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要旨:
Lake level fluctuations are important features in paleo-reconstructions that can be linked to past
climate changes. Closed-basin lakes on the southcentral
Tibetan Plateau record the balance between
monsoonal precipitation and evaporative loss. To date,
most studies provide only qualitative estimates of past
hydrological changes. For the first time, we applied
hydrogen isotopes (dD) of aquatic and terrestrial nalkanes
to quantify lake volume changes of Tangra
Yumco and compared values to newly calculated lake
volumes of Nam Co. We also used carbon isotopes of
sedimentary n-alkanes to reveal past climate and
environmental conditions around the lake. The water
volume of Tangra Yumco changed by 146 km3 in the
past 17.42 cal ka. Lake volume increased in two steps,
the first mainly initiated by glacial meltwater input
after 16 cal ka BP, and to a minor extent by first
strengthening of the Asian Summer Monsoon (ASM).
The second increase was caused by intensified summer
monsoon precipitation at 11.45 cal ka BP. After
8.0 cal ka BP, lake volume decreased because of arid
conditions, until an increase at 0.8 cal ka BP that was
probably linked to a wet spell during the Little Ice
Age. The lake level changes of Tangra Yumco and
Nam Co were affected simultaneously by the ASM,
although their amplitudes differed because of different
local conditions, such as basin morphology or the
blocking effect of neighboring mountains, which
influences the rainout of air masses and wind-induced evaporation.
