HR: 09:00h
AN: PP21A-05 INVITED     [PDF]
TI: Holocene ITCZ Migration Recorded in Stalagmites From Oman (Southern Arabia)
AU: * Fleitmann, D
EM: fleitman@geo.unibe.ch
AF: Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, Bern, 3012 Switzerland
AU: Burns, S J
EM: sburns@geo.umass.edu
AF: Department of Geosciences, Morrill Science Center, University of Massachusetts, Amherst MA 01002, Amherst, MA 01002 United States
AU: Mudelsee, M
EM: mudelsee@rz.uni-leipzig.de
AF: Institute of Meteorology, University of Leipzig, Stephanstrasse 3, Leipzig, 04103 Germany
AU: Neff, U
EM: ulrich.neff@ablay-fodi.de
AF: Heidelberg Academy of Sciences, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Kramers, J
EM: kramers@geo.unibe.ch
AF: Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, Bern, 3012 Switzerland
AU: Mangini, A
EM: augusto.mangini@iup.uni-heidelberg.de
AF: Heidelberg Academy of Sciences, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Matter, A
EM: amatter@geo.unibe.ch
AF: Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, Bern, 3012 Switzerland
AB: The latitudinal migration of the ITCZ during boreal summer in response to the annual solar cycle and maximum surface heating determines the start, duration and end of the rainy season from across Northern Africa to India. The Dhofar area in Southern Oman sits at the northern limit of the summer migration of the ITCZ and the associated Indian Ocean monsoon rainfall belt. Annual precipitation in this region is highly seasonal, more than 80% of total annual precipitation falls during the summer monsoon months (July to September) when the ITCZ reaches its northernmost position. To date, the clouds are unable to rise higher than $\sim$1500 m because of a temperature inversion created by the convergence between the hot dry north-westerly winds and the low-level southwest monsoon winds. As a result, monsoon precipitation occurs as fine drizzle, seldom exceeding more than 5 mm d$^{-1}$. Variations in the mean latitudinal summer position of the ITCZ over Southern Arabia directly affect the height of the temperature inversion. For instance, a northward shift of the ITCZ into the Arabian Peninsula would lead to stronger convective cloud development and higher monsoonal rainfall over Southern Oman. Due to the so-called amount effect, $\delta$$^{18}$O values of precipitation become more negative (depleted). Such variations are accurately recorded in high-resolution $\delta$$^{18}$O records obtained from three Uranium-series dated stalagmites, which continuously cover the period from 10.3 and 2.7 and 1.4 and 0.4 kyr BP. The oxygen isotope profiles show three distinct features: 1) A rapid northward migration of the ITCZ and increase in monsoon precipitation respectively between 10.3 and 9.8 kyr BP is indicated by a sharp decrease in $\delta$$^{18}$O from -0.8$\permil$ to $\sim$-2$\permil$. 2) An interval of generally high monsoon precipitation lasting from 9.8 to 5.5 kyr BP with $\delta$$^{18}$O values averaging -2$\permil$. 3) A long-term gradual southward migration of the ITCZ and decrease in monsoon precipitation starting at around 8 kyr BP is indicated by a slow shift in $\delta$$^{18}$O from -2.2$\permil$ at 8 kyr BP to $\sim$-0.9$\permil$ (slightly more negative than $\delta$$^{18}$O values of modern stalagmites) at 2.7 kyr BP. Superimposed on the long-term trends are distinct decadal to multi-decadal variations in $\delta$$^{18}$O, which likely reflect changes in the convection activity over Southern Oman
DE: 3309 Climatology (1620)
DE: 3344 Paleoclimatology
DE: 3354 Precipitation (1854)
DE: 3374 Tropical meteorology
DE: 4870 Stable isotopes
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting