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为什么冰川会改变它的尺寸吗?如何differenciate改变冰川规模作为应对气候和自然的动力?

冰川流动变形时被自己的重量压垮。但他们也相应地前进或后退的各种气候因素。

我怎么区分冰川运动流动下的山谷冰川由于其动态特性,是应对气候变化?

回答

理解问题有几个基本条件,我们需要意识到。首先,我们可以看看气候方面的冰川。在这个例子中,我将集中在高山或山谷冰川在温带极地地区,我们有一个清晰的冬季和夏季。冬天雪积累的冰川由于结合许多来源,但主要是降雪,雪崩和雪飘。雪将积累在积雪深度较大的表面,但往往在冰川上部。原因是冰川形成的地方雪积累过剩,snow-catching地区,如果你愿意。所以在冬季冰川积雪覆盖着可能是更深的积雪在高海拔。在夏天会融化。融化在很大程度上是空气温度的影响随高度由于大气递减率(年代)。这意味着更少的融化将发生在高海拔和低海拔。 The net result is that the glacier is growing in thickness at higher elevations and decreasing in thickness at lower elevations. Clearly if no movement of the ice would occur the lower part of the glacier would vanish and the upper part be "infinitely" high. Enter ice dynamics. Ice deforms as a plastic material when its thickness is about 30-40 m of ice. This means that the ice can move by the ice body deforming akin to a dough. Hence the changes in glacier thickness due to accumulation and melting can be counteracted by the glacier moving excess mass from the upper part of the glacier to its lower part. As long as the climate is stable the glacier will receive roughly the same amount of snow every year and the loss of ice from melting would also be constant over years. The glacier will then be stable in size because the glacier flow compensates the gains and losses in different areas every year. If we get a change in climate the amount of snow accumulation and the melting will change due to changes in winter precipitation and summer temperature. This will affect the amounts of excess and deficit in the upper and lower parts of the glacier and also its dynamics. Looking at the terminus of the glacier we can view this as follows. A stable glacier is one where the melting at the terminus is compensated by ice flow replacing the ice loss by moving new ice into the position of the ice lost. If the melt at the terminus is larger (due to warming), then the ice loss will be larger than the ice flow trying to compensate the loss and the glacier terminus retreats. Note that ice flow continues (down valley) while the glacier retreats up-valley. For a climate cooling the melt decreases and ice will over-compensate the loss giving an advance of the glacier. Hence the answer is that you cannot split dynamics from climate in the response of a glacier. The simple description above can be complicated further but that is probably worthy of a course in glaciology or deeper study of a book on glaciology such as The Physics of Glaciers by Kurt Cuffey and W.S.B. Paterson (Academic Press 2006).

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