Environmental Engineering Reference
In-Depth Information
mountains. Terrestrial ice may enter the sea (or lakes) and remains attached to the parent
glacier as
ice shelves
or break off to form floating
icebergs
(Plate 15.1). Modern
Antarctic shelf studies stimulate awareness of the impact of glaciomarine environments
on shallow continental shelf seas and coastlines around former Pleistocene ice sheets in
North America and Europe.
Sea ice
covers 7 per cent of global ocean area on average, to
a mean thickness of 2-2·5 m. Sea water freezes in each hemisphere's winter and shrinks
by half in summer (Figure 15.2).
Ground ice
forms when pore water freezes in terrestrial
substrates and accumulates as perennial
permafrost
. It usually occurs where intense cold
and aridity stifle glacier development and underlies a further 25 per cent of modern land
surfaces.
Table 15.1 The size and extent of late Pleistocene
and Modern ice sheets and glaciers
Area (10
6
km
2
)
Modern ice
Volume
(km
3
)
Estimated maximum area of
Late Pleistocene ice (10
6
km
2
)
Volume
(10
6
km
3
)
Antarctic
13·50
32.0
Antarctic
14·50
37·7
Greenland
1·80
2.6
Greenland
2·35
8·4
Arctic basin
0·24
0.2
Laurentide ice sheet
13·40
34·8
Alaska
0·05
North American cordillera
2·60
1·9
USA (other)
0·03
Andes
0·03
Andes
0·88
European Alps 0·004
European Alps
0·04
Scandinavia
0·004
Scandinavian ice sheet
6·60
14·2
Asia
0·12
0.1
Asia
3·90
Africa
0·0001
Africa
0·0003
Australasia
0·001
Australasia
0·07
British ice sheet
0·34
0·8
Total
15·7
35·0
44·68
97·8
Notes
: The data are compiled from a wide range of sources which do not necessarily measure or
estimate ice cover or volume for the same geographical areas. Late Pleistocene (Late Devensian)
glacial maximum extent is estimated from geomorphic and other evidence. Global totals may
include other small glaciers.
