How does the availability of water in the critical zone change with climate? 

Silts modified after deposition by water table fluctuations in response to orbtial forcing. Near Tianshui, Gansu, China

Change in rainfall is undoubtedly an important component of changes in climate. But the availability of water is more important to ecosystems – including society – than rainfall itself. The availability of water is influenced not only by rainfall, but also by changes in evaporation and transpiration. We are studying past changes in water availability using paleosols and stalagmites. Time periods that were warmer than modern are of particular interest. Regions of interest include the East Asian ‘monsoon’ region and the southwest United States.

The photograph to the left shows Miocene sediments near Tianshui, China that have been modified by soil formation under periodically changing availability of water- hence the layering, which is not a primary sedimentary feature but rather a secondary pedogenic feature that records a rising and falling water table in this region 14 millions years ago. Former undergraduate student Emma Heitmann published her senior honors thesis on this section.

We are currently working with Lu Huayu and his group at Nanjing University on a section exposed near Jiaxian on the northern part of the Chinese Loess Plateau.