ACC28-P01

Room:Convention Hall

Time:May 25 18:15-19:30

Development of a simple snow load gauge using plastic bottles
IMANISHI, Yuichi1∗ ; OI, Takuma2
1

ERI, The University of Tokyo, 2 Toho Mercantile CO., LTD.

Gravity observations with a superconducting gravimeter is performed at the underground site of the Kamioka Observatory,
Institute for Cosmic Ray Research, The University of Tokyo. Since this station is located in an area where there is heavy
snowfall in winter, the observation is subject to a significant effect of snow load. We developed a simple snow load gauge using
plastic bottles with the aim of such hydrologic corrections. It is based on the principle of a snow pillow, which detects waterequivalent of snowpack in terms of pressure changes of the anti-freeze coolant inside the sensing unit, and is much smaller andcheaper than the existing products thanks to the usage of plastic bottles. A laboratory test of artificially loading the instruments
has revealed an almost linear relation between the load and the liquid pressure inside the bottles. The instrument was installed at
the top of Mt. Ikenoyama, above the Kamioka underground site, in order to observe in situ snow load. Resultant time series ofpressure changes turned out to be very similar to the observed gravity changes, suggesting that our instrument produced highlyplausible recordings of snow load. We plan to make this observation at multiple sites in the mountain in order to measure 2-D
distribution of snow load.
Keywords: snow load gauge, superconducting gravimeter, plastic bottle

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ACC28-P02

Room:Convention HallTime:May 25 18:15-19:30

Dependence of the size distribution of BC in snow on thawing temperature
KINASE, Takeshi1∗ ; KITA, Kazuyuki2 ; KONDO, Yutaka3 ; OHATA, Syo3 ; MOTEKI, Nobuhiro3 ;AZUMA, Kumiko4 ; OGAWA, Yoshimi4 ; SHIOBARA, Masataka4 ; MOTOYAMA, Hideaki4 ; HAYASHI, Masahiko5 ;HARA, Keiichiro5
1

Graduate school of science and engineering of Ibaraki Univ., 2 Collage of science, Ibaraki Univ., 3 Scool of science the universityof Tokyo, 4 National Institute of Polar Reserch, 5 Fukuoka Univ.
Black Carbon aerosols(BC), mainly consists of soot or soot like matter generated by the combustion of fossil fuel or biomass,absorb the solar radiation to heat the atmosphere. Moreover, BC deposited on snow decrease the snow albedo and contribute to
the warming in the higher latitudes. Therefore, BC have the significant influence on the climate but quantitative estimation of it
has a large uncertainty, For example, IPCC(2013) estimated the radiative forcing by BC on snow to 0.04(0.02-0.09)(W/m2 ), but
in Flanner et al.(2007) estimated to 0.049(0.007-0.12)(W/m2 ). The snow albedo is estimated by a radiative transfer model in thesnow layers considering snow grain size and impurities such as BC. The size distribution of BC particles in snow is significant
to estimate BC influence on the snow albedo.
We are measuring the size distribution of BC mass concentration in snow with the incandensence method (MacConel et al.
2007). Before the measurement, snow samples are melted and are aerosolized by a nebulizer. In these procedures, there are somefactors to reduce the accuracy or precision. One of them is the influence of the thawing temperature of snow samples on the size
distribution of BC in the thawing snow. Many researchers (e.g. Brandt et al., 2011) heated to thaw out snow faster. However,Schwarz et al.(2012) suggested that the size distribution of BC in the thawed snow could be varied with the thawing temperaturesignificantly. In this paper, we present the experiment to examine the thawing temperature influence on the measurement of BC
in snow by the incandensence method and the results.
We adopted two snow samples obtained at Hakusan and Shirouma in 2013 for this experiment. The snow samples are well
uniformed with a mixer and are divided into 9 bottles, respectively. 3 bottle samples were melted at 70 ℃,20 ℃ and 5 ℃,
respectively, using a water bass. Then, we measured the size distribution of BC mass concentration in the melted snow in eachbottle with the SP2 instrument.
The mass concentration of BC in the lower thawing temperature samples was higher than those in the higher temperaturesamples. Their ratio between samples melted at 5 ℃ and 70 ℃ was 40.8% for the Hakusan snow case, and 11% for Shirouma snowcase. Smaller size of BC was more sensitive to the thawing temperature. These result showed that the thawing temperature has asignificant influence on the mass concentration and size distribution of BC in thawing snow, and that lower thawing temperature
is better for the measurement of size distribution of BC mass concentration in snow. Because not only the temperature but also
thawing/preserve time may affect the size distribution of BC in the thawing snow BC, we are planning of next experiment toexamine the time influence.
Keywords: snow, BC, size distribution, SP2, thawing temperature

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ACC28-P03

Room:Convention Hall

Time:May 25 18:15-19:30

Surface albedo over snow-covered boreal forests, Alaska
SUGIURA, Konosuke1∗ ; KITAHARA, Yujiro2 ; NAGAI, Shin3 ; SUZUKI, Rikie3
1Univ. of Toyama/JAMSTEC, 2 Univ. of Toyama, 3 JAMSTEC

Previous research has demonstrated the high variations of the surface albedo in winter/spring in snow-covered regions invarious global climate models. In this study, we focus on the surface albedo over snow-covered forests which is suggested
probably too high in various global climate models. This study was carried out to verify the occurrence frequency of ice accretionand snow accretion in the boreal forest regions. Using the interval camera installed on the observation tower of 16 m in height at
the site located to the north of Fairbanks, Alaska, ice accretion and snow accretion in black spruce forest regions were measured.
Based on the results, the surface albedo variation of snow-covered forests and differences in the snow albedo parameterization
are discussed to contribute to a better understanding of the role of snow in the climate system.
Keywords: ice accretion, snow accretion, albedo, boreal forest

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ACC28-P04

Room:Convention Hall

Time:May 25 18:15-19:30

Long-traveling conditions for the rock-on-snow avalanche: insights from the field andlaboratory evidences
YAMASAKI, Shintaro1∗ ; KAWAGUCHI, Takayuki1 ; NAKAMURA, Dai1 ; YAMASHITA, Satoshi11Kitami Institute of Technology

On March 12, 2011, a large earthquake induced rock avalanches in Nagano and Niigata prefecture Japan. These rockavalanches travelled long, about 1 km to 1.5 km sliding on snow with apparent friction angle of 6? to 17.1?. It looks uncommon phenomena. Because rock avalanches often stop on snow covering steep slope. We hypothesized that the nature ofsnow dominate the mobility of the rock-on-snow avalanche, and flew rocks on snow 3.5-m-long slope varying snow hardness,and then we flew a rock and earth of 6 ton on 28-m long snow covering slope. Snow is low friction material but its aggregatesis effective cushion by self-deformation, so travelling on normal autochthonous snow cover and mixing snow into the fallingmaterial do not contribute such long travelling. However, hardened and consolidated snow provide it because of ice-like low
friction and impermeability. The consolidated snow is formed at the contact surface on snow cover by impulsive compressing.
Hence, when a falling material plunge into lower thick snow cover, consolidated snow is formed. Then, falling material slideon it by pushing following flow. When the forming consolidated snow basement, water and air are expelled from snow to upper
falling material, and they probably reduce friction. As the consolidated snow is impermeable, frictional heat and heart transferring produced snowmelt are kept on the consolidated snow, and it reduce further friction. With downsizing of falling material,
the resistivity against forehand snow cover decreases, and it leads to stopping. In addition, with lessening pressure of the fallingmaterial to underlying snow cover, forming impermeable consolidated snow stops, and water pressure disappear, and it leads
to stopping. Wet and granular snow is likely to be consolidated. Thus these snow covered area and/or season are preferablecondition of the long travelling rock-on-snow avalanches.
Keywords: snow cover, rock-on-snow avalanche, snow avalanche, rockfall, earthquake

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ACC28-P05

Room:Convention Hall

Time:May 25 18:15-19:30

The research expedition of the glacier and mountain permafrost in the Bhutan Himalayas
in 2014FUKUI, Kotaro1∗ ; FUJITA, Koji2 ; TSHERING, Phuntsho2
1

Tateyama Caldera Sabo Museum, 2 Nagoya University

The glacier and mountain permafrost research expedition was carried out in September and October of 2014 in the central partof the Bhutan Himalayas. The aims of this expedition were 1) to make a rock glaciers inventory and identify the lower limit ofmountain permafrost in the Bhutan Himalayas, and 2) to measure the ice thickness of the Gangjula glacier based on the ground
penetrating radar (GPR) soundings.
We identified total 81 rock glaciers. Active rock glaciers appeared above 4600 m. We estimated that mean annual air temperature at the terminus of the active rock glaciers are less than -0.8oC based on ERA-Interim data from 1979 to 2013. These indicatethat the lower limit of mountain permafrost in Bhutan Himalayas is 4600 m. This lower limit of mountain permafrost is slightly
lower than that in Khumbu Himal (5000-5300 m) and that in Kanchenjunga Himal (4800 m).
The Gangjula glacier is a small saddle glacier. Length=1.1 km, width=0.3 km, surface area=0.31km2 , elevation=4900-5200
m and the ELA=glacier top. We used GSSI SIR3000 + 100MHz antenna and got 6 cross and 1 longitudinal GPR profiles. The
results of GPR soundings indicated that the maximum thickness of the Gangjula glacier was 76 m.

Keywords: Bhutan, Himalaya, glacier, rock glacier, permafrost, ground penetrating radar

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ACC28-P06

Room:Convention Hall

Time:May 25 18:15-19:30

Seasonal variations in the thermal structures of proglacial lakes in the Southern Patagonia
Icefield
MINOWA, Masahiro1∗ ; SUGIYAMA, Shin1 ; SAKAKIBARA, Daiki1 ; SKVARCA, Pedro2
1

Institute of Low Temperature Science, 2 Museo del Hielo Patagonic

Patagonia Icefields are loosing ice mass at one of the greatest rates in the world. The icefields are characterized by a numberof outlet glaciers calving into lakes and the ocean. Many of these calving glaciers are retreating, but rates of the retreats are
significantly different in each glacier. For example, Glaciar Upsala retreated by 2.9 km over the period of 2008 ̶ 2011. Massloss from the glacier accounts for about 15% of the total mass loss from the Southern Patagonia Icefield in 2000 ̶ 2012. On theother hand, Glaciar Perito Moreno has shown no significant change in the terminus position over the past century. Recent studies
in Greenland and Alaska suggest the importance of melting of calving face below the sea surface for recent mass loss of calving
glaciers. Despite the increasing numbers of data from fjord of tidewater glaciers, little is known even in the thermal structure inlake, seasonal variation and how various water masses mix. To investigate the thermal structure of proglacial lake, we measured
temperature and turbidity of lake water in front of calving glaciers in the Southern Patagonia Icefield. Lake measurements
were carried out at Glaciar Upsala, which overs an area of 840 km2 and flows into a ∼600 m deep lake, and Glaciar Perito
Moreno, which overs an area of 259 km2 and flows into a shallower lake (∼200 m deep). We repeated measurements in summer(December, 2013) and spring (October, 2014) to investigate seasonal variations in the lake water properties.
Our results in spring showed relatively uniform water temperature and turbidity from the lake surface to the bottom, whereas
temperature and turbidity showed steeper vertical gradients in summer. These results are consistent in the two lakes. In summer,
water temperature in front of Glacier Upsala (2 ̶ 4o C) was colder than in spring, because of large amounts of subglacial
discharge from the glacier. Turbid and cold water (<1o C) was found at the deepest part of the lake (>500 m below the lakesurface), which is a strong indication of subglacial meltwater discharge. Contrasting to Glaciar Upsala, cold deep water wasmissing in the lake of Glaciar Perito Moreno both in summer and spring. In summer, water temperature (6o C) was warmer thanin spring by ∼3o C within whole lake, and in particular, warm water layer (∼8o C) observed at the lake surface (<5 m below thelake surface).
These data indicate different thermal structures in front of the two freshwater calving glaciers in Patagonia. The structure is
probably dependent on the bathymetry and subglacial discharge. Warmer lake is formed by relatively small amount of subglacial
discharge and shallow lake, which should play crucial roles in the melting of calving face below the lake surface.
Keywords: calving glacier, proglacial lake, subaqueous melt, Patagonia

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