Palaeoglacial and palaeoclimatic conditions in the NW Pacific, as revealed by a morphometric analysi
Palaeoglacial and palaeoclimatic conditions in the NW Pacific, as revealed by a morphometric analysi
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DOI：
10.1016/j.geomorph.2013.03.011
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发表时间：
2013-06
期刊：
影响因子：
3.9
通讯作者：
M. Spagnolo
中科院分区：
文献类型：
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作者：
M. Spagnolo
根据卫星图像和数字高程模型数据，系统地绘制了俄罗斯远东堪察加半岛冰川环的分布。共确定了3758个圆环，其中238个为活动冰川所占据。对剩余的3520个圆环进行形态学分析。这些圆环在方位角（方向）上显示出非常强的N偏倚，可能是由于日晒的方面相关变化造成的。这种N偏倚的强度被认为表明，半岛上以前的冰川作用通常是“边缘的”，主要是环状的，高峰延伸到区域平衡线高度之上。数据集中面向S和se的旋流是最高的，这一事实支持了这一观点，这表明冰川覆盖很少足以使面向S和se的冰川在低海拔地区发育。这些与方位角有关的环流高度变化的强度被认为反映了以前冰川时期相对无云的条件。这些边缘冰川和相对无云条件的特征反映了该地区以前的干旱，这种干旱可能在全球末次盛冰期和较早的冰进期加剧，这是由于北太平洋负压异常的发展（由劳伦泰德冰盖的增长驱动），再加上其他因素，包括海冰的范围和持续时间的增加。全球海平面的下降，海面温度的降低，以及山地冰川的局部增长。已发表的证据表明，在晚第四纪期间，堪察加半岛有时存在广泛的冰川作用，但本文提供的数据似乎表明，这些阶段相对较短，较小的环状冰川通常更具有该时期的特征。
The distribution of glacial cirques upon the Kamchatka peninsula, Far Eastern Russia, is systematically mapped from satellite images and digital elevation model data. A total of 3758 cirques are identified, 238 of which are occupied by active glaciers. The morphometry of the remaining 3520 cirques is analysed. These cirques are found to show a very strong N bias in their azimuth (orientation), likely resulting from aspect-related variations in insolation. The strength of this N bias is considered to indicate that former glaciation upon the peninsula was often ‘marginal’, and mainly of cirque-type, with peaks extending little above regional equilibrium-line altitudes. This is supported by the fact that S and SE-facing cirques are the highest in the dataset, suggesting that glacier-cover was rarely sufficient to allow S and SE-facing glaciers to develop at low altitudes. The strength of these azimuth-related variations in cirque altitude is thought to reflect comparatively cloud-free conditions during former periods of glaciation. It is suggested that these characteristics, of marginal glaciation and comparatively cloud-free conditions, reflect the region's former aridity, which was likely intensified at the global Last Glacial Maximum, and during earlier periods of ice advance, as a result of the development of negative pressure anomalies over the North Pacific (driven by the growth of the Laurentide Ice Sheet), combined with other factors, including an increase in the extent and duration of sea ice, a reduction in global sea levels, cooler sea surface temperatures, and the localised growth of mountain glaciers. There is published evidence to suggest extensive glaciation of the Kamchatka Peninsula at times during the Late Quaternary, yet the data presented here appear to suggest that such phases were comparatively short-lived, and that smaller cirque-type glaciers were generally more characteristic of the period.