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 Sorina Hanna 2006

Greenland Ice Sheet meltdown by global warming: myth or reality?. Edward Hanna (ehanna@sheffield.ac.uk) Senior Lecturer in Climate Change Department of Geography, University of Sheffield, UK 18 October 2007 talk to FreshNor workshop, Norrkoping, Sweden.  Sorina Hanna 2006.

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 Sorina Hanna 2006

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  1. Greenland Ice Sheet meltdown by global warming: myth or reality? Edward Hanna (ehanna@sheffield.ac.uk) Senior Lecturer in Climate Change Department of Geography, University of Sheffield, UK 18 October 2007 talk to FreshNor workshop, Norrkoping, Sweden  Sorina Hanna 2006

  2. E. Hanna main current research areas • Greenland Ice Sheet mass balance and links with climate change/global warming. • Sea-surface temperatures & air-sea interaction • (3) Atmospheric/storminess reconstructions using new daily-pressure-variability index and dpv spectrum analysis. • (4) Micrometeorology and downscaling of climate data • (5) Public communication of meteorology/climatology

  3. Greenland Ice Sheet evidence of global warming? J. Bamber Greenland DEM

  4. Some key collaborators * Philippe Huybrechts (Free Uni. Brussels) * Konrad Steffen & Russ Huff (CIRES, Colorado) * John Cappelen (Danish Meteorological Institiute) * Christopher Shuman (NASA Goddard Space Flight Center) * Joe McConnell (Desert Research Institute, Reno) * Trausti Jónsson (Icelandic Meteorological Office), Jon Olafsson & Hedinn Valdimarsson (Marine Research Institute) * Rob Allan (Hadley Centre, UK Met. Office)

  5. Greenland Ice Sheet front near Kangerlussuuaq, SW Greenland, August 2001

  6. Why is Greenland Ice Sheet important in global change? • Ice-sheet models predict that local warming >5degC over Greenland over 1000 years is likely to melt ~1/2 the ice sheet and contribute ~3 m to global sea-level rise (IPCC 2001). This would threaten many coastal cities. These models may be conservative estimates (Alley et al. 2005). • GrIS already nearing threshold (~3-4degC > mean C20th values) where it will likely melt irreversibly and contribute ~7 m to global sea level (Gregory et al. 2004, 2006).

  7. Greenland Ice Sheet-Arctic sea ice links • Reduced sea-ice associated with warmer airmass ( more Greenland melting). • More storms & moisture reaching Greenland ( more snow accumulation on ice sheet). • Which effect predominates??

  8. William Chapman, University of Illinois

  9. From David Stephenson’s (Dept. Meteorology, Uni. Reading) Web site

  10. Hanna et al. JGR 2005, updated

  11. Means, standard deviations and trends in modelled accumulation, runoff and surface mass balance for the Greenland ice sheet (km3 yr-1 water equivalent) “Current Cryospheric Contributions to Sea-level Rise and Variability”Steffen, K., et al. (2006) White Paper for Sea level Uncertainty Workshop for WMO and ISCU, Paris, June 6-9, 2006

  12. . Rates of elevation change along ATM flight lines during 1997-2003, superimposed on a map of elevation-change rates resulting from the 1993/94 and 1998/99 surveys [Krabill et al, 2000, 2004]. The region outlined in the southeast consistently thinned until 2001, and then thickened substantially between May 2001 and May 2003. “J” and “K” show Jakobshavn Isbrae and Kangerdlugssuaq Gletscher. The broken line indicates the 2000 meter contour. Differences between average summer temperatures (June/July/August), and those for 1961-90, are listed at coastal weather stations, for 1997-2002 (upper) and 1993-99 (lower).

  13. Greenland Mass Balance Thomas (2006)

  14. Greenland Ice Sheet: rates of surface-elevation change (dS/dt)Above (red), and below (blue) ~ 2000-m elevation Thomas (2006)

  15. Hypothesis Increased warmth from ocean may be causing enhanced melting and recent mass loss observed from Greenland Ice Sheet (since early 1990s). Test by examining correspondence between coastal Greenland air temperature and surrounding seas’ surface temperature

  16. Explore link between North Atlantic sea-surface temperatures & climate change • Iceland work

  17. Greenland Ice Sheet / climate: recent findings summary * Significant increases in Greenland summer air temperature, Ice Sheet melt & runoff since early-mid 1990s. - 2003, 2007, 2005 & 2001 & 2006 were warmest 5 years in last half century. * However, equally warm events between 1918-1947. * Greenland & global temps closely correlated since 1992 but not before then (1958-92) due to masking influence of North Atlantic Oscillation. * Increased runoff largely offset by increased snow accumulation. Massive snow accumulation in SE Greenland in winter 2002/3 & W Greenland winter 2004/5. * Net effect on surface mass balance close to zero for past few decades but likely overall mass loss from increased discharge (Rignot 2006). * High interannual variability in snowfall & summer melting, may increase with ongoing climatic change, making significant trends harder to discern.

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