HR: 12:05h
AN: PP42B-08    [Abstracts]
TI: Transient Simulation of Holocene Climate: Seasonal Trend Analysis and Implications for Proxy Interpretations
AU: * Timm, O
EM: timm@hawaii.edu
AF: International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Rd, Honolulu, HI 96822 United States
AU: Timmermann, A
EM: axel@hawaii.edu
AF: International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Rd, Honolulu, HI 96822 United States
AB: During the Holocene epoch the precessional cycle changed profoundly the seasonality of the incoming solar radiation. At the top of the atmosphere anomalies of the order of 20-30W/m² imposed a substantial external forcing on the climate system. Furthermore, the greenhouse gas concentrations increased during the late Holocene. We have simulated the Holocene climate epoch with an `Earth system Model of Intermediate Complexity' in a transient model integration. The temporal characteristics of the climate response to external forcing was analyzed. A trend analysis of surface temperature shows a general positive relation to the precessional forcing in low latitudes. However, the trends in boreal winter and summer season have opposite signs. As a result, the annual mean response in surface temperatures is reduced. Precipitation anomalies indicate shifts in the Intertropical Convergence Zone and increased Indian summer monsoon. In the polar regions the thermal inertia of the ocean and the sea-ice-albedo feedback cause a non-linear response to the precessional cycle. The temperature trend pattern in boreal winter depends on the model's CO₂ sensitivity and the past climate trajectory. The presented results have two major implications for climate proxies. Proxies from polar regions can provide valuable information for narrowing the model uncertainties in those regions. For low latitudes the seasonality is important for the climatic interpretation of proxies. Different seasonal response functions can put different weights on the integrated seasonal anomalies, thus leading to different results in timing and amplitude of the Holocene maximum.
DE: 1622 Earth system modeling (1225)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4910 Astronomical forcing
DE: 4930 Greenhouse gases
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005