Dye 3

Dye 3 is an ice core site and previously part of the DYE section of the Distant Early Warning line, located at in Greenland. As a DEW line base, it was disbanded in years 1990/1991.
An ice core is a core sample from the accumulation of snow and ice that has re-crystallized and trapped air bubbles over many years. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time. Ice cores contain an abundance of climate information.
Inclusions in the snow, such as wind-blown dust, ash, bubbles of atmospheric gas and radioactive substances, remain in the ice. The variety of climatic proxies is greater than in any other natural recorder of climate, such as tree rings or sediment layers. These include temperature, ocean volume, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, solar variability, sea-surface productivity, desert extent and forest fires.
Typical ice cores are removed from an ice sheet such as the ice cap internal to Greenland. Greenland is, by area, the world's largest island. The Greenland ice sheet covers about 1.71 million km² and contains about 2.6 million km³ of ice.

Greenland ice sheet

The 'Greenland ice sheet' is a vast body of ice covering 1.71 million km², roughly 80% of the surface of Greenland. It is the second largest ice body in the World, after the Antarctic Ice Sheet. The ice sheet is almost 2,400 kilometers long in a north–south direction, and its greatest width is 1,100 kilometers at a latitude of 77°N, near its northern margin. The mean altitude of the ice is 2,135 meters.
The ice in the current ice sheet is as old as 110,000 years. However,
it is generally thought that the Greenland Ice Sheet formed in the late Pliocene or early Pleistocene by coalescence of ice caps and glaciers. It did not develop at all until the late Pliocene, but apparently developed very rapidly with the first continental glaciation.
The ice surface reaches its greatest altitude on two north–south elongated domes, or ridges. The southern dome reaches almost 3,000 metres at latitudes 63°–65°N; the northern dome reaches about 3,290 metres at about latitude 72°N. The crests of both domes are displaced east of the centre line of Greenland. The unconfined ice sheet does not reach the sea along a broad front anywhere in Greenland, so that no large ice shelves occur.
On the ice sheet, temperatures are generally substantially lower than elsewhere in Greenland. The lowest mean annual temperatures, about −31 °C, occur on the north-central part of the north dome, and temperatures at the crest of the south dome are about −20 °C.
During winter, the ice sheet takes on a strikingly clear blue/green color. During summer, the top layer of ice melts leaving pockets of air in the ice that makes it look white. Positioned in the Arctic, the Greenland ice sheet is especially vulnerable to global warming. Arctic climate is now rapidly warming.

Distant Early Warning Line

Dye-2 and 3 were among 58 Distant Early Warning Line radar stations built by the United States of America between 1955 and 1960 across Alaska, Canada, Greenland and Iceland at a cost of billions of dollars.
After extensive studies in late 1957, the US Air Force selected sites for two radar stations on the ice cap in southern Greenland. The DYE stations were the eastern extension of the DEW Line. DYE-1 was on the West Coast at Holsteinsborg; DYE-4 on the East Coast at Kulusuk. Dye 2 was built approximately 100 miles east of Sondrestrom Air Base and 90 miles south of the Arctic Circle at an altitude of 7,600 feet. Dye 3 was located approximately 100 miles south-east of Dye 2 at an elevation of 8,600 feet.
The sites were constructed with materials provided through airlift from C-130D’s from the 17th Troop Carrier Squadron at Sewart Air Force Base, flying out of Sonderstrom Air Base.
The new radar sites were found to receive from three to four feet of snow each year. The snow was formed into large drifts by winds constantly blowing as much as 100 mph. To overcome this, the Dye sites were elevated approximately 20 feet above the ice cap surface. Dye 3 was completed in 1960. Due to snow accretion, the station was "jacked up" again in the late 1970s, but by the 1990s needed further elevation.
Instead, Dye 3 was closed as a radar station in the years 1990/1991.
Today, it is used as a training site for the 139th Airlift Squadron Flying LC-130’s.

Greenland Ice Sheet Project (GISP)

The Greenland Ice Sheet Project was a decade-long project to drill 20 ice cores in Greenland. GISP involved scientists and funding agencies from Denmark, Switzerland and the United States. Besides the U.S. National Science Foundation, funding was provided by the Swiss National Science Foundation and the Danish Commission for Scientific Research in Greenland. The ice cores provide a proxy archive of temperature and atmospheric constituents that help to understand past climate variations.
Annual field expeditions were carried out to drill intermediate depth cores at various locations on the ice sheet:

Dye 3 in 1971 to 372 m
North Site in 1972 to 15 m
North Central in 1972 to 100 m
Crête in 1972 to 15 m
Milcent in 1973 to 398 m
Dye 2 in 1973 to 50 m
Dye 3 in 1973, an intermediate drilling to c. 390 m
Crête in 1974 to 404.64 m
Dye 2 in 1974 to 101 m
Summit in 1974 to 31 m
Dye 3 in 1975 to 95 m
South Dome in 1975 to 80 m
Hans Tausen in 1975 to 60 m
Dye 3 in 1976 to 93 m
Hans Tausen in 1976 to 50 m
Hans Tausen in 1977 to 325 m
Camp Century in 1977 to 49 m
Dye 2 in 1977 to 84 m
Camp III in 1977 to 84 m
Dye 3 1978 to 90 m
Camp III in 1978 to 80 m.

“On most of the Greenland ice sheet, however, the annual accumulation rate is considerably higher than 0.2 m ice a⁻¹, and the delta method therefore works thousands of years backwards in time, the only limitation being obliteration of the annual delta cycles by diffusion of the water molecule in the solid ice....” Delta refers to the changing proportion of oxygen-18 in the different seasonal layers. “The main reason for the seasonal delta variations is that, on its travel to the polar regions, a precipitating air mass is generally cooled more in winter than in summer.” “... the annual layer thickness...decreases from 19 cm in 2,000-year-old ice to 2 cm in 10,000-year-old ice due to plastic thinning of the annual layers as they sink towards greater depths¹⁰.” “... volcanic acids in snow layers deposited shortly after a large volcanic eruption can be detected – as elevated specific conductivities measured on melted ice samples8, or as elevated acidities revealed by an electric current through the solid ice...”

Dye 3 cores

Although available GISP data gathered over the earlier seven years, pointed to north-central Greenland as the optimum site location for the first deep drilling, financial restrictions forced the selection of the logistically convenient Dye-3 location.

Dye 3 1971

Preliminary GISP field work started in 1971 at Dye 3, where a 372 meter deep, 10.2 cm diameter core was recovered using a Thermal drill type. Three more cores to depths of 90, 93, and 95 m were drilled with different drill types.

Dye 3 1973

For an intermediate drilling c. 390 m, the drill was installed 25 m below the surface at the bottom of the Dye 3 radar station. Some 740 seasonal δ¹⁸ cycles were counted, indicating that the core reached back to 1231 AD. Evident in this coring was that as melt water seeps through the porous snow, it refreezes somewhere in the cold firn and disturbs the layer sequence.

Dye 3 1975

A second core at Dye 3 was drilled in 1975 with a Shallow drill type to 95 m at 7.6 cm diameter.

Dye 3 1976

A third core at Dye 3 was drilled in 1976 with a Wireline drill type, 10.2 cm diameter, to 93 m.

Dye 3 1978

Another core at Dye 3 was drilled in 1978 using a Shallow drill type, 10.2 cm diameter, to 90 m.
Measurements of and in firn samples spanning the period 1895–1978 were taken from the Dye 3 1978 core down to 70 m.

Dye 3 1979–1981

In 1979, the initial Dye-3 deep bedrock drilling was started using a 22.2 cm diameter CRREL thermal coring drill to produce an 18 cm diameter access hole, which was cased, to a depth of 77 m. The large diameter casing was inserted over the porous firn zone to contain the drilling fluid.
After working out various logistical and engineering problems related to the development of a more sophisticated drilling rig, drilling to bedrock at Dye 3 began in the summer of 1979 using a new Danish electro-mechanical ice drill yielding a 10.2 cm diameter core. From July to August 1979 using ISTUK, 273 m of core was removed. At the end of the 1980 field season ISTUK had gnawed down to 901 m. In 1981 at a depth of 1785 m dust and conductivity measurements indicated the beginning of ice from the last glaciation. Coring continued and on August 10, 1981, bedrock was reached at a depth of 2038 m. The depth range for the Danish drill was 80–2038 m.
The Dye 3 site was a compromise: glaciologically, a higher site on the ice divide with smooth bedrock would have been better; logistically, such a site would have been too remote.
The borehole is 41.5 km east of the local ice divide of the south Greenland ice sheet.

Shear conditions

The Dye 3 cores were part of the GISP and, at 2037 meters, the final Dye 3 1979 core was the deepest of the 20 ice cores recovered from the Greenland ice sheet. The surface ice velocity is 12.5 ma⁻¹, 61.2° true. At 500 m above bedrock, the ice velocity is ~10 ma⁻¹, 61.2° true. The ice upstream and downstream from Dye 3 is flowing downhill on ~0.48 % mean slope. The bedrock temperature is −13.22 °C.