Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (K 37 U ') in sediment core ZY2 from the central mud are...Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (K 37 U ') in sediment core ZY2 from the central mud area.The SST records varied between 14.1 and 16.5°C (15.6°C on average),with 3 phases:(1) A high SST phase at 6.2-5.9 cal ka BP;(2) A low and intensely fluctuating SST phase at 5.9-2.3 cal ka BP;and (3) A high and stable SST phase since 2.3 cal ka BP.Variation of the SST records is similar to intensity of the Kuroshio Current (KC),and corresponds well in time to global cold climate events.However,the amplitude of the SST response to cooling events was significantly different in different phases.The SST response to global cooling event was weak while the KC was strong;and the SST response was strong while the KC was weak.The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a shelf branch of the KC and a compensating current induced by the East Asia winter monsoon.The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling,and both the Kuroshio and East Asian winter monsoon play important roles in the modulation mechanism.The SST records display a periodicity of 1482 years.The same period was found in the KC records,indicating that variation of the SST records in the central South Yellow Sea is strongly affected by KC intensity.The same period was also found in Greenland ice cores and North Atlantic and Arabian Sea sediment cores,showing a regional response of marine environmental variability in the East China Seas to that in the global oceans.展开更多
Considerable efforts have been made to extend temperature records beyond the instrumental period through proxy reconstructions,in order to further understand the mechanisms of past climate variability.Yet,the global c...Considerable efforts have been made to extend temperature records beyond the instrumental period through proxy reconstructions,in order to further understand the mechanisms of past climate variability.Yet,the global coverage of existing temperature records is still limited,especially for some key regions like the Tibetan Plateau and for earlier times including the Medieval Warm Period(MWP).Here we present decadally-resolved,alkenone-based,temperature records from two lakes on the northern Tibetan Plateau.Characterized by marked temperature variability,our records provide evidence that temperatures during the MWP were slightly higher than the modern period in this region.Further,our temperature reconstructions,within age uncertainty,can be well correlated with solar irradiance changes,suggesting a possible link between solar forcing and natural climate variability,at least on the northern Tibetan Plateau.展开更多
The proxy of U37 index is widely applied to K ’ reconstructing paleotemperature in the marine environment. However, the long-chain alkenones (LCAs) research is rarely reported in the liminic system. In this paper, we...The proxy of U37 index is widely applied to K ’ reconstructing paleotemperature in the marine environment. However, the long-chain alkenones (LCAs) research is rarely reported in the liminic system. In this paper, we studied LCAs in the surface sediments (0 —10 cm) of nine sulfate lakes in the Inner Mongolia Autonomous Region, Xinjiang Uygur Autonomous Region and Qinghai Province, China. LCAs are detected in eight of the nine lakes, except a dry salt lake —Lake Lop. The result shows that LCAs might be uni- versal in the sulfate lakes. In most of the surface samples, the sequence of the abundance of the long-chain alkenones is C37>C38>C39>C40. And C37︰4 methyl ketone is a predominant compound in the C37 alkenone homologue. Based on regres- sion analysis of U37 -ratios and the average annual, seasonal K ’ (spring, summer, autumn, winter) temperatures, the linear K ’ relativity of U37 -ratios and mean annual temperatures is superior to the others, and the correlation coefficient is 0.88 (r2 = 0.88). The linear relationship of U37 and the average K ’ annual temperature in different water chemistry environ- K ’ ments suggests that the mechanisms controlling U37 index in the saline lakes might be the same as those in the ocean environment. The alkenone unsaturation could become an important paleotemperature proxy in the lacustrine envi- ronment.展开更多
基金supported by the National Basic Research Program of China (2010CB428901)the National Natural Science Foundation of China (90211022 and 41020164005)
文摘Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (K 37 U ') in sediment core ZY2 from the central mud area.The SST records varied between 14.1 and 16.5°C (15.6°C on average),with 3 phases:(1) A high SST phase at 6.2-5.9 cal ka BP;(2) A low and intensely fluctuating SST phase at 5.9-2.3 cal ka BP;and (3) A high and stable SST phase since 2.3 cal ka BP.Variation of the SST records is similar to intensity of the Kuroshio Current (KC),and corresponds well in time to global cold climate events.However,the amplitude of the SST response to cooling events was significantly different in different phases.The SST response to global cooling event was weak while the KC was strong;and the SST response was strong while the KC was weak.The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a shelf branch of the KC and a compensating current induced by the East Asia winter monsoon.The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling,and both the Kuroshio and East Asian winter monsoon play important roles in the modulation mechanism.The SST records display a periodicity of 1482 years.The same period was found in the KC records,indicating that variation of the SST records in the central South Yellow Sea is strongly affected by KC intensity.The same period was also found in Greenland ice cores and North Atlantic and Arabian Sea sediment cores,showing a regional response of marine environmental variability in the East China Seas to that in the global oceans.
基金supported by the National Basic Research Program of China(2010CB833406, 2010CB428902)Hong Kong Rearch Grants Council(HKU 703809P)+1 种基金supported by the Special Equipment Grant from the University Grants Committee of the Hong Kong Special Administrative Region,China(SEG_HKU01)the CAS/SAFEA International Partnership Program for Creative Research Teams(KZZD-EW-TZ03)
文摘Considerable efforts have been made to extend temperature records beyond the instrumental period through proxy reconstructions,in order to further understand the mechanisms of past climate variability.Yet,the global coverage of existing temperature records is still limited,especially for some key regions like the Tibetan Plateau and for earlier times including the Medieval Warm Period(MWP).Here we present decadally-resolved,alkenone-based,temperature records from two lakes on the northern Tibetan Plateau.Characterized by marked temperature variability,our records provide evidence that temperatures during the MWP were slightly higher than the modern period in this region.Further,our temperature reconstructions,within age uncertainty,can be well correlated with solar irradiance changes,suggesting a possible link between solar forcing and natural climate variability,at least on the northern Tibetan Plateau.
文摘The proxy of U37 index is widely applied to K ’ reconstructing paleotemperature in the marine environment. However, the long-chain alkenones (LCAs) research is rarely reported in the liminic system. In this paper, we studied LCAs in the surface sediments (0 —10 cm) of nine sulfate lakes in the Inner Mongolia Autonomous Region, Xinjiang Uygur Autonomous Region and Qinghai Province, China. LCAs are detected in eight of the nine lakes, except a dry salt lake —Lake Lop. The result shows that LCAs might be uni- versal in the sulfate lakes. In most of the surface samples, the sequence of the abundance of the long-chain alkenones is C37>C38>C39>C40. And C37︰4 methyl ketone is a predominant compound in the C37 alkenone homologue. Based on regres- sion analysis of U37 -ratios and the average annual, seasonal K ’ (spring, summer, autumn, winter) temperatures, the linear K ’ relativity of U37 -ratios and mean annual temperatures is superior to the others, and the correlation coefficient is 0.88 (r2 = 0.88). The linear relationship of U37 and the average K ’ annual temperature in different water chemistry environ- K ’ ments suggests that the mechanisms controlling U37 index in the saline lakes might be the same as those in the ocean environment. The alkenone unsaturation could become an important paleotemperature proxy in the lacustrine envi- ronment.
