Under-ice physical oceanographic processes

• Published in: Journal of marine systems 1991, Vol.2 (1), p.143-152
• Main Authors: Prinsenberg, S.J., Grant Ingram, R.
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/0924-7963(91)90020-U

Although the sea ice cover is a stable platform to collect data from, it modifies the velocity and density structure of the underlying water column. The reasons for the seasonal changes of these physical oceanographic parameters need to be understood before changes in biological parameters can be explained. In shallow seas, tidal currents and tidal heights are reduced in amplitude and their phases advanced by the additional ice cover friction. Storm-generated currents with high frequencies are dampened by the ice cover, reducing further the energy for mixing in the surface layer. Offshore, the increase in mixing due to salt rejection from growing ice cover, offsets the reduction of mixing by currents and generally mixed layers are deeper in winter than in summer. In contrast, in coastal waters the larger fresh water flux due mainly to runoff, combined with the reduced current mixing, causes thinner surface mixed layers and larger fresh water plumes in winter. The friction in the ice-water boundary layer causes the rotation of tidal current ellipses to change direction from clockwise at mid-depth to counterclockwise at the surface with maximum currents occurring near the pycnocline. Examples of the physical oceanographic processes causing these vertical and seasonal variations in currents and density structures are shown for Hudson Bay and the Northwest Passage.