ABSTRACT

Moored instruments, consisting of Acoustic Doppler Current Profilers (ADCPs) to measure the water and ice velocities, and Ice Profiling Sonars (IPSs) to measure ice drafts, were deployed along the Northumberland Strait, in line with one of the bridge piers during the winter of 2000. The instruments were deployed in part to support measurements of ice forces on bridge piers being collected by the National Research Council. Current and wind forcing move the mobile pack ice at the bridge. Tidal currents moved the ice back and forth past the bridge piers while a mean ice drift of 10–15cm/s continually moved the pack ice to the southeast. Ice draft observations demonstrated that the ice regime at the bridge was dominated by ice rubble with keel-like events as deep as 8 meters. Furthermore, the great variability in ice draft distributions indicates that the pack ice properties were more dependent on the dynamic processes the pack ice had experienced rather than simply the thermodynamic ice growth process.

INTRODUCTION

From January until April of 2000, field programs were conducted to study pack ice properties in the southern Gulf of St. Lawrence and Northumberland Strait. Ice drift, ice draft and ocean current data were collected with moored Acoustic Doppler Current Profilers (ADCP) and Ice Profiling Sonars (IPS) (Belliveau et al, 2001). The instruments were deployed south of Prince Edward Island (P.E.I.), near the bridge piers of the 13km-long Confederation Bridge linking the Island with Canada's mainland (Fig.1). The data were gathered, in part to support a study of ice forces on bridge piers done by the National Research Council (Kubat et al., 2000). The bridge is located at the narrowest and shallowest portion of the Northumberland Strait, where currents are high. Ice in the middle of the Strait is generally not locally grown.

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