Hydroclimatic changes in China over the past millennium are characterized by the association of warm periods with wetter conditions in monsoonal regions but with drier conditions in westerly regions.Lake Qinghai,located at the margin of monsoonal regions,is thus critical to evaluating this proposal by studying its sediment archive.However,paleoclimatic results from this lake are still controversial,mostly due to uncertainties in sediment chronology and proxy interpretations.We here again analyze biomarkers,long-chain alkenones and n-alkanes,from a 2m sediment core,newly retrieved from the eastern lake (37o02'17.80"N,100°27'14.07〃E),at a relatively shallow (5m) water depth.The core chronology was established with ~(14)C dates,indicating the core spanning the last ca.1600 years.We have analyzed sediment materials at every one centimeter,with 204 samples in total,and based on our chronology,achieved a sampling resolution of ca.8 years.Over the past 1600 years,alkenone U_(37)~K' values varied between 0.15 and 0.50,and %C_(37.4) varied between 15% and 80% ,much larger than the range documented previously from a core retrieved from the lake center of the same lake (0.1 unit for U_(37)~K' and 15% ~45% for %C_(37.4)).P_(aq) (proportion of aquatic plants) values range from 0.2 to 0.7.High U_(37)~K' ,%C_(37:4) and P_(aq) values occurred during the current warm period (since 1850 A.D.) and the Medieval Warm Period (800 ~1400 A.D.) ,while during the Little Ice Age (1400 ~1850A.D.),those values showed little variability and remained low.During the transition from colder toward warmer conditions (ca.1850A.D.and 800A.D.),it appears that U_(37)~K' and Paq values increased first while %C_(37.4) changes lagged by ca.50~ 100 years (ca.900A.D.and 1900A.D.).Thus the biomarker records of temperature (U_(37)~K'),salinity (%C_(37:4)) and water depth (Paq) suggest that during the current warm period and the Medieval Warm Period,lake water was warmer and fresher and water level was higher,while being the opposite during the Little Ice Age.Despite different magnitude of changes in the alkenone indices documented from the shallow and deep water cores,the pattern of their changes is largely consistent.It confirms that in Lake Qinghai,warmer conditions were generally associated with wetter/fresher conditions and vice versa,the typical pattern in monsoonal regions and opposite to the association in westerly regions.It also appears that the extent of warmth and wetness during the current warm period has not exceeded that during the Medieval Warm Period.%C_(37) 4 value,up to 80%,during the Medieval Warm Period suggest extremely fresh conditions,at least in nearshore shallow waters in Lake Qinghai at the time.Our results further suggest that in Lake Qinghai with substantial salinity changes in the past,alkenone C_(37:4) should not be included for temperature calculation.Lastly,during climate transition from cold toward warm stages,salinity changes appear to lag temperature changes,possibly due to abrupt riverine input.If correct,then our current warm period is still at a transitional stage and has not entered into a stable warm stage yet.