Marine Ecosystem Dynamics Modeling Laboratory

The Arctic Ocean Tides

Previous tidal simulations for the Arctic Ocean were made using structured-grid finite-difference models. Highly referenced works are K&P [1993, 1994 and 1995] and Padman and Erofeeva [2004] (hereafter P&E). K&P developed a two-dimensional (2-D) (vertically-averaged) fully nonlinear barotropic Arctic tidal model with sea ice. With a uniform horizontal resolution of 13.89 km and proper parameterization of the bottom friction, this model provided a reasonable simulation of tidal elevation around the Arctic Ocean and described tidal effects in the sea ice cover. The 2-D assumption and horizontal resolution specified in the K&P model, however, limit its application to resolve the 3-D current features and complex tidal energy exchange between the Arctic and Atlantic Ocean through the Canadian Archipelago. P&E introduced a 2-D linear tidal model (AODIM-the Arctic Ocean Tide Inverse Model) to assimilate the tidal elevation in the Arctic Ocean by computing the inverse solution with all available tidal gauge data. With a horizontal resolution of 5 km, the inverse assimilated tidal elevation shows a better match with observations with smaller overall standard deviation errors. In addition to the 2-D limitation, the linear assumption used in P&E, however, makes this model incapable of resolving residual currents and tide-induced water transports in coastal regions where the interaction of tidal currents with topography is highly nonlinear. Although P&E‘s horizontal grid spacing is ~3 times smaller than that in K&P‘s model, it is still insufficient to resolve the complex geometry within the Canadian Archipelago.

To satisfy the need for an improved model for Arctic Ocean research, we have applied AO-FVCOM to simulate the tides in the barotropic and stratified ice-free Arctic Ocean including Baffin Bay and Hudson Bay/Strait, respectively. Geometrical flexibility of the AO-FVCOM grid allows us to construct meshes without restriction from the meridional convergence of latitude and longitude and any need for “grid rotation”. The singularity at the North Pole is removed by using a spherical-polar stereographic projection nested grid at the pole. The model evaluation was made by comparing it with observational data and presently available tidal models in the Arctic Ocean.

Animation of Semidiurnal Tidal Elevation and Near-surface Tidal Currents

The semidiurnal tides are relatively small in the deep Arctic basins and larger in the Hudson Strait/Bay, southern Baffin Bay, the Denmark Strait west of Iceland, and the White Sea. Numerous amphidromic points occur along (or near to) the coast, indicating that the semidiurnal tidal phases at two very close locations can differ significantly. The M2 tidal motion around Iceland and Spitsbergen Island are characterized by the clockwise round-island wave.

Click the play button on the right to view the full size of the animation

Enlarged View of M2 Tidal Elevation and Near-surface Tidal Current in Canada Archipelago
The Canadian Archipelago consists of numerous islands which are separated by narrow and deep straits. The bathymetry of this region is not well known because of the thick land-fast and pack ice. The model tidal amplitudes vary significantly in this region from a few to over 100 cm. Based on the 78 tide gauge station data, the mean and maximum tidal amplitudes are 41.2 (116.7) cm for M2 and 16.1 (48.1) cm for S2. During spring tides, the maximum tidal elevation of these four constituents exceeds 150 cm, which accounts for about 80% of the observed spring tide (with 96 tidal constituents) in this area.

Click the play button on the right to view the full size of the animation

Animation of Diurnal Tidal Elevation and Near-Surface Tidal Currents
The diurnal tidal amplitudes are roughly 10 times smaller than the semidiurnal tidal amplitudes. The diurnal K1 and O1 tides have similar horizontal patterns in amplitude but different phase distributions. Both diurnal tides are characterized by trains of trapped shelf waves along the Greenland shelfbreak and around Greenland as first described byKowalik and Proshutinsky [1993, 1995], however, FVCOM co-tidal charts reveal additional locations for this phenomenon due to its much higher grid resolution. The model K1 and O1 phases differ significantly in the Greenland Sea and Arctic Basin. For example, around Spitsbergen Island, the K1 tide exhibits one node on the southwest and three nodes on the south side while the O1 tide has no nodes in these two areas. Along the Alaskan coast, the K1 has many nodes while the O1 has only one.

Click the play button on the right to view the full size of the animation

Enlarged View of Diurnal Tidal Elevation and Near-surface Tidal Currents in Canadian Archipelago
Canadian Archipelago is the energy sink area for the diurnal tidal wave propagating from Baffin Bay. The shelf of the Archipelago is characterized with the topographic-intensified tidal waves consisting of a train of eddy-like current flow over the slope.

Click the play button on the right to view the full size of the animation

Enlarged View of Diurnal Tidal Elevation and Near-surface Tidal Currents in Baffin Bay
The shelf of Baffin Bay, western coast of Greenland, is characterized by a slope-internsified coastal wave consisting of trains of “eddies”. Sizes and intensities of these eddies are related to the 3D slope of the shelf.

Click the play button on the right to view the full size of the animation

Tidal Comparison Tables
M2 tide S2 tide O1 tide K1 tide

Posted on January 27, 2014