HR: 1340h
AN: GC13A-0951    [Abstracts]
TI: Dust Generation From the Sahara-Sahel Region: New Insights From Helium-4 in a Red Sea Coral
AU: * Bhattacharya, A
EM: bhattac@fas.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 20,Oxford street, Cambridge, MA 02138, United States
AU: Mukhopadhyay, S
EM: sujoy@eps.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 20,Oxford street, Cambridge, MA 02138, United States
AB: Mineral dust emitted from arid and semi-arid regions of North Africa is an important component of the Earth's climate. Over the last four decades dust emissions from the Sudano-Sahel region have increased dramatically, which has been related to prolonged droughts in the region. However, in the absence of long term dust records in the extratropical region, downwind of the African sources, it is difficult to quantitatively constrain the factors responsible for the observed trends in dust activity in North Africa. Here we present a long term (>100 years) proxy record of annual dust fluxes from the Sahara-Sahel region using Helium isotopic measurements from a Red Sea coral. The coral sample was collected in 1995 from the northern Red Sea (27°43 N, 34°07 E). Our previous work has demonstrated that corals incorporate dust into their skeleton in proportion to the atmospheric column abundance and ⁴He is an effective tracer of the dust. We find that high ⁴He fluxes in the Red Sea coral occur in the 1880's, 1900's 1910's, 1920's 1940's, 1970's and early 1980's, all associated with drought events in the Sudano-Sahel region. Low ⁴He fluxes in the 1930's are associated with wet episodes in the Sahel, while the lowest ⁴He fluxes are in the 1950's, associated with the wettest decade of the 20^th century. Our ⁴He-based proxy record of dust is correlated with instrumental records of rainfall in the Sahara-Sahel region. Thus, long-term precipitation and drought patterns in the region can be reconstructed from the ⁴He- based proxy record of dust in corals. We also find that in addition to rainfall, coupled ocean-atmospheric phenomenon such as the North Atlantic Oscillation and El Nino-Southern Oscillation and hurricanes affect dust mobilization in the Sahara-Sahel region. Furthermore, the ⁴He based record of dust flux suggests that dust export from the Sahara-Sahel region during the late 1880's was as high as that observed during the 1980's. Hence, high dust emissions from the Sahara-Sahel region in the latter part of the 20^th century region were not unique events. Such observations have important implications in evaluating the role played by dust from North Africa in drying up of the Sahel and in understanding the feedback mechanisms of dust in the global climate system.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3354 Precipitation (1854)
DE: 4914 Continental climate records
DE: 4916 Corals (4220)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting