Rekonstrukcja geometrii powierzchni lodowców z maksimum ostatniego zlodowacenia (LGM) w polskich Tatrach Wysokich (zlewnie Roztoki i Rybiego Potoku)

Abstract

Reconstruction of surface geometry of the last glacial maximum (LGM) glaciers in the Polish High Tatra Mts. (drainage basins of Roztoka and Rybi Potok).A b s t r a c t . A reconstruction of the last glacial maximum (LGM) ice surface geometry in the Polish High Tatra Mts. (drainage basins of Roztoka and Rybi Potok) is based on detailed field mapping of glacial trimlines. Obtained field data provide evidence of the ice surface elevation within the ice accumulation areas and in some cases they indicate direction of ice flow. The LGM ice-surface geometry is presented as a digital elevation model (DEM) which was created using geographic information system (GIS). Calculations of ice thickness and ice volume are based on DEM of present land topography. Reconstruction of the ice extent within ablation area is created using archival data. During LGM, the Roztoka glacier and the Rybi Potok glacier were a typical valley glaciers included into a huge glacial system being a dendritic glacier. According to acumulation area ratio (AAR) method, equilibrium line of these glaciers was situated at an elevation of about 1400 m a.s.l. It shows that nearly the whole area of the drainage basins of Roztoka and Rybi Potok have been an ice accumulation area supplying the Biała Woda glacier during LGM. Equilibrium line altitude (ELA) depression in relation to modern ELA (2300 m a.s.l.) was about 900 m. Assuming temeperature lapse rate of 0,6oC/100 m, a mean summer temperature in the Tatra Mts. was lowered of about 5,5oC. Ice area and its volume calculated for accumulation areas indicate that their relations to one another are nearly identical. It can be evidence for similar precipitation in both the Roztoka and the Rybi Potok drainage basins and an indicator of atmospheric circulation pattern which have determined climate in the Tatra Mts. during LGM.