Winnipeg Free Press - PRINT EDITION

Anatomy of an ice shove: An uncommon phenomenon

Development of an 'ice tsunami' a matter of probability: researcher

  • Print

It sounds like the stuff of speculative fiction: A wall of ice materializes on a lakeshore within the space of minutes, toppling trees and smashing structures in its path.

But scientists say the ice that devastated Ochre Beach on Dauphin Lake last week was merely an uncommon phenomenon, capable of occurring on the shore of almost any large temperate body of water when sustained high winds send free-floating pieces of ice in motion.

The phenomenon that damaged or destroyed 27 properties on the southern shore of Dauphin Lake on Friday is formally known as an ice shove. Engineers and geographers describe these events as unusual but hardly unknown.

Over the past two months, ice shoves have also destroyed or threatened property in Lake Mille Lacs, Minn., Lake Winnebago, Wis., Alberta Beach, Alta., and Lake Champlain, N.Y.

"This is a fairly normal thing to happen. It's just a matter of timing," said Klaus Hochheim, a research associate at the University of Manitoba's Centre for Earth Observation Science. "It's just getting the right combination of factors. It's all probability."

'This is a fairly normal thing to happen. It's just a matter of timing. It's just getting the right combination of factors. It's all probability'

-- Klaus Hochheim, research associate at the U of M's Centre for Earth Observation Science

The first factor is the presence of ice floating on a large body of water that's in the process of thawing. While solid sheets won't move, any form of free-floating ice -- large blocks or smaller shards -- can be pushed around by wind.

When the wind is strong enough and blows long enough to push that ice in one direction, it can become an ice shove when it hits the shore. The leading edge of this mass of ice will stop, forcing the trailing ice to pile up on top of it.

Given enough momentum, the resulting pile can surge onto the shore.

"It's like a freight train, and you have all these cars at the back end with nowhere to go," said Jay Doering, a University of Manitoba civil engineering professor. "Some have even referred to it as an ice tsunami."

The reason ice shoves may be unfamiliar to Manitobans is this phenomenon likely occurs most often in unpopulated areas and therefore goes unreported. The most wind-exposed sections of Manitoba's largest lakes are largely undeveloped areas such as the beach ridges at Delta Marsh on Lake Manitoba and Netley Marsh on Lake Winnipeg, both of which bear scars from ice shoves.

"We know from previous shoreline damage that ice piling happens regularly," said Minnesota State geologist Harvey Thorleifson, a former Manitoban.

What was unusual about the event at Ochre Beach was the extreme amount of property damage. The final damage tally -- as well as the number of homes and cottages that will wind up being completely lost -- will not be known until the cleanup is completed, said Doug McNeil, deputy minister of Manitoba Infrastructure and Transportation.

The height of the ice pile on Dauphin Lake was also extreme, although ice piles as high as 12 metres have been documented. The low gradient on the shore of all of Manitoba's Great Lakes presents little resistance to the forward progress of ice piles.

While bridge piers are designed to withstand the pressure of moving ice, homes and cottages cannot.

"A wooden house is nothing," Doering said.

In theory, it could be possible to forecast ice shoves by placing transmitters on ice floes, similar to the ones U of M scientists use to monitor the movements of Arctic sea ice.

In practice, however, this would be difficult, Doering surmised.

"You'd need real-time information about the ice and then have to notice someone turned on the wind," he said.

Ice shoves also are not dependent on high water levels. Dauphin Lake stood at 856.1 feet above sea level over the weekend, which is 0.7 feet above the upper target level for the lake and almost five feet below the crest of the 2011 spring flood.

bartley.kives@freepress.mb.ca

default video player to use on WFP

Republished from the Winnipeg Free Press print edition May 14, 2013 A4

History

Updated on Tuesday, May 14, 2013 at 6:19 AM CDT: replaces photos, adds video, adds slideshow

Fact Check

Fact Check

Have you found an error, or know of something we’ve missed in one of our stories?
Please use the form below and let us know.

* Required
  • Please post the headline of the story or the title of the video with the error.

  • Please post exactly what was wrong with the story.

  • Please indicate your source for the correct information.

  • Yes

    No

  • This will only be used to contact you if we have a question about your submission, it will not be used to identify you or be published.

  • Cancel

Having problems with the form?

Contact Us Directly
  • Print

You can comment on most stories on winnipegfreepress.com. You can also agree or disagree with other comments. All you need to do is be a Winnipeg Free Press print or e-edition subscriber to join the conversation and give your feedback.

You can comment on most stories on winnipegfreepress.com. You can also agree or disagree with other comments. All you need to do is be a Winnipeg Free Press print or e-edition subscriber to join the conversation and give your feedback.

Have Your Say

New to commenting? Check out our Frequently Asked Questions.

Have Your Say

Comments are open to Winnipeg Free Press print or e-edition subscribers only. why?

Have Your Say

Comments are open to Winnipeg Free Press Subscribers only. why?

The Winnipeg Free Press does not necessarily endorse any of the views posted. By submitting your comment, you agree to our Terms and Conditions. These terms were revised effective April 16, 2010.

letters

Make text: Larger | Smaller

LATEST VIDEO

Key of Bart: Let It Blow

View more like this

Photo Store Gallery

  • MIKE.DEAL@FREEPRESS.MB.CA 100615 - Tuesday, June 15th, 2010 The Mane Attraction - Lions are back at the Assiniboine Park Zoo. Xerxes a 3-year-old male African Lion rests in the shade of a tree in his new enclosure at the old Giant Panda building.  MIKE DEAL / WINNIPEG FREE PRESS
  • A Canada goose makes takes flight on Wilkes Ave Friday afternoon- See Bryksa’s 30 Day goose a day challenge- Day 09- May 11, 2012   (JOE BRYKSA / WINNIPEG FREE PRESS)

View More Gallery Photos

Poll

Should Canada send heavy military equipment to Ukraine?

View Results

View Related Story

Ads by Google