Environment Counts | Dome Fuji ice core sampling shows strong correlation between CO2 concentration and temperature
Author: Geoff Zeiss – Published At: 2012-04-08 13:34 – (1523 Reads)
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A deep ice core down to 2503 m depth was drilled at Dome Fuji station, East Antarctica, during the 1993-96 Japanese Antarctic Research Expedition inland operations. A second deep core was started in 2003. Drilling was carried out and a depth of 3035.22 m was reached. This core greatly extends the climatic record of the first core, and, according to a first, preliminary dating, it reaches back to 720,000 years. The analysis of the 2503-m Dome Fuji ice core, obtained under the 1st Dome Fuji Drilling Project, reveal good correlation between air temperature and concentration of CO2. The palaeoclimate record in the ice core from Dome Fuji station, Antarctica, Annals of Glaciology, Volume 29, Number 1, June 1999 , pp. 176-178(3)
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The Antarctic ice sheet preserves paleoclimate information in the form of physical and chemical stratigraphy. A deep ice core down to 2503 m depth was drilled at Dome Fuji station, East Antarctica, during the 1993-96 Japanese Antarctic Research Expedition inland operations. Oxygen isotope measurements were conducted on 50 cm long samples selected from the entire core length. A paleo-temperature profile was obtained for the past 340 ka by assuming the same conversion factors for the past relation as exist today between isotope ratio and both surface temperature and accumulation rate, in the inland region of Dronning Maud Land.
Annals of Glaciology, Volume 29, Number 1, June 1999 , pp. 176-178(3)
A second deep core was started in 2003. Drilling was carried out during four subsequent austral summers from 2003/2004 until 2006/2007, and by then a depth of 3035.22 m was reached. The drill did not hit the bedrock, but rock particles and refrozen water have been found in the deepest ice, indicating that the bedrock is very close to the bottom of the borehole. This core greatly extends the climatic record of the first core, and, according to a first, preliminary dating, it reaches back until 720,000 years. The ice of the second Dome F core is therefore the second-oldest ice ever recovered, only outranged by the EPICA Dome C core.
Motoyama, H. (2007). “The second deep ice coring project at Dome Fuji, Antarctica”. Scientific Drilling 5: 41–43.
Dating Based on the Oxygen/Nitrogen Ratio
Kawamara et al. (2007) utilized a new procedure for estimating absolute chronologies based on the theory that O2/N2 in these cores is depleted relative to the atmospheric ratio because of physical fractionation during air-bubble formation at ~100 m depth. The magnitude of this depletion is claimed to be controlled by the magnitude of snow metamorphism, driven by local summer insolation when the layer was originally at the
surface.
“Although the exact mechanisms are currently not well understood, empirical evidence indicates that the O2/N2 variation is probably phase-locked to the local summer solstice insolation, with negligible climatic influences. Using this technique, the independent Dome Fuji and Vostok O2/N2 chronologies agree within 1 kyr, indicating robustness of the method.â€
Assuming the putative relationship between summer insolation and O2/N2 ratio is indeed correct, the beauty of this method is that one can calculate the chronology of the insolation curves accurately, and therefore the absolute chronology does not depend on assigning dates to features in the isotope depletion curves. At any depth, the chronology is determined from the O2/N2 ratio, and the isotope depletion at that depth is thereby assigned a date. It only assumes that the O2/N2 ratio is proportional to SH insolation.
Donald Rapp, Ice Ages and Interglacials Updates March 2011.
