Showing papers by "Hubertus Fischer published in 2003"

Transient Changes in the Global Carbon Cycle \\During the Last Glacial/Interglacial Transition

Abstract: The global carbon cycle plays a significant role in glacial/interglacial transitions. On one hand because carbon reservoirs and exchange rates are subject to external climateconditions, on the other hand because changes in carbon dioxide concentrations lead to amplification and mediation of regional climate variations. Time slice experimentswere so far unable to unambiguously explain the driving forces of the glacial/interglacial change in atmospheric CO2 of about 100 ppmv. Additional information can begained from the temporal evolution of the carbon cycle using transient model runs. Here we used a coupled atmosphere/biosphere/ocean box model of the global carboncycle to quantify changes in CO2 and d13C observed in Antarctic ice core records. To this end the model is transiently driven by various proxy records overthe last 25,000 years. First results show that the estimated increase in the terrestrial biosphere together with the measured atmospheric pCO2 are difficult to reconcilewith current theories of oceanic changes in the carbon cycle. In addition a significant role of the biosphere on changes in the isotopic composition of atmospheric CO2is supported.

The North-GRIP record of sea-salt and mineral-dust aerosols revealing new insight into long-range atmospheric transport properties during the last glacial period.

Abstract: The North-GRIP ice core provides continuous records of sea salt and mineral dust aerosols from the last glacial period. A large number of soluble ions were analysed by ion chromatography and have opened up for new possibilities looking into details in the relationship between ion composition and climate conditions. Changes in ion compositions seem to be related to changes in particle size distributions as an effect of fractionation during long-range atmospheric transport.Analysis of ion-compositions in the North-GRIP ice core suggests that long-range atmospheric transport patterns remained nearly unchanged during the Dansgaard/Oeschger events and were constant through most of the last glacial period. However in sections of the early part of the last glacial period the analysis shows a prominently different pattern of ion composition. These differences are associated with differences in particle size distributions and indicate major differences in circulation patterns during the early part of the last glacial period.