0°
sequence (see Chapter 2). Since variations in sea surface
temperature also influence fluxes of heat and fresh water
Weddell
Q
u
e
e
to the atmosphere, this forms a feedback mechanism –
I
L n
c
a
M
a
e
r Sea
u
d

L
S
s
e
a
n
changes to the ocean caused by meltwater from ice sheets
h
n
d
e
lf
Filchner
directly influence how much snow builds up on the ice
Ronne
Ice Shelf
P
A
e
n
Ice
Amery
sheets themselves. Ice sheets are thus an active and im-
n
t
a
i
n
r
c
s
t
Shelf
Ice
u
i
c
l
a
Shelf
portant part of an interconnected climate system.
Bellings- T
East Antarctic
hausen
90° W
r
a South Pole
n
Ice Sheet
90°E
The ice cover in Greenland and Antarctica has two com-
Sea
s
West Antarctic
a
n
t
ponents (Figure 6A.1) – thick, grounded, inland ice that
A Ice Sheet
a
r
m
c
t
i
rests on a more or less solid bed, and thinner floating ice
u
c
Ross
d
n
M
d
o
shelves and glacier tongues. An ice sheet is actually a gi-
s
Ice Shelf
u
L
a
n
e
n
n
t
ant glacier, and like most glaciers it is nourished by the

a
i
l
k
e
s

S
i
e
n W
a
s
continual accumulation of snow on its surface. As succes- Ro
ss
Se
a
sive layers of snow build up, the layers beneath are gradu-
70°S
Magnetic
ally compressed into solid ice. Snow input is balanced by
180°
South Pole
glacial outflow, so the height of the ice sheet stays approxi- Figure 6A.2: Antarctica.
mately constant through time. The ice is driven by gravity
to slide and to flow downhill from the highest points of
the interior to the coast. There it either melts or is carried arctica by far the highest of the continents. Straddling
away as icebergs which also eventually melt, thus return- the South Pole, Antarctica is cold even during summer.
ing the water to the ocean whence it came. Much of the continent is a cold desert with very low pre-
cipitation rates. Thus, in contrast to Greenland, only a
Outflow from the inland ice is organized into a series of tiny proportion of the mass loss from the Antarctic Ice
drainage basins separated by ice divides that concentrate Sheet occurs by melting from the surface – summer-
the flow of ice into either narrow mountain-bounded time melt from the margins of the ice sheet only occurs
outlet glaciers or fast-moving ice streams surrounded in the northern Antarctic Peninsula and the northern-
by slow-moving ice rather than rock walls. In Antarctica most fringes of East Antarctica. Instead, most ice loss
much of this flowing ice has reached the coast and has from Antarctica is from basal melting and iceberg calv-
spread over the surface of the ocean to form ice shelves ing from the vast floating ice shelves.
that are floating on the sea but are attached to ice on
land. There are ice shelves along more than half of Ant- The West Antarctica Ice Sheet (WAIS) drains mostly
arctica’s coast, but very few in Greenland. into the Ross Ice Shelf, at the head of the Ross Sea; but
also into the Filchner/Ronne Ice Shelf (two connected
Antarctica ice shelves), at the head of the Weddell Sea; and into
small ice shelves along the Amundsen Sea coast. The
Antarctic inland ice ranges in thickness up to 5000 m, Ross and Filchner/Ronne ice shelves are each about the
with an average thickness of about 2400 m, making Ant- area of Spain (see Figure 6A.2).
102 GLOBAL OUTLOOK FOR ICE AND SNOW