Satellite measurements of the icy
surface of Antarctica have detected an
active system of lakes under ice that is
about one kilometer deep. Scientists are
still uncertain about the role that the
underground water plays in the movement
of the so-called ice streams that may
contribute to a rise in sea level.
Very precise measurements from a
research satellite called ICEsat
identified changes on the surface as
lakes underneath the ice filled and
drained as much as two cubic kilometers
of water during the three-year study.
The lakes are under moving sections of
ice, called ice streams, that flow into
the Ross Ice Shelf. The existence of
water under the ice streams has been
known for some time, but what's
surprising is how much water is involved
and how fast it moves.
Lead author Helen Amanda Fricker says
it's an important process to understand
because of its potential impact on sea
levels as ice flows off Antarctica and
into the ocean. "Well, it's important
because the ice streams are the
mechanism whereby the ice is transported
form the deep interior of Antarctica out
to the Ocean, and so if you have changes
in the amount of water which is
underneath the ice, then you will change
the speed at which the ice is
transported," she said.
The water under the ice streams acts as
a lubricant to ease the travel of the
ice toward the sea. So you would think
that more water under the ice would
result in faster-moving ice. But that's
not what's happening. NASA scientist
Robert Bindschadler says it illustrates
how much more they need to learn. "And
there is this conundrum, the fact that
this ice stream is slowing down, yet
most of the water produced under these
ice streams over these three years is
not getting out. How do you reconcile
those two," he said.
Although global warming could result in
rising sea levels from melting ice,
particularly ice covering Greenland,
Bindschadler says global warming is not
a factor in these lakes underneath the
Antarctic ice sheet. |
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人造卫星的观测显示，南极洲的冰层下面有很多活水湖，深达一公里。科学家还不能确定这些湖泊对冰流的移动起什么作用，但是冰河可能影响到海平面的上升。
科学家利用一个人造卫星对南极洲的表面进行了3年的精确测量，在这段期间，南极冰层下面的湖水发生升降幅度，水量的增减达两立方公里。这些湖泊在冰流的下面，冰流是移动的冰层，流向“罗斯冰架”。科学家原先已经知道冰流的下面有水，但是有这样多的湖水以及流动的如此快速，让他们感到惊奇。
主写研究报告的佛瑞克说，这是一个必须加以了解的重要过程，因为南极洲的冰在流入海洋之后，可能对海平面产生影响。佛瑞克说：“这一点之所以重要是因为冰流把南极洲深处的冰运送到海洋，冰层下面水的多少会改变冰的移动速度。”
冰流下面的水有润滑剂的作用，使冰能够顺畅的流向海洋。人们或许认为冰层下面的水越多，冰的流动也越快，然而实际的情形并不是这样。美国航空及航天局的科学家宾兹查德勒说，从这一点可以看出还有多少是我们所不知道的。宾兹查德勒说：“目前一个难以理解的难题是：冰流的速度正在缓慢下来，但是冰流下面在这三年当中，产生的水大部份并没有流入海洋，你如何解释这两个事实呢？”
虽然地球暖化的结果使冰--特别是覆盖格陵兰的冰溶解，导致海平面上升，但是宾兹查德勒说，地球暖化和南极冰层下面的湖泊并没有关系。 |
