This table is created from the Tbl_9.txt and Tbl_10.txt files as prepared by
INSROP Project I.4.2 as part of INSROP Phase 2. The table records refer to the
center point of analysis squares, as included in the Tbl_8 shapefile set, which
is a part of the dataset provided by INSROP Project I.4.2.
Modal orientation and specific length of discontinuities in the ice cover
The tables present distributions of the specific length of discontinuities and
the first mode of their orientation. The calculations were performed by the
50x50 km grid squares, which cover the entire navigation area along the routes
selected in the framework of WP1 Project. The distributions of characteristics in
each square were calculated for the monthly periods for the Laptev,
East-Siberian and Chukchi Seas from October to December and from April to June and for
the Kara Sea from April to May and from November to December.
All calculations were performed on the basis of the database on
discontinuities in the ice cover of the Arctic Seas described below:
The database on the discontinuity characteristics in the ice cover of the
Chukchi, East-Siberian and Laptev Seas for April-June, October-December and the
Kara Sea for April-May and November-December, which is created under the national
programs was used (INSROP WP No. 68-1996, 1.4.1).
The secondary database includes mean monthly values of the following
discontinuity characteristics:
- specific length;
- first orientation mode;
- second orientation mode
- frequency of occurrence of the first modal range;
- frequency of occurrence of the second modal range.
Definitions and calculation algorithms of these characteristics were outlined
in INSROP WP No. 68-1996, 1.4.1. The number of observations included to the
secondary database is presented in Tables 1.1 and 1.2. The Table contains the
number of charts, each of them presenting generalized data for 1 to 5 days.
Table 1.1. Kara Sea
Year Months
April May June October November December
1979 5 6 - - - -
1980 6 5 - - - -
1981 6 6 - - - -
1982 - 3 - - 16 17
1983 6 5 - - - -
1984 - 15 - - 19 -
1986 - - - - - 8
1987 - 10 - - - -
1991 4 1 - - - -
1992 7 - - - - -
1993 9 8 - - 1 6
1994 6 5 - - 7 8
1995 7 5 - - 2 1
1996 8 2 - - - 6
1997 6 - - - - -
All years 70 71 - - 45 46
Table 1.2. Laptev, East-Siberian and Chukchi Seas
Year Months
April May June October November December
1979 5 6 1 - - -
1980 6 6 4 5 5 6
1981 6 6 6 4 5 6
1982 - 7 28 21 29 27
1983 6 5 6 - - -
1984 - 17 1 31 19 -
All years 23 47 46 61 58 39
The generalized characteristics of discontinuities were calculated for the
50x50 km grid squares, which cover the whole of the ship navigation area along the
routes selected within the WP 1 framework. The X-axis of the calculation grid
is parallel to the 130°E meridian and the Y-axis is parallel to the 140°W
meridian. The southward axis directions were assumed to be positive directions. In
the adopted coordinate system the North Pole has the following coordinates
Xp=650 km, Yp=2150 km.
The angles that characterize the discontinuity orientation are read out from
the positive X-axis direction counterclockwise from 0 to 180°.
Path: <NSR_DATA>\icesnow\i_4_2
Table type: DText table.
* Discontinuities in ice - Specific length
3216 records, 8 descriptive fields.
Fields: [<Name>] -- <Alias> (type of field)
[Square_no] -- "Square No." (Numeric, no decimals)
[Month] -- "Month" (Numeric, no decimals)
[Num_obs] -- "Number of observations" (Numeric, no decimals)
Number of discontinuity observations in the given square
[Sl_0_19] -- "0 - 19 m/kmē" (Numeric, 1 decimal)
Frequency of occurrence (%) of the first specific length range
[Sl_20_39] -- "20 - 39 m/kmē" (Numeric, 1 decimal)
Frequency of occurrence (%) of the second specific length range
[Sl_40_59] -- "40 - 59 m/kmē" (Numeric, 1 decimal)
Frequency of occurrence (%) of the third specific length range
[Sl_60_79] -- "60 - 79 m/kmē" (Numeric, 1 decimal)
Frequency of occurrence (%) of the fourth specific length range
[Sl_80_99] -- "80 - 99 m/kmē" (Numeric, 1 decimal)
Frequency of occurrence (%) of the fifth specific length range
Discontinuities in ice - Specific length