Floe size

Technical description - Floe size for route S by year and month

Technical description - Floe size for route N by year and month

General description

These tables were prepared by Work Package 2 (Box B) as part of INSROP Phase 2 (See Working Paper no. 121). The tables include Year, Month and a number of fields with numeric names. These numbers refer to ship route segments included in the Tbl_1 shapefile set, which is a part of the dataset provided by INSROP Project I.4.2. These segments are an extract of the ship routes as defined in INSROP Working paper no. 108 (1998), prepared by Work Package 1 (Box B) as part of INSROP Phase 2.

The calculation of the prevailing size of the ice floes (parameter 12) is based on the data of visual airborne observations of ice floe size distribution (Shilnikov, 1973). The ice floe size distribution is estimated using a scale of 10 units (A handbook..., 1981; International symbols for sea charts and sea ice nomenclature, 1984). These observations were carried out during the 1954 to 1985 period from February to August. In connection with an irregular character of these observations the data are available only in 30% of cases. In the absence of observation data the prevailing floe size can be estimated on the basis of statistical relations with other characteristics.

In the wintertime (October-May) the ice floe size distribution (P) changes from 0 to 5 units and is estimated by a distance between the cracks and leads.

Floe size distribution (P),	Distance between cracks,
(conventional units)	(km)
0	no
1	> 10
2	5-10
3	3-5
4	2-3
5	< 2

The prevailing ice floe size (km) was determined over the winter months on the basis of data on floe size distribution using an empirical formula (Borodachev, 1974):

L = 50 / (1 + 1.85*P + 0.7*Pē) (1)

In the summer (June-September) the ice floe size distribution (P) changes from 5 to 10 units and is estimated by a relative area of the ice floes with a size of more than 0.5 km from 0.1-0.5 km and less than (<0.1 km). In the event the observation data are absent, the ice floe size distribution in the summer can be determined with sufficient accuracy by empirical formula (Appel, Gudkovich, 1977):

P = 56.5 - 0.15*N + R (2),

where N is ice concentration (N = {0,..,10}), R is the ice stage of melting (R = {0,..,5}).

For estimating a typical floe size during this period the integral functions of ice floe size distribution can be used (Gorbunov, Timokhov, 1974):

Phi(r) = (1 / rmē)*(r - rm)ē (3),

here rm is the maximum ice floe size (m) which is connected with the P value (Russian national scale) by a ratio (Appel, Gudkovich, 1977):

rm = 50*Pē - 1200*P + 7000 (4),

Assuming for the most typical ice floe size Phi(r) = 0.5 (this means that 50% of the area of the ice cover is occupied by ice floes with a size rm and more), the prevailing ice floe size (km) can be determined using formulas (3) and (4):

L = 0.0006*rm (5),

Technical description - Floe size for route S by year and month

Table source file name: p12_s.txt

Path: <NSR_DATA>\icesnow\workpackage2

Table type: DText table.

* Floe size for route S by year and month

456 records, 144 descriptive fields.

Fields: [<Name>] -- <Alias> (type of field)

[Year] -- "Year" (Numeric, no decimals)

[Month] -- "Month" (Numeric, no decimals)

[1] -- "1" (Numeric, no decimals)

...

[142] -- "142" (Numeric, no decimals)

Technical description - Floe size for route N by year and month

Table source file name: p12_n.txt

Path: <NSR_DATA>\icesnow\workpackage2

Table type: DText table.

* Floe size for route N by year and month

456 records, 132 descriptive fields.

Fields: [<Name>] -- <Alias> (type of field)

[Year] -- "Year" (Numeric, no decimals)

[Month] -- "Month" (Numeric, no decimals)

[201] -- "201" (Numeric, no decimals)

....

[330] -- "330" (Numeric, no decimals)