Ice shelves: frequently asked questions

Canada's remaining ice shelves are found within the Fiords along the northwest coast of Ellesmere Island in Nunavut, approximately 800km from the North Pole. As of the summer of 2008, these ice shelves are undergoing almost daily changes, with some ice shelves collapsing completely and others calving large ice islands and accompanying ice fragments.

• the Ex-Markham Ice Shelf
• the Ward Hunt Ice Shelf (calved two ice islands between July 22nd and July 24th 2008)
• the Ex-Ayles Ice Shelf (entire shelf calved to form an ice island on August 13, 2005)
• the Milne Ice Shelf
• the Petersen Ice Shelf (has lost over a third of its area since August 2005)
• and the Serson Ice Shelf (60% of the shelf calved off in July 2008)

An Ice Shelf is a floating ice sheet of considerable thickness showing 2 m or more above sea level, attached to the coast. They usually have great horizontal extent and a level or gently undulating surface. Ice shelf growth occurs by annual snow accumulation and also by the seaward extension of land glaciers. Limited areas may be aground. The seaward edge is termed an ice front.

To learn more on how an ice island forms and the factors affecting the drift of large masses of ice please see the Ice Shelves.

An Ice Island is a large piece of floating ice protruding about 5 m above sea level, which has broken away from an Arctic ice shelf. They have a thickness of 30-50 m and an area of from a few thousand square metres to 500 km² or more. They are usually characterized by a regularly undulating surface giving a ribbed appearance from the air.

An Iceberg is a massive piece of ice of greatly varying shape, protruding 5 m or more above sea level, which has broken away from a glacier and which may be afloat or aground. They may be described as tabular,domed, pinnacled, wedged, drydocked or blocky. Sizes of icebergs are classed as small, medium, large and very large.

Note: Ice Island is an Arctic term. In Antarctica, ice islands and calved-off glacier ice are both called icebergs.

• The break-up of Canada’s ice shelves is significant because these ice shelves harbour unique ecosystems. It takes a long time for these ice shelves to form. This ice will not be replaced any time soon.
• Arctic sea ice has experienced enhanced summertime retreats for several years, adding to evidence of significant warming near the North Pole. These break-ups serve as a sentinel to the changing arctic environment.
• Issues may also arise if the ice islands make their way south into navigable waters.

Absolutely. Scientists will measure the thickness, internal structure, and extent of the ice shelves using GPS and radar measurements. They will also install an automated weather station near one of the ice shelves to keep track of air temperatures in the area in real time. Additionally, scientist will collect samples of microbial DNA from some of the ice-dammed or “epishelf” lakes, to assess the biodiversity and community structure of these unique ecosystems. For more information visit the Northern Ellesmere Ice Shelves, Ecosystems, and Climate Impact Website.

Only time will tell. Many variables control the movement of the ice islands including wind, water currents, time of year, the location of the pack ice along Ellesmere Island’s east coast, the Beaufort Gyre, and the size of the ice island fragments, to name just a few.

To find out more information on a specific ice island’s location please go to its on-line tracking page: - Only Ayles has this as of August 25, 2008

• the Ex-Markham Ice Shelf (Collapsed August 2008),
• the Ward Hunt Ice Shelf (calved two ice islands between July 22nd and July 24th 2008),
• the Ex-Ayles Ice Shelf (entire shelf calved to form an ice island on August 13, 2005),
• the Milne Ice Shelf,
• the Petersen Ice Shelf (has lost over a third of its area since August 2005),
• and the Serson Ice Shelf (60% of the shelf calved off in July 2008).

• Distribution of Freshwater - Glaciers and Icefields (Natural Resources Canada)
• Glaciers of North America - GLACIERS OF CANADA; Glaciers of the Arctic Islands; Ellesmere Island Ice Shelves and Ice Islands by Martin O. Jeffries (PDF; 925 KB)
• Vincent, W.F., J.A.E. Gibson, M.O. Jeffries. Ice-shelf collapse, climate change, and habitat loss in the Canadian high Arctic. Polar Record 37 (201): 133-142 (2001).(PDF; 1.25 MB)
• Arctic Ice Shelf Loss Summer 2008

We estimate ice thickness using a number of satellites, highlighted by the Canadian Space Agency RADARSAT-1, MacDonald Dettwiler and Associates LTD RADARSAT-2, as well as US national Oceanic and Atmospheric Administration (NOAA) and European Space Agency (ESA) platforms. We also use aircraft and ship based observations. We collaborate with our international sister Ice Services (e.g. the U.S. National Ice Center and the National Snow and Ice Data Center), as well as academics.

There are 75 to 100 voyages in the Canadian Arctic each summer - this number also includes multiple voyages by the same vessel.

The Canadian Ice Service thanks NASA, The Canadian Space Agency, and MacDonald, Dettwiler and Associates LTD. for providing imagery used on this web site.