1. The melting ice in Greenland - from local to regional scale Sebastian H. Mernild Climate, Ocean, and Sea Ice Modeling Group (COSIM) Los Alamos National Laboratory, New Mexico, USA Email: mernild@lanl.gov Copenhagen, November 24

2. D. Rumsfeld, former U.S. Secretary of Defense “There are things we know. There are things we know we don’t know. There are things we don’t know we don’t know.”

3. Source: Roberts et al. 2010.

4. Outline - Arctic temperatures change, - Local glacier observations (1995-2010), - Greenland Ice Sheet (GrIS) surface melt extent (1960-2080), - GrIS surface mass balance (1950-2080), - GrIS tipping point, - GrIS mass budget and area loss. Source: Roberts et al. 2010.

5. Source: NOAA/NCDC 1880-present: ~0.7 to 0.8 degree C 1960-present: ~0.6 degree C 2000-present: ~<0.1 degree C Same trend for: Hadley, GISS, and CCSM. Every year this century has been among the top 10 warmest years since instrumental records began, despite solar radiation being relatively weak over the past years Source: Allison et al. 2009.

6. Annual temperature anomaly vs. latitude: 1880-2007 Source: National Aeronautics and Space Administration (NASA). Jan Apr Jul Oct Annual temperature: 1957-2009 Winter temperature: 1957-2009

7. Local glaciers and ice caps mass loss: Glaciers around the globe have been shrinking since the end of the Little Ice Age (1900), with increasing rates of ice loss since the early 1980s. The ongoing trend of worldwide and rapid glacier shrinkage may lead to the complete deglaciation of large parts of many mountain regions by the end of the 21 st century. The figure does not include contributions from: Greenland Ice Sheet, local glaciers in Greenland, and Antarctica. Source: Koç et al. 2009.

8. Source: M. Nolan, University of Alaska Fairbanks (UAF). 2006 Source: UAF. 1925 Source: S. Mernild, LANL. Local glaciers and ice caps mass loss:

9. Local glacier mass loss: Source: Mernild et al. review Nature Geoscience The only local glacier in Greenland where long-term observations of both surface mass balance and glacier front fluctuations are available: since 1931, the glacier terminus has retreated by about 1300 m. Average retreat ~16 m yr -1 ; in 2009/10 ~30 m 2009/10 average terminus melt rate 4.5 to 5.2 m, twice the average value of approximately 2.5 m. 1931 2006 Source: B. Hasholt, University of Copenhagen. Local glacier mass loss:

10. Source: Mernild et al. review Nature Geoscience. MG is representative of many hundreds of local glaciers found in East Greenland outside the Greenland Ice Sheet, and these observations quantitatively document the general retreat of local glaciers in Southeast Greenland under ongoing climate warming. Local glacier mass loss: In 13 of the last 15 years, the MG had a negative surface mass balance, Greatest annual mass loss in 2009/10 of 2.16 m w.eq. Since 1995 the MG is significantly out of equilibrium and will likely lose approximately 60% of its area and 70% of its volume, even in the absence of further climate change. Bahr et al. (2009): Global average, glaciers and ice caps must lose at least 27% of their volume (the equivalent of an 18-cm rise in global average sea level) to return to equilibrium. (α r =AAR/AAR 0, where p s =α r –1 and p v =α r g –1, where p s is the fractional area change, p v is the fractional volume change, and g=1.36 is an empirical constant)

11. Greenland Ice Sheet (GrIS): Source: R. Greve, University of Hikkaido. Water balance equation: P – (E + Su) – R ± ΔS = 0 ± η P = precipitation, E = evaporation, Su = sublimation, R = runoff/calving, ΔS = change in storage (snow/ice), and η = error. Runoff

12. Satellite-derived GrIS surface melt extent, 1979-2008 Source: K. Steffen, University of Colorado. Simulated GrIS surface melt extent Source: Mernild et al. 2009 (HYP)

13. Simulated GrIS surface melt extent and summer mean temperature Maximum surface melt extent Source: Mernild et al. in review (GRL) - Increasing melting period since 1972 of approximately 40–50 days, - Increasing melting intensity, - A sort of oscillation in melt intensity.

14. 2010 Observed GrIS surface melt duration and frequency Source: T. Mote, University of Georgia. Difference (days) in summer 2010 melt duration compared to 1979–2007 Summer 2010 melt frequency in % of total days

15. The GrIS 1950-2080 IPCC scenario A1B modeled by the DMI HIRHAM4 RCM (using boundary conditions from ECHAM5 AOGCM) GrIS Surface maximum melt extent We detected an ~90% increase in maximum surface melt extent (0.48×10 6 km 2 ) from 1950 to 2080. The average 1950–1959 maximum modeled melt extent was 30%, and 56% for 2070– 2080. The greatest difference in modeled melt extent occurs in the southern part of the GrIS. To the NW and NE of the GrIS the changes in melt extent are less pronounced. The greatest number of melt days is seen in the south eastern part of the GrIS. The largest change in the number of melt days was visible in the eastern part of the GrIS (~50–70%), and is lower to the west (~20– 30%) (1950–2080). The reason is likely the projected change in sea ice extent and thickness in adjacent seas. Source: Mernild et al. 2010 (JHM)

16. Source: Mernild et al. 2009 (HYP) GrIS Surface mass balance, including runoff P: 631±32 km 3 yr -1 E and SU: 110±14 km 3 yr -1 R: 397±62 km 3 yr -1 ΔS: 124±83 km 3 yr -1 Other surface studies: P: 635–675 km 3 yr -1 R: 340–400 km 3 yr -1 ΔS: 110–310 km 3 y -1 Source: Box et al. 2006, Fettweis 2007, Hanna et al. 2008, Ettema et al. 2009. Source: Mernild et al. 2009 (HYP)

17. The rate of SMB loss, lead to an enhanced average loss of 331 km 3 through 1950 to 2080, and to an average SMB level of -99 km 3 for the period 2070–2080. The GrIS surface freshwater runoff is equivalent to an eustatic rise in sea level, from 0.8±0.1 (1950–1959) to 1.9±0.1 mm sea level equivalent (SLE) yr -1 (2070–2080). The accumulated GrIS freshwater runoff contribution from surface melting equals 160 mm SLE from 1950 through 2080. GrIS surface conditions: Source: Mernild et al. 2010 (JHM) The GrIS 1950-2080 IPCC scenario A1B modeled by the DMI HIRHAM4 RCM (using boundary conditions from ECHAM5 AOGCM)

18. Tipping point def.: SMB will loss mass year after year, resulting in its eventual removal (Bamber et al. 2010) Tipping Point: beginning of the 2040s ~1.2°C based on the IPCC A1B modeled by the HIRHAM4 RCM for Arctic. ~0.6°C global. Other studies indicates around 3.0°C or higher (Bamber et al. 2010) Continuously irreversible, for how long time? The GrIS 1950-2080 IPCC scenario A1B modeled by the DMI HIRHAM4 RCM (using boundary conditions from ECHAM5 AOGCM) Source: Mernild et al. 2010 (JHM)

19. GrIS mass budget and area loss Estimates of the net mass budget of the GrIS since 1960. Dotted boxes represent estimates used by IPCC AR4 (IPCC, 2007). The solid boxes are post-AR4 assessments (L = Luthcke et al. 2006, W= Velicogna and Wahr 2006; WT = Wouters et al. 2008; CZ = Cazenave et al. 2009; M = Mernild et al. 2009; V = Velicogna 2009). M Source: Allison et al. 2009, updated.

20. GrIS mass budget and area loss Source: Mernild et al. 2010 (TC) Below: Glacier front ice area loss from the 35 greatest outlet glaciers - 2009/10: 419 km 2 (Petermann 290 km 2 ). - Thickness Petermann, average ~0.1 km, loss = ~29 km 3 - Since 2000: average 150 km 2 yr -1 from front glaciers. Left: Ice discharge observations Helheim - Indicating significant increase in Helheim ice discharge of 13.2 km 3 since 2000.

21. GrIS mass budget and area loss Below: Glacier front ice area loss from the 35 greatest outlet glaciers - 2009/10: 419 km 2 (Petermann 290 km 2 ). - Thickness Petermann, average ~0.1 km, loss = ~29 km 3 - Since 2000: average 150 km 2 yr -1 from front glaciers. Left: Ice discharge observations Jakobshavn - Indicating significant increase in Jakobshavn ice discharge of 12.0 km 3 since 2000. Source: I. Howat, Ohio State University.

22. Source: Mernild 2008 20002175 2350 2000 21752350 Year 2350: Temperature rise up to 8-10 degrees C, Change in GrIS area up to 25%, volume up to 20%, GrIS contributes to the global sea level rise by up to 1.25 m. The thermal expansion will be another ~1.25 m. The total rise is expected to be up to 2.5 m from the GrIS. Based on data from IPCC (the average from seven different climate models) Future GrIS mass budget and area loss

23. Questions!