Tidal forcing on sea-ice drift and deformation in the western Weddell Sea in early austral summer, 2004

Abstract

Sea-ice drift and deformation in the western Weddell Sea in early austral summer of 2004 are characterised using in situ data from a meso-scale array of 24 drifting ice buoys. Horizontal GPS-derived position measurements are available from drifting buoys deployed as part of the Ice Station POLarstern [ISPOL] experiment for 26 days during late November and December 2004, at various temporal resolutions and spatial accuracies. These data form the basis for sea-ice velocity and deformation measurements across the meso-scale ISPOL array and at two remote sites. Analysis of the sea-ice velocities reveals coherence for sea-ice drift at separations of less than 70 km; and a correlation length scale of 60 km. Within the limits of the ISPOL array, at larger separations zonal ice drift remains correlated, while meridional ice drift becomes uncorrelated. This together with the east-west gradient in ice velocities indicates the influence of bathymetry, via tidal forcing, on local dynamic processes. Atmospheric forcing also contributes to the sea-ice drift: about 40% of variability in the sea-ice velocity is explained by changes in wind velocity, which is significantly less than other studies have found for the region during winter. Sea-ice deformation has been derived for the overall array and four sub-arrays. There appeared to be no spatial scale dependency of ice deformation, although considerable spatial variability was observed between sub-arrays. The net divergence of the ISPOL array was in excess of 30%, with the largest contributions to divergence being from the southern section and along the eastern side of the overall ISPOL array. Temporal variability for all deformation parameters is dominated by high-frequency (sub-daily) processes, namely tidal forcing and inertial response. Low-frequency (multiple days) processes, including atmospheric changes, played a secondary role in forcing sea-ice deformation during ISPOL. r

Assessment of radiation forcing data sets for large-scale sea ice models in the Southern Ocean

“…The Polarstern was anchored to a floe composed of patches of thick and thin FY embedded with a matrix of second-year ice (SY) and drifted within 67-691S and 54-561W. The drift was generally to the North with occasional diversions southward (Heil et al, 2008). Modal total thickness (e.g., snow+ ice) ranged from 1.2-1.3 to 2.4-2.9 m for FY and SY ice, respectively Tison et al, 2008).…”

“…First, increasing horizontal model resolution improves simulation of the ice edge on some locations, but does not explain all simulation errors (Mathiot, 2009). Second, the effects of velocity divergence, formation of frazil/pancake ice and of snow cover (flooding, superimposed and snow ice formation) are more prevalent in the Antarctic than in the Arctic (e.g., Heil and Allison, 1999;Nicolaus et al, 2006;Heil et al, 2008;Lewis et al, 2011), and because these processes are not completely understood, they may not be adequately represented in current models. Finally, there are uncertainties associated with the forcing that are an important issue: at this stage, they complicate model physics improvements.…”

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

“…In a similar way, the parameterization of tides in the Arctic Ocean Model Intercomparison Project (AOMIP) led to a more realistic ventilation of ocean heat through atmosphere-ocean exchanges in tidal leads [Holloway and Proshutinsky, 2007]. Heil et al [2008] also studied the drift and deformation of sea ice in the Weddell Sea using an array of drifting ice buoys. The sea ice velocity variance over the continent shelf was found to be dominated at semidiurnal frequencies by tides rather than inertial response.…”

Satellite-Based Sea Ice Navigation for Prydz Bay, East Antarctica

“…Severe ice conditions can significantly reduce the progress or even beset a vessel. The variability of sea ice conditions, especially near the Antarctica coast, is often complex and transient as it is driven by synoptic atmospheric forcing or changing ocean currents, then modified by ice compression, divergence, shear or a mixture of all forms of deformation [1,2]. In recent years, several vessels have been delayed or entrapped in the Antarctic sea ice.…”