ice-atmosphere interaction (2): melting of greenland ice sheet by: eric dobroka
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Ice-Atmosphere Interaction (2):
Melting of Greenland Ice Sheet
By: Eric DoBroka
Professor Edward HannaProfessor of Climate Change
-Edward Hanna received a BS in Planetary Science (First Class Honors) from University College London in 1995
-He was appointed as lecturer in climate change in 2003 in Sheffield, UK -Member of both Meteorological and Astronomical Societies; International Glaciological Society
-Published over 80 research papers
-Got questions? Call +44-144-222-7965
Increased Runoff from Melt from the Greenland Ice Sheet: A Response to Global Warming
(2008)
Greenland IS Going Green!!
22
Attributes significant ice melt for 3 reasons:
1) Increased Summertime Temperatures (Numerous records smashed)
2) Significant Increasing Trend in Water Runoff
3) Change in NAO from positive to less positive/more neutral state
Where’d all the ice go??
Topography of Greenland
1) Increased Summertime Temperatures
Top 10 Warmest Summers in Southern Greenland
2) Excessive Water Runoff
1998, 2003, and 2006 were respectively the first, second, and third highest runoff years
5 highest runoff years have all occurred since 1995
During these years, significant 24.3% increase in runoff (113 cubic km as opposed to the standard deviation of 68.7 cubic km)
3) Changing of the North Atlantic Oscillation
Breaks down after the early 1990s
Changes in atmospheric circulation (jet Streams)
Positive Phase for most of period between 1960s and 1980s
More neutral phase
Less positive state reduced the insularity of Greenland by encouraging WAA over land masses
Conclusions Both Greenland and the Northern Hemisphere summer
temperatures exhibit common strong warming trends since the early 90s
Period of temperature recovery from volcanic eruptions Significant glacier melting is in fact taking place at an
alarming rate Uncertainties: As observed since 1987 at Summit,
summer temps near top of the ice sheet have declined slightly
Dichotomous Response due to high thermal inertia, higher atmospheric cooling, or changes in wind, cloud, radiation patterns?
Aud Venke Sundal
University of Leeds (UK)
Several publications on changingclimate, glaciers; effectson Norway
Geological Mapping (GIS)
“Aud Venke Sundal.”- I Norge er mye av løsmassene avsatt av rennende vann. Slike masser består av grov sand og grus med lite finstoff, noe som gjør at radongassen som blir
Melt-induced speed-up of Greenland ice sheet offset by efficient subglacial drainage (2011)
Fluctuations in surface melting effects speeds of glaciers and ice sheets
Impact of warming climate decreases acceleration of Greenland’s flow despite melting??
Satellite observations of ice motion in SW Greenland
Rates of ice speed positively correlated w/ degree of melting; mean flow rates are NOT
Warmer years, ice flow is 3x shorter; overall flow slower
Explored spatial and temporal variations comparing velocities Overall, significant
flow increase in summer for all 6 glaciers w/ speed-ups of 50% to 125%
Seasonal surface melting drives seasonal cycles in ice sheet flow
Dependent upon altitude
Mirrors mountain glaciersMelt induced
acceleration of flow ceases during years of high melting once subglacial drainage becomes efficient!!
Video Clip of Greenland Ice Melt
https://www.youtube.com/watch?v=b4QjyrGkaUg
Conclusions Data shows that subglacial drainage system
in SW Greenland evolves in response to variable surface melting similar to mountain glaciers.
Rates of surface melting at the Greenland ice sheet are predicted to double
over the course of this century. Would add .15m to .4m in sea level rise
Conclusions Cont. BUT….their data is first to
indicate a drop in summer speed-up of glaciers in years of high melting compared to years of low melting
Supports views that subglacial drainage system may adjust to accommodate increased melting
Uncertainties “The net effect of melt-
induced speed-up and efficient drainage remains uncertain.”
Let’s Play 20 QuestionsNo really let’s not
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