![Antarctica map indicating Antarctic Peninsula](https://upload.wikimedia.org/wikipedia/commons/1/19/Antarctica_map_indicating_Antarctic_Peninsula.JPG)
The Larsen Ice Shelf is a long
ice shelf
An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The b ...
in the northwest part of 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 ...
, extending along the east coast of the
Antarctic Peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín 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 Antarctic ...
from
Cape Longing
Cape Longing () is a rocky cape on the east coast of Graham Land, Antarctica, forming the south end of a large ice-covered promontory which marks the west side of the south entrance to Prince Gustav Channel. It was discovered by the Swedish Antarc ...
to
Smith Peninsula. It is named after Captain
Carl Anton Larsen
Carl Anton Larsen (7 August 1860 – 8 December 1924) was a Norway, Norwegian-born Whaling, whaler and Antarctic explorer who made important contributions to the exploration of Antarctica, the most significant being the first discovery of fos ...
, the master of the Norwegian whaling vessel ''
Jason
Jason ( ; ) was an ancient Greek mythological hero and leader of the Argonauts, whose quest for the Golden Fleece featured in Greek literature. He was the son of Aeson, the rightful king of Iolcos. He was married to the sorceress Medea. He w ...
'', who sailed along the ice front as far as 68°10' South during December 1893. In finer detail, the Larsen Ice Shelf is a series of shelves that occupy (or occupied) distinct
embayment
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a narr ...
s along the coast. From north to south, the segments are called Larsen A (the smallest), Larsen B, and Larsen C (the largest) by researchers who work in the area.
Further south, Larsen D and the much smaller Larsen E, F and G are also named.
The breakup of the ice shelf since the mid-1990s has been widely reported, with the collapse of Larsen B in 2002 being particularly dramatic. A large section of the Larsen C shelf broke away in July 2017 to form an iceberg known as
A-68.
The ice shelf originally covered an area of , but following the disintegration in the north and the break away of iceberg A-17, it now covers an area of .
Ice shelf
![Antarctic shelf ice hg](https://upload.wikimedia.org/wikipedia/commons/b/b2/Antarctic_shelf_ice_hg.png)
The collapse of Larsen B has revealed a thriving
chemotrophic ecosystem 800 m (half a mile) below the sea. The discovery was accidental.
U.S. Antarctic Program
The United States Antarctic Program (or USAP; formerly known as the United States Antarctic Research Program or USARP and the United States Antarctic Service or USAS) is an organization of the United States government which has presence in the A ...
scientists were in the north-western
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 ...
investigating the sediment record in a deep glacial trough of roughly (twice the size of
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
or
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
).
Methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
and
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
associated with
cold seep
A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the see ...
s is suspected as the source of the chemical energy powering the ecosystem. The area had been protected by the overlying ice shelf from debris and sediment which was seen to be building up on the white microbial mats after the breakup of the ice shelf. Clams were observed clustered about the vents.
The former Larsen A region, which was the farthest north and was just outside the
Antarctic Circle
The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. S ...
, had previously broken up in the middle of the present
interglacial
An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...
and reformed only about 4,000 years ago. The former Larsen B, by contrast, had been stable for at least 10,000 years.
The ice of the shelf is renewed on a much shorter time-scale and the oldest ice on the current shelf dates from only two hundred years ago. The speed of
Crane Glacier
Crane Glacier (), is a narrow glacier which flows in an east-northeasterly direction along the northwest side of Aristotle Mountains to enter Spillane Fjord south of Devetaki Peak, on the east coast of the Antarctic Peninsula. Sir Hubert Wil ...
increased threefold after the collapse of the Larsen B, likely due to the removal of a buttressing effect of the ice shelf.
Data collected in 2007 by an international team of investigators through satellite-based radar measurements suggests that the overall ice-sheet mass balance in Antarctica is increasingly negative.
[Perlman, David (2008) "Antarctic Glaciers Melting More Quickly" San Francisco Chronicle (26 January) p. A2]
online
/ref>
Breakup
The Larsen disintegration events were unusual by past standards. Typically, ice shelves lose mass by iceberg
An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The ...
calving and by melting at their upper and lower surfaces. The disintegration events were linked by ''The Independent
''The Independent'' is a British online newspaper. It was established in 1986 as a national morning printed paper. Nicknamed the ''Indy'', it began as a broadsheet and changed to tabloid format in 2003. The last printed edition was publis ...
'' newspaper in 2005 to ongoing climate warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
in the Antarctic Peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín 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 Antarctic ...
, about 0.5˚C (0.9˚F) per decade since the late 1940s.[Connor, Steve (2005) "Ice shelf collapse was biggest for 10,000 years since Ice Age" ''The Independent,'' London (4 August)]
online
/ref> According to a paper published in ''Journal of Climate'' in 2006, the peninsula at Faraday station warmed by 2.94˚C (5.3˚F) from 1951 to 2004, much faster than Antarctica as a whole and faster than the global trend; anthropogenic
Anthropogenic ("human" + "generating") is an adjective that may refer to:
* Anthropogeny, the study of the origins of humanity
Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows:
* Human im ...
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
causes this localized warming through a strengthening of the winds circling the Antarctic.
Larsen A
The Larsen A ice shelf disintegrated in January 1995.
Larsen B
From 31 January 2002 to March 2002 the Larsen B sector partially collapsed and parts broke up, of ice thick, an area comparable to the US state of Rhode Island
Rhode Island (, like ''road'') is a U.S. state, state in the New England region of the Northeastern United States. It is the List of U.S. states by area, smallest U.S. state by area and the List of states and territories of the United States ...
. In 2015, a study concluded that the remaining Larsen B ice-shelf would disintegrate by 2020, based on observations of faster flow and rapid thinning of glaciers in the area.
Larsen B was stable for at least 10,000 years, essentially the entire Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
period since the last glacial period. By contrast, Larsen A was absent for a significant part of that period, reforming about 4,000 years ago.
Despite its great age, the Larsen B was clearly in trouble at the time of the collapse. With warm currents eating away the underside of the shelf, it had become a "hotspot of global warming". It broke over a period of three weeks or less, with a factor in this fast break-up being the powerful effects of water; ponds of meltwater formed on the surface during the near 24 hours of daylight in the summertime, flowed down into cracks and, acting like a multitude of wedges, levered the shelf apart. Other likely factors in the break-up were the higher ocean temperatures and the decline of the ice of the peninsula.
In the austral winter of 2011, a large expanse of sea ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
formed over the embayment
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a narr ...
that was once covered by the land-fast shelf of fresh-water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
glacial ice
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
of Larsen B. This enormous ice pack
An ice pack or gel pack is a portable bag filled with water, refrigerant gel, or liquid, meant to provide cooling. They can be divided into the reusable type, which works as a thermal mass and requires freezing, or the instant type, which cools ...
persisted through January 2022 when it suddenly broke-up over the course of a few days, "taking with it a Philadelphia-sized piece of the Scar Inlet Ice Shelf," according to NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
scientists examining images from the Terra
Terra may often refer to:
* Terra (mythology), primeval Roman goddess
* An alternate name for planet Earth, as well as the Latin name for the planet
Terra may also refer to: Geography Astronomy
* Terra (satellite), a multi-national NASA scienti ...
and Aqua
Aqua is the Latin word for water. It is used in many words which relate to water, such as aquatic life. In English, it may also refer to:
Arts
* Aqua (color), a greenish-blue color
Business
* Aqua (skyscraper), an 82-story residential skysc ...
satellites.
Larsen C
, Larsen C was the fourth largest ice shelf in Antarctica, with an area of about .
Satellite radar altimeter measurements show that between 1992 and 2001, the Larsen Ice Shelf thinned by up to 0.27 ± 0.11 meters per year. In 2004, a report concluded that although the remaining Larsen C region appeared to be relatively stable,[Riedl C, Rott H, Rack W (2004) "Recent Variations of Larsen Ice Shelf, Antarctic Peninsula, Observed by Envisat" ''Proceedings of the 2004 Envisat & ERS Symposium'', Salzburg, Austria]
online
/ref> continued warming could lead to its breakup within the following decade.[Rignot, Eric (2007) "Mass Balance and Ice Dynamics of Antarctic Peninsula Glaciers for IPY2007-2008" Proposal #359, International Polar Year Expression of Intent.]
The breakaway process for the iceberg had begun by mid-2016. On 10 November 2016 scientists photographed the growing rift running along the Larsen C ice shelf, showing it running about long with a width of more than , and a depth of . By December 2016, the rift had extended another to the point where only of unbroken ice remained and calving was considered to be a certainty in 2017. This was predicted to cause the calving of between nine and twelve percent of the ice shelf, , an area greater than the US state of Delaware
Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent Del ...
, or twice the size of Luxembourg
Luxembourg ( ; lb, Lëtzebuerg ; french: link=no, Luxembourg; german: link=no, Luxemburg), officially the Grand Duchy of Luxembourg, ; french: link=no, Grand-Duché de Luxembourg ; german: link=no, Großherzogtum Luxemburg is a small lan ...
. The calved fragment was predicted to be thick and to have an area of about . The resulting iceberg was predicted to be among the largest icebergs ever recorded, unless it would break into multiple pieces.
On 1 May 2017 members of MIDAS reported that satellite images showed a new crack, around long, branching off the main crack approximately behind the previous tip, heading toward the ice front. Scientists with Swansea University in the UK say the crack lengthened from 25 May to 31 May, and that less than of ice is all that prevents the birth of an enormous iceberg. "The rift tip appears also to have turned significantly towards the ice front, indicating that the time of calving is probably very close," Adrian Luckman
Adrian J. Luckman is a British glaciologist and professor of geography at Swansea University in Wales. He is a lead researcher for Project Midas, which monitored the Larsen C iceberg and the Larsen Ice Shelf.
Biography
Luckman received a Bache ...
and Martin O'Leary wrote on Wednesday in a blog post for the Impact of Melt on Ice Shelf Dynamics and Stability project, or MIDAS. "There appears to be very little to prevent the iceberg from breaking away completely." The larger swath of the Larsen C ice shelf that sat behind the calved iceberg "will be less stable than it was prior to the rift" and may rapidly disintegrate in the same manner as Larsen B did in 2002.
In June 2017 the speed of the imminent Larsen C iceberg accelerated, with the eastern end moving at per day away from the main shelf. As discussed by the Project MIDAS researchers on their site: "In another sign that the iceberg calving is imminent, the soon-to-be-iceberg part of Larsen C ice shelf has tripled in speed to more than 10 meters per day between 24 and 27 June 2017. The iceberg remains attached to the ice shelf, but its outer end is moving at the highest speed ever recorded on this ice shelf."
On 7 July the Project MIDAS blog report stated: "The latest data from 6th July reveal that, in a release of built-up stresses, the rift branched several times. Using data from ESA's Sentinel-1
Sentinel-1 is the first of the Copernicus Programme satellite constellation conducted by the European Space Agency. This mission was originally composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, which shared the same orbit ...
satellites, we can see that there are multiple rift tips now within 5 km (3.10 miles) of the ice edge. We expect that these rifts will lead to the formation of several smaller icebergs."
On 12 July 2017, Project MIDAS announced that a large, portion of Larsen C had broken from the main ice shelf at some point between 10 and 12 July. The iceberg, designated A-68, weighs more than a trillion tons and is more than thick.
Project MIDAS updated their blog information on 19 July 2017 regarding Larsen C by revealing that a possible new rift appeared to be extending northwards from the point where A-68 had broken off in mid-July. The project researchers felt this questionable new rift might turn towards the shelf edge, compounding the risk that it would "continue on to Bawden ice rise" which is considered "a crucial point of stabilization for Larsen C Ice Shelf."
As is true of all floating ice shelves, A68's departure from Antarctica had no immediate effect on global sea levels. However, a number of glaciers discharge onto the shelf from the land behind it, and they may now flow faster due to reduced support from the ice shelf. If all the ice that the Larsen C shelf currently holds back were to enter the sea, global waters would rise by an estimated .
Larsen D
The Larsen D Ice Shelf is between Smith Peninsula in the south and Gipps Ice Rise. It is considered to be generally stable. Over roughly the past fifty years it has advanced (expanded) whereas comparable George VI
George VI (Albert Frederick Arthur George; 14 December 1895 – 6 February 1952) was King of the United Kingdom and the Dominions of the British Commonwealth from 11 December 1936 until Death and state funeral of George VI, his death in 1952. ...
, Bach
Johann Sebastian Bach (28 July 1750) was a German composer and musician of the late Baroque period. He is known for his orchestral music such as the '' Brandenburg Concertos''; instrumental compositions such as the Cello Suites; keyboard w ...
, Stange
is a List of municipalities of Norway, municipality in Innlandet county, Norway. It is located in the Traditional districts of Norway, traditional district of Hedemarken. The administrative centre of the municipality is the village of Stangebye ...
, and Larsen C ice shelves have retreated (to a much greater net extent). The most recent survey of Larsen D measured it at 22,600 km2. There is fast ice along the entire front. This makes it difficult to interpret the ice front because the semi-permanent sea ice varies in thickness and may be nearly indistinguishable from shelf ice.''Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years.'' The Cryosphere Discussions. 3 pp579-630.
/ref>
Gallery
File:Antarctic Peninsula, the Larsen Ice Shelf, and the sea ice covered waters around the region.jpg, Clear view of the Antarctic Peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín 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 Antarctic ...
, the Larsen Ice Shelf, and the sea ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
covered waters around the region.
File:Larsen B March 2013.jpg, Larsen B area in March 2013
File:LarsenC-detail photo 2016315 lrg.jpg, 2016 rift in Larsen C, detail
File:Larsen c crack nasa worldview 20170712.jpg, Imagery from NASA's Aqua
Aqua is the Latin word for water. It is used in many words which relate to water, such as aquatic life. In English, it may also refer to:
Arts
* Aqua (color), a greenish-blue color
Business
* Aqua (skyscraper), an 82-story residential skysc ...
MODIS
The Moderate Resolution Imaging Spectroradiometer (MODIS) is a satellite-based sensor used for earth and climate measurements. There are two MODIS sensors in Earth orbit: one on board the Terra (EOS AM) satellite, launched by NASA in 1999 ...
showing the complete break of the ice shelf as of 12 July 2017
File:Larsen C breaks.jpg, Radar imagery from ESA's Sentinel-1B
Sentinel-1 is the first of the Copernicus Programme satellite constellation conducted by the European Space Agency. This mission was originally composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, which shared the same orbit ...
taken on 12 July 2017, showing the complete break
See also
* Glacial motion
Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes. Most lakes in the world occupy basins scoured out by glaciers. Glacial motion can be fast (up to , ob ...
* List of Antarctic ice shelves
This is a list of Antarctic ice shelves.
Ice shelves are attached to a large portion of the Antarctic coastline. Their total area is 1,541,700 km2. Names are also listed in the Scientific Committee on Antarctic Research, Gazetteer. The ...
* Larsen Inlet Larsen Inlet is an inlet, long in a north–south direction and wide, between Cape Longing and Cape Sobral along the east coast of Graham Land, Antarctica. Carl Anton Larsen, a Norwegian whaling captain, reported a large bay in this area in 1893, ...
* Sea level rise
Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...
Notes and references
External links
*
"Break up of the Larsen Ice Shelf, Antarctica"
NASA Earth Observatory.
Coastal-change and Glaciological Map of the Larsen Ice Shelf Area, Antarctica, 1940-2005
United States Geological Survey
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
Antarctic ice rift close to calving, after growing 17km in 6 days
(Swansea University, Project Midas - June 2017)
{{coord, 67, 30, S, 62, 30, W, scale:8000000, display=title
Argentine Antarctica
British Antarctic Territory
Chilean Antarctic Territory
Geography of the British Antarctic Territory
Ice shelves of Antarctica
Landforms of the Antarctic Peninsula