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Title Sea Ice Conditions, and Meteorological and Oceanographic Observations at Saroma-ko Lagoon, Hokkaido, December1998-November 1999

Author(s) SHIRASAWA, Kunio; ISHIKAWA, Masao; TAKATSUKA, Toru; DAIBO, Takaharu; AOTA, Masaaki; FUJIYOSHI,Yoshihiro

Citation 低温科学. 物理篇. 資料集, 58, 45-62

Issue Date 2000-03-24

Doc URL http://hdl.handle.net/2115/18823

Type bulletin (article)

File Information 58_p45-62.pdf

Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP

Kunio SHIRASAWA, Masao ISHIKAWA, TOfU TAKATSUKA, Takaharu DAIBO, Masaaki

AOTA and Yoshihiro FUJIYOSHI 1999 Sea Ice Conditions, and Meteorological and

Oceanographic Observations at Saroma-ko Lagoon, Hokkaido, December 1998 - November

1999. Low Temperature Science, Ser. A., 58. Data Report.

Sea Ice Conditions, and Meteorological and Oceanographic Observations at * ** Saroma-ko Lagoon, Hokkaido, December 1998 - November 1999 '

Kunio SHIRASAWA, Masao ISHIKAWA, Toru TAKATSUKA,

Takaharu DAlBO, Masaaki AOTA

(Institute of Low Temperature Science, Hokkaido University)

and

Yoshihiro FUJIYOSHI

(Saroma Research Center of Aquaculture, Takara, Hokkaido)

(Received December 1999)

Abstract: Long-term meteorological data have been collected at a permanently installed 5-m tower

at a cape of Saroma-ko Lagoon to characterize the general meteorological and climatological

features at the lagoon. Time series of air temperature, wind azimuth and speed, and solar radiation

obtained from the meteorological tower, together with water temperature and salinity obtained from

a mooring station were reported during the period from December 1998 through November 1999.

Freeze-up, breakup and duration of complete ice coverage of the lagoon were also reported.

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Key words: Meteorological and Oceanographic Variables, Sea Ice, Saroma-ko Lagoon

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46 Kunio SHIRASA W A et a1

I. Introduction

Saroma-ko Lagoon located on the Okhotsk Sea coast of Hokkaido is 149.2 km2 in area,

19.5 m in maximum depth and 14.5 m in mean depth (Fig. 1). The lagoon has two inlets which

are connected to the Sea of Okhotsk. About 90 % of the total inflow from the sea to the lagoon

passes through the first inlet opened in 1927. The remainder passes through the second inlet

which was built in December, 1978. The opening of the inlets might have caused changes in the

water mass and current circulation of the lagoon, and in the exchange processes of the water

between sea and lagoon waters. Also, freshwater input which is mainly supplied by two major

rivers causes a reduction of salinity to less than 32 PSU. During winter most of the lagoon

surface is covered with sea ice. The Saroma Research Center of Aquaculture in Sakaeura has

been monitoring ice conditions at the lagoon for thirty five years. It is shown from year-to-year

changes in the duration of complete ice coverage in the lagoon that the trend of variations

appears to decrease for the past ten years (Fig. 2). In winters 1988/89, 1990/91, 1992/93 and

1996/97 the lagoon surface was not completely covered with sea ice. The Saroma Research

Center has been also operating a 5-m meteorological tower at the cape of Kimuaneppu (Fig. 1)

in cooperation with the Sea Ice Research Laboratory of Hokkaido University to characterize the

general meteorological and climatological features at the lagoon. In this report, time series of

meteorological and oceanographic variables during the period from December 1998 through

November 1999 are shown. Time series data of meteorological variables were reported for the

period from December 1991 through December 1992 by Shirasawa et al. (1993), for January

1993 through November 1995 by Shirasawa et al. (1995), for December 1995 through

November 1996 by Shirasawa et al. (1996), for November 1996 through November 1997 by

Shirasawa et al. (1997) and for December 1997 through November 1998 by Shirasawa et al.

(1998).

II. Meteorological and Oceanographic Observations

A location map of the meteorological tower at Kimuaneppu (44°06.08'N 143°56.12'E)

is shown in Fig. 1. A thermometer, a pyrheliometer and a wind sensor were installed at the

heights of 2.9, 4.2 and 5.0 m, respectively, of the 5-m tower set up at the cape of Kimuaneppu in

1989. Instantaneous values of those sensors were recorded at every 10 min and stored in a data

acquisition system (Intelligent Data-Stocker DS-64K2 and LM-30K, Kona Sapporo Co.). The

threshold value for the wind speed was 2 ms· l• Time series of wind speed and azimuth, air

Sea Ice Observations at Saroma-ko Lagoon 47

temperature and solar radiation during the period from December 1998 through November 1999

at each month are shown in Fig. 3. Values for those graphs were obtained at a sampling interval

of 10 min except for stick diagrams of wind vector on the uppermost frame in the figure, which

were produced by data at a sampling interval of one hour.

A mooring system to monitor the water temperature and salinity was installed at the

east side of the central part of the lagoon (44°07.77'N 143°52.17'E) (Fig. 1). The water

temperature and salinity measured at the depth of 3m were collected at sampling intervals of

10-30 min. Time series of water temperature and salinity are shown in Fig. 3, together with the

period of complete ice coverage of the lagoon surface. It appears that the water temperature

reached to almost freezing temperature at mid-January, but there was a time lag between the

freeze-up day of complete ice coverage and the freezing temperature at the central lagoon. In

general, at the beginning of freeze-up of the lagoon, frazil ice is formed at the surface and

destroyed mainly caused by atmospheric forcing. This phenomenon repeats for some period

before ice becomes more stable and the lagoon surface is completely covered with a level ice

sheet.

Shown in Fig. 4 is a time series of wind rose at each month, indicating that the WNW

wind along the Okhotsk Sea coast is predominant during the period from December through

March. The southerly wind gets more frequent from April through November.

Acknowledgments. We wish to thank the Saroma Research Center of Aquaculture in Sakaeura

for their kind offers to use their facilities. Funding for this work was partly obtained from the

Japanese Ministry of Education, Science and Culture (Monbusho) through grants-in-aid for

Scientific Research, from the Japan Society for the Promotion of Science and from the

Sasakawa Scientific Research Grant from the Japan Science Society.

References

Shirasawa, K., Ikeda, M., Takatsuka, T., Ishikawa, M., Aota, M., Ingram, G., Belanger, c., Peltola, P.,

Takahashi, S., Matsuyama, M., Hudier, E., Fujiyoshi, Y., Kodama, Y., and Ishikawa, N.

(1993) Atmospheric and oceanographic data report for Saroma-ko Lagoon of the SARES

(Saroma-Resolute Studies) Project, 1992. Low Temperature Science, Ser. A., 52. Data

Report. 69-167.

Shirasawa, K., Ikeda, M., Ishikawa, M., Takatsuka, T., Aota, M., and Fujiyoshi, Y. (1995)

Meteorological observation data report for Saroma-ko lagoon, Hokkaido, January 1993 -

48 Kunia SHIRASA W A et al

November 1995. Low Temperature Science, Ser. A., 54. Data Report. 19-80.

Shirasawa, K., Ikeda, M., Ishikawa, M., Takatsuka, T., Aota, M., and Fujiyoshi, Y. (1996) Sea ice

conditions and meteorological observations at Saroma-ko lagoon, Hokkaido, December

1995 - November 1996. Low Temperature Science, Ser.A., 55. Data Report. 47-77.

Shirasawa, K., Ikeda, M., Ishikawa, M., Takatsuka, T., Aota, M., and Fujiyoshi, Y. (1997) Sea ice

conditions and meteorological observations at Saroma-ko lagoon, Hokkaido, November

1996 - November 1998. Low Temperature Science, Ser. A., 56. Data Report. 9-34.

Shirasawa, K., Ishikawa, M., Takatsuka, T., Ikeda, M., Daibou, T., Aota, M., and Fujiyoshi, Y. (1998)

Sea ice conditions and meteorological observations at Saroma-ko lagoon, Hokkaido,

December 1997 - November 1998. Low Temperature Science, Ser. A., 57. Data Report.

63-79.

Sea Ice Observations at Saroma-ko Lagoon

Sea of Okhotsk

Fig. 1. A location map of Saroma-ko Lagoon.

o CD o

1965

o 0 o

1970

•

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o 0

o

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Year

1985

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10

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I I I ,

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49

Fig. 2. Freeze-up, breakup and duration of complete ice coverage at Saroma-ko lagoon during the period from 1964 through 1999. The arrow indicates the date of the opening of the second inlet in December 1978.

50

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I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

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Fig. 3. Wind speed and azimuth, solar radiation, air and water temperatures, salinity and duration of complete ice coverage during the period from December 1998 through November 1999.

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Sea Ice Observations at Saroma-ko Lagoon

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52

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Sea Ice Observations at Saroma-ko Lagoon

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Complete Ice Coverage

53

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Sea Ice Observations at Saroma-ko Lagoon 57

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Kunio SHIRASAWA et al

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Sea Ice Observations at Saroma-ko Lagoon

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60 Kunio SHIRASAWA et a1

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Kunia SHIRASAWA et al

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Fig. 4. Wind roses for each month during the period from December 1998 through November 1999 at Kimuaneppu.