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The Paleosalinity-Based Climate Record of the Past Millennium at Qinghai Lake, China
Reference
Zhang, E., Shen, J., Wang, S., Yin, Y., Zhu, Y. and Xia, W.  2004.  Quantitative reconstruction of the paleosalinity at Qinghai Lake in the past 900 years.  Chinese Science Bulletin 49: 730-734.

What was done
Based on a relationship between the shell-length of the ostracod Limnocythere inopinata and the salinity of the water in which it lives, which was developed by Yin et al. (2001) from data gathered from fifty lakes of different salinities scattered across the Tibetan Plateau, the salinity history of Qinghai Lake (the largest inland saline lake in China) was reconstructed for the period AD 1100-2000 using ostracod shell-length data derived from a 114-cm sediment core.

What was learned
The authors report that "low salinity during 1160-1290 AD showed the humid climate condition [of] the Medieval Warm Period in this area, while the high salinity during 1410-1540 AD, 1610-1670 AD and 1770-1850 AD [corresponded with] the three cold pulses of the Little Ice Age with a dry climate condition," where the evidence for the occurrence of these warm and cold intervals comes from the climate change studies of Yao et al. (1990) and Wang (2001).

What it means
Clearly, the paleosalinity record of Qinghai Lake parallels the climate history of the surrounding region, and even meshes with that of much of the rest of the world.  Of special interest in this regard, therefore, is the fact that Qinghai Lake's current salinity has not even reached the halfway point of the distance between the near-record high salinity of the last cold peak of the Little Ice Age and the record low salinity experienced during the Medieval Warm Period, which suggests that the level of warmth recently experienced in this region of China is nowhere near that experienced there during the Medieval Warm Period, when, of course, there was much less CO2 in the air than there is currently.  Also, it is instructive to note that the salinity drop that marks the "beginning of the end" of the last stage of the Little Ice Age began sometime prior to 1850, in harmony with the Northern Hemisphere temperature history of Esper et al. (2002), but in striking contradiction of the Northern Hemisphere temperature history of Mann et al. (1998, 1999), which does not depict any increase in temperature until after 1910, some 60 years later.

References
Esper, J., Cook, E.R. and Schweingruber, F.H.  2002.  Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability.  Science 295: 2250-2253.

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1998.  Global-scale temperature patterns and climate forcing over the past six centuries.  Nature 392: 779-787.

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1999.  Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations.  Geophysical Research Letters 26: 759-762.

Wang, S.W.  2001.  Advances in Modern Climatological Studies.  China Meteorological Press, Beijing, China, pp. 127-131.

Yao, T.D., Xie, Z.C., Wu, X.L. et al.  1990.  Climatic change since Little Ice Age recorded by Dunde Ice Cap.  Science in China, Series B 34: 760-767.

Yin, Y., Li, W.C., Yang, X.D. et al.  2001.  Morphological responses of Limnocythere inopinata (Ostracoda) to hydrochemical environment factors.  Science in China, Series D 44 (supplement): 316-323.


Reviewed 22 September 2004