Isotopic balance of the Greenland Ice Sheet: modelled concentrations of water isotopes from 30,000 BP to present

Polar ice cores contain a complex record of climate and ice flow that can be used to decode climate history. Interpretation of ice core records requires the flow signature to be either simple or removable. When the signature is complex, computer modelling can become a powerful aid to interpretation. By combining an ice dynamics model with tracer deposition and transport models, the stratification of individual tracers can be calculated. In this way the time-evolving three-dimensional chemical stratigraphy can be simulated. By linking an ice tracer dynamics model with models of atmosphere and ocean tracer dynamics, coupled models of the global geochemical cycling of water isotopes can be developed. Such models hold promise for an integrated interpretation of the marine and ice-core climate records. As a first step along this path, we apply tracer transport modelling to simulate the temporal and spatial variations of water isotopes in the Greenland Ice Sheet over the past 30,000 years and calculate the influence of Greenland ice volume and isotopic chemistry on the isotopic content of the ocean. We find that the Greenland Ice Sheet maintained its maximum ice volume from 18,000 to 15,000 BP but was isotopically lightest at 11,000 BP. The sea-level equivalent of ice volume changes occurring over the past 30,000 years did not exceed 2.1 in and the volume-averaged influence on ocean chemistry did not exceed 0.025parts per thousand for delta(18)O and 0.20parts per thousand for deltaD and at the Last Glacial Maximum (taken as 21,000 BP) these values were respectively 1.9 in for ice volume, 0.022parts per thousand for delta(18)O and 0.17parts per thousand for deltaD. (C) 2001 Elsevier Science Ltd. All rights reserved.