Arctic environmental security and abrupt climate change - Environmental and Human Security in the Arctic - page 104

taxing events may be permanently damaged if pushed beyond a particular
limit state. Once this limit state is exceeded, the ability of groups to respond
and adapt is undermined in crucial ways, possibly resulting in the society
falling to a lower level of stability. Fragility is not a matter, as some political
analyses would suggest, of a binary stable/unstable categorization, but rather
describes how vulnerable a group is to a stability shift (catastrophe set) to an
entirely different set of relationships and adaptive capacity. When combined,
these factors of vulnerability help to describe those system components or
conditions that need to be assessed if we are to understand potential security
risks of abrupt climate change. One can begin by considering the geographic
region where the climate system is most sensitive and potentially fragile, the
Arctic.
Abrupt climate change risks in the Arctic
The Arctic may provide a useful illustration of how foresight of environmen-
tal conditions and knowledge of non-linear effects can contribute to a greater
understanding of potential impacts. Rather than examine global models of
average climate change, a number of potential tipping points exist in Arctic
ecosystems that can trigger abrupt climate changes worldwide, and these are
reviewed here.
Greenland and Arctic ice melting
The geopolitical implications of loss of Arctic summer sea ice are potentially
profound, but are beyond the scope of this assessment. From an ecological
perspective, loss of sea ice will affect global albedo measures and wildlife, but
would not have any effect on either sea level or freshwater intrusion into deep
ocean currents. The more problematic issue for Arctic climate systems is the
stability of the Greenland ice sheet (GIS), a frozen reservoir of fresh water
locked into 2.85 million km 3 of ice that has existed since the late Pliocene
period over 100,000 years ago. Should the entire ice sheet melt, the resulting
melt water would raise global sea levels by approximately 7 metres (23 feet),
while significant melting may affect the salinity and stability of the ther-
mohaline circulation (THC) that drives the warm waters of the Gulf Stream
(Alley et al . 2003).
Original estimates of global climate change assumed the long-term stabil-
ity of the Greenland ice sheet, indicating that any significant melting of the ice
sheet would take hundreds of years, if not millennia (IPCC 2001). More recent
observations of ice melt indicated that the rate of net runoff was far higher
than expected, and that loss of GIS was accelerating rapidly. The melt rate
exceeded possible scenarios from ice sheet models, and scientists soon discov-
ered that water intrusion to the glacial bases through moulins (cavities worn
into the glaciers) resulted in lower friction between the glacial and underlying