Voinov and Zakharchuk: Large-Scale Variations of Sea Level in the Laptev Sea
35
in Arctic seas on the basis of data for the summer period, and they also indicated a similar fact.
It will be coordinated with theoretical representations according to which the shelf waves are
always distributed in cyclonical direction with reference to the open ocean (Efimov et ai, 1985).
Provided that limit of the phase speed for the shelf waves is equal in magnitude to c <:::,j. L
and width of the shelf (L) in the Laptev Sea varies from 400 up to 800 kms and j (the inertial
frequency) from 1.380 . 10- 4 up to 1.432.10- 4 radls, we shall obtain that c <:::, 9 + 18 m/s. The
calculated phase speeds of the shelf waves (Table 3) do not exceed this limit, so it does not
contradict to our hypothesis.
In the zonal low-frequency waves, two directions of currents, 0° and 180°, must prevail.
Two-dimensional probability density of vectors of current velocities will have two modes in
this case. Since the shelf waves in the Laptev Sea propagate eastward, the two-dimensional
probability density of the vectors of current velocities should be similar to those of the zonal
low- frequency waves.
Estimations of the two-dimensional probability densities of the daily mean vectors of current
velocity at moorings obtained in different years (1959-1980 ) in the open part of the Laptev Sea
showed in most cases a two-mode structure (Ipatov, 1997, unpublished data). This result to
some extent confirms wave nature of current perturbations for the synoptical scale.
Conclusions
The maximum variance of large-scale level variations in the Laptev Sea is associated with the
sea level variations for the periods less than I year (from 66 up to 81 % of the total variance).
13 to 24% of the total variance acccount for the long-period tides and 5 - 18% of the variance
is due to interannual variability. The sea level oscillations in the synoptical range are a nonstationary modulated process. Intensity of the oscillations of the synoptical scale reveals strong
interannual and innerannual variability. This variability is increases landwards, reaching the
maximum quantity at Dunay and Tiksi stations. In most of the cases the maximum of the
intensity of the oscillations for the synoptic scale occurs in autumn- winter months.
The observed nodal tide is not in agreement with the equilibrium theory. Investigations for
other seas are necessary for further evidence. The values of the admittance amplitudes and
phases of the monthly tide deviate much from the equilibrium tide. The observed amplitude and
phase of the fortnightly tide deviates from the equilibrium one as in the case of the tide Mm.
The mean admittance amplitude of the tide Mf in the Laptev Sea is equal to 0.50. The observed
mean amplitude tide Mm in the Laptev Sea is 1.45 times greater than the mean equilibrium
amplitude. Apparently the resonant conditions are observed in the Laptev Sea at a monthly
period.
The level variations in the synoptical range represent predominantly progressive waves in the
range of less than 60 days. Propagation speeds of these waves for the periods 5 - 46 days has
shown that their magnitudes (1.3 - 5.2 rnIs) correspond to the phase speeds of the shelf waves.
The wave lengths are comparable with spatial scales of atmospheric cyclones.
Two-dimentsional distribution density of current vectors for the years 1959 - 1980 confirms a
wave nature for synoptical scale currents.
References
Alekseyev, G.V. and N.V. Mustafin (1972) On statistical structure of non-periodic fluctuations of a level of the
Arctic seas (in Russian). Prabl. Arktik., 40, 13- 22.
Bannov-Baykov, Yu.L. (1974) About statistical structure of the large-scale sea level variations in high latitudes
35
in Arctic seas on the basis of data for the summer period, and they also indicated a similar fact.
It will be coordinated with theoretical representations according to which the shelf waves are
always distributed in cyclonical direction with reference to the open ocean (Efimov et ai, 1985).
Provided that limit of the phase speed for the shelf waves is equal in magnitude to c <:::,j. L
and width of the shelf (L) in the Laptev Sea varies from 400 up to 800 kms and j (the inertial
frequency) from 1.380 . 10- 4 up to 1.432.10- 4 radls, we shall obtain that c <:::, 9 + 18 m/s. The
calculated phase speeds of the shelf waves (Table 3) do not exceed this limit, so it does not
contradict to our hypothesis.
In the zonal low-frequency waves, two directions of currents, 0° and 180°, must prevail.
Two-dimensional probability density of vectors of current velocities will have two modes in
this case. Since the shelf waves in the Laptev Sea propagate eastward, the two-dimensional
probability density of the vectors of current velocities should be similar to those of the zonal
low- frequency waves.
Estimations of the two-dimensional probability densities of the daily mean vectors of current
velocity at moorings obtained in different years (1959-1980 ) in the open part of the Laptev Sea
showed in most cases a two-mode structure (Ipatov, 1997, unpublished data). This result to
some extent confirms wave nature of current perturbations for the synoptical scale.
Conclusions
The maximum variance of large-scale level variations in the Laptev Sea is associated with the
sea level variations for the periods less than I year (from 66 up to 81 % of the total variance).
13 to 24% of the total variance acccount for the long-period tides and 5 - 18% of the variance
is due to interannual variability. The sea level oscillations in the synoptical range are a nonstationary modulated process. Intensity of the oscillations of the synoptical scale reveals strong
interannual and innerannual variability. This variability is increases landwards, reaching the
maximum quantity at Dunay and Tiksi stations. In most of the cases the maximum of the
intensity of the oscillations for the synoptic scale occurs in autumn- winter months.
The observed nodal tide is not in agreement with the equilibrium theory. Investigations for
other seas are necessary for further evidence. The values of the admittance amplitudes and
phases of the monthly tide deviate much from the equilibrium tide. The observed amplitude and
phase of the fortnightly tide deviates from the equilibrium one as in the case of the tide Mm.
The mean admittance amplitude of the tide Mf in the Laptev Sea is equal to 0.50. The observed
mean amplitude tide Mm in the Laptev Sea is 1.45 times greater than the mean equilibrium
amplitude. Apparently the resonant conditions are observed in the Laptev Sea at a monthly
period.
The level variations in the synoptical range represent predominantly progressive waves in the
range of less than 60 days. Propagation speeds of these waves for the periods 5 - 46 days has
shown that their magnitudes (1.3 - 5.2 rnIs) correspond to the phase speeds of the shelf waves.
The wave lengths are comparable with spatial scales of atmospheric cyclones.
Two-dimentsional distribution density of current vectors for the years 1959 - 1980 confirms a
wave nature for synoptical scale currents.
References
Alekseyev, G.V. and N.V. Mustafin (1972) On statistical structure of non-periodic fluctuations of a level of the
Arctic seas (in Russian). Prabl. Arktik., 40, 13- 22.
Bannov-Baykov, Yu.L. (1974) About statistical structure of the large-scale sea level variations in high latitudes