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Please Excuse the Tidal Bore

Contributing Editor Jordan Schaul recalls yesterday’s tide that brought a surge of water to the Alaska Wildlife Conservation Center campus. It was reminiscent of the great tidal bores that are particularly pronounced during the equinox.

My colleagues and I pretty much rowed in to work yesterday as the tide nearly engulfed our campus. 

A few times a year, like yesterday when the tide was unusually high, we move some of the animals to high ground.  Our other animals typically find refuge at certain elevations within their expansive enclosures. Some remain at higher ground and others like the bears, muskox, bison and moose choose to frolic in the flood plains. The bison, in particular, muck through the cold water and mud to graze as if  it was just another, slightly more interesting day.

"J.B." and "Patrone" wade through a tidal flood near Alaska's Cook Inlet (Photo by Jordan Schaul)

At a maximum height of 3.0 meters and at an average speed of 20 kilometers per hour, a tidal bore is a true tidal wave. It creeps in and before you know it the water is rising all around you.

Yesterday, a particulalryly high tide brought a surge of water that flooded almost every enclosure from the musk ox exhibit to the Sitka black-tailed deer pen.  Yesterday’s influx of water was not the result of a tidal bore per se, but it still brought a great influx of water on to the campus.

Remember that every tidal bore is a tidal wave, but not all tidal activites are actual tidal bores.

At the Alaska Wildlife Conservation Center, the animals seem to take it in stride, although some new to the phenomenon like orphans of the year seem to be a little frazzled. 

On the other hand, our staff always seems to scramble with frantic determination despite the predictability of these tidal events.  And I suppose we should, as tidal influxes can prove to be dangerous to people and wildlife. 

Some surfers and daring swimmers have succumbed to the tidal activity, and on rare occasions curious bystanders get swept into the surging water and drown. 

For wild animals, these natural events can be just as catastrophic, leaving them bewildered if not incapacitated or dead. Scavenging carnivores and raptors can be found feeding in the wake of these tidal bores.

The Turnagain Arm is a glacial fjord and a branch or arm of Cook Inlet which feeds into the Gulf of Alaska.  During equinoctial periods of Spring and Fall, this particular tidal bore reaches an impressive  height. In fact, it has the second highest range of the two tidal bores observed in North America.

The highest range for a bore in North America and in the world for that matter is found at Canada’s Minas Basin–an inlet of the Bay of Fundy which feeds into the Gulf of Maine.

As mentioned, here at the center we are used to the tidal influx of the nearby estaurine waterway. We routinely move animals that may be in danger out of harms way. Some like our adult gizzly bears find this fluctuation in water level–what I consider to be real environmental enrichment–to be a heck of a lot of fun. Others like our yearling bear cubs found the experience a little more unsettling, but everyone turned out just fine. Presumably, next years orphans of the year will experience the bore tide for the first time.

Yearling Kodiak cubs "Taquka" and "Shaguyik" following their first really high tide (Photo by Jordan Schaul)