A 60,000-year record of hydrologic variability in the Central Andes from the hydrogen isotopic composition of leaf waxes in Lake Titicaca sediments

Indian source: "Sacred Lake currently receives no Atlantic-derived precipi- tation, and its elevation, northeastern slope exposure, and rainfall seasonality make it particularly susceptible to changes in the Indian Ocean monsoons. In contrast, equatorial lakes in central Kenya (e.g. Lake Naivasha) and the western Rift Valley (e.g. Lake Edward, Uganda/ Congo) receive a mixture of Indian- and Atlantic-derived moisture, and hence are sensitive to both monsoons (Nicholson, 1996). " Moisture transport and temperature influence: "The strength of low-level equatorial westerlies in the Indian Ocean has been linked to East African lake levels as well as Mt. Kenyas glaciers, with stronger (weaker) winds inhibiting (enhanc- ing) precipitation in East Africa (Hastenrath, 2001). Overall, these west- erlies have increased in strength since the 1880s. This important Indian Ocean forcing may explain Sacred Lakes particular sensitivity to these changes, and recent drying may have also been locally enhanced by a re- cent rise in temperature (via an upward shift in the ZMR and/or in- creased evaporation of soil water)"

strength of Indian ocean moisture transport

In East Africa, stable isotopes in modern precipitation have been shown to reflect large-scale atmospheric circulation processes (Vuille et al., 2005), and the ?18O of precipitation (and by inference, the ?D of precipitation) on Mt. Kenya has been shown to be a good indicator of moisture balance (Barker et al., 2001). Leaf wax ?D reflects ?Dprecip, after a series of offsets due to soil water evaporation, fractionation of leaf water relative to xylem water, and biosynthesis (Sachse et al., 2012).

Air temperature has 2 influences: "air temperature is important for the elevation of the zone of maximum rainfall (ZMR) on Mt. Kenya" and for soil/lake evaporation. "Recent drying may have also been locally enhanced by a recent rise in temperature (via an upward shift in the ZMR and/or increased evaporation of soil water)."