Moulins, Calving Fronts and Greenland Outlet Glacier
Acceleration  The first mechanism for explaining the change in
velocity is the “Zwally effect”, which relies on meltwater
reaching the glacier base and reducing the friction through a
higher basal water pressure. A moulin is the conduit for the
additional meltwater to reach the glacier base. This idea,
proposed by Jay Zwally, was observed to be the cause of a brief
seasonal acceleration of up to 20 % on the Jakobshavns Glacier
in 1998 and 1999 at Swiss Camp (Zwally et al., 2002). The
acceleration lasted two-three months and was less than 10% in
1996 and 1997 for example. They offered a conclusion that the
“coupling between surface melting and ice-sheet flow provides a
mechanism for rapid, large-scale, dynamic responses of ice
sheets to climate warming”. The acceleration of the three
glaciers had not occurred at the time of this study and they
were not concluding or implying that the meltwater increase was
the cause of the aforementioned acceleration. Howeve