In the following description of our current research projects, the number refer to references in our publication list.

• Marine and freshwater reservoir effects (apparent 14C age relative to that of the contemporaneous atmosphere). In these studies we have employed a variety of techniques to determine environmental, geographical and temporal variations as well as the effect of freshwater mixing into the marine environment (refs. 5, 10, 12, 13, 23, 45, 48, 52, 64, 69, 71).
• Stable-isotope studies (13C, 15N and later 34S) of food chains with implications for reconstructing palaeodiets and correcting for reservoir effects in 14C dating of humans and animals in archaeological and zoological studies (refs. 13, 40, 42, 45, 49, 64, 69, 72, 73, 75, 76, 77). What started as study of the dietary subsistence of Greenland Vikings (ref. 13) has turned into a natural science research project on food chains in its own right (refs. 69, 75, 76, 77) with the AMS Dating Centre as the responsible holder of a Carlsberg-Foundation research grant (1 million DKK in 1998-2000). We have recently acquired a stable-isotope masse spectrometer, with funding from the Research Councils’ “expensive equipment programme”, which can measure all those isotopes as well as deuterium. These studies will now be an even more central part of our research and subject of the Ph.D. project of Jesper Olsen.
• Methods for extracting CO2 from sea-, fresh- and ground-water samples for dating or use as a geochemical tracer (refs. 2, 11, 12, 16, 28, 29, 44, 48, 35). New methods for correcting and interpreting groundwater 14C concentrations in groundwater and sea-sediment porewater in terms of true age (refs. 2, 29, 48). At our initiative, collaboration was established with the Danish Geological Survey (GEUS) to apply our knowledge from Icelandic studies to 14C dating of Danish groundwaters (e.g. ref. 16). • 14C Bomb-pulse dating of recent material (post nuclear bomb, i.e. AD 1950) with a precision of 1-2 years in forensic applications and especially in airborne heavy-metal pollution studies using peat profiles as archives (refs. 20, 38, 60, 61). The latter study, a collaboration with the Department of Environmental Chemistry, University of Southern Denmark, introduced a novel dating technique with much higher resolution than the traditionally applied 210Pb dating technique.
• New techniques for sample preparation and dating: 1) Burnt or cremated bone has hitherto been inaccessible to 14C dating, but following an international break-through in this area, we have taken up a development programme funded by an SHF grant, administered from the AMS Dating Centre. Infrared spectroscopy analysis has been taken up as a means of characterising the material and the degree of burning of the bone to be dated. 2) Our research programme in collaboration with a geologist and archaeologists from Finland and USA, involving several hundred dates over the last few years, has finally demonstrated the feasibility of dating ancient buildings based on specific chemical fractions of the carbonate content in lime mortar (refs. 27, 41, 56). Testing of the technique on different types of mortar has been carried out on early buildings of Scandinavian and roman origin where the age is known from dendrochronology, tile stamps or written sources.
• Instrumental development: Isotopic measurements for ice core dating and climate reconstruction. Jesper Olsen has now developed the deuterium/hydrogen-ratio measuring precision to three times better than specifications, allowing annual layer counting of ice cores and climate reconstruction to be taken to higher levels of resolution. This programme is part of a recently established research collaboration with Dr. S.J. Johnsen, Geophysics Department of the Niels Bohr Institute, Univ. of Cph., based on shared peripheral equipment at the AMS Dating Centre and exchange of masters’ and Ph.D. students. The same techniques have now been made available to research in hydrology (e.g. N.O. Jørgensen, Geology, Univ. of Cph.).