Constraints on paleoclimate from 11.5 to 5.0 ka from shoreline dating and hydrologic budget modeling of Baqan Tso, southwestern Tibetan Plateau

C-14 dating of shoreline deposits of closed-basin lake Baqan Tso in the western Tibetan Plateau shows that lake level regressed from the undated highstand (46 m above modern, 4.3 x modern surface area) of likely earliest Holocene age by 11.5 ka, and remained larger than modern until at least approximate to 5.0 ka. The shoreline record broadly matches other regional climate records, with lake level closely following Northern Hemisphere summer insolation overprinted by sub-millennial lake-level oscillations. A model coupling modem land runoff and lake surface heat closely reproduces estimated modem precipitation of approximate to 240 mm/yr. We estimate that the Baqan Tso basin required approximate to 380 mm/yr precipitation to sustain the maximum early Holocene lake area, a 55% increase over modem. Precipitation increases, not glacial meltwater, drove lake-level changes, as Baqan Tso basin was not glaciated during the Holocene. Our estimate assumes early Holocene insolation (approximate to 1.3% overall increase), and mean annual increases of 2 degrees C in temperature, and 37% in relative humidity. We additionally developed a Holocene precipitation history for Baqan Tso using dated paleolake areas. Using the modern and early Holocene model results as end-members, we estimate precipitation in the western Tibetan Plateau which was 300-380 mm/yr between 5.0 and 11.5 ka, with error of +/- 29-57 mm/yr (+/- 12-15%). (C) 2014 University of Washington. Published by Elsevier Inc. All rights reserved.