Sediment-laden ice in the minas basin: formation, melt rate and acoustic detection

The Bay of Fundy is home to the largest tides in the world. For more than a century, engineers have dreamedof technologies to harness the enormous power of the tides as they surge in and out of the Bay. This goal hasbecome even more compelling in recent years as Canada considers the options for reducing its emissions ofgreenhouse gasses. Tidal power generation is an attractive option because tides, although intermittent, arepredictable, unlike the sun and the wind. Predictability gives tidal power generation an advantage because iteases the incorporation of this renewable and sustainable power source into the electrical grid.The majority of interest in tidal power generation is focussed on development of in-stream tidal turbines.Somewhat like underwater windmills, in-stream tidal turbines rotate as tidal currents flow past them. NovaScotia Power Inc., in 2009, placed a large demonstration turbine in the Minas Passage, and the company isactively involved in trying to understand the risks posed to the environment by the turbine and also the risks to the turbine posed by the environment. An environmental risk posed to turbines by the environment is sediment-laden ice blocks. On the intertidal flats of the Bay in winter, enormous blocks of ice form that incoporate large quantities of sediment into their structure when they form. So much sediment can be incorporated into these blocks that they become denser than sea water. When they release from the flats, the blocks can be transported long distances beneath the sea surface. A strike by a large block could damage or destroy a tidal turbine. Unfortunately, little is known about the formation, release, melting or detection of sediment-laden ice blocks that form on intertidal flats. The goal of the this research is to fill these gaps in understanding by observing the formation and release of ice in the Bay, to study its melt rate in the lab and field, and to develop tools to detectice with acoustics. This work is a partnership between Dalhousie's Department of Oceanography and Nova Scotia Power Inc.