The tropical Indian Ocean(TIO) displays a uniform basin-wide warming or cooling in sea surface temperature(SST) during the decay year of El Niδo-Southern Oscillation(ENSO) events. This warming or cooling is called the tropical Indian Ocean Basin Mode(IOBM). Recent studies showed that the IOBM dominates the interannual variability of the TIO SST and has impacts on the tropical climate from the TIO to the western Pacific. Analyses on a 148-year-long monthly coral δ 18 O record from the Seychelles Islands demonstrate that the Seychelles coral δ 18 O not only is associated with the local SST but also indicates the interannul variability of the basin-wide SST in the TIO. Moreover, the Seychelles coral δ 18 O shows a dominant period of 3–7 years that well represents the variability of the IOBM, which in return is modulated by the inter-decadal climate variability. The correlation between the Seychelles coral δ 18 O and the SST reveals that the coral δ 18 O lags the SST in the eastern equatorial Pacific by five months and reaches its peak in the spring following the mature phase of ENSO. The spatial pattern of the first EOF mode indicates that the Seychelles Islands are located at the crucial place of the IOBM. Thus, the Seychelles coral δ 18 O could be used as a proxy of the IOBM to investigate the ENSO teleconnection on the TIO in terms of long-time climate variability.
The question of whether or not global warming has paused since more than ten years ago, namely "warming hiatus", has attracted the attention of climate science community including the IPCC. Some authors have attributed the "warming hiatus" to the internal changes in the climate system, i.e., the recombination of ocean-atmosphere circulations. Therefore, it is necessary to propose higher requirements on reconstructing circulation background of climate change for the past millennium. However, the analyses of changes in atmospheric circulation over the last millennium as well as the conclusions of related regional climate patterns are so widely different and contradictory, bringing uncertainties to our understanding of regional even global climate change to a great extent. On the other hand, in the last 10 years the high-precision U/Th-dated stalagmite oxygen isotope ratio(δ^(18)O) sequences provided an accurate chronological frame for the paleoclimate study of the middle and late Pleistocene, in which all authors from China took the Chinese stalagmite δ^(18)O as the summer monsoon index without exception. However, this point of view misleads the climate scientists into thinking that the stalagmite δ^(18)O can be as the proxy of precipitation amount. Nevertheless, it is well known that all of these records have a lot in common in the low frequency trend. However, most sequences cannot be calibrated by instrumental precipitation records, and thus the uncertainty of the climate research framework of China and even of the world has increased. Therefore, it is imperative for climatology to clarify the origin of contradiction and to reduce the uncertainty as early as possible. On the basis of analyzing the significance of stalagmite δ^(18)O in the monsoon regions of China, the author tries to propose a new circulation proxy in this paper: integrating the Chinese stalagmite oxygen isotope sequence to reconstruct the tropical Pacific sea surface temperature gradient, i.e., the large-scale ENSO-like state over the past
Sabina przewalskii is the longest living endemic tree species in the northeastern Tibetan Plateau,and has been widely employed in tree ring based climate research in China.However,most dendroclimatic reconstructions have been primarily based on empirical relationships between tree growth and climate factors identified by statistical assessment.To date,the physiological relationships between tree growth and their limiting climate factors have not been properly assessed.Here,we simulated the physiological response of Sabina przewalskii tree growth to major limiting climate factors based on the Vaganov-Shashkin (VS) model.The VS modeled results validated the relationships between tree ring and climate factors constructed by statistical models,both approaches suggesting that precipitation during the early growing season,especially in May and June,has significant effect on tree growth,while temperature mainly affects tree growth by warming-induced drought and by extending the growing season.Under current and projected climate scenarios,our modeling results predict an increase in radial growth of Sabina przewalskii around the Qaidam Basin,with the potential outcome that regional forests will increase their capacity to sequester carbon.
