Posts tagged Greenland
![The figure above is a [very] simple model displaying isostatic rebound of Greenland if its ice sheet were not present. The Greenland ice sheet (GISh) is 2,500 km north-south, 1,000 km east-west, 3 km thick, and covers almost 2 million square kilometers (or 80% of the island). Because of the weight of GISh, the continental lithosphere is depressed in an elastic motion. If the GISh were to be removed, the lithosphere would rise in reaction. This rebounding process is known as isostasy and in case of ice sheets, glacial rebound.
Underneath any vast ice sheet is a land surface not unlike any other ice-free surface on earth. It has valleys, hills, plains, etc. Therefore, we see that in Greenland the underlying topography, the Bedrock (or simply the Bed), is shaped as a concave, and with the removal of the ice sheet it rises and assumes a less curved form.
PS: Please note that this is purely for visualization purposes and not to be used in scientific analysis.](http://27.media.tumblr.com/tumblr_ltdut3Ejs91qff4ofo1_400.jpg)
The figure above is a [very] simple model displaying isostatic rebound of Greenland if its ice sheet were not present. The Greenland ice sheet (GISh) is 2,500 km north-south, 1,000 km east-west, 3 km thick, and covers almost 2 million square kilometers (or 80% of the island). Because of the weight of GISh, the continental lithosphere is depressed in an elastic motion. If the GISh were to be removed, the lithosphere would rise in reaction. This rebounding process is known as isostasy and in case of ice sheets, glacial rebound.
Underneath any vast ice sheet is a land surface not unlike any other ice-free surface on earth. It has valleys, hills, plains, etc. Therefore, we see that in Greenland the underlying topography, the Bedrock (or simply the Bed), is shaped as a concave, and with the removal of the ice sheet it rises and assumes a less curved form.
PS: Please note that this is purely for visualization purposes and not to be used in scientific analysis.
One of the projects we’re working on here at the Lamont-Doherty Earth Observatory is assessing spatial extent of subglacial features under the Greenland ice sheet using airborne geophysics. This is to better understand the dynamics of the ice sheet and to monitor the affects of climate change on its flow.
This is the world’s most authoritative atlas. It’s published every four years. This edition, published on Thursday, September 15th 2011, is full of changes that the editors were forced to make because of climate change — shrinking lakes, changing coastlines, and whole new islands exposed by melting glaciers. Maps in the 13th edition of the Atlas show large areas of the eastern and southern coasts of Greenland coloured brown and pink, and the permanent ice cap now covering a significantly smaller area than it did in the 1999 12th edition of the atlas. The atlas suggests that 300,000 sq km, or 15%, of Greenland’s ice cover had been lost in the period. Find out more.
UPDATE:
Leading scientists have accused the world’s top cartographers of making a blunder in their representation of the effects of climate change in Greenland, prompting a robust defence by the map-makers’ publisher.
A spokeswoman for Times Atlas robustly defended the 15% figure and the new map on Monday, September 19th 2011:
“We are the best there is. We are confident of the data we have used and of the cartography. We use data supplied by the US Snow and Ice Data Centre (NSIDC) in Boulder, Colorado. They use radar techniques to measure the permanent ice. We have compared the extent of the ice surface in 1999 with that of 2011. Our data shows that it has reduced by 15%. That’s categorical.”
The publishers of the Times Atlas were forced to admit on Tuesday, September 20th 2011, that they were wrong to claim the Greenland ice pack had shrunk by 15%, as Arctic scientists rounded on the company for misinterpreting data and failing to consult them.
IceBridge, a six-year NASA mission, is the largest airborne survey of Earth’s polar ice ever flown. It will yield an unprecedented three-dimensional view of Arctic and Antarctic ice sheets, ice shelves and sea ice. These flights will provide a yearly, multi-instrument look at the behavior of the rapidly changing features of the Greenland and Antarctic ice.
Data collected during IceBridge will help scientists bridge the gap in polar observations between NASA’s Ice, Cloud and Land Elevation Satellite (ICESat) — in orbit since 2003 — and ICESat-2, planned for late 2015. ICESat stopped collecting science data in 2009, making IceBridge critical for ensuring a continuous series of observations.
IceBridge will use airborne instruments to map Arctic and Antarctic areas once a year. IceBridge flights were conducted in March/May 2009 and 2010 over Greenland and in October/November 2009 and 2010 over Antarctica. Other smaller airborne surveys around the world are also part of the IceBridge campaign.
A Focus on the Thinning Northwest Greenland Glaciers
Satellite measures showing thinning ice on the Northwest Greenland glaciers prompted Operation IceBridge to include annual flights over this region. The area runs along the Baffin Bay coast, which is often covered in fog and low lying clouds forcing delays and reschedules. With the end of our season in sight we were forced to complete the flight in less than optimal conditions.
As we flew further south, approaching Upernavik, we encountered a dense cloud layer running inland along the glacier for several miles, and stopping at about the 2000 foot elevation. The scenery above the clouds showed high snowy peaks prompting a quick look at a digital elevation model of Greenland. The elevation around Upernavik and surrounding areas can reach up to 6000 feet, evident in the peaks we observed during the flight. This upper elevation was cloud free and we were able to collect data for monitoring any changes in ice thickness in these higher elevations.
[Above] The Pituffik Glacier – Although the temperature is getting warmer and the seasonal melting process has begun, there is a considerable amount of sea ice present. When their time comes, and when the sea ice has melted, the crevassed sections of the glacier break off and float as icebergs.
The arctic is home to several species of wildlife, some of whom are circumpolar. As we prepare to wrap up this season in Greenland Ithought I would share a few images of its charismatic residents. As summer approaches (it is presently at 23 degrees F), it has become possible to observe some of these species around the base. These include the Arctic Fox Vulpus lagopus, Arctic Hare Lepus arcticus, Snow Bunting Plectrophenax nivalis, Glaucous Gull Larus hyperboreus, (Greenlandic) Gyrfalcon Falco rusticolus, and the Common Raven Corvus corax.
[Above] “Greenlandic” Gyrfalcon (Falco rusticolus)
[Above] Arctic Hare (Lepus arcticus)
A First Visit to North Greenland - Part II (Science Mission Over Greenland’s North Glaciers)
Our science mission on Monday, May 9th involved flights over the north and northwest of Greenland, specifically the Steensby, Ryder and Hagen glaciers as well as the Fald Ice Cap in Kronprins Christian Land. The Steensby Glacier passes through the Sherard Osbron Fjord, while the Ryder Glacier is constrained by the Victoria Fjord. This was my first flight on the P3 and the scenery was nothing short of breathtaking. I found the sheer dimensions of the fjord cliffs particularly interesting. Fjords are visual testaments to the dynamicity of our planet. The fjords in north Greenland were quite steep, at almost 90o, and appeared to be carved with surgical precision. These were formed in the last glacial period as Greenland was covered with ice and snow, the weight of which depressed the crust and glaciers cut through surrounding rock. Since the end of the last ice age, a phenomenon called ‘crustal rebound’ took place, in which the formerly depressed land masses slowly rose. This process is called isostasy, and it has resulted in those awe-inspiring cliffs.
Middle Ordovician – Lower Silurian cliffs surround the Sherard Osborn Fjord and the Victoria Fjord.
Outside the scientific community, glaciers are sometimes thought of as ‘just a block of ice’, but quite frankly they are sort of landmasses in their own right and close to inland islands. They are solid, they are dynamic, and they have layers which attest to their existence. They have several surficial features, like crevasses, shown below. These are the equivalent to fractures in rock and are formed due to a combination of factors such as the disparity in the glacier’s speed and the stress generated by flow over an uneven terrain. Furthermore, the glacier’s lower layers are more malleable than its upper layers hence resulting crevasses.
Crevasses forming on the Ryder Glacier. The photo does not give justice to scale. These features are easily 100m wide.
- Part I
Yesterday’s mission on the NASA P3 above northeastern Greenland. It was a good flight, there were some interesting features such as glaciers, crevasses, cliffs and ice streams, but for 2/3 of the time there was an endless view of the ice cap. The seats were typical of a 40-year old aircraft, meaning not very comfortable.
The 4am Sun in north Greenland on May 8th, 2011.
Wind conditions in north Greenland this evening, thankfully it’s gotten better since the morning…
A First Visit to North Greenland - Part I
After a five-hour flight from Baltimore Washington International Airport, I landed at the Thule Air Base in northwestern Greenland as part of Columbia University’s team in NASA’s Operation IceBridge (OIB). The program is a six-year campaign of annual flights to each of Earth’s polar regions that began in the Fall of 2009. The flights in March and April carry researchers over Greenland and the Arctic Ocean while the ones in October and November take them over the Earth’s southern ice-covered regions. Both sets of flights study changes to the Earth’s sea ice, ice sheets, and glaciers. Data collected will help scientists bridge the gap between NASA’s Ice, Cloud and Land Elevation Satellite (ICESat-I), which retired in February 2010; and ICESat-II, scheduled to launch in 2014.
Thule Air Base is the United States Air Force’s northernmost base and is located some 1,100 kilometers north of the Arctic Circle, and 1,500 kilometers south of the North Pole on the northwest side of Greenland. It is approximately 900 km east of the North Magnetic Pole.
Greenland is called “Kalaallit Nanaat” in the local Inuit language. It is a country in the Kingdom of Denmark and is the largest island in the world. “Thule” is from the Latin word with the same spelling meaning ― northernmost part of the habitable world. More than 80 percent is covered either by the ice cap or smaller glaciers. According to scientific measurements, the greatest thickness of the ice cap above sea level is about 3 kilometers. If the entire 2,850,000 cu.km of ice were to melt, it would lead to a global sea level rise of 7.2m.
The US Air Base at Thule was (still is?) of strategic importance during the Cold War. It is part of the USAF Ballistic Missile Early Warning System (BMEWS) and houses the first operational ballistic missile detection radar. It was built at the height of the Cold War and provides a long-range warning of a ballistic missile attack over the polar region of the Northern Hemisphere.
In 1968, a USAF B-52 Bomber armed with four hydrogen bombs, crashed near the air base causing the nuclear payload to rupture and disperse, which resulted in widespread radioactive contamination.Three of the four nuclear warheads were recovered. The fourth is buried somewhere beneath the ice and snow around Thule.
Thule from above
Continued… Part II
