INSTAAR Univ. of Colorado

1. Global Glacier and Ice Cap contributions to Sea Level RiseW.T. Pfeffer*, INSTAAR/University of Colorado Calving and subglacial flood, Columbia Glacier, Alaska, 2004 W.T. Pfeffer *with contributions from AMAP/SWIPA Glacier and Ice Cap working group, Mark Dyurgerov, Mark Meier INSTAAR Univ. of Colorado

2. Steric (thermal expansion) • Upper ocean (top 700 m) • Lower ocean) • Eustatic (new water) • Antarctica • Greenland • Glaciers and Ice Caps (GIC) • Terrestrial storage • Ground water • Surface water • a. Reservoir storage • 3. Relative (local) • a. Dynamics (winds/currents) • b. Gravitational • c. Isostatic rebound • d. Coastal subsidence • 1. Infrastructure loading • 2. SLR loading • 3. Upstream sediment trapping • 4. Groundwater depletion fromDomingues et al, Nature 2008 Components of Sea Level Rise (SLR) - Relative Contributions Objective: Assess current eustatic SLE contributions from all sources with meaningful uncertainties, and forecast future SLE on useful time scales (decades-century) with meaningful uncertainties. INSTAAR Univ. of Colorado

3. Current work: SWIPA glacier and ice cap module (AMAP) Radic and Hock (in press) improved estimates of global GIC volume. and others… Glacier and Ice Cap regions (from Radic and Hock in press) INSTAAR Univ. of Colorado

4. Glacier and Ice Cap global area is poorly constrained: Earlier evaluations did not consider GIC surrounding Greenland and Antarctica SLE (m) 0.50 0.72 from Dyurgerov and Meier, 2005 Global GIC volume “known” to within ~22 cm SLE INSTAAR Univ. of Colorado

5. Glacier and Ice Cap volume summary (current 2009) factor 1/k adjusts for missing data Glacier and Ice Cap regional volumes (from Radic and Hock in press) INSTAAR Univ. of Colorado

6. Data (area) sources: Inventoried regions: WGI-XF Greenland: Weng (1995) > de Woul (2008) Antarctica*: Shumski (1969), Dyurgerov and Meier (2005), Hock et al (2009) Other uninventoried regions: GGHYDRO 2.3 (Cogley, 2003) Glacier and Ice Cap mass loss summary (current 2009) *Antarctic total : 169 x 103 km2 (Shumski, 1969) Mainland only: 132 x 103 km2 (Hock et al, 2009) Ant. Peninsula only: 116 x 103 km2 (Rignot et al 2008) Glacier and Ice Cap regions (from Radic and Hock in press) INSTAAR Univ. of Colorado

7. e.g. WGI-XF missing Bering Glacier, Alaska Devon Ice Cap, Canada Flade Isblink, Greenland Generally, observations missing in Greenland, Antarctica, USA: WGI-XF Data set: biased toward small land-terminating glaciers unmeasured not analyzed unmeasured unmeasured >> Major uncertainties in most basic inventory items: e.g. area, volume >> Nearly complete lack of knowledge of properties needed for modeling e.g. topography, velocities, bed topography, size/location of outlets, etc INSTAAR Univ. of Colorado

8. Global mass balance of GIC: No new comprehensive assessment since Dyurgerov and Meier, 2005* Global assessment relies on records from ca. 300 glaciers out of ~400,000 total. Number of monitored glaciers is declining. From data compilation of Dyurgerov and Meier, 2005 *but see Dyurgerov, “Reanalysis of Glacier Changes Between the IGY and IPY, 1960-2008)” in prep. INSTAAR Univ. of Colorado

9. Glacier and Ice Cap mass loss summary Global (current 2005) 402± 95 GT/yr in 2006 INSTAAR Univ. of Colorado

10. Glacier and Ice Cap mass loss summary for Arctic only (current 2009) INSTAAR Univ. of Colorado

11. Glacier and Ice Cap mass loss summary (current 2009) SWIPA 5C in Review INSTAAR Univ. of Colorado

12. GRACE gravity from Peltier, 2009 showing Greenland and Alaska mass loss rates, corrected for isostacy. INSTAAR Univ. of Colorado

13. Other recent developments:Antarctic Glaciers and Ice Caps SLE contribution 1961-2004 = 0.79 ± 0.34 mm/yr (Hock et al, 2009)Global GIC committed future SLE contribution ~ 0.18 m even with further climate change (Bahr et al, 2009)Calving flux from GIS very poorly known but is ~30-40% of total mass loss where observed (Svalbard, Russian Arctic) INSTAAR Univ. of Colorado

14. UPDATE: 379 ± ~38 GT/yr (1993-2006) Dyurgerov, “Reanalysis of Glacier Changes Between the IGY and IPY, 1960-2008)” in prep. Glaciers and Ice Caps: No comprehensive summation* since Meier et al (2007):-402 ± 95 GT/yr (for 2006)Newer observations (2008) for Alaska show ca. 80-110 GT/yr 402 ± 95 GT/yr (2006) INSTAAR Univ. of Colorado

15. Individual Ice/Eustatic Components:Greenland mass loss summary (current 2009) INSTAAR Univ. of Colorado

16. Individual Ice/Eustatic Components: Antarctica mass loss summary (current 2009) INSTAAR Univ. of Colorado

17. Relative contributions (current 2009) GIC: 402±95 GT/yr 46% Greenland: 267±38 GT/yr 31 % Antarctica: 196±30 GT/yr 23 % TOTAL: 865 GT/yr = 2.4 mm/yr SLR % SLR updated previous total was 645 GT/yr = 1.8 mm/yr (Meier et al 2007) from Meier et al 2007 with updates from Rignot (2008 a,b) and others (*Dyurgerov in prep result) INSTAAR Univ. of Colorado

18. The future: Projection of SLR rates forward to 2100 by extrapolation of present-day rates(assuming mass balance acceleration remains constant) 14 GT/yr2 INSTAAR Univ. of Colorado

19. Projection of SLR rates forward to 2100 by extrapolation of present-day (last ca. 5 years) forward with dynamics Projected contributions to 2100: Greenland .44 m 41% (V) Antarctica .38 m 36% (V) GIC .25 m 25% (M) TOTAL 1.06 m Projected dynamics (Pfeffer et al 2008): Eustatic: ~ 0.52 to 1.71 m with dynamic projection Total SLR w/ nominal 0.30 m steric component: ~0.82 to 2.01 m by 2100 INSTAAR Univ. of Colorado

20. Projection of SLR rates forward to 2100 by extrapolation of present-day (last ca. 5 years) forward with dynamics Examine range of mass balance acceleration: Greenland -30 ± 11 GT/y2 Antarctica -26 ± 14 GT/y2 GIC -12 ± 6 GT/y2 0.55 m SLE Gld. 0.41 m SLE Ant. 0.28 m SLE GIC Using Velicogna 2009 values for Greenland and Antarctica, Meier et al 2007 values for GIC 0.14 m SLE INSTAAR Univ. of Colorado

21. One complication: West AntarcticaLoss of Ross and/or Filchner-Ronne ice shelves is not imminent, but possible in next century, by submarine melt.Forecast including dynamic response changes in this case.But see recent work by Powell et al on timing of Pliocene W. Ant. collapse INSTAAR Univ. of Colorado

22. Summary:Present day SLE contributions, next-century projected contributions, and uncertainties for Greenland, Antarctica, and GIC are all ~comparable and significant.GIC observational record is improving in some respects (e.g. GRACE, small-scale airborne altimetry) but at risk of being extinguished in other respects (e.g. mass balance components, velocities INSTAAR Univ. of Colorado

23. Recommendations for GIC:1. Complete GLIMS inventory, continue/expand GIC mass balance measurement programs. 2. NEED DATA TO GO INTO GLIMS: Glacier outlines esp. in Antarctica and Patagonia.3. Update/revamp WGI to include full range of GIC. Significant data missing from Antarctica, North America, Russian Arctic, Patagonia and High Asian Arctic4. Remote sensing data needed: Altimetry, InSAR: location/speed of outlets, Airborne/shipborne soundings: bathymetry in front of outlets, depth sounding in outlets, microwave observations: snow facies, etc.5. Groundtruth: Velocity, mass balance observations. INSTAAR Univ. of Colorado

24. Illulissat, Greenland, 2007 W.T. Pfeffer INSTAAR Univ. of Colorado

25. Over-prediction of future sea level rise may be as expensive as under-prediction:1. For very large SLR predictions, planners start applying triage: Which 20% will be saved, and which 80% will be sacrificed?2. Strong tendency to devalue land placed on seaward side of limit of inundation. Incentive for long-term investment falls without positive defensive action, but forecast will likely come first. Over-prediction of future sea level rise may more expensive than under-prediction. INSTAAR Univ. of Colorado

26. INSTAAR Univ. of Colorado

27. Projection of net SLR forward to 2100 by extrapolation of present-day (last ca. 5-10 years) forward without dynamics 2100 Sea level equivalent (m) Sea level equivalent (m) 0.41 m SLE No Dynamic Projection – this is strictly empirical projection of observed present-day rates forward to 2100 INSTAAR Univ. of Colorado

28. Projection of SLR rates forward to 2100 by extrapolation of present-day (last ca. 5 years) forward with dynamics Estimated SLR to 2100 with dynamics using Pfeffer et al 2008, high- and low-range estimates. Dynamic response applies to allcategories: GIC, Greenland, and Antarctica INSTAAR Univ. of Colorado

29. Components of Sea Level Rise (SLR) - Relative Contributions Significant uncertainties apply to all components INSTAAR Univ. of Colorado

30. Urgency of response varies with rate of environmental change What are rates A & B? Rate A may be ~20th C rate; B much harder to estimate A B INSTAAR Univ. of Colorado

31. Cost of uncertainty (value of reducing uncertainty) varies over time What are time scales C and D? C: Possibly ~ 1 year (reducing uncertainty in sea level forecast on much shorter time scales isn’t useful). D: Possibly 50-100 years (reducing uncertainty in sea level forecast 500 years from now isn’t politically/economically usable). Long-term determinations not useful in the absence of medium-short term determinations INSTAAR Univ. of Colorado

32. Uncertainty in predictions of future Ice Sheet and Glacier/Ice Cap response GIC rate uncertainty is initially greater than Greenland or Antarctic rate uncertainty, but will become less at some point in the future (> 50 years) as GIC volume diminishes. INSTAAR Univ. of Colorado

33. Uncertainty in predictions of future Ice Sheet and Glacier/Ice Cap response GIC net contribution will be surpassed by Greenland and Antarctic contribution at some point in the future (> 50 years) as GIC volume and loss rate diminishes. But all magnitudes are significant within the century time scale. INSTAAR Univ. of Colorado