On the modification of tides in a seasonally ice‐covered sea

Abstract

[1] New observations from eight moorings located in Foxe Basin, Hudson Strait, and Hudson Bay are used to study the seasonal variability of the M 2 tide. Significant seasonal variations of the M 2 surface elevation are found in all these regions and at all seasons. The largest variations occur during winter while both elevation increase (Hudson Strait) and decrease (Hudson Bay, Foxe Basin) are observed. These variations are found recurrent at the stations where multiyear observations are available. Observations from a velocity profiler are consistent with a seasonal damping of the tides because of friction under ice. Numerical simulations with a sea ice-ocean coupled model and realistic forcing qualitatively reproduce most of the features of the observed variability. The simulations show that the winter M 2 variations are essentially caused by the under-ice friction, albeit with strong regional differences. Under-ice friction mostly occurs in a limited region (Foxe Basin) and can account for both increased and decreased M 2 elevations during winter.

Tide‐induced vertical mixing in the Laptev Sea coastal polynya

“…We note that the shear arising from friction may also have a role in modifying the barotropic tidal currents below the ice cover. The freezeup onset usually results in damped tidal flow underneath the ice [e.g., St‐Laurent et al , 2008] (e.g., Figure 17). The under‐ice damping of the barotropic tide contributes to an enhancement in the shear and hence baroclinicity of the tide.…”

“…These waves, known as internal or baroclinic tides, may play an important role in promoting shear instabilities, turbulence, and the mixing of seawater properties [e.g., Padman and Dillon , 1991; D'Asaro and Morison , 1992; Muench et al , 2002]. Furthermore, the ice cover modifies shallow water tidal dynamics due to the additional friction in the boundary layer of the ice‐water interface [e.g., Prinsenberg and Bennett , 1989; Prinsenberg and Ingram , 1991; St‐Laurent et al , 2008]. The under‐ice damping of the tidal flow contributes to an enhancement in the shear and hence baroclinicity of the tide.…”

The effects of tides on the water mass mixing and sea ice in the Arctic Ocean

“…Moreover, tidal amplitudes and phases exhibit strong seasonal variability, first documented for velocity by Howarth [] for European shelf seas and for the AO by St‐Laurent et al . []. Ice conditions and stratification affect the tidal amplitudes, with relative anomalies (defined as the maximum of seasonal or interannual difference divided by mean amplitude) of up to 0.35–0.50 (Figures d and e).…”

Global M2 internal tide and its seasonal variability from high resolution ocean circulation and tide modeling

“…The seasonal cycle, which stems from the changing response of the ocean to the tidal forces, can be much larger and affect both barotropic and baroclinic tides. Barotropic tides can be modified by seasonal changes of stratification [ Kang et al , 2002; Müller , 2012], of sea‐ice coverage [ St‐Laurent et al , 2008], and of meteorological conditions, whereas baroclinic tides are sensitive to stratification and mean flow conditions [ Gerkema et al , 2004; Jan et al , 2008].…”