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house gases remaining in the atmosphere, which in itself depends on the capacity
of the world waters to retain them.
The composition of the aforementioned altered hydrosphere still needs to be
assessed. The uncertainty associated with this task is by no means trivial since it
involves the summing together of all uncertainties such as the projection of future
greenhouse gases and ocean acidification due to an increase in dissolved CO
2
(Hall-
Spencer et al., 2008).
That said, as stated in Sec. 5.4, it is well-known that the planetary water budget
is dominated by the oceans. Freshwater only constitutes 2.75% of the total, of which
glaciers and ice sheets account for 75%, with the remaining 25% coming from fresh
and groundwater. Such numbers indicate that even if potable water is essential
for life (and freshwater something which mankind gives precedence to over other
types of environmental issues), when it comes to defining a macroscopic model
of the crepuscular hydrosphere, freshwater is of almost no consequence
7
(Valero
et al., 2011)
8
. The composition of the exhausted bulk hydrosphere can therefore be
approximated with a reasonably high level of confidence to that of seawater, which
is given by Millero et al. (2008) (Table 5.5) or Quinby-Hunt and Turekian (1983)
(Table 5.6). The surface temperature assumed is that of the crepuscular atmosphere
(17
o
C).
10.3.3 The crepuscular continental crust
According to the USGS (2007), the mass of global non-fuel industrial mineral re-
sources is in the order of 10
15
kg. When the rest of the minerals are considered, the
total quantity of concentrated minerals increases by one or two orders of magnitude,
to around 10
17
kg. The amount of possible available conventional and unconven-
tional fossil fuels meanwhile, is around 10
16
kg, according to the WEC (2007). This
means that all concentrated mineral resources of fuel and non-fuel origin represent
only 0.001% of the Earth's upper continental crust total mass (around 10
22
kg, based
on Yoder (1995)). Therefore, the authors can state with no significant error, that
the crepuscular continental crust can be approximated to the average mineralogical
composition of the current Earth's upper crust.
7
Moreover, it is unlikely that all ice sheets and glaciers would have been melted, especially of
those of Antartica. However, land ice such as that covering the Arctic or Greenland would probably
disappear completely, reducing the fresh water budget substantially. In the same way, forest areas
will notably shrink. That said, Thanatia represents a limit, rather than a precise picture of the
Earth's future.
8
Even if the current ice sheet melting rate is estimated at more than 300 billion tons per year,
it represents less than 0.0009% of the total mass of the Antarctic and Greenland ice sheets which
together hold 33 million cubic km of ice. Such amount of ice is enough to rise global sea level
by 70 metres (Rignot and Thomas, 2002). Therefore if the rates of melting observed were to
continue, the ice sheets could add nearly 15 cm to the rise in global sea levels by 2050 but would
not significantly alter the ocean's composition (Rignot et al., 2011).
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