【作者】 杨帆；

【导师】 温家洪；

【作者基本信息】 上海师范大学 ， 自然地理学， 2011， 硕士

【摘要】 南极冰盖的物质和能量变化对全球海平面变化,地球表面的能量平衡,全球水循环等有着重要的影响。南极动力机制作用研究,特别是南极冰盖动力过程的数值模拟仍存在很多不确定性,因此为了更准确地理解其动力过程,精确预测冰盖演化方向和变化状况,在特定区域建立冰盖动力模型显得尤为重要。本文首次以东南极冰盖最大的冰川盆地—Lambent冰川盆地为重点研究区域。利用高精度的DEM、厚度、基岩高程数据;采用新的计算方法重新计算了Amery冰架的底部冻融速率;整理最新的PCMEGA数据,并对着陆线附近的高程、冰厚度和基岩高程数据进行了构建;构建流域内表层冰温数据。基于ArcGI S Matlab两大软件划分冰川主流线,并参照上述数据,提取点数据。基于Matlab构建流线模型,模拟冰盖上的压力,应力,应变率,并绘制与距离相关的响应曲线。主要结果如下:(1) Lambent冰川盆地中的Amery冰架底部融化速率的最大值为22.1xn行r.在冰架前缘和冰架西部地区存在冰架海冰再冻结的情况,冻结速率约为2.4mlyr a在冰架西端沿海边缘区域的融化速率要明显偏高,那里也是冰流较为活跃的地区。与先前结果对比,本文所得结果在最大值上要低巧%左右,最小值要相差大约三倍。相比冰架边缘,冰架内部融化速率低,也进一步反映了Amery冰架整体上处于一个稳定的状态。(2) Amery冰架底部融化速率的最大值为22.1 mlyr,在冰架前缘和冰架西部地区存在冰架海冰再冻结的情况,冻结速率约为2.4mlyr。在冰架西端沿海边缘区域的融化速率要明显偏高,那里也是冰流较为活跃的地区。本文所得底部融化速率最大值要比前人(Wen, 2010 )研究结果要偏低1S%左右,底部冻结速率最大值要相差大约三倍。冰架内部稳定,而边缘区域的融化速率较大,Amery冰架整体上处于一个稳定的状态。(3)通过应力、应变率变化的动力过程建立函数和方程,构建冰流模型。该模型体系包括四大模型。分别是冰盖地形模型;水平和垂直流速模型;冰温变化模型;以及流线应力场模型。(4)冰川盆地边缘的流速模型表明,在在冰川盆地边缘附近冰流水平速度接近0,而_巨水平速度和垂向速度变化特征明显。在接近冰川盆地边缘的地方驱动应力为零,表明在这一区域内冰盖基本是保持稳定状态。(5)冰川盆地边缘附近表面温度分布状况相对简单,在冰川盆地内部附近表面温度分布相对比较复杂,冰盖内部温度分布总体呈现随着深度增加而增加在接近着陆线的区域的温度增加速率较快,这是由于应力增加带来的热量的消耗所致。(6)模拟结果表明冰盖存在一个应力变化极值区。在距离着陆线0-200km区域内,应力具有Glen’s flow law应力值最大在40-SSkPa之间.水平应力在距离着陆线距离1 OOkm左右处达到最大值,然后向内部边缘与垂直方向快速衰减,至盆地边缘趋于零。垂直应力相对于水平应力来说,数值相对较小,最大应力数值范围65-80kPao应力的增大带来的热通量,造成了着陆线附近的冰温增加。(7) Fisher冰川、Mellor冰川和LamberC冰川的三条流线的应变率最大值分别为0.0992/yr, O.Ob351/yr和。0724/yr。每条主流线在靠近着陆线的区域的应变率最大,这主要是由于该区域内冰流流速及其交汇影响。在应变率极值数值,直接影响着冰流汇流区和延伸的冰架上游,可能加速冰架前端纵向裂缝和破碎的产生,从而影响冰山崩解的响应过程。更多还原

【Abstract】 The change of Antarctic ice sheet mass and energy effect on the global sea level change, and the Earth’s surface energy balance, such as the global water cycle have an important impact. Dynamic mechanism of the role of Antarctic research, particularly the Antarctic ice sheet numerical simulation of the dynamic process of many uncertainties still exist, so in order to more accurately understand the dynamic process, to accurately predict the direction of development and changes in ice conditions, ice build momentum in a particular region model is very important.This is the first east of the Antarctic ice sheet is the largest ice-flow system- Lambert Glacier-Amery lce Shelf system far key research areas. Carry out research in the basin of the ice sheet dynamics, the establishment of numerical model of flow lines for the "Antarctic ice sheet" that today’s long-term impact on human life and to contribute to the development of scientific problems. Main contents and conclusions are as follows:By high-precision DEM, thickness, bedrock elevation data, and the new calculation method of the Amery lce Shelf,1 recalculate the bottom of the freezing and thawing rate; finishing the latest PCMEGA data, and landing near the line of elevation, ice thickness and bedrock Elevation data were constructed. ArcG1S and Matlab software based on two main lines by glaciers, and the light of the above data, the data extraction points. Construction of flow lines based on Matlab model to simulate the ice sheet on the pressure, stress, vertical shear rate, the level of shear rate and draw distance associated with the response curve(1) Create a new calculation method. Amery Ice Shelf at the bottom to re- calculate the melting rate. It was found that the leading edge and the ice shelf ice shelf ice shelf ice west there is the case then freeze, freezing rate of about 2.4mlyr, the whole ice shelf bottom melting rate of maximum maximum 22.1 mlyr. The western end of the ice shelf melting rate of the coastal edge of the area is significantly high. Compared with the previous results, this results in the maximum value of about 15% lower on, to a difference of about three times the minimum. Melting rate of ice shelves within the lower range of the melting rate of}the outflow of large, Amery Ice Shelf is further reflected in a generally stable state.(2) Stress, strain rate changing in the dynamic process of establishing the function and equations to build the ice flow model. The model system consists of four models. Are the ice terrain model; horizontal and vertical flow model; ice temperature change models; and rail lines, time and stress model.(3) The simulation results show that changes in ice cover there is a mutation in the stress zone. Although the ice sheet elevation with increasing distance from the landing lines decrease linearly, but in the line of 200-}OOkrr} from the landing area near the surface slope has undergone an obvious change in the slope of the slope from the previous negative value of the slope after slope is positive. Meanwhile, in the region before the driver strain was positive, driven stress increases with distance; strain w’as positive after the driver, driver stress with distance increases.(4) The edge of glacier flow model shows that basin, near the edge of the glacier basin, the surface temperature distribution is relatively simple, the glacier surface temperature distribution near the basin is relatively complex. Ice temperature distribution within the overall increase with depth show }ed the characteristics of simulation results also show that glacial ice flow near the edge of the basin close to 0. the horizontal velocity, and the horizontal velocity and vertical velocity variations obvious. Glacier Basin, near the edge of the driving stress is zero, indicating that the ice sheet in this region is basically stable state.{5) Building an ideal model of ice flow lines, flow lines have been ice momentum, mass and energy balance of the various evolution curve, that in the fixed boundary conditions, the ice sheet in a stable state of the physical characteristics and our current understanding of the Antarctic ice sheet is consistent. Solving the continuity in the specific model equations, consider the ice temperature at the bottom of simulation boundary- conditions required on the computer simulation the stability of this approach makes the changes in vertical velocity at the edge of the basin with glacier is lar},ely consistent understanding The. Evolution has been quantitatively stable state ice ice flow cross-section elevation, temperature field. stress field change. which is conducive to better analyze the evolution of ice sheet changes in the details of the various physical processes.The simulation work for the Lambert glacier basin, the dynamics of ice flow to provide many basic data, but also for th.e first time numerical simulation of the ice extended to the region. For the LAS system, the dynamics of ice streams to provide reference for further research, but also contribute to the whole dynamic process of East Antarctica.更多还原