One of the remarkable features of the coastline of northern Ellesmere Island, Nunavut, is the presence of a series of ice shelves: 10-50 m-thick ice floating on the sea and attached to land. The ice is mostly the result of slow accretion of sea ice, and the present features are believed to have started to form some 4000 years ago. The early explorers in the region (Nares Expedition in 1875/76 and Peary Expedition in 1906) noted an extensive fringe of this thick,
undulating ice that extended all the way along the northern Ellesmere coastline. We estimate that about 90% of this was lost over the course of the 20th century, and by the year 2000 all that remained of this continuous fringe was a series of six ice shelves located in bays or at the seaward end of fiords (Vincent et al. 2001). This remaining ice has undergone additional break-up and loss over the last few years. In 2001 the largest of these features, the Ward Hunt Ice Shelf, cracked in two and released 3 billion tonnes of freshwater that were dammed behind it in the Disraeli Fiord epishelf lake (Mueller et al. 2003). The Ayles Ice Shelf moved 5 km seaward in the 1960s but was recemented in place by the formation of multiyear landfast sea ice over the subsequent decades (Jeffries 1986). In August 2005 during a period of record minimum sea ice and record maximum temperatures, the Ayles Ice Shelf broke out of the fiord and over the next year moved about 50 km to the west as an ice island.
The six ice shelves along the northern Ellesmere coastline, High Arctic Canada, in 2004 (Mueller et al. 2006). The Ayles Ice Shelf broke out in August 2005.
The Ellesmere ice shelves are now known to be a rich habitat for microbial communities, supporting an estimated total microbial biomass of over 10,000 tonnes dry weight (Mueller et al. 2006). The microbes grow as benthic mats and films in meltwater ponds that form in the long troughs associated with the undulations in the ice. These ice-mats are dominated by brightly pigmented, filamentous cyanobacteria, but also contain many other biota: viruses, bacteria, micro-algae and other eukaryotic protists, and even microinvertebrates such as nematodes and flatworms. These microscopic worlds are providing insights into how life may have survived and evolved during periods of extreme cold during the Precambrian glaciations (Vincent et al. 2004a,b).
The Ward Hunt Ice shelf Showing the frozen meltwater ponds associated with its undulating surface topography.
Sampling the brightly pigmented microbial mats on the Markham Ice Shelf (Vincent et al. 2004a).
References:
Jeffries, M.O. 1986. Ice island calvings and ice shelf changes, Milne Ice Shelf and Ayles Ice Shelf, Ellesmere Island, NWT. Arctic 39: 15-19.
