Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 309

tion? This may be one of the most important questions being faced by the future tundra and
northern boreal forest ecosystems.
In the oceans, cryospheric change is also the proximate cause of the most significant
ecosystem and socioeconomic impacts. We have already discussed the layer of very low
salinity (almost fresh) water that has been accumulating in (and extending beyond) the
Beaufort Sea and its potential to enhance acidification of the Arctic Ocean. According
to the 2011 SWIPA team, this reservoir (which has only appeared in recent years) now
amounts to 7,700 km 3 of freshwater - equivalent to 1 metre of water over the entire contin-
ent of Australia. Oceanographers and climate scientists are watching the fate of this water
with interest - partly because it inhibits mixing with underlying waters, partly because of
its impact on upper ocean pH and partly because of events that occurred during the last
interglacial period. Very sudden injections of freshwater resulting from the collapse of the
Laurentide ice sheet are thought to have very significantly weakened the Atlantic meridi-
onal overturning circulation (AMOC) andhence also weakened the Gulf Stream. 19 This led
to major climate repercussions around the world, especially in Europe, which experienced
a dramatic cooling. However, the amount of freshwater involved in the Laurentide event
vastly exceeds that likely to be suddenly available in the present-day Arctic. Nevertheless,
IPCC AR5 considers that “[i]t is very likely that the AMOC will weaken over the 21st cen-
tury. Best estimates and ranges for the reduction are 11% (1 to 24%) in RCP2.6 and 34%
(12 to 54%) in RCP8.5.” 20 You will recall that at the moment, some researchers fear that
RCP6.0 or even RCP8.5 appears to be the GHG emission pathway that world economies
are following. There is a little good news in that most scientists consider it is very unlikely
that the AMOC will undergo a rapid collapse in the present century.
Sea ice supports a unique (epontic) ecosystem founded on algae and amphipods that
occupy the undersurface of the ice. It is a major element of a food web that leads via Arctic
cod to seabirds (especially the ivory gull), marine mammals and, ultimately, the polar bear.
Clearly, the epontic food web itself will become rare as the surface area of available ice is
diminished. However, it appears that in some areas, such as the Beaufort Sea, the epontic
algae and amphipods have been in decline for some time. This is probably because they are