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The present researches at our laboratory are as below:

1) The influences of wild fire and glacier-melt on discharge and material fluxes of the Yukon River, Alaska (since 2004).

 The upper left photo (photographed in Sep. 2009) shows meltwater discharge from a subglacial channel of the Gulkana Glacier, Alaska (site PC in the lower map). This glacier is located in the headwater region of the Yukon River, Alaska. In order to investigate how the glacier-melt responds to the climate change like global warming, our laboratory monitored the water turbidity in the proglacial Phelan Creek in the glacier-melt seasons (June – Sep.) of 2001 to 2009, under cooperation with the U.S. Geological Survey. The upper right photo (June 2004) shows a smoky condition but under fine weather condition at the same site. The smoke came continually from the large wild fire in the lower forest region, which continued about three months from mid-June. The recent global warming induces the tendency of increasing fire events by increasing aridity. The meltwater discharge and accompanying sediment load can respond to such events of small time scale by producing different heat fluxes to the glacier surface. Hence, we will investigate the glacial response to the climate change on large time scale and such fire events on small time scale.

 The lower right photo (June 2010) shows the lowest region of the Yukon River, Alaska (site PLS in the lower map). We investigate how glacier-melt and wild fire affect water discharge and material fluxes of the Yukon River at this site. The Yukon drainage basin (gray zone in the map) includes only 1.1 % glacier-covered area. However, the glacier-melt in the summer greatly affects the magnitude of water discharge, sediment load, and POC & PON fluxes. The characteristic fluxes could also influence the ecosystem on the coastal region of the Bering Sea. We are now investigating how the glacier-melt contributes to the material cycles in the Bering Sea.

  • ガルカナ氷河①
  • ガルカナ氷河②

2) The characteristics of water and material cycles in intermittently open coastal lagoons (since 2010)

 Our laboratory has been investigating water, sediments and chemical cycles in the five coastal lagoons of the eastern Hokkaido, Japan, facing the Pacific Ocean. One of the lagoons, the Oikamanai Lagoon, opens a few times s year to the Pacific Ocean by breaking the sand bar at a located lowest point. The sand-bar breakage occurs by the overflow of the lagoon water supplied by influent rivers. Wild birds such as Japanese red crown (one of special natural products), swan and heron make their habitat in the back marshes of the lagoons. The hydrological research in 2010 – 2012 revealed that, under closed condition, most of the lagoon water flows out as confined groundwater through the sand bar to Pacific Ocean. This confined aquifer is gravelly and was built up probably by the mega tsunami in the early 17th century. Currently, in order to know the relations between the past sandbar forming and mega tsunami, we are conducting field observations and numerical experiments about the change of material cycles during the sandbar formation.

  • Sounding and TOPO survey in Oikamanai Lagoon (Nov. 2010)

    Sounding and TOPO survey in
    Oikamanai Lagoon (Nov. 2010)

  • Oikamanai Lagoon (left) and Pacific Ocean (Right) (Nov. 2010)

    Oikamanai Lagoon (left) and Pacific Ocean
    (Right) (Nov. 2010)

  • Rugosa rose blooming on the coast (July 2012)

    Rugosa rose blooming on the coast
    (July 2012)

3) The characteristics of sediment road and their agents in the multi-faulted Oikamanai River basin, Tokachi, Japan (since 2011)

 The Oikamanai River basin, a back catchment of the Oikamanai Lagoon, has many faults, frequently producing landslides on the basin slope. Hence, irrespective of the relatively large forested area (about 88 % of the basin area), the sediment load of the Oikamanai River keeps high over the year. It is important to explore where the sediment sources are located and how the sediments are drained out. we explore (a) how rainwater or snowmelt water percolates into soil layers and flows out to the river, and (b) how the water then erodes the soil on the basin slope. In order to answer these questions, we have been monitoring water turbidity, water temperature water level and meteorology at a few points of the Oikamanai River since 2011.

  • Oikamanai River basin (July 2012)

    Oikamanai River basin
    (July 2012)

  • Oikamanai River and red-crowned cranes (Apr. 2012)

    Oikamanai River and red-crowned cranes
    (Apr. 2012)

  • Observations on grassland slope in the river basin

    Observations on grassland slope
    in the river basin

4) The non-freezing mechanism of a volcanic deep lake in Hokkaido (since 2010).

 Following the Köppen-Geiger climate classification, Hokkaido belongs to a subarctic region. Arctic to subarctic climates are known to be sensitive to global warming as symbolized by a relatively high increase in winter temperature. Volcanic deep caldera lakes like Lake Masyu and Lake Kuttara doesn’t freeze frequently since the beginning of the 21st century. We found out that, if the present rate of the winter temperature increase continues, Lake kuttara is expected to become non-frozen by 2019. Hence, in order to clarify how the lake thermally responds to the intra- and inter-annual climate change, water temperature measurements at the whole layer of Lake Kuttara are now performed throughout the year. Henceforth, our study will focus on the thermal adjustment of the lake to the cooling from outside.

Lake Kuttara(Shiraoi Town) | 8 March 2012 (completely frozen) | 1 March 2007 (non-frozen)

5) The effects of the Noboribetsu hydrothermal system on surrounding water regions (since 2013)

 The demand for water resources is growing all over the world. It is necessary to clarify the hydrothermal system for the development of new water resources and for the management of sustainable groundwater resources. A variety of geothermal and hydrothermal conditions exist in the Noboribetsu area, Hokkaido, which produces neutral to acidic hot springs. The high δD and δO18 values for the hot springs suggest that they originate in magmatic water. Also, this area, including Lake Kuttara neighboring to Noboribetsu, exhibits the high geothermal gradient at 90℃/km. However, a short knowledge of the geological structure makes us difficult to discuss the whole hydrothermal systems. Hence, we are exploring relations between the thermal variations at lake bottom and the Noboribetsu geothermal activity by monitoring water temperature in Lake Kuttara and a boiling pond.

The effects of the Noboribetsu hydrothermal system on surrounding water regions (since 2013)

6) The influence of glacier melt on Asian monsoon drainage basins: from past to future

It is well known that in these days glaciers on alpine belts such as Alaska and Himalaya are retreating rapidly. This retreat means an increase of glacier melt, which greatly affects the riverflow recharged by glacier melt. As previously shown, the Yukon River, Alaska, is one of such examples, and also the Brahmaputra River, Bangladesh, is intensely affected by the glacier melt of Himalaya to Tibet. The gray zone in the below left figure shows the Brahmaputra River basin. The right photo shows our survey in Imja Glacial Lake (lake-level altitude, 5010m a.s.l.) in the Nepal Himalaya. Such glacier lakes are formed and glowing on or around the glacier toes by the retreat of glaciers. Hereafter, we will continue to explore the physical and chemical conditions of such lakes and rivers as affected by the glacier shrinkage continuing through past to future.

Note) Field Training and Management

We have a hut for field observations in the Hiyamizu-sawa stream catchment in the Jozankei hot spring region south of Sapporo. We do training here for field experiments. May undergraduate and graduate students come here to know how the stream is produced, and to study how to measure streamflow and meteorology (April 2012, left and middle photos in the below). The laboratory members remove snow on the hut’s roof every February (February 2006; right photo in the below). After this work, we enjoy bathing ourselves in hot spring water in a Jozankei hotel.

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