Ice core records of atmospheric CO2 around the last three glacial terminations

Air trapped in bubbles in polar ice cores constitutes an archive for the reconstruction of the global carbon cycle and the relation between greenhouse gases and climate in the past. High-resolution records from Antarctic ice cores show that carbon dioxide concentrations increased by 80 to 100 parts per million by volume 600 ± 400 years after the warming of the last three deglaciations. Despite strongly decreasing temperatures, high carbon dioxide concentrations can be sustained for thousands of years during glaciations; the size of this phase lag is probably connected to the duration of the preceding warm period, which controls the change in land ice coverage and the buildup of the terrestrial biosphere.</jats:p

Lie Algebraic Similarity Transformed Hamiltonians for Lattice Model Systems

We present a class of Lie algebraic similarity transformations generated by exponentials of two-body on-site hermitian operators whose Hausdorff series can be summed exactly without truncation. The correlators are defined over the entire lattice and include the Gutzwiller factor $n_{i\uparrow}n_{i\downarrow}$, and two-site products of density $(n_{i\uparrow} + n_{i\downarrow})$ and spin $(n_{i\uparrow}-n_{i\downarrow})$ operators. The resulting non-hermitian many-body Hamiltonian can be solved in a biorthogonal mean-field approach with polynomial computational cost. The proposed similarity transformation generates locally weighted orbital transformations of the reference determinant. Although the energy of the model is unbound, projective equations in the spirit of coupled cluster theory lead to well-defined solutions. The theory is tested on the 1D and 2D repulsive Hubbard model where we find accurate results across all interaction strengths.Comment: The supplemental material is include

Aging to Equilibrium Dynamics of SiO2

Molecular dynamics computer simulations are used to study the aging dynamics of SiO2 (modeled by the BKS model). Starting from fully equilibrated configurations at high temperatures T_i =5000K/3760K the system is quenched to lower temperatures T_f=2500K, 2750K, 3000K, 3250K and observed after a waiting time t_w. Since the simulation runs are long enough to reach equilibrium at T_f, we are able to study the transition from out-of-equilibrium to equilibrium dynamics. We present results for the partial structure factors, for the generalized incoherent intermediate scattering function C_q(t_w, t_w+t), and for the mean square displacement msd(t_w,t_w+t). We conclude that there are three different t_w regions: (I) At very short waiting times, C_q(t_w, t_w+t) decays very fast without forming a plateau. Similarly msd(t_w,t_w+t) increases without forming a plateau. (II) With increasing t_w a plateau develops in C_q(t_w, t_w+t) and msd(t_w,t_w+t). For intermediate waiting times the plateau height is independent of t_w and T_i. Time superposition applies, i.e. C_q=C_q(t/t_r) where t_r=t_r(t_w) is a waiting time dependent decay time. Furthermore C_q=C(q,t_w,t_w+t) scales as C_q=C(q,z(t_w,t) where z is a function of t_w and t only, i.e. independent of q. (III) At large t_w the system reaches equilibrium, i.e. C_q(t_w,t_w+t) and msd(t_w,t_w+t) are independent of t_w and T_i. For C_q(t_w,t_w+t) we find that the time superposition of intermediate waiting times (II) includes the equilibrium curve (III).Comment: 9 pages, 11 figures, submission to PR

Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica

A high-resolution ice-core record of atmospheric CO2 concentration over the Holocene epoch shows that the global carbon cycle has not been in steady state during the past 11,000 years. Analysis of the CO2 concentration and carbon stable-isotope records, using a one-dimensional carbon-cycle model,uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial-scale changes of atmospheric CO2 concentrations

The CO\u3csub\u3e2\u3c/sub\u3e Concentration of Air Trapped in Greenland Ice Sheet Project 2 Ice Formed During Periods of Rapid Climate Change

The CO2 content of air occluded in Greenland Ice Sheet Project 2 (GISP2) ice formed over two separate intervals of rapidly changing climate, centered at approximately 46 and 63 kyr B. P., is as much as 90 ppm more during warm periods (interstadials) than during cold periods (stadials). These CO2 variations are superimposed on changes in annual layer thickness and δ18O of the ice and do not show the 200- to 700-year offsets which would be expected for concurrent variations in the atmosphere and the ice. The CO2 concentrations during the stadials are similar to the atmospheric values recorded by Antarctic ice of the same age, so processes occurring in the ice after bubble enclosure must be enriching the air trapped in GISP2 ice formed during the interstadials. This conclusion is supported by Ca content and electrical conductivity measurements of the ice, which show that adequate carbonate is present to produce these enrichments and that CO2 content is high only when the electrical conductivity (a proxy for H+ concentration) is high. High-resolution mapping of one 4-cm section of ice shows a 200-ppm increase in the CO2 content of the trapped air, from approximately 275 to 475 ppm. Analyses of the total inorganic carbon of ice from both the LGM and Holocene show that most of the Ca in the ice is from CaCO3 and that the δ13CO2 approaches that of soil and marine carbonates. These results show that the CO2 record preserved in ice can be altered by in situ decarbonation reactions and that only ice containing either abundant carbonate or essentially no carbonate contains a reliable record of paleoatmospheric CO2

Nonlinear interfacial waves in a constant-vorticity planar flow over variable depth

Exact Lagrangian in compact form is derived for planar internal waves in a two-fluid system with a relatively small density jump (the Boussinesq limit taking place in real oceanic conditions), in the presence of a background shear current of constant vorticity, and over arbitrary bottom profile. Long-wave asymptotic approximations of higher orders are derived from the exact Hamiltonian functional in a remarkably simple way, for two different parametrizations of the interface shape.Comment: revtex, 4.5 pages, minor corrections, summary added, accepted to JETP Letter

Historical Biomass Burning: Late 19th Century Pioneer Agriculture Revolution in Northern Hemisphere Ice Core Data and its Atmospheric Interpretation

Ice core data from Yukon and Greenland spanning from ∼1750 to 1950 indicate that between ∼1850 and ≤1910 a clear atmospheric signal exists of an episodic biomass burning event that is referred to as the Pioneer Agriculture Revolution. This is best seen in NH4+ ion and particulate concentrations but also in some limited black carbon concentration data, where for all three quantities maximum levels reach about 3 times the prerevolution background concentrations. Tree cellulose δ13C data and some early, controversial, French, air CO2 data, occurring within the same time interval, are interpreted as providing other independent evidence for the same, mainly North American, late 19th century biomass burning event. Some hitherto problematic northern hemisphere ice core derived CO2 concentration data may now be interpreted as containing a biomass burn signal, and these data are compared, especially as to the time of occurrence, with all the other results. A global carbon cycle model simulation of atmospheric CO2 mixing ratios using a maximum input of 3 Gt(C)/yr at northern midlatitudes produces “anomalous” CO2 levels close to some of the ice core carbon dioxide values. However, other values in this data set do not reasonably represent fully mixed atmospheric values. This suggests that these values might be transients but still “tracers” for biomass burning. Nevertheless, it appears possible that interhemispheric CO2 gradients of similar magnitude to the present one could have existed briefly late last century

Measurement of the W-pair Production Cross-section and W Branching Ratios at s\sqrt{s}=205 and 207 GeV

The cross-section for the process e+e-->W+W- was measured with the data sample collected by DELPHI at centre-of-mass energies up to 209 GeV and corresponding to a total integrated luminosity of about 209 pb^-1. The branching ratios of the W decay were also measured; from them the value of |Vcs| was extracted. The results are compared with the most recent calculations in the frame of the Standard Model