North Atlantic Deep Water Formation: Information From Ice Cores 
Hans Oeschger 
Physics Institute, University of Bern, SWITZERLAND 
In the following, the main results of measurements of the CO 9 concentration of air 
occluded in natural ice during periods of climatic change are presented, as well as other 
measured ice core parameters. Elements of an interpretation of the data in terms of mechanisms 
of changing environmental systems are briefly discussed. 
I. CO, concentration measurements on air occluded in ice cores (Greenland and Antarctica) 
The last 100 y 
- Preindustrial value (1800-1850): 280+5 ppm (measurements on samples of different size 
with laser IR-spectroscopy and gas-chromatography). 
- During last 1000 y fluctuations are not to be excluded, but are probably less than 10 (to 
20) ppm (averaged over the 20 y required for gas enclosure). 
The glacial-postglacial transition (Fig. 1) 
- Low CO2 concentrations between 25,000 and 15,000 BP: 180 to 200 ppm. 
- Transition to values in the 280 to 300 ppm range ca. 13,000 BP, probably almost in phase 
with 0/80 shift; indications of lower values during period 10,000 to 11,000 BP (Younger Dryas); 
final transition to Holocene values of 300+20 ppm at around 10,000 BP (Holocene values influenced 
by higher COg content of melt layer ice). 
AGE (ky BP) 
10Be (104g) 0 
RO = oO 
Ww 
680 (ee) - 
1750 1800 1850 1900 1950 
DEPTH (m) 
Fig. 1. 19Be concentrations (104 atoms per g of ice), COg concentrations (ppm) and 6180 as 
measured in the Dye 3 ice core. Top: Tentative time marks, as suggested by the comparison 
with European lake sediments (Fig. 4). 
