Flow dynamics near the bottom of Greenland ice sheet revealed by the Summit ice core analysis

long-term environmental record on the Earth can be obtained from Greenland ice sheet studies. Acontinuous deep ice core retrieved at Summit，Central Greenland by GRIP in 1992.核心分析reveals abrupt climatic fluctuations existed duringEemian/Sangamon interglacial period. However，a possibility that this is an artifact caused by complica ted flow behaviors near the ice sheetbottom is pointed out.This study revealed the following findings under an international研究合作与其他更广泛的成员。1)Mechanical property studies showed the followingIce sheet flow is dominated by crystallographic anisotropy of Ice in plastic deformationImpurity concentration type/level affects the formation process of crystal orientationDifferential flows distribution characteristics associated with the stess field in the ice sheetin a small scale exist near cloudy bands.2) a new flow law is obtained by使用实验室测试results of核心样本for ice sheet dynamics considerations. The application of this law to The建议的position shows that ice flow只是关于complicated bottom tends to be unstable easilyand the flow is quite sensitive to the bottom topography.3) A详细核心分析on the Summitcore,considering the above ice flow behaviors and其他核心数据shows at least one abrupt climaticchange during Late Eemian is real. Further studies are planned and proceeded by performing theNorth GRIP project。

A long-term environmental record on the Earth can be obtained from Greenland ice sheet studies. A continuous deep ice core was retrieved at Summit, Central Greenland by GRIP in 1992. Core analysis reveals abrupt climatic fluctuations existed during Eemian/Sangamon interglacial period. However, a possibility that this is an artifact caused by complica ted flow behaviors near the ice sheet bottom is also pointed out.This study revealed the following findings under an international research collaboration with other GRIP members.1) Mechanical property studies showed the following results.・Ice sheet flow is dominated by crystallographic anisotropy of ice in plastic deformation processes.・ Impurity concentration type/level affects the formation process of crystal orientation distribution characteristics associated with the stess field in the ice sheet.・ Differential flows in a small scale exist near cloudy bands.2) A new flow law is obtained by using laboratory test results of core samples for ice sheet dynamics considerations. The application of this law to the Summit position shows that ice flow just above the complicated bottom tends to be unstable easily and the flow is quite sensitive to the bottom topography.3) A detailed core analysis on the Summit core, considering the above ice flow behaviors and other core data shows that at least one abrupt climatic change during Late Eemian is real. Further studies are planned and proceeded by performing the North GRIP project.