Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier.Essentials of Geology, 3rd edition, Stephen Marshak It is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of

ice Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...

from a

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

, iceberg, ice front, ice shelf, or crevasse. The ice that breaks away can be classified as an iceberg, but may also be a growler, bergy bit, or a crevasse wall breakaway.Glossary of Glacier Terms
Ellin Beltz, 2006. Retrieved July 2009. Calving of glaciers is often accompanied by a loud cracking or booming sound before blocks of ice up to high break loose and crash into the water. The entry of the ice into the water causes large, and often hazardous waves. The waves formed in locations like Johns Hopkins Glacier can be so large that boats cannot approach closer than . These events have become major tourist attractions in locations such as

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

. Many glaciers terminate at oceans or freshwater lakes which results naturallyARCTIC, Vol. 39, No. 1 (March 1986) P. 15-19, ''Ice Island Calvings and Ice Shelf Changes, Milne Ice Shelf and Ayles Ice Shelf, Ellesmere Island, N.W.T.''
, Martin O. Jeffries, 1985, University of Calgary. Retrieved 18 July 2009. with the calving of large numbers of icebergs. Calving of

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

's glaciers produce 12,000 to 15,000 icebergs each year alone. Calving of ice shelves is often preceded by a rift. An ice shelf in steady state calves at roughly the same rate as the influx of new ice, and calving events may occur on sub-annual to decadal timescales to maintain an overall average mean position of the ice shelf front. When calving rates exceed the influx of new ice, ice front retreat occurs, and ice shelves may grow smaller and weaker.

Causes

It is useful to classify causes of calving into first, second, and third order processes. First order processes are responsible for the overall rate of calving at the glacier scale. The first order cause of calving is longitudinal stretching, which controls the formation of crevasses. When crevasses penetrate the full thickness of the ice, calving will occur. Longitudinal stretching is controlled by friction at the base and edges of the glacier, glacier geometry and

water pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and ev ...

at the bed. These factors, therefore, exert the primary control on calving rate. Second and third order calving processes can be considered to be superimposed on the first order process above, and control the occurrence of individual calving events, rather than the overall rate. Melting at the waterline is an important second order calving process as it undercuts the subaerial ice, leading to collapse. Other second order processes include tidal and seismic events, buoyant forces and melt water wedging. When calving occurs due to waterline melting, only the subaerial part of the glacier will calve, leaving a submerged 'foot'. Thus, a third order process is defined, whereby upward buoyant forces cause this ice foot to break off and emerge at the surface. This process is extremely dangerous, as it has been known to occur, without warning, up to from the glacier terminus.

Calving law

Though many factors that contribute to calving have been identified, a reliable predictive mathematical formula is still under development. Data is currently being assembled from ice shelves in

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

and Greenland to help establish a 'calving law'. Variables used in models include properties of the ice such as thickness, density,

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

c-axis fabric
and impurity loading. A property known as 'ice front normal spreading stress' may be of key importance, despite it not normally being measured. There are currently several concepts upon which to base a predictive law. One theory states that the calving rate is primarily a function of the ratio of tensile stress to vertical compressive stress, i.e., the calving rate is a function of the ratio of the largest to smallest principle stress. Another theory, based on preliminary research, shows that the calving rate increases as a power of the spreading rate near the calving front.

Major calving events

Filchner-Ronne Ice Shelf

In October, 1988, the A-38 iceberg broke away from the Filchner-Ronne Ice Shelf. It was about 150 km x 50 km. A second calving occurred in May 2000 and created an iceberg 167 km x 32 km.

Amery Ice Shelf

A major calving event occurred in 1962 to 1963, resulting in an iceberg approximately 10,000 sq km in size. In the 1990's scientists identified an exceptionally large rift forming a section at the front of the shelf. Expecting a calving event was imminent, the section was informally named the 'loose tooth". After over 2 decades of anticipation and study, the "tooth" finally calved on Sept. 26, 2019, forming a 1,636 sq km (632 sq mi), 315 billion tonne iceberg known as D-28

Ward Hunt Ice Shelf

The largest observed calving of an ice island happened at Ward Hunt Ice Shelf. Sometime between August 1961 and April 1962 almost of ice broke away.

Ayles Ice Shelf

In 2005, nearly the entire shelf calved from the northern edge of

Ellesmere Island Ellesmere Island (; ) is Canada's northernmost and List of Canadian islands by area, third largest island, and the List of islands by area, tenth largest in the world. It comprises an area of , slightly smaller than Great Britain, and the total ...

. Since 1900, about 90% of Ellesmere Island's ice shelves have calved and floated away. This event was the biggest of its kind for at least the past 25 years. A total of of ice was lost in this event. The largest piece was in area, which is slightly larger than the City of

Manhattan Manhattan ( ) is the most densely populated and geographically smallest of the Boroughs of New York City, five boroughs of New York City. Coextensive with New York County, Manhattan is the County statistics of the United States#Smallest, larg ...

Larsen Ice Shelf

This large ice shelf, located in the

Weddell Sea The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha C ...

, extending along the east coast of

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martin in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica. ...

, consists of three segments, two of which have calved. In January 1995, the Larsen A Ice Shelf containing of ice thick calved and disintegrated. Then the Larsen B Ice Shelf calved and disintegrated in February 2002.

Jacobshavn Isbræ Glacier

Also known as the Ilulissat Glacier or Sermeq Kujalleq in western Greenland, in an ongoing event, 35 billion tonnes of icebergs calve off and pass out of the fjord every year. Photographer James Balog and his team were examining this glacier in 2008 when their cameras caught a piece of glacier the size of

Lower Manhattan Lower Manhattan, also known as Downtown Manhattan or Downtown New York City, is the southernmost part of the Boroughs of New York City, New York City borough of Manhattan. The neighborhood is History of New York City, the historical birthplace o ...

fall into the ocean. The calving event lasted for 75 minutes, during which time the glacier retreated a full mile across a calving face three miles (five kilometers) wide. Adam LeWinter and Jeff Orlowski captured this footage, which is featured in the film '' Chasing Ice''.

Glacier surfing

First conceived in 1995 by Ryan Casey while filming for

IMAX IMAX is a proprietary system of High-definition video, high-resolution cameras, film formats, film projectors, and movie theater, theaters known for having very large screens with a tall aspect ratio (image), aspect ratio (approximately ei ...

, this sport involves a surfer being towed into range by a jet ski and waiting for a mass of ice to calve from a glacier. Surfers can wait for several hours in the icy water for an event. When a glacier calves, the mass of ice can produce waves. Rides of lasting for one minute can be achieved.

References

External links

University of Chicago article"Chasing Ice" captures largest glacier calving ever filmed
{{glaciers Glaciers Glaciology Articles containing video clips Water ice