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The Context of Palaeohydrology |
1 School of Geography, University of Oxford, 1 Mansfield Road, Oxford OX1 3TB, UK
Kings’ College, Cambridge CB2 1ST, UK
2 Laboratoire de Geologie du Quaternaire, CEREGE, Europole de l’Arbois, BP 80, F-13545, Aix-en-Provence Cedex 04, France
During the arid Late Glacial and Last Glacial Maximum (between approximately 30 000 and 13 000 calendar years ago), vegetation cover retreated and large areas of the continents were occupied by desert and semi-desert vegetation. The result of this general decrease in biological activity would have been a decrease in the size of the land carbon reservoir, and a decrease in the rate of chemical rock weathering. By contrast, during the early-mid-Holocene, conditions in many areas seem to have been moister than today due to a more active hydrological cycle. All of these processes would have affected the global carbon cycle and altered the amplitude and timing of the climate fluctuations themselves. In effect, the climatic shift between glacial and interglacial conditions creates a very large ‘missing source’ of carbon, perhaps amounting to thousands of gigatonnes, to account for the carbon uptake by the land system during the present interglacial, and thus carbon cycle models of the late Quaternary may need to be revised extensively.
