1. Threatened Ice sheet Integrity By: Carl Egede Bøggild The University Centre in Svalbard, UNIS Department of Arctic Geophysics

2. Sea level and climate sensitivity

3. Is the Greenland ice sheet threatened? yes/no/don’t know – is all true New observational methods has proven that past knowledge was not sufficient The mass balance becomes ever more negative No absolute method to assess the mass balance – and different methods deviate

4. Greenland sea level and ocean circulation

5. Ice sheet model predictions An irreversible melt down may occur if around ¼ of the ice sheet mass is lost

6. The principle of instability Dynamic effect

7. An overview of results Climate models Gravity satellite Laser altimetry Radar altimetry SAR

8. Why is it so difficult to measure changes?

9. Melt water reaching the base

10. Changes in calving fluxes Is ice discharge climate or weather dependent?

11. Ice sheet memory: response to the LIA

12. Even different climate models produce different results

13. Increased observed surface melt

14. Is there a consensus? IPCC: “loss of the Greenland ice sheet is likely not to occur in the 21st century” Ice dynamics in the future: -Assume that the flow acceleration will persist unchanged -Scale up ice sheet discharge -Assume that the present imbalance is only transient

15. How does all this relate to short lived pollutants?

16. First results - Aerosols and BC remains on the ice margin surface -15% albedo reduction => 1 meter of annual melt

17. Results from NE-Greenland Impurity: aerosols + micro organisms

18. The effect of the “agricultural revolution” Forest clearing in North-America can potentially have caused more BC Model conditions: Excess BC 2 times, period 150-50 yr bp

19. McConnell et al. 2007. 20th-Century Industrial Black Carbon Emissions Altered Arctic Climate Forcing. Science Vol. 317. no. 5843, pp. 1381 - 1384 Modern industrial soot

20. First guess Storage: 500-2000 yrs Short lived pollutants are not short lived in Greenland Residence time to be estimated by modelling