Climate and biome simulations for the past 21,000 years

摘要: Abstract This paper reports on a set of paleoclimate simulations for 21, 16, 14, 11 and 6 ka (thousands years ago) carried out with the Community Climate Model, Version 1 (CCM1) National Center Atmospheric Research (NCAR). climate model uses four interactive components that were not available in our previous NCAR CCM0 ( COHMAP, 1988 Science, 241, 1043–1052; Wright et al., 1993 Global Since Last Glocial Maximum, University Minnesota Press, MN): soil moisture, snow hydrology, sea-ice, mixed-layer ocean temperature. The new also use estimates ice sheet height size from Peltier 1994 , 265, 195–201), synchronize astronomically dated orbital forcing atmospheric CO2 levels corrected radiocarbon to calendar years. CCM1 agree their most general characteristics. 21 ka is cold dry, response presence sheets lowered levels. period 14–6 ka has strengthened northern summer monsoons warm mid-latitude continental interiors changes. Regional differences between can be traced effects either or boundary conditions. simulates processes more realistically, but additional degrees freedom allow ‘drift’ toward less realistic solutions some instances. are expressed terms equilibrium vegetation using BIOME 1, indicate large shifts biomes. Northern tundra forest biomes displaced southward at glacial maximum subtropical deserts contract mid-Holocene when strengthen. These changes could, if simulated interactively, introduce feedbacks. total area vegetated land remains nearly constant through time because exposure shelves sea level largely compensates covered by expanded sheets.