Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 270

suggested that given further increases in GHG forcing, we may see nonlinear
trends of ice sheet disintegration (relative to temperature), which would mean
higher estimates of ice mass loss and of sea level rise (and drastic increases in
stress levels for the modellers).
2. Solid mass discharge is widespread. It is also accelerating with increasing rates,
gradually moving northwards along the west coast of Greenland in parallel
with the gradient of regional warming.
3. The acceleration of fast-flowing marine terminating glaciers coincides with re-
treat of the terminus.
4. The increase in speed of these glaciers is believed to be related to the warming
of ocean water underlying the floating tongue (ocean forcing). When the
weakening effect of the latter has resulted in calving, the flow resistance is re-
duced for the ice upstream.
Therefore, previous estimates of ice sheet loss that did not take account of solid mass dis-
charge (such as from iceberg formation) must now be considered as significant underestim-
ates.
The previous paragraphs may be a little too technical for some readers. Therefore,
here is the “take home message”: The Greenland ice sheet is presently losing mass at a rate
of at least about 200 Gt/year. If this loss increases to follow present model predictions, we
will have a rise in eustatic sea level by 2100 of between 10 and 19 cm (3.9 and 7.5 inches,
respectively). I will define “eustatic” a little later, but for now, just think of it as a theoret-
ical sea level that irons out the effects of local and regional factors that can influence sea
level, such as variations in gravity and water density. If we try to account for our lack of
understanding of dynamical processes and solid mass discharge, the maximum goes up to
about 40 cm (15.7 inches) of eustatic sea level alone. Remember that this is just for the
amount of melting we can expect to have occurred from the Greenland ice sheet by 2100.
One final nugget to make the reader sit up: At what global mean temperature would
we expect to see a complete loss of the Greenland ice sheet (resulting in an increase in