Article

Siegenthaler, U. et al. Stable carbon cycle-climate relationship during the Late Pleistocene. Science 310, 1313-1317

Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Bremen, Germany
Science (Impact Factor: 31.48). 12/2005; 310(5752):1313-7. DOI: 10.1126/science.1120130
Source: PubMed

ABSTRACT A record of atmospheric carbon dioxide (CO2) concentrations measured on the EPICA (European Project for Ice Coring in Antarctica) Dome Concordia ice core extends the
Vostok CO2 record back to 650,000 years before the present (yr B.P.). Before 430,000 yr B.P., partial pressure of atmospheric CO2 lies within the range of 260 and 180 parts per million by volume. This range is almost 30% smaller than that of the last
four glacial cycles; however, the apparent sensitivity between deuterium and CO2 remains stable throughout the six glacial cycles, suggesting that the relationship between CO2 and Antarctic climate remained rather constant over this interval.

Download full-text

Full-text

Available from: Jean Jouzel, Aug 10, 2015
4 Followers
 · 
191 Views
  • Source
    • "The orbital forcing during MIS 11 was characterized by a different phasing of obliquity and precession leading to lower amplitude insolation cycles compared to the Holocene (Loutre and Berger 2003). In contrast to the differences in orbital parameters, the greenhouse gas concentrations in the atmosphere during MIS 11 were similar to the preindustrial Holocene (Siegenthaler et al. 2005). Until now, the coherency of sea-surface temperature (SST) trends during MIS 11 has never been assessed on a global basis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To examine the sea-surface temperature (SST) evolution during interglacial Marine Isotope Stage (MIS) 11, we compiled a database of 78 SST records from 57 sites. We aligned these records by oxygen-isotope stratigraphy and subjected them to an Empirical Orthogonal Function (EOF) analysis. The principal SST trend (EOF1) reflects a rapid deglacial warming of the surface ocean in pace with carbon dioxide rise during Termination V, followed by a broad SST optimum centered at ~410 thousand years (ka) before present (BP). The second EOF indicates the existence of a regional SST trend, characterized by a delayed onset of the SST optimum, followed by a prolonged period of warmer temperatures. The proxy-based SST patterns were compared to CCSM3 climate model runs for three time slices representing different orbital configurations during MIS 11. Although the modeled SST anomalies are characterized by generally lower variance, correlation between modeled and reconstructed SST anomalies suggests a detectable signature of astronomical forcing in MIS 11 climate trends.
    Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC), Edited by Michael Schulz, André Paul, 01/2015: pages 13-18; Springer., ISBN: 978-3-319-00693-2
  • Source
    • "However, for a number of reasons, carbonate weathering surely deserves more attention: 1) Given the size of the carbonate reservoir compared to that of the atmospheric reservoir, any transient imbalance between continental chemical weathering and oceanic carbonate precipitation is likely to produce atmospheric CO 2 perturbations. Proxies recorded in ice cores over the last 800 ka (Petit et al., 1999; Siegenthaler et al., 2005; Lüthi et al., 2008) suggest that parameters known to impact chemical weathering fluxes (temperature, precipitation, distribution of carbonate platform, ecosystem fertilization, atmospheric pCO 2 ) have varied over periods shorter than 500 ka. These relatively rapid environmental changes are likely to cause global changes in the chemical weathering flux to the ocean, which might lead to departure from steady-state of the carbonate cycle and create imbalance in the carbon cycle. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the controls on carbonate weathering in a well-drained pure carbonate area subject to strong environmental gradients, the Jura Mountains, Western Europe. The water chemistry of sampled springs and re-surgences is dominated by Ca 2+ (87 to 96 Eq% of the cationic charge) and HCO 3 − (90 to 97 Eq% of the anionic charge), reflecting the overwhelming imprint of calcium carbonate dissolution by atmospheric/biogenic CO 2 . Ca 2+ concentration, which directly gives access to the amount of calcium carbonate dissolved per unit of water runoff, shows a gradual two-fold decrease (from 3000 to 1400 μmol/L) along the elevation gradient (from 300 to 1200 m). After discussing the possible influence of each environmental parameter on the observed water chemistry gradient, a decreasing soil pCO 2 (the main source of acidity) with increasing altitude appears as the most likely explanation. As no spatial and temporal record of soil pCO 2 are available for the Jura Mountains, we performed soil pCO 2 modeling using the ecological and hydrological ASPECTS model that allows reconstructing carbon and water exchange fluxes between the vegetation, soil and atmosphere. Modeling results suggest that soil pCO 2 decreases with altitude in response to both the change in vegetation species from deciduous-dominated forest in the lowlands to evergreen-dominated forest above 800 m (responsible for 65% of the varia-tion) and the change in climate and soil properties (responsible for 35% of the variation). Carbonate weathering would thus be strongly sensitive to the type of vegetation, which drives both temporal and spatial variations of soil carbon and water budgets. Based on field observations, we show that carbonate weathering rates are 20– 30% higher under deciduous vegetation cover than under conifers (at a given water runoff value), in agreement with modeling results. Chemical denudation rates of carbonate in the Jura Mountains vary from 152 to 375 t/km 2 / yr, corresponding to 60–150 mm/ka of carbonate being removed. Carbonate weathering within the 10,000 km 2 of the study area accounts for an atmospheric CO 2 consumption of 0.3 TgC/yr, showing that carbonate rocks have an enhanced capacity of atmospheric CO 2 neutralization at least transiently. This study demonstrates that car-bonate weathering is sensitive to the ecosystem dynamics, a conclusion that might be much more general, and suggests that carbonate weathering and associated CO 2 consumption fluxes quickly react to any global change or land use modification.
    Chemical Geology 12/2014; 390:74-86. DOI:10.1016/j.chemgeo.2014.10.010 · 3.48 Impact Factor
  • Source
    • "However, for a number of reasons, carbonate weathering surely deserves more attention: 1) Given the size of the carbonate reservoir compared to that of the atmospheric reservoir, any transient imbalance between continental chemical weathering and oceanic carbonate precipitation is likely to produce atmospheric CO 2 perturbations. Proxies recorded in ice cores over the last 800 ka (Petit et al., 1999; Siegenthaler et al., 2005; Lüthi et al., 2008) suggest that parameters known to impact chemical weathering fluxes (temperature, precipitation, distribution of carbonate platform, ecosystem fertilization, atmospheric pCO 2 ) have varied over periods shorter than 500 ka. These relatively rapid environmental changes are likely to cause global changes in the chemical weathering flux to the ocean, which might lead to departure from steady-state of the carbonate cycle and create imbalance in the carbon cycle. "
Show more