Here is a sampling of projects that we’re working on:

Mapping past precipitation changes using closed-basin lakes

Shoreline deposits and sediments in closed-basin lakes preserve high-fidelity records of the timing and magnitude of past lake level changes. We precisely U-Th date carbonates from these lakes, then combine these ages with measurements of isotopic proxies reflecting temperature and water balance to map precipitation through space and time. Our ongoing work is focused in the U.S. Great Basin and the Altiplano of northern Chile, led by Christine Chen and former student Elena Steponaitis.

An example: D. McGee, J. Quade, R.L. Edwards, W.S. Broecker, H. Cheng, P.W. Reiners, N. Evenson, 2012. Lacustrine cave carbonates: Precisely dated recorders of paleohydrologic change in Lake Bonneville. Earth and Planetary Science Letters 351-352, 182-194.

High Country News article on our work in the U.S. Great Basin

Tracking windblown mineral dust

Mineral dust from the world’s deserts is an important tracer of atmospheric circulation patterns and an active player in Earth’s radiation balance and biogeochemical cycles. Our work reconstructs past variations in dust deposition in marine sediments using uranium and thorium isotopes. Our ongoing work reconstructing North African dust emissions points to dramatic, sometimes abrupt changes in North African climate and provides insight into the role of dust as an amplifier of African climate change. New projects include work to document past changes in atmospheric circulation in East Asia by using Sr, Nd and Pb isotopes to track changes in dust source, and measurements of Th isotopes in seawater to improve our understanding of modern dust deposition in the ocean. Christopher Kinsley, Charlotte Skoniezcny, Irit Tal and former postdoc Chris Hayes spearhead this work.

An example: D. McGee, P.B. deMenocal, G. Winckler, J.-B. Stuut, L.I. Bradtmiller. The magnitude, timing and abruptness of changes in North African dust deposition over the last 20,000 years. Earth and Planetary Science Letters, 371-372, 163-176.

MIT News article on this paper

Tracing hydroclimate changes using stalagmites

Cave stalagmites offer records of atmospheric circulation and hydrology that combine high temporal resolution (decadal to annual), long temporal coverage (reaching back to several hundred thousand years), spatial distribution across large areas of the continents, and precise chronologies anchored by uranium-thorium dating. Led by the efforts of Ben Hardt, Gabriela Serrato Marks and Irit Tal, we are developing stalagmite records from a variety of regions around the world, including Vietnam, Madagascar, Mexico, Brazil, central Asia and the western U.S. In addition to performing U/Th dating, our lab is also developing precipitation records using trace element ratios in stalagmites.

An example: E. Steponaitis*, A. Andrews*, D. McGee, J. Quade, W.S. Broecker, Y.-T. Hsieh*, B. Shuman, S.J. Burns, H. Cheng. Mid-Holocene drying of the U.S. Great Basin recorded in Nevada speleothems. Quaternary Science Reviews, doi:10.1016/j.quascirev.2015.04.011.

MIT News article on this paper

Understanding precipitation changes using models and theory

In addition to developing records of past hydrological changes, we also work closely with collaborators using models and theory to try to understand the dynamics of these past changes. Past work sought to understand the drivers behind past dust emission changes. More recent work has investigated the energetics behind tropical precipitation changes at a wide range of timescales, providing a framework for understanding past shifts in the tropical rainbelt associated with the Intertropical Convergence Zone.

An example: D. McGee, A. Donohoe, J. Marshall, D. Ferriera, 2014. Changes in ITCZ location and cross-equatorial heat transport at the Last Glacial Maximum, Heinrich Stadial 1, and the Mid-Holocene. Earth and Planetary Science Letters 390, 69-79.