A team of scientists and filmmakers embarked on a five-week mission to document the life-cycle of icebergs from their birth to death, hoping to reveal new scientific knowledge in the BBC/Discovery co-production "Operation Iceberg".
The team were looking to understand the forces making icebergs break off their mother glaciers and find out what happens to them once they are afloat on their epic ocean journey.
These pages document the scientific work carried out at Store Glacier, West Greenland, by Alun Hubbard and the crew of SV Gambo during the time spent filming there this summer.
Operation Iceberg begins October 30th on BBC Two and at a later date in the US.
2012 field season
Feel free to download and use these images as you wish, but please acknowledge the source and photographer.
Northern lights at Store Glacier [8.7mb; 15s] Credit: Nolwenn Chauché
Researchers from Aberystwyth and St. Andrews Universities are currently trying to further understand the interactions that occur between the ocean and Greenland's calving ice margins. Various geophysical techniques are being employed, but perhaps the most useful is multibeam sonar, which essentially uses sound pulses to accurately measure the position of the glacier underwater at a given time. To do this at Store Glacier, SV Gambo was used in order to get the instruments as close to the glacier as possible. The results below show the surrounding land and ice surface, the topography of the submarine lanscape immediately in front of the glacier, and the data points reflected off the glacier below sea level.
3D fly-through of the submarine glacier front and topography [4.3mb; 33s] Credit: Richard Bates
By carrying out repeat surveys of the glacier front, in combination with taking measurements of ocean temperature and salinity, ice velocity and time-lapse photography, it is expected that the feedbacks that determine the rate of mass lost at the calving margin will be further understood. Initial results indicate that cold water emanating from the base of the glacier front actively erodes the bottom sections, however it is warm currents entering the fjords that create large undercuts, and eventual instabilities of the ice front. By recognising the processes that are currently occuring, future predictions of mass loss under a changing climate can be more accurately made.
Uummannaq Bay offers an excellent location to study the interactions between the ocean and Greenland's fast-flowing outlet glaciers. The presence of a submarine trough at 450 m depth across the continental shelf allows deep water from Baffin Bay to enter and fill the deeper inner fjords (map right). The deep, warm water found under 450 m (Mortensen, 2011), is thought to produce a high degree of submarine melting of Greenland's glaciers (Rignot 2010; Motyka 2011), and could trigger an instability of the glacier snout as has been suggested for Jakobshavn glacier (Holland, 2008). Moreover the presence of two major outlet glaciers (Lille and Store) inside the same bay allows for comparison between the responses of the glaciers to a similar ocean forcing.
Store Glacier is a fast-flowing outlet with a calving rate of 14±3 km3 per year (Weidick and Bennike, 2007) corresponding to 7% of West Greenland's total annual discharge (Rignot, 2008). The Uummannaq fjords are wide (5km) and deep (>800 m) allowing the deep oceanic water to be stored in large quantities and to come in contact with the glacier fronts. The maximum depth of Store Glacier's calving front of 500 metres plays an important role for the area of contact between the warm and deep water at the ice front.
Birth of an iceberg
Calving is the separation of ice blocks from a glacier's margin. Most calving occurs at margins that stand or float in water: the calved blocks become icebergs. Calving at marine margins accounts for much of the mass loss from ice sheets - more than 90% from Antarctica and about 50% from Greenland (Cuffey & Patterson, 2010)
Birth of an iceberg [20.9mb; 2m22s] Credit: Richard Bates
Icebergs come in a variety of sizes, generally ranging from 1 to 75 metres above sea level. The largest known iceberg reported in the North Atlantic was 168 metres above sea level, making it the height of a 55 storey building. The large iceberg in the video below calved from Store Glacier during the summer of 2012 and floated west into Baffin Bay where it subsequently melted. Its size is estimated to be ~1 million m3.
Icebergs at Store Glacier [19.3mb; 2m04s] Credit: Richard Bates
Nolwenn Chauché, Centre for Glaciology, Aberystwyth University, UK
Cuffey, K.M. and Patterson, W.S.B., 2010: The Physics of Glaciers, 4th edition. Butterworth-Heinemann, Oxford.
Holland, D.M., Thomas, R.H., de Young, B., Ribergaard, M.H. and Lyberth, B., 2008: Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters. Nature Geoscience 1, 659-664.
Mortensen, J., Lennert, K., Bendsten, J. and Rysgaard, S., 2011: Heat sources for glacial melt in a sub-Arctic fjord (Godthåbsfjord) in contact with the Greenland Ice Sheet. Journal of Geophysical Research 116, C01013, doi:10.1029/2010JC006528.
Motyka, R.J., Truffer, M., Fahnestock, M., Mortensen, J., Rysgaard, S. and Howat, I., 2011: Submarine melting of the 1985 Jakobshavn Isbræ floating tongue and the triggering of the current retreat. Journal of Geophysical Research 116, F01007, doi:10.1029/2009JF001632.
Rignot. E., Box, J.E., Burgess, E. and Hanna, E., 2008: Mass balance of the Greenland ice sheet from 1958 to 2007. Geophysical Research Letters 35, L20502, doi:10.1029/2008GL035417.
Rignot, E., Koppes, M. and Velicogna, I., 2010: Rapid submarine melting of the calving faces of West Greenland glaciers. Nature Geoscience 3, 187-191.
Weidick, A. and Bennike, O., 2007: Quaternary glaciation history and glaciology of Jakobshavn Isbrae and the Disko Bugt region, West Greenland: a review. Geological Survey of Denmark and Greenland Bulletin 14, 1-78.