Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 271

sea level of 7.0 m)? The best estimate is 3.1°C above preindustrial times. In 2012, Alexan-
der Robinson and colleagues reported that the ice sheet is more sensitive than previously
thought and suggested that an ice-free state could occur in a temperature range of 0.8 to
3.2°C, with a best estimate of 1.6°C. The global mean temperature increase over the period
1880-2012 reported in IPCC AR5 was 0.85°C. It is generally accepted that the Greenland
ice sheet may not vanish according to present predicted warming for perhaps up to 1,000
years, but remember that the Arctic has already seen a warming that is a good deal higher
than 0.85°C. At the back of my mind, I am also recalling that RCP6.0 is projected to give
us a global temperature anomaly of 3.0°C by 2100.
Mountain glaciers and mountain ice caps: The global storage offrozen ice isnotre-
stricted to the Greenland and Antarctic ice sheets. What about the state of the Arctic moun-
tain glaciers and mountain ice caps?
Well, they contain sufficient ice to raise the sea level by 0.41 metres (16.1 inches) if
they were all to melt entirely. Of 20 Arctic glaciers and ice caps (reported by Sharp and
colleagues in 2011 and 2012) for Alaska, Arctic Canada, Iceland, Svalbard, Norway and
Sweden for 2009-2011, 19 glaciers and ice caps had a negative mass balance. The satellite
GRACE measurement of mass loss from all the glaciers and ice caps in the Canadian Arctic
Islands was 96 (+/−49) Gt in 2010-2011. This is the largest loss calculated for this region
since GRACE observations began in 2002. It is interesting that the region has been sitting
in the same North Atlantic Oscillation and Arctic Oscillation atmospheric circulation pat-
tern of warm air that has caused significant melting on the Greenland ice sheet. Total mass
loss from Arctic mountain glaciers is thought to have probably been more than 150 Gt/year
over the last 10 years. It is therefore similar in magnitude to the total mass loss so far from
theGreenland ice sheet. Interestingly,inarecent global studybyGardnerandcolleagues, it
was estimated that the 19 glaciated regions of the globe (excluding Greenland and Antarc-
tic ice sheets) have lost ice at a rate of 259 (+/−28) Gt/year between 2003 and 2009. This is
roughly equivalent to the combined ice sheet loss from Greenland and Antarctica and could
account for 29% (+/−13) of the observed sea level rise over the same period. Of course, al-
though the contributions to sea level rise from these two sources (Antarctic and Greenland