Contribution of oceanic and vegetation feedbacks to Holocene climate change in monsoonal Asia

Abstract

Abstract.The impact of vegetation-atmosphere and ocean-atmosphere interactions on the mid-to late Holocene climate change as well as their synergy is studied for different parts of the Asian monsoon region, giving consideration to the large climatic and topographical heterogeneity in that area. We concentrate on temperature and precipitation changes as the main parameters describing monsoonal influenced climates.For our purpose, we analyse a set of coupled numerical experiments, performed with the comprehensive Earth system model ECHAM5/JSBACH-MPIOM under present-day and mid-Holocene (6 k) orbital configurations (Otto et al., 2009b). The temperature change caused by the insolation forcing reveals an enhanced seasonal cycle, with a pronounced warming in summer (0.58 K) and autumn (1.29 K) and a cooling in the other seasons (spring: −1.32 K; winter: −0.97 K). Most of this change can be attributed to the direct response of the atmosphere, but the ocean, whose reaction has a lagged seasonal cycle (warming in autumn and winter, cooling in the other seasons), strongly modifies the signal. The simulated contribution of dynamic vegetation is small and most effective in winter, where it slightly warms the near-surface atmosphere (approx. 0.03 K). The temperature difference attributed to the synergy is on average positive, but also small. Concerning the precipitation, the most remarkable change is the postponement and enhancement of the Asian monsoon (0.46 mm/day in summer, 0.53 mm/day in autumn), mainly related to the direct atmospheric response. On regional average, the interactive ocean (ca. 0.18 mm/day) amplifies Correspondence to: A. Dallmeyer (anne.dallmeyer@zmaw.de) the direct effect, but tends to weaken the East Asian summer monsoon and strongly increases the Indian summer monsoon rainfall rate (0.68 mm/day). The influence of dynamic vegetation on precipitation is comparatively small (<0.04 mm/day). The synergy effect has no influence, on average.

Spatial variability of Holocene changes in the annual precipitation pattern: a model-data synthesis for the Asian monsoon region

“…Fig. 15 Pure contribution of the atmosphere-ocean interaction to the mid-Holocene to present-day annual precipitation change (mm/day) as simulated by the coupled atmosphere-ocean-vegetation model ECHAM5/JSBACH-MPIOM (for details see Dallmeyer et al 2010). The grey line marks the Tibetan Plateau Fig. 14 Differences in the seasonal precipitation cycle between midHolocene and present-day (mm/day) for the regions a N India and b CE China (cf.…”

“…In the high resolution simulation, the number of points where the model results agree with the reconstructed moisture signal is increased by 30 % compared to the low resolution simulation and the heterogeneous pattern of moisture change is better represented. The pure contribution of the oceanatmosphere interaction to the annual precipitation signal derived from coupled atmosphere-ocean-vegetation simulations in ECHAM5/JSBACH-MPIOM (for details we refer to Dallmeyer et al 2010) is illustrated in Fig. 15.…”

“…To assess the robustness of our results and conclusions, we compare the reconstructed moisture index with results from coarse-resolution simulations ( Fig. 13) conducted with the comprehensive Earth system model ECHAM5/JSBACH-MPIOM (referred to as T31 AOV , Dallmeyer et al 2010) and performed within the Paleoclimate Modelling Intercomparison Project Phase II (PMIP2, Braconnot et al 2007a, b). We only considered simulations conducted in fully coupled atmosphere-oceanvegetation models.…”

“…The strength of these interactions reveals regional dissimilarities in the Asian monsoon domain as well as contradictory contributions to the Holocene climate change in different climate models (see Dallmeyer et al 2010 and references therein). To assess the performance of the different models, the model results have to be validated to paleoclimate reconstructions.…”

Simulation and Comparison Between Mid-Holocene and Preindustrial Indian Summer Monsoon Circulation Using a Regional Climate Model

“…Around 6000 years before present (e.g., [3,4]) the Indian monsoon penetrated further into the inner domain of the Asian continent implying a wetter climate. Modeling studies related this enhancement of the monsoon to the impact of changing solar summer insolation on climate (e.g., [5][6][7]). The enhanced annual solar cycle affected a higher meridional temperature gradient between the Eurasian land surface and the Indian Ocean with an intensified cross equatorial monsoonal wind and moisture advection over the Arabian Sea and the Bay of Bengal and *Address correspondence to this author at the Freie Universität Berlin, Institute for Meteorology, Carl-Heinrich-Becker-Weg 6-10, D-12165 Berlin, Germany; Tel: +49 30 838 71149; E-mail: stefan.polanski@met.fu-berlin.de more rainfall in summer.…”