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Holocene thermal optimal and climate variability of East Asian monsoon inferred from forest reconstruction of a subalpine pollen sequence, Taiwan |
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| Authors: | PM Liew CY Lee CM Kuo |
| Institution: | aDepartment of Geosciences, National Taiwan University, 1, Sec. 4, Roosevelt Rd. Taipei, Taiwan, R.O.C. bChinese Petroleum Coperation, 3, Sungren Rd, Shinyi Chiu, Taipei 10110, Taiwan, R.O.C. |
| Abstract: | The East Asian monsoon Holocene optimal period has been debated both about duration and whether conditions were a maximum in thermal conditions or in precipitation. In this study we show Holocene climate variability inferred by a forest reconstruction of a subalpine pollen sequence from peat bog deposits in central Taiwan, based on modern analogues of various altitudinal biomes in the region. A warmer interval occurred between 8 and 4 ka BP (calibrated 14C years) when the subtropical forests were more extensive. The Holocene thermal optimum is represented by an altitudinal tropical forest at 6.1–5.9 ka BP and 6.9 ka BP and only the latter was accompanied by wet conditions, indicating decoupling of thermal and precipitation mechanism in the middle Holocene. Abrupt and relative severe cold phases, shown by biome changes, occurred at about 11.2–11.0 ka BP; 7.5 ka BP; 7.2 ka BP; 7.1 ka BP; 5.2 ka BP, 5.0 ka BP and 4.9 ka BP. A spectral analysis of pollen of a relatively cold taxon — Salix, reveals that the time series is dominated by a 1500 yr periodicity and similar to the cold cycle reported in the marine records of Indian and western Pacific Oceans. The cold–warm conditions inferred by the change of forests show close relationship to solar energy in comparison with the production rate of Be-10. |
| Keywords: | Holocene thermal optimal East Asian monsoon forest reconstruction abrupt change |
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