Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year
Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year
复制标题
DOI：
10.5194/tc-5-569-2011
复制
发表时间：
2011-01-01
期刊：
影响因子：
5.2
通讯作者：
Young, N.
中科院分区：
文献类型：
--
作者：
Bindschadler, R.;Choi, H.;Young, N.
国际极年项目ASAID的参与者使用结合Landsat-7图像和ICESat/GLAS激光测高的定制软件，以15米的分辨率绘制了南极冰盖的两个冰-动力转变--接地冰特征边界和自由浮动边界。陆冰边界长53610公里，74%毗邻漂浮冰架或出口冰川，19%毗邻开阔或海冰覆盖的海洋，7%的边界冰终止于陆地上。自由浮动的边界，在这里被称为静水线，是冰架上最靠近陆地的位置，它表达了海洋潮汐振荡的全部幅度。它绵延27521公里，是不连续的。接地冰边界的位置(一西格玛)精度从陆地和开阔海洋末端的+/-52米到出口冰川的+/-502米不等。静压线的位置不太好，误差超过2公里。每条线上的高程是从6个候选数字高程模型中选择的，基于它们与ICESat高程值的一致性和从陆地卫星图像推断的表面形状。通过应用积雪修正系数和漂浮准则，将静水线上的高程转换为冰的厚度。将BEDMAP汇编的数据和其他空中数据与ASAID的海拔高度和冰层厚度进行比较，得出ASAID指定的五个置信度水平的地表高度+/-3.6、+/-9.6、+/-11.4、+/-30和+/-100米的定量(一西格玛)不确定度。沿着接地冰边界的超过一半的表面高程和超过三分之一的静力线高程被列为最高的两个置信度类别。ASAID计算的冰架厚度与BEDMAP汇编的数据之间的比较表明，ASAID冰层厚度的薄冰偏差为41.2+/-71.3米。静力线与地面冰边界之间的偏移量之间的关系与基于波束理论的预测只有微弱的匹配。地图产品以及生成它们的定制软件和各种中间产品都可以从国家冰雪数据中心获得。
Two ice-dynamic transitions of the Antarctic ice sheet - the boundary of grounded ice features and the freely-floating boundary - are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74% abuts to floating ice shelves or outlet glaciers, 19% is adjacent to open or sea-ice covered ocean, and 7% of the boundary ice terminates on land. The freely-floating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded ice boundary vary an order of magnitude ranging from +/-52 m for the land and open-ocean terminating segments to +/-502 m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma) uncertainties of surface elevations of +/-3.6, +/-9.6, +/-11.4, +/-30 and +/-100 m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2+/-71.3m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line from the grounded ice boundary only weakly matches a prediction based on beam theory. The mapped products along with the customized software to generate them and a variety of intermediate products are available from the National Snow and Ice Data Center.