Geoscience Reference
In-Depth Information
Figure 13.19
Simulations of changes in
surface temperatures (˚C) from 1880-89
to 2040-49 employing greenhouse gas
and anthropogenic aerosol forcing.
Source
: Houghton
et al
. (1996). Reproduced
by permission of the IPCC and Cambridge
University Press.
northern Europe melted. By 6000 years ago, sea-level
had risen by about 120 m from the glacial low stand.
Subsequently, the fluctuations have been only a few tens
of cm. During the twentieth century, the mean rise based
on tide gauges was between 1.0 and 2.0 mm/yr.
Sea-level changes are influenced by the following
mechanisms (those of short timescales - i.e. tens of
years - italicized):
2
Changes in ocean water volume (e.g. thermal expan-
sion and contraction; salinity changes; changes in
atmospheric pressure).
3
Changes in earth crustal levels:
•
Tectonic (e.g. rise of ocean ridges; sea-floor
subsidence; plate movements).
•
Isostatic (e.g. tectonic loading; ice and water
loading).
1
Changes in ocean water mass associated with
changes in water storage within the atmosphere-
earth-ocean-ice system (see Figure 4.1). Exchanges
with glaciers and ice sheets are well recognized, but
changes in ground water (aquifers) and those due to
reservoir and dam building are poorly known.
4
Changes in the global distribution of water:
•
Terrestrial rotation effects.
•
Global axis changes.
•
Terrestrial gravity variations.
