Ice-Atmosphere Interaction (2): Melting of Greenland Ice Sheet By: Eric DoBroka

Professor Edward Hanna Professor of Climate Change -Edward Hanna received a BS in Planetary Science (First Class Honors) from University College London in 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

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 Breaks down after the early 1990s  Changes in atmospheric circulation (jet Streams) Changes in atmospheric circulation (jet Streams)  Positive Phase for most of period between 1960s and 1980s Positive Phase for most of period between 1960s and 1980s  More neutral phase More neutral phase  Less positive state reduced the insularity of Greenland by encouraging WAA over land masses 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 changing climate, glaciers; effects on 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 glaciers  Melt induced acceleration of flow ceases during years of high melting once subglacial drainage becomes efficient!!

Video Clip of Greenland Ice Melt

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 Questions No really let’s not