Arctic environmental security and abrupt climate change - Environmental and Human Security in the Arctic - page 105

rock, effectively lubricating the movement of ice over stone. Other non-linear
dynamics were also at work, such as force imbalances between calving sec-
tions of the glacier and inland sheets. The resulting changes in conditions,
combined with higher summer temperatures in Greenland of some 2 degrees
Celsius, have resulted in significant reductions in glacial cover and thick-
ness in some regions (especially coastal areas, where summer temperatures are
often above freezing). More recent estimates of GIS stability indicate that the
GIS itself may largely disappear by the end of the century, an abrupt shift that
is matched by past climatological records (Rignot and Kanagaratnam 2006;
Solomon et al . 2007).
The potential impacts of GIS melting are twofold. The first and more obvi-
ous concern is rising sea level, a risk that has been downplayed in standard
IPCC projections at least until the end of the twenty-first century (IPCC 2001,
2007). In the potential abrupt climate change scenarios of sudden warming,
accelerated ice melt from Greenland could raise sea levels by anywhere from
1-4 metres in the short term or decadal measure, and up to 7 metres in a
worst case scenario (Alley et al . 2003). Historical climate records indicate
that abrupt rises in sea level are possible, and would cause obvious and severe
dislocation in coastal areas globally. The areas at most risk of coastal flooding
or inundation are easily mapped, although the cascading effects of large-scale
dislocation must be assessed and measured according to regional social, eco-
nomic and political systems.
The second impact of GIS melt is the possible interaction between a sud-
den influx of freshwater into the north Atlantic, and the stability of the THC
of ocean currents. The THC consists of global undersea currents, moving vast
quantities of energy from warmer to cooler regions, and past climate shifts are
attributed to cessation of such energy movements. Climate researchers have
hypothesized that the sudden cooling recorded at the end of the Younger
Dryas Period 11,400 years ago, a drop of 10 degrees Celsius over a decade, was
caused by the sudden release of melt water from the Saint Lawrence in North
America (Alley et al . 2009; Rabe et al . 2011). The fresh water released into the
north Atlantic decreased the density and salinity of the waters at the north-
ern edge of the warm Gulf Stream, preventing the water from sinking. This
action effectively shut down the global THC, and may have been the cause of
the sudden, global cooling of the period. Recent scientific reports have indi-
cated that the northern extent of the Gulf Stream has been shortening, with
regional impacts of more severe winters in the British Isles and Scandinavia,
although it is difficult to discern long-term trends from natural variation
(Bryden et al . 2005). The risk of global warming turning to sudden global
cooling is plausible, considering past and geologically recent climatological
records, and the global impacts would be severe in terms of food security and
shocks to fragile ecosystems (Schneider 2003).