Direct effect of ice sheets on terrestrial bicarbonate, sulphate and base cation fluxes during the last glacial cycle: minimal impact on atmospheric CO2 concentrations
glaciers; chemical denudation rates; global geochemical cycles; atmospheric CO2 concentrations
Abstract :
[en] Chemical erosion in glacial environments is normally a consequence of chemical weathering reactions dominated by sulphide oxidation linked to carbonate dissolution and the carbonation of carbonates and silicates. Solute fluxes from small valley glaciers are usually a linear function of discharge. Representative glacial solute concentrations can be derived from the linear association of solute flux with discharge. These representative glacial concentrations of the major ions are similar to 25% of those in global river water. A 3-D thermomechanically coupled model of the growth and decay of the Northern Hemisphere ice sheets was used to simulate glacial runoff at 100-year time steps during the last glacial cycle (130 ka to the present). The glacially derived fluxes of major cations, anions and Si over the glaciation were estimated from the product of the glacial runoff and the representative glacial concentration. A second estimate was obtained from the product of the glacial runoff and a realistic upper limit for glacial solute concentrations derived from theoretical considerations. The fluxes over the last glacial cycle are usually less than a few percent of current riverine solute fluxes to the oceans. The glacial fluxes were used to provide input to an oceanic carbon cycling model that also calculates changes in atmospheric CO2. The potential change in atmospheric CO2 concentrations over the last glacial cycle that arise from perturbations in glacial solute fluxes are insignificant, being < 1 ppm.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Tranter, Martyn; University of Bristol > School of Geographical Sciences > Bristol Glaciology Centre
Munhoven, Guy ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) - Pétrologie et géochimie endogènes
Sharp, Martin J; University of Alberta > Department of Earth and Atmospheric Sciences
Brown, Giles H; University of Wales, Aberystwyth > Institute of Geography and Earth Sciences > Centre for Glaciology
Jones, Ian W; University of Bristol > School of Geographical Sciences > Bristol Glaciolog Centre
Hodson, Andy J; University of Sheffield > Department of Geography
Hodgkins, Richard; Royal Holloway, University of London > Department of Geography, Royal Holloway, University of London
Wadham, Jemma L; University of Bristol > School of Geographical Sciences > Brsitol Glaciology Centre
Language :
English
Title :
Direct effect of ice sheets on terrestrial bicarbonate, sulphate and base cation fluxes during the last glacial cycle: minimal impact on atmospheric CO2 concentrations
Publication date :
2002
Journal title :
Chemical Geology
ISSN :
0009-2541
Publisher :
Elsevier Science Bv, Amsterdam, Netherlands
Special issue title :
The global carbon cycle and its changes over glacial–interglacial cycles
Volume :
190
Issue :
1-4
Pages :
33-44
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique NERC - Natural Environment Research Council
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