It is important for us to know that the spatial scales of the observed submesoscale eddies at high latitudes are close to the mesoscale eddies (2 and 5 km,
respectively). Hence, these two processes cannot be separated and treated independently, by some specific parameterizations valid for each single process, as it is
used at mid-latitudes (see the “gray zone” depicted on Fig. 1).
This fact exhibits the fundamental problem for the AO modeling with the horizontal resolution of about 1 km. From the physical point of view it will be
attractive to model submesoscale eddies explicitly with the model resolution of the
order of the first hundreds of meters, but in this case we will get in the nonhydrostatic regime and should use another numerical model, not to mention the
growing computational cost.
Internal Waves and Tides
The tidal force in the AO is small and the tides are generated by the incident waves,
mainly from the Atlantic. The M 2 semidiurnal tide generates the internal tide of the
same frequency over the slopes of the bottom topography. Singularity exists in the
equation for the normal modes of vertical velocity w [9]:
d
2 w
dz 2 +
N
2
ðzÞ
g
dw
dz
+
N
2
ðzÞ − ω
2
ω 2 − f 2 k
2 w = 0,
where k is the wave vector and ω is the frequency. The propagation of the internal
tide in the form of free wave is bounded by the critical latitude. It means that intense
vertical mixing due to the M 2 internal tide collapse may occur at the critical latitude
∼75° N. This collapse may be enhanced by the bottom topography as well. Theoretical and modeling aspects of non-hydrostatic nature of the ocean dynamics over
steep slopes in the straits were examined in [28].
The other source of internal waves is the decay of mesoscale and submesoscale
eddies. Internal waves may be produced directly by mesoscale eddies, along with
the submesoscale eddies in the same spatial-temporal scales range [12].
Moving sea ice may also generate internal waves in the AO, especially in
summer, when the fresh and warm upper layer exists. These internal waves change
air-ocean drag, and their instability leads to enhanced turbulent mixing at the mixed
layer [11].
As indicated in [2] who analyzed observations over the Yermak Plateau, the
“Dissipation of near-inertial wave energy in the upper ocean is of crucial importance in the Arctic Ocean and must be properly accounted for. If sufficiently elevated, the dissipation can play a significant role in irreversible vertical mixing in the
Arctic Ocean, in the cold halocline layer in particular.” The mixing should be
parameterized and taken into account in the terms of F ⃗ , Q θ , Q S . Thus, mixing (say,
in the popular K-profile parameterization scheme [8]) is specified by background
564
N. G. Iakovlev
respectively). Hence, these two processes cannot be separated and treated independently, by some specific parameterizations valid for each single process, as it is
used at mid-latitudes (see the “gray zone” depicted on Fig. 1).
This fact exhibits the fundamental problem for the AO modeling with the horizontal resolution of about 1 km. From the physical point of view it will be
attractive to model submesoscale eddies explicitly with the model resolution of the
order of the first hundreds of meters, but in this case we will get in the nonhydrostatic regime and should use another numerical model, not to mention the
growing computational cost.
Internal Waves and Tides
The tidal force in the AO is small and the tides are generated by the incident waves,
mainly from the Atlantic. The M 2 semidiurnal tide generates the internal tide of the
same frequency over the slopes of the bottom topography. Singularity exists in the
equation for the normal modes of vertical velocity w [9]:
d
2 w
dz 2 +
N
2
ðzÞ
g
dw
dz
+
N
2
ðzÞ − ω
2
ω 2 − f 2 k
2 w = 0,
where k is the wave vector and ω is the frequency. The propagation of the internal
tide in the form of free wave is bounded by the critical latitude. It means that intense
vertical mixing due to the M 2 internal tide collapse may occur at the critical latitude
∼75° N. This collapse may be enhanced by the bottom topography as well. Theoretical and modeling aspects of non-hydrostatic nature of the ocean dynamics over
steep slopes in the straits were examined in [28].
The other source of internal waves is the decay of mesoscale and submesoscale
eddies. Internal waves may be produced directly by mesoscale eddies, along with
the submesoscale eddies in the same spatial-temporal scales range [12].
Moving sea ice may also generate internal waves in the AO, especially in
summer, when the fresh and warm upper layer exists. These internal waves change
air-ocean drag, and their instability leads to enhanced turbulent mixing at the mixed
layer [11].
As indicated in [2] who analyzed observations over the Yermak Plateau, the
“Dissipation of near-inertial wave energy in the upper ocean is of crucial importance in the Arctic Ocean and must be properly accounted for. If sufficiently elevated, the dissipation can play a significant role in irreversible vertical mixing in the
Arctic Ocean, in the cold halocline layer in particular.” The mixing should be
parameterized and taken into account in the terms of F ⃗ , Q θ , Q S . Thus, mixing (say,
in the popular K-profile parameterization scheme [8]) is specified by background
564
N. G. Iakovlev