Abstract
Abstract. Mid-Holocene ocean and vegetation feedbacks over East Asia are investigated by a set of numerical experiments performed with the version 4 of the Community Climate System Model (CCSM4). With reference to the pre-industrial period, most of the mid-Holocene annual and seasonal surface-air temperature and precipitation changes are found to result from a direct response of the atmosphere to insolation forcing, while dynamic ocean and vegetation modulate regional climate of East Asia to some extent. Because of its thermal inertia, the dynamic ocean induced an additional warming of 0.2 K for the annual mean, 0.5 K in winter (December–February), 0.0003 K in summer (June–August), and 1.0 K in autumn (September–November), but a cooling of 0.6 K in spring (March–May) averaged over China, and it counteracted (amplified) the direct effect of insolation forcing for the annual mean and in winter and autumn (spring) for that period. The dynamic vegetation had an area-average impact of no more than 0.4 K on the mid-Holocene annual and seasonal temperatures over China, with an average cooling of 0.2 K for the annual mean. On the other hand, ocean feedback induced a small increase of precipitation in winter (0.04 mm day−1) and autumn (0.05 mm day−1), but a reduction for the annual mean (0.14 mm day−1) and in spring (0.29 mm day−1) and summer (0.34 mm day−1) over China, while it also suppressed the East Asian summer monsoon rainfall. The effect of dynamic vegetation on the mid-Holocene annual and seasonal precipitation was comparatively small, ranging from −0.03 mm day−1 to 0.06 mm day−1 averaged over China. In comparison, the CCSM4 simulated annual and winter cooling over China agrees with simulations within the Paleoclimate Modeling Intercomparison Project (PMIP), but the results are contrary to the warming reconstructed from multiple proxy data for the mid-Holocene. Ocean feedback narrows this model–data mismatch, whereas vegetation feedback plays an opposite role but with a level of uncertainty.
Highlights
Paleoclimate modeling is one of the most important aspects in past climate change research
The impact of interactive ocean and vegetation on the mid-Holocene climate change over East Asia are investigated by utilizing a new generation of the earth system model Community Climate System Model version 4 (CCSM4)
Based on the fully coupled CCSM4 AOVGCM experiments, the mid-Holocene annual and seasonal temperature changes over China resulted mainly from the imposed orbital forcing and the reduction of atmospheric concentrations of greenhouse gases, and the simulated annual and winter cooling over China was contrary to the warming reconstructed from multiple proxy data
Summary
Paleoclimate modeling is one of the most important aspects in past climate change research. Jiang et al (2012) showed that interactive ocean induced a warming effect on annual, winter, and autumn (September–November) temperatures, while interactive vegetation had little impact on annual and seasonal temperature over China In this respect, the differences between the PMIP AGCM and AOGCM (AOGCM and AOVGCM) control simulations introduced a bias into the role of ocean–atmosphere (vegetation–atmosphere) interaction on the mid-Holocene climate as discussed by Jiang et al (2012). The differences between the PMIP AGCM and AOGCM (AOGCM and AOVGCM) control simulations introduced a bias into the role of ocean–atmosphere (vegetation–atmosphere) interaction on the mid-Holocene climate as discussed by Jiang et al (2012) Another key purpose of this study is to examine pure ocean and vegetation feedbacks over East Asia during the mid-Holocene using rigorous experiments of climate models.
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