Map of Lewis-Glacier - Mt. Kenya 1983 (pdf 600 kB)

In February of 1983 a new terrestrial photogrammetric survey of Lewis Glacier (0° 9' S) has been made, from which the present topographic map has been produced in a scale of 1:5000. Simultaneously a survey of 1963 was evaluated giving a basis for computations of area and volume changes over the 20 year period: Lewis Glacier has lost 22 % of its area and 50 % of its volume. Based on maps and field observations of moraines 10 different stages were identified. Changes of area and volume can be determined for the periods after 1890, two older, undated stages are presumed to be of Little Ice Age-origin. Moderate losses from 1890 to 1920 were followed by strong, uninterrupted retreat up to present. In this respect Lewis Glacier behaves as all other equatorial glaciers that were closer examined. Compared to alpine glaciers the development was similar up to 1950. In the following years, however, the glaciers of the Alps gained mass and advanced while Lewis Glacier experienced its strongest losses from 1974 to 1983.

1983年2月，研究人员对南纬0°9′的刘易斯冰川（Lewis Glacier）开展了新一轮地面摄影测量（terrestrial photogrammetric survey），并基于该测量成果绘制了比例尺为1:5000的现时地形图。与此同时，研究人员对1963年的测绘数据进行了解译处理，以此为该冰川1963年至1983年间的面积与体积变化计算提供了依据：结果显示，刘易斯冰川的面积缩减了22%，体积减少了50%。基于地形图与冰碛物野外观测结果，研究人员共识别出10个不同的冰川演化阶段。1890年之后的各时段冰川面积与体积变化均可被定量测定，另有两个未标定年代的早期阶段被推测为小冰期（Little Ice Age）成因。1890年至1920年间冰川出现小幅消融，此后便进入持续强烈的退缩状态，直至今日。在该方面，刘易斯冰川与其他已被深入研究的赤道冰川表现一致。与高山冰川（alpine glaciers）相比，二者的演化进程在1950年之前基本相似；但在此之后的年份中，阿尔卑斯地区的冰川出现了物质积累与前进现象，而刘易斯冰川则在1974年至1983年间经历了最为剧烈的消融损失。