an introduction to the greenland ice sheet · 2013-01-10 · an introduction to the greenland ice...
TRANSCRIPT
An Introduction to the Greenland Ice Sheet
The Greenland ice sheet covers ~80% of Greenland’s 2.2
million km2 area. It is thought to have formed around 2 million
years ago when glaciation in the Northern hemisphere became
extensive.
Currently, it holds around 2.9 million km3 of ice – about 7
metres of potential sea level rise.
Since the 1980s the ice sheet has had a negative mass balance.
This means it has been losing ice more quickly than it has been
gaining it. These losses have recently accelerated: during the last
five years the ice sheet has lost almost 300 km3 more ice each
year than it has gained.
Melting from 1979 to 2011 – the ice
sheet has melted more intensively over
the last decade than previously.
The larger the text, the stronger the melting.
Warm water from the Atlantic ocean
can reach the edges of the ice sheet,
undercutting and melting the ice.
Snow falls and collects in the ice
sheet interior – the accumulation
zone. Over time the snow compacts,
turning into ice. Around 680 km3 of
ice collect each year.
Where glaciers flow into the ocean,
chunks of ice fracture off the glacier front.
The faster a glacier flows, the more icebergs
tend to be produced, so more ice is lost.
Iceberg calving accounts for about 50% of ice
loss from Greenland.
Meltwater from the ice sheet runs
off into the ocean. About 50% of ice
from Greenland is lost as water. Most
runoff happens during high summer.
Outlet glaciers around Greenland are
concentrated streams of ice flowing very quickly
towards the ocean. Jakobshavn Isbrae (see map)
flows at speeds in excess of 15km per year. It
drains roughly 10% of Greenland's annual ice loss.
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? What we don’t know
• How the world’s climate will change
• The exact causes of glacier sliding and iceberg calving in relation to
climate change
• How quickly the ice sheet will change over the coming decades and
centuries
What we do know
• Approximately how much ice is currently being lost by melting and iceberg
calving
• In response to a warming climate, the ice sheet will continue to lose mass
• Ice sheet models suggest that an arctic warming of 3oc could be enough to
lead to a complete loss of the ice sheet
During the summer, ice at lower
altitudes melts. In the ablation zone
there is more melting than snowfall. The
water collects into lakes and streams. Often,
this water can get to the ice sheet bed. This
is important in changing the speed at which
the ice above flows and slides. See the next
board for more details...