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December
20, 2006 New research into
the way the
Antarctic ice sheet adds ice to the ocean reveals that tidal motion
influences
the flow of the one of the biggest ice streams draining the West
Antarctic Ice
Sheet. This unexpected
result shows that
the Rutford Ice stream (larger than Reporting this week
in the
journal Nature, British Antarctic
Survey (BAS) glaciologist Hilmar Gudmundsson says, ‘We've
never seen anything like
this before. The discovery that the spring-neap tidal cycle exerts such
a
strong influence on an ice stream tens of kilometers (miles) away is a
total
surprise. For such a large mass of ice to respond to ocean tides like
this
illustrates how sensitively the Antarctic Ice Sheet reacts to
environmental
changes. Glaciologists need now to rethink how the Antarctic Ice Sheets
reacts
to external forces. ' The variations in
flow of the
Rutford Ice Stream are related to the vertical motion of the ocean
caused by
the gravitational effects of the sun and moon. Every two weeks sees
large
tides, the so-called spring tides which are followed by small tides,
the neap
tides. Scientists expect movement of the floating ice shelves, but the
Rutford
Ice Stream is grounded in the shallow waters of the Antarctic
continental
shelf. So far, Rutford Ice
Stream is the
only ice stream where this type of temporal variation has been
observed, but it
is likely that the phenomenon is widespread, and so important to
incorporate in
computer models predicting the future contribution of the ice sheets to
sea
level rise.
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