Paleoclimatic research using speleothems (cave deposits)

Stalagmite in Cave of the Bells, Santa Cruz County, AZ. Note ring (~1.2cm) on formation for scale

The southwestern US is surprisingly lacking in continuous, long paleoclimate records. The few available tree-ring records that span the past 1000-2000 years indicate a history of decade-century scale droughts that surpass anything we have seen in the 20th century. To develop a clear picture of "megadrought" recurrence and extent, and to link these droughts to potential causes, requires more data on past variations. We are developing records from cave deposits (speleothems) that can provide the continuous perspective on past climate change in the Southwest that is needed to understand the history of regional climate variability and sensitivity.

In collaboration with several other UA faculty, students, and local cave researchers, we have sampled several caves in SE Arizona. With NSF (ESH) and UA support, we are making significant headway in the development of climate records from local caves. We have collected sampled ranging in age from the recent millennium to nearly 275,000 years old. Stable isotopic analyses of selected samples show significant variations associated with the deglaciation and millennial variability similar to patterns seen in the North Atlantic, and Holocene data show century-scale variability that resembles solar forcing. Over the past millennium, our records complement those from tree-ring reconstructions and point to substantial multidecadal drought variability. We are optimistic that this approach will fill a long-vacant gap in our understanding of climate change in the southwestern US. New support is in hand to expand this work into Mexico, with a focus on the Holocene history of the monsoon (doctoral work of Sarah Truebe).

We have been collecting cave dripwater samples at one site since 2003, and isotopic analysis of these waters indicate that although the caves see primarily winter precipitation, exceptionally strong monsoons can influence cave waters as well. A better understanding of modern climatic controls on speleothem formation will improve paleoclimate interpretations; we are expanding our dripwater monitoring to other local cave sites.

Recent presentations given on these results:(linked as pdf's)

Cole, J. E., J. D. Wagner, J. W. Beck, P. J. Patchett, and G. M. Henderson (2006), Mechanisms of Abrupt Climate Change: Insights From the Western US and Implications for the Future, EOS - Transactions, American Geophysical Union, Fall Meeting Supplement, 87, Abstract PP13A-1581.

Cole, J. E., J. D. M. Wagner, J. W. Beck, P. J. Patchett, and G. M. Henderson (2007), Holocene hydroclimate of the Sonoran desert: Results from Cave of the Bells, Arizona, Eos Trans. AGU, 88(23), Jt. Assem. Suppl., Abstract #U42B-07.

Cole, J. E., J. T. Overpeck, J. D. M. Wagner, J. W. Beck, P. J. Patchett, and G. M. Henderson (2007), Holocene variability in the North American monsoon and links to other monsoon systems, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract #PP13D-01.

Jennifer Wagner, Julia Cole, and Warren Beck in Arkenstone Cave. Photo by William Peachey.

Collaborating faculty: Jon Patchett, Warren Beck, and Jay Quade (UA); Gideon Henderson (Oxford)

Students and staff: Jennifer Wagner (PhD 2006), Toby Ault (Ph.D. candidate), Sarah Truebe (incoming PhD candidate 2008), Alena Kimbrough (undergraduate Mellon fellow), Heidi Barnett (Lab manager), Dennis Hoburg (field assistant)

External collaborators: William Peachey (Colossal Cave), Sheridan Stone (Fort Huachuca), Jerry Trout (USFS)