「双语阅读」移动中的阿拉斯加冰川 Malaspina on the Move

1986 - 2000

尽管南极洲和格陵兰岛的冰流失量更大，而且看起来更加剧烈，但北极岛屿和中纬度山脉的冰川流失却相当显着。 NASA 领导的一个研究小组最近开发了一种工具，可以帮助研究人员调查 30 多年来自冰川的冰速数据，这是检测地球冰（冰冻圈）如何变化的关键变量。

由于没有两个冰川完全相同，因此了解山地冰川如何变化以及它们的流动在未来将如何变化变得复杂。例如，阿拉斯加东南部的马拉斯皮纳冰川可能不会快速移动，但冰川内的运动是复杂的。

上面的动画是由Landsat 5和7卫星在1986年至2003年间采集的一系列假彩色图像组成的。移动的冰以蓝色阴影出现。棕色线是冰碛——土壤、岩石和其他碎片被冰川刮起并沉积在其两侧的区域。这些碎片经常被困在内部的岩石带中，两条冰川在此处汇合并汇合在一起。

阿拉斯加这一地区的冰川会周期性地激增，这意味着它们会迅速向前倾斜一到几年。无论冰川是前进还是后退，都会发生涌动。在整个动画中，马拉斯皮纳似乎正在撤退，增加的融水和撤退的冰正在导致湖泊（右下）扩大。碎片的锯齿形图案是由冰的速度变化引起的。

“冰川都有自己的个性，因此对单个冰川的详细研究通常不适用于整个地区，”美国宇航局喷气推进实验室的冰川学家亚历克斯·加德纳说。“为了在了解海平面上升和适应大规模水资源方面取得进展，我们需要了解适用于整个地区的冰川流动的基本特征。”

Though ice losses from Antarctica and Greenland make up a greater volume and seem more dramatic, the losses from glaciers on Arctic islands and middle-latitude mountain ranges have been quite significant. A NASA-led research team has recently developed a tool to help researchers investigate more than 30 years of ice velocity data from glaciers, a key variable for detecting how Earth’s ice (the cryosphere) is changing.

Understanding how mountain glaciers change, and how their flow will change in the future, is complicated by the fact that no two glaciers are exactly alike. Malaspina Glacier in southeastern Alaska, for example, may not be moving fast but the motion within the glacier is complex.

The animation above was composed from a sequence of false-color images acquired between 1986 and 2003 by the Landsat 5 and 7 satellites. The moving ice appears in shades of blue. Brown lines are moraines—areas where soil, rock, and other debris have been scraped up by the glacier and deposited at its sides. This debris often gets trapped as internal ribbons of rock where two glaciers merge and become one at a confluence.

Glaciers in this area of Alaska periodically surge, meaning they lurch forward quickly for one to several years. Surging can happen whether a glacier is advancing or retreating. Throughout the animation Malaspina appears to be retreating, and the increased meltwater and retreating ice is causing the lake (bottom-right) to expand. The zigzag pattern of the debris is caused by changes in velocity of the ice.

“Glaciers all have their own personalities, so a detailed study of a single glacier often doesn’t apply to a region as a whole,” said Alex Gardner, a glaciologist at NASA’s Jet Propulsion Laboratory. “To make progress on understanding sea level rise and adapting large-scale water resources, we need to know the fundamental characteristics of glacier flow that apply over entire regions.”