This interesting Wikipedia article discusses the various types of sea ice and informs us that pack ice is largely formed from ocean water that freezes away from land and drifts together to form large masses of ice. Most winters (though that of 2009-2010 was an exception), large parts of the Gulf of St Lawrence are covered by pack ice, which often extends out into the Cabot Strait and drifts southward to the waters off the northeastern coast of Cape Breton. When this ice begins to break up, much of it gets pushed by winds and tides into Cape Breton’s coastal waters. In the French colonial days when winters were far more severe than they are today, this nearly constant interference with winter navigation caused the French to eventually abandon the fine defensive position of their initial Fort Sainte-Anne near Port Dauphin (now Englishtown) for what proved in the end to be the much less defensible, though ice-free, harbour at Louisbourg.¹
Anyone who has crossed the open waters of the narrow outlet of St Anns Harbour that flows north into St Anns Bay (at the far left of the photo above) on the Englishtown ferry has likely observed just how fast the currents run through this relatively small aperture. The photographer reports that, “Between winds and tides there are a lot of currents moving in many directions in this area of the channel. You also get small whirlpools created by the tidal currents hitting the normal currents and currents created by the wind. This action can sometimes cause the ice to spin as it travels in or out of the channel.” The open water between the stacks of ice results from the way the pack ice is forced about by these currents.
This intriguing view looks toward the Englishtown shore from near the ferry landing on the Jersey Cove side of the channel and shows some of the fantastic shapes of the pack ice that the winds and tides push up from St Anns Bay against the normal flow through these waters back into St Anns Harbour.
¹ See the first chapter and the initial part of the second chapter of Robert J. Morgan’s account of this era in Rise Again! The Story of Cape Breton Island, Book One for an extended discussion of the broader context which led to taking this decision.↩