The Response Of The Streamflow And Glacier No.1to The Height Change Of The0℃Isotherm Height In Summer At The Headwater Of The Urumqi River In The Tianshan Mountains

Based on the data of the0℃isotherm height of Urumqi air sounding stationfrom1960to2011, and the data of average daily streamflow from1985to2006coming from three hydrological observation station from the headwater of the UrumqiRiver (Glacier No.1hydrological observation station, Ice-free Cirque hydrologicalobservation station and Master Control hydrological observation station) in theheadwater of the Urumqi River in summer season of Tianshan and the data of dailyaverage streamflow of Urumqi hydrological observation station and the observationdata of Glacier No.1from1960to2006. The paper first analyzes the variation trendand some sudden changes situation of0℃isotherm height during nearly52yearsapplying statistical methods, Mann-Kendall methods and so on; secondly analyzes the0℃isotherm height and the variation trend of daily average streamflow of theheadwater of the Urumqi River in summer season from1985to2006and thecorrelation between them; at last quantitatively analyzes the correlation between the0℃isotherm height and No.1Glacier from1960to2011in summer season. Themain conclusions are made as follows through the research:(1) From1960to2011, the0℃isotherm heights are all on the rise, but the risingextents are different, in which the0℃isotherm height of July shows the mostobvious rising trend, followed by summer season. The0℃isotherm height of June,August and summer season all show the declining trend first and then rise instead, andthe0℃isotherm height of July presents a steady upward trend. During nearly52years the0℃isotherm height shows a rise trend as a whole, however, there a greatdifference of the changes among different years. In general, the0℃isotherm heightof June, July, August and the whole summer in the1970’s all show a declining trend,and then from the1990’s to2000and later the0℃isotherm height presents a risetrend, which explains that the temperature presents a declining trend in the1970’s,which however presents an obvious rising trend after the1990’s. Through theMann-Kendall, the0℃isotherm height of July changes suddenly in2001, andthrough the significance test, it shows an obvious sudden change. In July, it starts thesudden change in1994. In August, the sudden change all happens in1999,2003and2006, during which the most obvious sudden change happens especially in1999. Thesummer season begins the sudden change in1995.(2) From1985to2006, the streamflow of the headwater of the Urumqi Riverpresents a rise trend, in which the rise trend of the Glacier No.1hydrologicalobservation station and the streamflow of the Ice-free Cirque hydrological observationstation is not obvious, and Master Control hydrological observation station variationisn’t obvious too, however, the streamflow of the Master Control hydrologicalobservation station rises more obviously with a bigger amplitude variation, and the0℃isotherm height is also on the rise. The daily0℃isotherm heights are all on therise except that there is a little declination in1997and barely changes in1990. Thechange trend of the average daily streamflow of the Glacier No.1hydrologicalobservation station, the Ice-free Cirque hydrological observation station and theMaster Control hydrological observation station differs from one another, the average daily streamflow of the Glacier No.1hydrological observation station declines slightlyin1990and between2004and2005; the average daily streamflow of the Ice-freeCirque hydrological observation station shows a declining trend in1985,1987andfrom1991to2002; the average daily streamflow of the Master Control hydrologicalobservation station declines slightly in1990,1992and between2004and2005andhardly changes in1995, and it shows a rise trend in the other years. The correlationbetween the average daily streamflow sequence and the0℃isotherm height sequenceof Glacier No.1hydrological observation station, Ice-free Cirque hydrologicalobservation station and Master Control hydrological observation station in June, Julyand August are roughly the same. The average daily streamflow sequence has the bestcorrelation with the0℃isotherm height sequence of Glacier No.1hydrologicalobservation station, most of which are through the0.01significance test, followed bythe Master Control hydrological observation station, and the worst one is the Ice-freeCirque hydrological observation station. The cumulative number of the days of themaximum correlation coefficient of the0℃isotherm height sequence and theaverage daily streamflow sequence of the three hydrological observation station are3or4days. From1985to2006, the regression model of the0℃isotherm heightsequence and the average daily streamflow sequence of Glacier No.1hydrologicalobservation station can all be through the significance test of the equation, whichindicates that there exists nonlinear relationship between the0℃isotherm heightsequence and the average daily streamflow sequence.(3) From1960to2006, the accumulation and the mass balance of Glacier No.1both present a declining trend, in which the accumulation declines significantly, theablation quantity, the equilibrium-line altitude and the0℃isotherm height all show arise trend. Through the polynomial fitting curve, we could find out that the ablationquantity, the equilibrium-line altitude and the0℃isotherm height decline first andthen show a rise trend. The accumulation presents a steady declining trend. The massbalance shows a whole trend of declination after the rise. Through the related analysis,the0℃isotherm height is positively correlated with the ablation quantity and theequilibrium-line altitude, which means with the rise of the equilibrium-line altitude,the ablation quantity increases, and the equilibrium-line altitude uplifts; the0℃isotherm height is negatively correlated with the accumulation and the mass balance,which indicates that with the rise of the0℃isotherm height, the accumulationdecreases, and the mass balance reduces.