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
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220 |
Page 221 |
Page 222 |
Page 223 |
Page 224 |
Page 225 |
Page 226 |
Page 227 |
Page 228 |
Page 229 |
Page 230 |
Page 231 |
Page 232 |
Page 233 |
Page 234 |
Page 235 |
Page 236 |
Page 237 |
Page 238