals of Glaciology 43 巻頁： 142-147 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Ice-core and snow samples collected on Belukha glacier, Russian Altai mountains, were analyzed for n-alkanes by gas chromatography. On the basis of the total concentrations (T-HCs), carbon preference index (CPI) values and the plant wax contributions (WaxCn), it is suggested that mountain glaciers on the Asian continent received higher loading of n-alkanes from natural and anthropogenic sources than the Greenland ice sheet. It appears that the loading and variation of n-alkanes on glaciers in the Altai are approximately the same as those of the mountain in general, because the concentrations, CPI values and WaxCn percentages of n-alkanes in Sofiyskiy glacier, also in the Russian Altai, are at the same levels as or slightly greater than those in ice-core and snow samples from Belukha glacier. It seems that the n-alkanes on Belukha glacier are derived mainly from higher plant wax and petroleum exhaust other than from diesel engines. Vertical profiles of T-HCs and CPI values of n-alkanes show that the non-WaxCn portions and T-HCs have recently increased with a decrease in CPI values on Belukha glacier. A similar trend of n-alkanes was reported for Sofiyskiy glacier, indicating that the influence of human activities has gradually increased around the Altai.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00021

Use of ice cores from glaciers with melting for reconstructing mean summer temperature variations. 査読有り

Nakazawa F, Fujita K

Annals of Glaciology 43 巻頁： 167-171 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

This study examines a new method for reconstructing mean summer temperature variations by using an ice core from a wet-snow zone on a summer-accumulation-type glacier. In July 2001, a 25.1 m deep ice core was recovered from the accumulation area of Sofiyskiy glacier (49°47′ N, 87°43′ E; 3435 m a.s.l.), located in the southern Chuyskiy range of the Russian Altai mountains, and a 4.5 m deep pit was excavated about 50 m northwest of the drill site. The observation site has a positive balance even during summer when melting occurs. The summer balance for each year from 1990 to 2000 was estimated from Pinaceae and Artemisia pollen peaks in these samples. Pinaceae pollen marks spring, whereas Artemisia pollen marks autumn. Moreover, meltwater intrusion did not reach the previous year's accumulation. Thus, the ice between these pollen peaks in the same year was used to estimate a summer balance. The reconstructed summer balance variations were negatively correlated with mean summer temperature variations (r = -0.72, P < 0.05). This study shows that, for summer-accumulation-type glaciers such as Sofiyskiy glacier, the most important climate factor controlling the glacier's surface mass balance is mean summer temperature. Therefore, the summer layer thickness in an ice core can be used as a proxy for reconstructing mean summer temperature variations.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00025

Estimation of atmospheric transmissivity of solar radiation from precipitation in the Himalayas and Tibetan Plateau. 査読有り

Matsuda Y, Fujita K, Ageta Y, Sakai A

Annals of Glaciology 34 巻頁： 344-350 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

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 <40 W m-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.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00052

A snow algal community on Akkem Glacier in the Russian Altai Mountains. 査読有り

Takeuchi N, Uetake J, Fujita K, Aizen VB, Nikitin S

Annals of Glaciology 43 巻頁： 378-384 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Snow algae are cold-tolerant algae growing on snow and ice and have been reported on glaciers in many parts of the world. Blooms of snow algae can reduce the surface albedo of snow and ice and significantly affect their melting. In addition, snow algae found in ice cores can be potential indicators of the paleo-environment, making them of great interest both to the biology and the geophysics of glaciers. A snow algal community was investigated in 2002 and 2003 on Akkem glacier in the Russian Altai mountains, where no information on its biological community has previously been available. Five species of snow algae including green algae and cyanobacteria were observed on the glacier. Red snow due to a bloom of algae (Chloromonas sp.) was visually apparent in the snow area during our study periods. The total algal cell-volume biomass on the glacier ranged from 97 to 1156 μL m-2, which is equivalent to that reported previously on glaciers in the Himalaya and Alaska. The community structure showed that Mesotaenium berggrenii and/or Ancylonema nordenskioeldii, which are common species on glaciers in the Northern Hemisphere, were dominant in the ice area, while Chloromonas sp. was dominant in the snow area. Such community structures are similar to those on Alaskan and Arctic glaciers but differ from those on Himalayan and Tibetan glaciers, even though the Altai mountains are geographically closer to the Himalaya and Tibet than to Alaska. The difference in algal communities between the Altaic and other glaciers is discussed together with physical and chemical conditions affecting the algae.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00056

Preliminary observations of sub-surface and shallow ice core at July 1st Glacier, China in 2002-2004. 査読有り

Uetake J, Sakai A, Matsuda Y, Fujita K, Narita H, Matoba S, Duan K, Nakawo M, Yao T

Bulletin of Glaciological Research 23 巻頁： 85-93 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

The albedo reduction on glacier surfaces in past summers due to microbiological activities and mineral particles should be considered to reconstruct precise fluctuation of glacier mass balance. However, there is little knowledge on preservation of the microorganisms and the mineral particles in glacier ice. In particular, influence of superimposed ice formation on these preservations is unknown. As the first step to understand the albedo reduction process and to reconstruct surface albedo changes on glaciers in northwestern China, where superimposed ice formation has an impact on glacier mass balance, we report the glacier surface level changes, seasonal and annual changes of stratigraphy and analyzed results of short ice cores at upper parts of the July 1st Glacier from 2002 to 2004. Surface melting on the glacier was accelerated by dark-colored materials composed of cryoconite and mineral particles. The glacier surface level was lowered year by year and ELA (Equilibrium Line Altitude) was much higher than that in the 1970s and 1980s. An ice core of 1.82m length included five cyanobacterial layers. As cyanobacteria grow during summer, these layers may be useful as markers for summer layers and allow to infer surface albedo changes in the past. Average annual snow mass balance estimated from the cyanobacterial peaks in the core is 313 mm, which corresponds to the annual precipitation observed near the terminus of the July 1st Glacier. These results would open up the possibilities that we could reconstruct past mass balance and albedo effects.

Hydrological observations at July 1st Glacier in northwest China from 2002 to 2004. 査読有り

Sakai A, Matsuda Y, Fujita K, Duan K, Pu J, Yamaguchi S, Nakawo M, Yao T

Bulletin of Glaciological Research 23 巻頁： 33-39 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Hydrological observation was carried out at the July 1st Glacier in the Qilian mountains, northwest China, during the glacier melting season from 2002 to 2004. Water discharge was measured using two methods, current meter and salt water. The results of these methods showed a good correspondence. A logger for water level was settled at the glacier terminus in 2002 and at the foot of the end-moraine in 2003 and 2004. Then, variations in discharge were evaluated based on the relationship between discharge and water level. Total observed runoff depth from the basin was 834 mm in 2002. The average value of water budget components, such as precipitation, glacier mass balance, evaporation at the glacier and glacier-free area, were evaluated in 2002 from observation and meteorological data. The results indicated that the discharge from the glacier area was 6 times larger than that of the glacier-free area mainly due to glacier shrinkage.

Meteorological observation at July 1st Glacier in northwest China from 2002 to 2005. 査読有り

Sakai A, Matsuda Y, Fujita K, Matoba S, Uetake J, Satow K, Duan K, Pu J, Nakawo M, Yao T

Bulletin of Glaciological Research 23 巻頁： 23-31 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Meteorological observations were carried out at July 1st Glacier (J1G) in Northwest China. An automatic weather station was established at the glacier terminus 4295 m a.s.l. altitude from June 2002 to August 2005. Manual meteorological observations and dust particle counting have also been conducted at the Base Camp during the summers of 2002, 2003 and 2004. The catch ratio of the precipitation was calibrated, separating it into rain and snow depending on the air temperature, which relation has been observed at Base Camp. The calibrated annual precipitation in 2002 was about 340 mm, which was more than 20% above the observed value. Inter-annual variations in the meteorological data revealed that there were remarkable wet calm and cloudy periods during the summer 2002.

* Thirty-year history of glacier melting in the Nepal Himalayas. 査読有り

Fujita K, Thompson LG, Ageta Y, Yasunari T, Kajikawa Y, Sakai A, Takeuchi N

Journal of Geophysical Research - Atmospheres 111 巻 ( D3 ) 頁： D03109 2006年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

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.

http://www.agu.org/pubs/crossref/2006/2005JD005894.shtml

Stable isotopes in daily precipitation at Dome Fuji, East Antarctica. 査読有り

Fujita K, Abe O

Geophysical Research Letters 33 巻 ( 18 ) 頁： L18503 2006年

Topographical survey of July 1st Glacier in Qilian Mountains, China. 査読有り

Fujita K, Sakai A, Matsuda Y, Narama C, Naito N, Yamaguchi S, Hiyama K, Pu J, Yao T, Nakawo M

Bulletin of Glaciological Research 23 巻頁： 63-67 2006年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

In order to evaluate recent glacier shrinkage in the arid region of China, surveys using a global positioning system (GPS) and digital theodolite with laser distance meter were carried out on the July 1st glacier in the Qilian Mountains from 2002 to 2004. Benchmarks and stakes on around the glacier were installed in 2002. A new 2002 map was carefully superposed on a map created in 1975 using a salient moraine ridge and boundary of the accumulation area, since no ground control point was available in the old 1975 map. A retreat of the glacier termini has been detectable since 1956 with a notable retreat occurring between 2002 and 2003. Surface flow velocities were obtained by repeated measurements of a stake network. The new map and benchmarks provide basic information for future survey studies.

Snow algae in a Himalayan ice core: new environmental markers for ice core analyses and their correlation with summer mass balance. 査読有り

Yoshimura Y, Kohshima S, Takeuchi N, Seko K, Fujita K

Annals of Glaciology 43 巻頁： 148-153 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Snow algae in a shallow ice core (6.98 m long) from Yala glacier in the Langtang region of Nepal were examined for potential use as environmental markers in ice-core analysis. The ice core, taken at 5350 m a.s.l. in 1994, was estimated to contain 11 annual layers from 1984 to 1994 from the profile of algal biomass. Algal biomass in each annual layer was noted to be correlated with air temperature, and the following two environmental indices which were calculated from air temperature and precipitation at Kyangjing (3920 m a.s.l.), the village nearest to Yala glacier: estimated mean snow-cover thickness (MST) and estimated summer mass balance (SMB). Both parameters reflect snow-cover thickness on algal layers, which would be a major determinant of the light available for algal growth on the glacier. Snow algal biomass in the ice core appears to be a good environmental marker for indicating air temperature and accumulation during summer, which is important for understanding the mass balance of summer-accumulation-type glaciers in this region.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00022

氷河変動と海水準に関する最近の研究. 査読有り

藤田耕史

雪氷 68 巻 ( 6 ) 頁： 625-637 2006年

Five decades of shrinkage of the July 1st Glacier, Qilian Mountains, China. 査読有り

Sakai A, Fujita K, Duan K, Pu J, Nakawo M, Yao T

Journal of Glaciology 52 巻 ( 176 ) 頁： 11-16 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

A survey of July 1st glacier, Qilian Shan, China, was carried out in 2002. Previously, the glacier's boundary had been recorded in 1956, and further research had been carried out in the mid-1970s and 1980s. Our survey reveals that area shrinkage and surface lowering have accelerated in the past 15 years. Surface elevation changes can result from changes in accumulation, surface melting and emergence velocity. The contributions of these elements to surface lowering are evaluated at the lower part of the glacier from observations of surface velocity, ice thickness and precipitation, and from temperature data near the glacier. Apart from the effect of glacier ice redistribution, our analysis reveals quantitatively that the recent accelerated glacier shrinkage has been caused by increasing temperature. Furthermore, it is established that meltwater discharge from the glacier in the past 17 years has increased due to glacier shrinkage, by about 50% over that from 1975 to 1985.

http://www.ingentaconnect.com/content/igsoc/jog/2006/00000052/00000176/art00002

Aeolian dust experiment on climate impact: An overview of Japan-China joint project ADEC. 査読有り

Mikami M, Shi GY, Uno I, Yabuki S, Iwasaka Y, Yasui M, Aoki T, Tanaka TY, Kurosaki Y, Masuda K, Uchiyama A, Matsuki A, Sakai T, Takemi T, Nakawo M, Seino N, Ishizuka M, Satake S, Fujita K, Hara Y, Kai K, Kanayama S, Hayashi M, Du M, Kanai Y, Yamada Y, Zhang XY, Shen Z, Zhou H, Abe O, Nagai T, Tsutsumi Y, Chiba M, Suzuki J

Global and Planetary Change 52 巻 ( 1-4 ) 頁： 142-172 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

The Aeolian Dust Experiment on Climate Impact (ADEC) was initiated in April 2000 as a joint five-year Japan–China project. The goal was to understand the impact of aeolian dust on climate via radiative forcing (RF). Field experiments and numerical simulations were conducted from the source regions in northwestern China to the downwind region in Japan in order to understand wind erosion processes temporal and spatial distribution of dust during their long-range transportation chemical, physical, and optical properties of dust and the direct effect of radiative forcing due to dust. For this, three intensive observation periods (IOP) were conducted from April 2002 to April 2004.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VF0-4JVTBVS-1&_user=119029&_coverDate=07/31/2006&_alid=844915395&_rdoc=1&_fmt=high&_orig=search&_cdi=5996&_sort=d&_docanchor=&view=c&_ct=1&_acct=C000009318&_version=1&_urlVersion=0&_userid=119029&md5=9b8a345dbee7ce91ab9e5786e7c8139e

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