The progressive drying of the Sahel from 1960’s to early 1990’s has had devastating social, economic, and environmental consequences. An environmental consequence of the droughts in the Sudano-Sahel region has been enhanced mineral dust loads in the atmosphere. The increased dust loads may have provided an amplifying feedback in the drying of the Sahel in the second half of the 20^th century. Globally, dust mobilized in the Sahara and Sahel regions of Africa is transported as far as the Americas, and affects processes from nutrient cycling in the Amazon to cyclogenesis and regional air quality in the Caribbean and southeast USA. Clearly, variability in dust emission in the Sahara-Sahel region can have important environmental consequences. Current climate models suggest anywhere from a 60% decrease to a 10% increase in dust emission rates from the Sahara-Sahel region over the next century. Likewise, models predict the Sahel getting both wetter and drier over the next century. Hence, the predicted sign and magnitude of dust flux and precipitation variations remain model dependent. There are no high-resolution long-term records of dust emission that can be utilized to benchmark climate models and to understand how the Sahel will respond to future climate change. So my group has embarked on reconstructing past variations in dust emission and precipitation patterns at very high resolution. To do this we are using a novel technique: corals as high-resolution dust archives and ⁴He to trace the total amount of mineral dust incorporated into the coral. Our initial results are extremely promising (see Figure 1-3). We are finding that the severe Sahel droughts of the 1980's are not unprecedented in the historical record and dust emission rates in the 19th century were much higher than in the 20th century.

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Click here for a recent poster of our work.