Abstract
In the Arctic Ocean, semidiurnal-band processes including tides and
wind-forced inertial oscillations are significant drivers of ice motion,
ocean currents and shear contributing to mixing. Two years (2013-2015)
of current measurements from seven moorings deployed along °E from the
Laptev Sea shelf (~50 m) down the continental slope into
the deep Eurasian Basin (~3900 m) are analyzed and
compared with models of baroclinic tides and inertial motion to identify
the primary components of semidiurnal-band current (SBC) energy in this
region. The strongest SBCs, exceeding 30 cm/s, are observed during
summer in the upper ~30 m throughout the mooring array.
The largest upper-ocean SBC signal consists of wind-forced oscillations
during the ice-free summer. Strong barotropic tidal currents are only
observed on the shallow shelf. Baroclinic tidal currents, generated
along the upper continental slope, can be significant. Their radiation
away from source regions is governed by critical latitude effects: the S
baroclinic tide (period = 12.000 h) can radiate northwards into deep
water but the M (~12.421 h) baroclinic tide is confined
to the continental slope. Baroclinic upper-ocean tidal currents are
sensitive to varying stratification, mean flows and sea ice cover. This
time-dependence of baroclinic tides complicates our ability to separate
wind-forced inertial oscillations from tidal currents. Since the shear
from both sources contributes to upper-ocean mixing that affects the
seasonal cycle of the surface mixed layer properties, a better
understanding of both inertial motion and baroclinic tides is needed for
projections of mixing and ice-ocean interactions in future Arctic
climate states.