This table was prepared by Work Package 2 (Box B) as part of INSROP Phase 2
(See Working Paper no. 121). The table includes 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.
Calculation of the direction of total currents
The total currents in the Arctic Seas are formed under the influence of:
- the wind or wind-driven ice drift on the water surface (drift currents);
- a non-uniform distribution of the pressure forces (gradient currents);
- tidal forces (tidal currents).
The contribution of tidal currents to the total current can be neglected due
to their periodical character. The gradient currents are governed, on the one
hand, by the non-uniform distribution of atmospheric pressure and surge
distortions of the level surface and on the other hand, by a non-uniform density field
resulting from non-uniform temperature and salinity fields (density currents).
That is, for calculating the total currents it is necessary to take into account
the atmospheric pressure, wind stress at the water surface and spatial
distribution of water temperature and salinity.
The area of the Arctic Ocean is insufficiently covered with information on the
spatial temperature and salinity distribution to estimate mean current speed
for every month of the year. The variability of the density fields of water of
the Arctic Ocean is comparatively small. Hence it can be suggested that the use
of mean multiyear values of water temperature and salinity for calculating the
density currents will not result in significant errors.
For calculating the field of density currents a widespread dynamic method was
employed (Zubov, 1947). The calculation of wind-driven currents was performed
by means of a modified Davies's model (Davies, 1981).
The calculation of total currents included the following 5 stages:
1. Based on mean multiyear data on sea water temperature and salinity
distribution for the summer and winter seasons and using a dynamic method, the
components of the density current vectors were calculated.
2. Based on the available archive of surface atmospheric pressure fields and
using a three-dimensional barotropic model of ice and ocean dynamics the
components of wind-driven current components were calculated.
3. By means of algebraic summation of the density and wind-driven current
components the components of total currents were calculated.
4. The components of total currents were interpolated to the middles of
sub-segments of the selected routes.
5. Based on the total current components, its direction was calculated
relative to meridian of location.
Path: <NSR_DATA>\oceanriv\workpackage2
Table type: DText table.
* Total currents direction for route S by year and month
396 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)
Total currents direction for route S by year and month