HR: 10:20h
AN: GC11A-01    [PDF]
TI: Cold to Warm and Warm to Cold: A Comparison of rates and signatures of climate change going into and out of the Younger Dryas
AU: Popp, T
EM: trevor.popp@colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: * White, J
EM: james.white@colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Sveinbjornsdottir, A
AF: University of Iceland, Dunhaga 3, Reykjavik, 107 Iceland
AU: Masson-Delmotte, V
AF: IPSL/LSCE, UMR CEA-CNRS, CE Saclay, Gif/Yvette, 91191 France
AU: Johnsen, S
AF: Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen Juliane Maries Vej 30, Copenhagen, 2100 Denmark
AU: Jouzel, J
AF: IPSL/LSCE, UMR CEA-CNRS, CE Saclay, Gif/Yvette, 91191 France
AB: The most recent, very large (15 degrees C change in mean annual temperature) and very abrupt (50 years or less) climate change recorded in Greenland ice cores is the end of the Younger Dryas (YD). While this cold to warm transition has been extensively studied in ice cores using tools such as stable isotopes in ice, gas concentrations, stable isotopes in gases, snow chemistry, snow accumulation, and electrical conductivity of ice, the start of the YD has received much less attention in ice core analyses. In contrast, we have better theories for how the YD began, than how it ended. We focus here on the Greenland ice core record of the beginning of the YD, with an eye to the speed and nature of this abrupt climate change, and what the ice evidence may tell us concerning the fingerprint, and thus potential processes, of climate change left by this event. The first challenge is identifying the beginning of the YD in the ice core. Warm to cold transitions in isotopes in ice cores can be muted if winter snows are lost as a result of the colder conditions. This appears to be the case in the Greenland cores. Deuterium excess, which records ocean conditions during moisture evaporation, on the other hand, retains its sharpness. At the beginning of the YD, XS changes in NorthGRIP in a matter of years, a signal similar in size and speed to that seen at the end of the YD, but opposite in sign. Other signals are not similar in size and speed, however. These differences between the beginning and end of the YD will be discussed, and can reveal clues to the nature and timing of the climate changes. For example, continental dust does not change (increase) rapidly at the beginning of the YD cold period, but rather is delayed by decades. This suggests that there may be is a lag in the production of dust as ecosystems slowly dry and transform in response to the climate change.
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting