Average time scale for Dome Fuji ice core, East Antarctica

Three different approaches to ice-core age dating are employed to develop a depth-age relationship at Dome F: (1) correlation of the ice-core isotope record to the geophysical metronome(Milankovich surface temperature cycle) inferred from the deep borehole temperature profile at Vostok,(2) importing a known chronology from another(Devils Hole) paleoclimatic signal, and(3) direct ice sheet flow modeling. Inverse Monte Carlo sampling is used to constrain the accumulation rate reconstruction and ice flow simulations in order to find the best-fit glaciological time scale matched with the two other chronologies. General uncertainty of the different age estimates varies from 2 to 6kyr on average and reaches 6-14kyr at maximum. Whatever the causes of this discrepancy might be, they are thought to be of different origins, and the age errors are assumed to be independent. Thus, the average time scale for the Dome F ice core down to a depth of 2500m(ice age of 335kyr) is deduced consistently with all three age-depth relationships within the standard deviation limits of ±3.3kyr, and its accuracy is estimated as 1.4kyr on average. The constrained ice-sheet flow model allows extrapolation of the ice age-depth curve further to the glacier bottom and predicts the ages at depths of 2800, 3000, and 3050m to be 615±70, 1560±531, and 2985±1568kyr, respectively

Paleoclimatic reconstructions based on borehole temperature measurements in ice sheets : possibilities and limitations

International Symposium on Physics of Ice Core Records. Shikotsukohan, Hokkaido, Japan, September 14-17, 1998

キホウ ヲ フクム ヒョウショウ コオリ ノ アツミツ カンワ カテイ ノ リロン テキ ケンキュウ

この解説は, 筆者らがロシアにおいて1983年から1989年にかけて行った一連の研究のレビューである。均一な気泡を含む氷の圧密(あるいは膨張)過程の理論的検討を行う。極地氷床における密度の深度プロファイルおよび掘削後の体積膨張をシミュレーションするための数学的モデルを展開し, それを東南極ボストークにおける掘削コアに適用する。また, 気泡から空気水和物結晶への遷移に対する簡単なモデルを提案する。This paper presents a brief review of the authors\u27 earlier research on polar ice density modeling carried out and published (in the main) during 1983-1989 in Russia. A theoretical approach to macrocontinuum description of bubbly ice densification (expansion) on the basis of averaging asymptotic methods is considered. Mathematical models for the simulation of polar ice sheet density variations versus depth and for the prediction of deep ice core volume relaxation after its recovery are developed and tested on real situations at Vostok Station, East Antarctica. A simplified model of the equilibrium transformation of bubbles entrapped in ice into air hydrate crystals is proposed

Diffusion of air molecules in polar ice sheets

International Symposium on Physics of Ice Core Records. Shikotsukohan, Hokkaido, Japan, September 14-17, 1998

Modelling dynamics of glaciers in volcanic craters

General equations of ice dynamics are re-examined, using scale analysis, in order to derive a simplified thermomechanically coupled model for ice flow and heat transfer in ice caps filling volcanic craters. Relatively large aspect ratios between crater depths and diameters, low surface temperatures and intense volcanic heating are the principal characteristics of such craters. The conventional boundary-layer (shallow-ice) approximation is revised to account for these conditions and, in addition, the variable density of the snow, firn and bubbly ice. Large crater depths and intense bottom melting result in low longitudinal balance velocities, controlled by both shear and longitudinal stresses, and hence small surface slopes. In such situations ice can be assumed to be linearly viscous. A flowline model of the glacier dynamics is developed using this assumption. Explicit predictive formulas for ice-particle trajectories and age—depth relations, thus obtained, suggest that the age of ice at the bottom of glaciers in volcanic craters on Kamchatka Peninsula, Russia, may reach hundreds or thousands of years. Ice cores from these glaciers represent unique climatic and volcanic archives