Environmental Engineering Reference
In-Depth Information
et al. (2008) assume in their sea level rise sensitivity study for Antarctica
a doubling of outlet glacier velocities in Pine Island and Thwaites Glacier
within the first decade, and ice loss acceleration from the Antarctic Penin-
sula at the same rate than melt increase at present-day rates of surface mass
balance change, resulting in a sea level rise of 0.12 m by 2100, just from
the increase in ice discharge.
Summary of Sea Level Change
Greenland and Antarctic ice sheets together would contribute up to
0.285 m sea level under the AR4 A1B warming scenario, assuming a dou-
bling in ice discharge for the Greenland outlet glaciers, and the Amundsen
Coast Basin in Antarctica. Such an increase in ice discharge has already
been observed for several regions in Greenland. Glaciers and ice caps are
expected to contribute 0.37±0.02 m sea level rise under the same warm-
ing scenario, and thermal expansion is expected to contribute 0.23±0.09
m by 2100.
Thus, the sea level rise by 2100 is expected to be at least 0.60±0.11 m
from thermal expansion and ice loss from glaciers and small ice caps only.
Assuming additional ice loss from Greenland at the rate, the total global sea
level rise would be about 0.65±0.12 m by 2100. Doubling in ice discharge
for both Greenland and Antarctica, the sea level increase could be as high
as about 0.88 ±0.12m by 2100. The estimated range in sea level rise in 2100
is therefore from about 0.5 to 1 m.
The dynamic response of ice sheets to global warming is the largest
unknown in the projections of sea level rise over the next century. Vermeer
and Rahmstorf (2009) made a semi-empirical projection linking sea level
to temperatures from past observations; their statistical projection for a tem-
perature scenario A1B (IPCC AR4: 2.3-4.3°C increase for 2100) predicts a
SLR of 0.97-1.56 m above 1990 by 2100. This is consistent with what hap-
pened during warming in the last interglacial time period (LIG) and cannot
be ruled out. The LIG warming was caused by perturbations of Earth's orbit
(Overpeck et al., 2006) and arrived much more gradually than is projected
for human-induced warming, so a faster sea level rise in the future than in
the LIG would not be surprising. On the other hand, changes in the LIG
were linked to ice at low elevation, which could behave differently from
that at high elevation in the interior of Greenland.
