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North
• Site
North Central
Su'!"mit
Camp Century and
GISP drill sites
0>1000 m depth
o 400 - -
100 - -
SOOkm
32
Fig. 1. Camp Century and GIS?
drill sites on the Greenland ice
sheet. The dotted curve shows
the mam ice divide that encloses
the West Greenland discharge
area. The deep drill sIte at Dye
3 in South Greenland is located
some 45 km from the ice divide,
but the deepest part of the ice
core was deposIted much farther
to the South, probably close to
the South Dome.
(0.62 %0 per °C 17/). Other parameters i nfl uence the 6 value to some
degree /8,9/. Of special interest in this context is the effect of changi
ng sea-i ce cover, i. e. the changi ng di stance to the open ocean, whi ch
affects the degree of cool i ng of preci pitat i ng ai r masses, and thereby
6, but not necessarily the mean air temperature on the ice sheet. However,
for many purposes a 6 profil e along an ice core may be interpreted as a
secular record of low troposphere temperatures /10,11/.
2.1. Dating of the Dye 3 ice core.
The isotopic composition of the snow, as well as the impurity concentrations,
vary in an annual cycle /12-15/. Therefore, detailed and continuous
profiles of these parameters may be used for identification of the individual
annual layers in an ice core and, hence, for absolute dating by counting
the layers downwards from surface. Up till now, the absolute 6 18 0
dating of the Dye 3 ice core has been extended back to more than 6000 yrs.
B.P. (before present).
INVl