Geoscience Reference
In-Depth Information
Table 2.1 Distribution of water in the climate system
Percentage of
Volume of
Mass of
Location
global water
water (km
3
)
water (kg)
Oceans
97%
1.37 10
10
1.37 10
22
Ice (glaciers, sea ice)
2%
2.9 10
8
2.9 10
20
Groundwater
0.7%
9.5 10
7
9.5 10
19
Lakes
1 10
−2
1.25 10
6
1.25 10
18
Soils
5 10
−3
6.5 10
5
6.5 10
17
Atmosphere
1 10
−3
1.3 10
5
1.3 10
17
Rivers and streams
1 10
−4
1.7 10
4
1.7 10
16
Biosphere
4 10
−5
6 10
3
6 10
15
important role of the atmospheric circulation in the global hydrologic cycle.
The climatological water cycle is completed when surface and underground
runoff transport water from the land to the oceans.
Water cycles rapidly through some components of the climate system, and
much more slowly through others. The average residence time for a water va-
por molecule in the atmosphere is only about 1 week. Residence times for
water in other parts of the climate system range from days in soils and riv-
ers, to many decades in glaciers and lakes, to 10,000 years or more in deep
groundwater.
Precipitation is highly variability in space and time, making it difficult to
observe and requiring a long averaging time to form a reliable climatology.
While excellent rainfall records have been kept in some regions—such as India,
Atmosphere
Net transport from
ocean to land: 36
Evapotranspiration
from land: 71
Precipitation
onto the
ocean: 398
Evaporation
from the
ocean: 434
Precipitation
onto land: 107
Runo• from land: 36
Ocean
Land
Figure 2.24 Estimated climatological fluxes (in 10
15
kg/yr) of water
in the climate system.
