Yetang Hong

Correlation between Indian Ocean summer monsoon and North Atlantic climate during the Holocene

There has been a number of investigations for the correlation between the Asia monsoon and the North Atlantic climate for the last glacial; however, little research has been done for the present interglacial, the Holocene. Here we present for the first time a high-resolution composite proxy record for the Indian Ocean summer monsoon spanning around 12 000 years based on the δ13C time series of both a single plant species (Carex mulieensis) remains cellulose and the total plant assemblage cellulose in the Hongyuan peat bog from the Tibet Plateau. The records show that the strength of the Indian Ocean summer monsoon had abrupt variations during the last 12 000 years. The weakest monsoon occurred in the Younger Dryas period. Following rapid strengthening from around 11 200 to 10 800 a BP the monsoon kept a generally strong level for around 5300 years. From around 5500 a BP onwards the monsoon strength tended to gradual decrease. In addition, there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales, which superimpose the general tendency of the monsoon variation. In every case when the ice-rafted debris events in the North Atlantic occurred, the summer monsoon strength decreased correspondingly. These evidences show that teleconnection between the Indian Ocean summer monsoon and the North Atlantic climate is present not only in the last glacial but also in the Holocene, which may be linked to abrupt reorganizations of the ocean thermohaline circulation, leading to redistribution of energy, changing temperature and moisture gradient over the southern subtropical Indian Ocean, and eventually controlling the variability of the Indian Ocean summer monsoon.

A 6000-year record of changes in drought and precipitation in northeastern China based on a δ13C time series from peat cellulose

We report a new peat delta C-13 proxy record for humidity or precipitation based on C3 plants from northeastern China. The record reveals two times of significant climate shift and eight severe drought periods during the past 6000 years, all of which have the nature of widespread global occurrence. The variability of precipitation shows periodicities of around 70, 80, 90, 107, 110, 123, 134, 141, 162, 198, 205, 249, 278, 324, 389, 467, 584, 834 and 1060 years. The occurrence and persistent times of drought and periodicities of precipitation show good correspondence with solar variability. The remarkable correlations between peat delta C-13, peat delta O-18 and atmospheric Delta C-14 suggest that on timescales of decades to centuries the changes in drought and precipitation are likely caused by variations of atmospheric circulation and atmosphere-ocean interactions in large-scale patterns that seem to be related to solar variability

Increasing summer rainfall in arid eastern-Central Asia over the past 8500 years

A detailed and well-dated proxy record of summer rainfall variation in arid Central Asia is lacking. Here, we report a long-term, high resolution record of summer rainfall extracted from a peat bog in arid eastern-Central Asia (AECA). The record indicates a slowly but steadily increasing trend of summer rainfall in the AECA over the past 8500 years. On this long-term trend are superimposed several abrupt increases in rainfall on millennial timescales that correspond to rapid cooling events in the North Atlantic. During the last millennium, the hydrological climate pattern of the AECA underwent a major change. The rainfall in the past century has reached its highest level over the 8500-year history, highlighting the significant impact of the human-induced greenhouse effect on the hydrological climate in the AECA. Our results demonstrate that even in very dry eastern-Central Asia, the climate can become wetter under global warming.

Humification degrees of peat in Qinghai-Xizang Plateau and palaeoclimate change

In this article we report a new and sensitive palaeoclimate proxy indicator-humification degrees of peat. Based on the comparison of humification degrees with other climate proxy records, such as λ13C time series of theC. mulieensis remains cellulose in the same peat profile, we suggest that humification degrees of peat in Qinghai-Xizang Plateau can served as a palaeoclimate proxy indicator. The higher the humification degrees of peat, the warmer-wetter the climate; on the contrary, the lower the humification degrees, the colder-drier the climate. Due to the simple method of determination, humification degree of peat is worthy studying and applying further.

Evidence for solar forcing of climate variation from δ18O of peat cellulose

There have been a number of investigations for examining the possible link between long-term climate variability and solar activity. A continuous δ18O record of peat cellulose covering the past 6 000 years and the response of climate variation inferred from the proxy record to solar forcing are reported. Results show that during the past 5 000 years the abrupt climate variations, including 17 warming and 17 cooling, and a serious of periodicities, such as 86, 101, 110, 127, 132, 140, 155, 207, 245, 311, 820 and 1 050 years, are strikingly correlative to the changes of solar irradiation and periodicity. These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.

Biological effect of rare-earth elements on anti-oxidation enzymes in wheat under acid rain stress

Based on pot-culture experiments, the biological effect of rare-earth elements (REE) on antioxidation enzymes of wheat under acid rain stress was studied. The results show that both acid rain and REE can affect the activity of anti-oxidation enzymes of wheat to different extents. Under the acid rain stress, anti-oxidation enzymes (CAT, SOD) of wheat showed single peak curve with the decrease of pH values. After REE were applled, variation of activities of anti-oxidation enzymes was relatively stable and the peak value of variation curve would move in the direction of increased acidity. Under low acidity of acid rain, REE could reduce the sensitivity of anti-oxidation enzymes of wheat to acid rain stress significantly and promote the resistance of anti-oxidation enzymes of wheat to acid rain.

Climatic change over the past 8 000 years in Caohai District, Guizhou

Conclusions1.Over the past 8 000 years, notable changes in moist regime and temperature took place in Caohai District. The peat archives in this area recorded some hemispheric climatic events, such as three new ice ages and the Medieval Warm Period occurring in the northern hemisphere. This indicates that this area is sensitive to global changes.2.Over the past 8 000 years, Caohai District is typical of the warm-moist—cool-dry climate.

An improved method for analysis of oxygen isotope in organic matter

Conclusions1.The high-temperature pyrolysis reaction of cellulose and organic matter have an optimal reaction condition: 95°C, 4–14 mg cellulose, and 15–30 min.2.Under the optimal condition, the formed CO or CO2, and the sample have the same λ18O value. It is unnecessary to recover oxygen from CO.3.The data are accurate and reliable, and the operation method is simple and economic.