Precipitation Changes, Uncertainties, and Associated Impacts to the Arctic Environment

1. Precipitation Changes, Uncertainties, and Associated Impacts to the Arctic Environment Michael Rawlins Alexander Shiklomanov Richard Lammers Katelyn Dolan Charles Vorosmarty Arctic Research Consortium of the United States 2007 Annual Meeting and Arctic Forum May 24, 2007

2. Summary Statement: It is very likely that precipitation over the past century has increased across the mid and high-latitudes of the Northern Hemisphere---with the largest trends having come during winter---and recent model simulations suggest that future increases are likely to occur.

3. 20th Century Precipitation Changes

4. “It is probable that there was an increase in arctic precipitation over the past century” Arctic Climate Impacts Assessment, 2005

5. The largest increases have occurred during winter Arctic Climate Impacts Assessment, 2005

6. • All 21 AR4 models have increasing trend in ensemble mean • Only 4 have an ensemble run with a negative trend result Kattsov et al., JGR, in press

7. Winter trends are similar to annual means Summer shows no systematic changes Kattsov et al., JGR, in press

8. Frequency of summer wet days and days with heavy rains Sun and Groisman, 2000, Int. J. Climatol.

9. Trends in annual precipitation for the western part of the former USSR(years: 1936-1997) North of 60 N: Significant trend in TOTAL and HEAVY (90th percentile) P South of 55 N: Significant trend in TOTAL,HEAVY and VERY HEAVY (99th) P

10. Key Uncertainties in Estimating Arctic Precipitation • The sparse network of in situ observations • The difficulty in obtaining estimates of solid precipitation in windy environments • Slow progress in exploiting remote sensing techniques for measuring high-latitude precipitation • Compounding effects of elevation on precipitation Arctic Climate Impacts Assessment, 2005

11. Counterintuitive precipitation trends, relative to discharge trend, partially explained by gage density change Rawlins et al., 2006, GRL

12. Gauge undercatch is a significant problem, especially in winter January Correction Factor July Correction Factor Yang et al., 2005, GRL

13. Most General Circulation Models (GCMs) tend to overestimate precipitation... http://igloo.atmos.uiuc.edu/IPCC/

14. Future Precipitation Changes

15. Precipitation increases (2000-2100) are projected to be greatest during winter across high northern latitudes December-February June-August IPCC 4th Assessment, 2007

16. • All model suggest future precipitation increases across region 60N – pole • Departures range between 5 to 15 cm (~ 10% to 30% of mean) http://igloo.atmos.uiuc.edu/IPCC/

17. The models suggest that precipitation increases across the Arctic will far exceed the global trends. Kattsov et al., JGR, in press

18. Winter Cyclones in the NCAR CCSM3 • Increased cyclone-associated precipitation • Increased atmospheric precipitable water * * * Percent Increase in Precipitable Water * * * Finnis et al., JGR, in press

19. Magnitude of P-E changes (1950-2050) vary widely among models and are significantly correlated with initial precipitation conditions Holland et al., JGR, in press

20. Changes in Snowfall and Impact on River Runoff

21. Discharge from the major Russian rivers has increased... Peterson et al., 2002, Science

22. ...but annual precipitation does not explain the increase Berezovskaya et al., 2002, GRL

23. Discharge trends are greatest in the north where permafrost is most extensive... A. Shiklomanov, U. New Hampshire

24. Derived Snowfall Derived Rainfall ...and where snowfall increases are also noted Rawlins et al., 2006, GRL

25. The snowfall trends are consistent, spatially, with trends in observed runoff

26. Scenarios for future snowfall show both winners and losers Rawlins et al., 2007, in prep.

27. Larger changes emerge for the more extreme A2 emissions scenario Rawlins et al., 2007, in prep.

28. Summary • In situ data show an increase in 20th century precipitation. Largest increase in winter season. • Positive snowfall trends are noted where increases in Eurasian river discharge have occurred. • Models depict future precipitation and P-E increases, but spread is significant. • Estimates of derived snowfall useful for regional water resource assessments.