<Month
This table was created from the ipres-<monthno file as prepared by INSROP
project I.5.8. The table records refer to the routes_c shapefile set, which
includes points defining 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.
Sea ice conditions
Ice concentration, thickness, and pressure are the major direct factors
influencing ship speed. Ice concentration was extracted from AARI 10-day Arctic Ocean
EASE-Grid Sea Ice Observations. These gridded ice charts represent a
reformatting by the National Snow and Ice Data Center (NSIDC), of information contained
in Russian Arctic and Antarctic Research Institute (AARI) digital sea ice
charts. AARI digitized arctic sea ice concentrations and stages of development from
original source charts as part of an international data exchange program. The
AARI source charts were developed from aircraft and satellite observations made
for shipping purposes; they provide extremely detailed information. AARI
encoded these paper charts in digital Sea Ice Grid (SIGRID) format. But due to the
difficulties of vizualizing, extracting, and working with data in SIGRID, NSIDC
is now providing AARI data in NSIDC's Equal Area SSM/I Earth (EASE) Grid. The
EASE-Grid format makes it easier to compare observed ice concentration or ice
types with the same parameters derived from satellite data. AARI sea ice data in
the EASE-Grid North azimutal projection are gridded at a 12.5-km resolution, for
both western (24°W to 110°E) and eastern (105°E to 130°W) sectors. Data extend
from 1953 through 1990, and are available via ftp (URL:
http://www-nsidc.colorado.edu/NSIDC/CATALOG/ENTRIES/nsi-0050.html in compressed tar format.
In the EASE-Grid presentation, the original SIGRID data have been condensed to
five layers: total sea ice concentration, multi-year ice concentration,
first-year ice concentration, and new ice concentration. The fast-ice area is also
shown in the fifth layer. Project I.5.8 have processed this information and
extracted ice concentrations for each point along the transitional routes.
Ice pressure is one of the most important factors in slowing ship speed or
even stopping an icebreaker. Ice compression and its probability along the NSR was
simulated based on atmospheric pressures from 1946 through 1997. Assuming that
the ice drifts along isobars (Zubov, 1945 Doronin, Kheysin, 1977) ice drift
velocities can be calculated using geostrophic relationships, and after that
divergence of the ice drift velocities can be calculated. The ice pressure can be
calculated as follows:
Pi = Ap * div(Vi)
Ap = 0 if div(Vi) < 0
Ap = 10^7 if div(Vi) > 0,
where Pi is ice pressure; Ap is coefficient of ice compression. Simulated ice
pressure was ranged in four groups: No ice pressure ( when div(Vi) < 0 ), low,
medium, and high ice pressure.
Path: <NSR_DATA>\icesnow\i_5_8
Table type: DText table.
* Ice pressure - <month>
335 records, 5 descriptive fields.
Fields: [<Name>] -- <Alias> (type of field)
[No] -- "No" (Numeric, no decimals)
[No pressure] -- "No pressure" (Numeric, 1 decimal)
[Light] -- "Light" (Numeric, 1 decimal)
[Medium] -- "Medium" (Numeric, 1 decimal)
[High] -- "High" (Numeric, 1 decimal)
Ice pressure - <Month>