Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 269

as the Jakobshavn Isbra, or Sermeq Kujalleq (which drains 6.1% of the ice field), can have
overwhelming ramifications. The former is one of the most studied glaciers in Greenland
and each year sends about 35 Gt of iceberg down the fjord towards the little town of Ilulis-
sat and the open sea. Like most fjords, this one is very deep until it reaches a shallower
sill (located close to the village). Here, the larger bergs from the Jakobshavn Isbra ground
on the bottom, where they may remain for months or even years in a colossal traffic jam
before losing mass by melting and escaping into the bay. In the bay itself, you can usually
see a fleet of up to 100 bergs that have finally escaped to embark on their long voyage -
first north and then south as they follow the ocean currents of Baffin Bay and Davis Strait.
The Titanic berg is thought to have been a child of the Jakobshavn Isbra.
When an ice sheet is in contact with the ocean - either directly or via outlet glaciers -
it is vulnerable to oceanic forcing (heating from the seawater below). Ice breaking off from
a floating ice shelf or floating glacier is carried away by ocean currents, where it is subject
to the enormous heat capacity of the ocean and may finally melt hundreds of kilometres
from its source. The resulting loss of lateral resistance associated with the now broken-off
ice isthoughttoincrease theflowofice fromthefeeding ice sheet asitreoccupies thevoid.
In the face of these technical difficulties, climate scientists have historically tended to not
include solid mass discharge in their estimates of future ice loss and sea level rise. It was,
for example, noted as a major information gap but not included in IPCC AR4. However,
as concluded in the SWIPA report, solid mass discharge from the Greenland ice sheet is at
least as important as SMB in contributing to ice loss from Greenland.
Here are some general conclusions concerning the importance of solid mass discharge
reached by the 2011 SWIPA team and reinforced by some more recent publications:
1. Solid mass discharge could well be the more significant driver of total mass
balance loss. Glaciological studies, such as a 2012 aerial photographic survey
in north-west Greenland (by Kjaer and colleagues), show not only a substan-
tial mass loss but also attribute this loss primarily to short-lived dynamic
events rather than changes in the surface mass balance. As a result, it is being