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Trend Attribution of Eurasian River Discharge to the Arctic Ocean

Trend Attribution of Eurasian River Discharge to the Arctic Ocean. Jennifer Adam Dennis Lettenmaier Department of Civil and Environmental Engineering University of Washington. April 9, 2006 PCC Graduate Climate Conference. Study Period 1930-2000.

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Trend Attribution of Eurasian River Discharge to the Arctic Ocean

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  1. Trend Attribution of Eurasian River Discharge to the Arctic Ocean Jennifer Adam Dennis Lettenmaier Department of Civil and Environmental Engineering University of Washington April 9, 2006 PCC Graduate Climate Conference

  2. Study Period 1930-2000 -18 -12 -6 0 6 Mean Annual Air Temperature, C Study Domain Indigirka Lena Yenisey Ob’ Severnaya Dvina

  3. Annual trend for the 6 largest rivers Discharge, km3/yr Peterson et al. 2002 Discharge, km3 1950 1960 1970 1980 40 Monthly Means Ob’ GRDC 30 Discharge, m3/s 20 10 J F M A M J J A S O N D Observed Stream Flow Trends • Discharge to Arctic Ocean from six largest Eurasian rivers is increasing, 1936 to 1998: +128 km3/yr (~7% increase) • Most significant trends during the winter (low-flow) season • Purpose of study: to investigate what is causing this Winter Trend, Ob’

  4. Climate and the Arctic • Currently experiencing system-wide change: All subsystems affected! • Rivers, temperature, precipitation, permafrost, snow, wetlands, glaciers, vegetation zonation, fire frequency, insect infestations… • Implications to global climate: • Albedo feedback • Greenhouse gas emissions/uptake • Ocean circulation feedback

  5. Thermohaline Circulation (heat) (salt) Freshening of the Arctic Ocean deep water formation in the Northern Atlantic slowed-down or “turned-off” www.noaa.gov

  6. Stream Flow Trend Attribution • Water Balance: Storage,S: ground water/ice, lakes, surface ice… ? ? ? • Hypothesized contributors – • Acceleration of the hydrologic cycle: P , E? • Permafrost Degradation: dS/dt, E? • Reservoir Operation: dS/dt?, E? • Other: fires, land use, wetlands, clouds, … • Published authors to date all say, “we don’t know”: McClelland et al. (2004), Berezovskaya et al. (2004), Pavelsky and Smith (2006)…

  7. Affects of Permafrost Change on Stream Flow • Seasonal effects: • Increase in late fall/winter stream flow? • Annual increase via melt of excess ground ice: * massive ice * flakes or thin layers * expanded soil pores

  8. Continuous , 90-100% Isolated, <10% Discontinuous, 50-90% Seasonally Frozen Ground Sporadic, 10-50% Permafrost Distribution Lena: 100% permafrost (all types) Yenisey: 89% permafrost (all types) Ob’: 26% permafrost (all types) Brown et al. 1998

  9. 0.4 (+) Correlation 0.2 0.0 T/Q Correlation (-) Correlation -0.2 -0.4 -15 -10 -5 0 Air Temperature, C Annual Air Temperature/Stream Flow Correlation COLD: no T control on Q THRESHOLD: T control through permafrost melt WARM: T control through Evapotranspiration

  10. Trend Analysis • Selection of trend test: * Sensitive to seasonal differences in trend • Varying periods between 1936 and 1998 • Test for 99% significance, two-tailed • Calculate trends for precipitation, temperature, and stream flow (gauged and reconstructed (McClelland et al. 2004))

  11. Precipitation Trends, 99% Temperature Trends, 99% Lena Yenisey Ob’ Secondary Basins C/year mm/year

  12. Stream Flow Trends, 99% Lena Yenisey 1940 1960 1980 2000 1940 1960 1980 2000 Trend, mm/year Ob’ 1940 1960 1980 2000

  13. Precipitation Trends (for periods with stream flow 99%) Lena Yenisey 1940 1960 1980 2000 1940 1960 1980 2000 Trend, mm/year Ob’ 1940 1960 1980 2000

  14. Lena • Reservoir • Precipitation • Permafrost? • ET? Yenisey • Permafrost • Reservoir • Precipitation? Ob’ • Precipitation • ET • Reservoir? Stream Flow/Precipitation Trends Gauged Precipitation Trend, mm/yr Stream Flow Trend, mm/yr Reconstructed Precipitation Trend, mm/yr

  15. Current and Future Work • Off-line macro-scale hydrologic land surface modeling • Captures stream flow trends outside permafrost regions (Ob, S. Dvina) • Problems with permafrost simulations identified: • Needs dynamic bottom boundary temperatures (at soil damping depth) • Needs incorporation of excess ground ice • Stream flow predictions – using downscaled GCM precipitation and temperature predictions • Fully coupled (with GCM) feedback exploration

  16. Questions?

  17. Stream Flow Trends, 99% Ob’ Indigirka Lena Aldan (Lena) Lena(head) Ob’(head) Yenisey S. Dvina mm/year

  18. Precipitation Trends, 99% Temperature Trends, 99% Lena Yenisey Ob’ Secondary Basins C/year mm/year

  19. Precipitation Trends (for periods with stream flow 99%) Ob’ Indigirka Lena Aldan (Lena) Lena(head) Ob’(head) Yenisey S. Dvina mm/year

  20. Lena • Reservoir • Precipitation • Permafrost? • ET? Yenisey • Permafrost • Reservoir • Precipitation? Ob’ • Precipitation • ET • Reservoir? Stream Flow Trend, mm/yr Precipitation Trend, mm/yr Stream Flow/Precipitation Trends Gauged Recon. Gauged

  21. Affects of Permafrost Change on Stream Flow • Seasonal effects: • Increased ALD, delay of freeze-up Increase in late fall/winter stream flow? • Annual increase via melt of excess ground ice: ice in excess of the volume of the soil pores had the soil been unfrozen * massive ice * flakes or thin layers * expanded soil pores

  22. Permafrost Primer Unfrozen Frozen Frozen Unfrozen Permafrost: Coldest climates Active Layer Depth (ALD) The hydrologically active layer Seasonally Frozen Ground: Moderate to Cold climates Warming can cause the ALD to increase and/or the extent of permafrost to decrease – both affect runoff generation

  23. mm/year mm/month 300 Lena 80 40 200 3 6 9 12 0 1940 1960 1980 2000 Precipitation Data mm/year mm/month Lena 100 600 50 400 0 3 6 9 12 1940 1960 1980 2000 UW(gauge-based) Gauge-Based Reanalysis UW Data Development mm/year Lena short-term variability + long-term variability + monthly climatology Stream Flow Data Reconstructed Gauged

  24. 0.4 0.4 (+) Correlation 0.2 0.2 0.0 0.0 T/Q Correlation T/Q Correlation (-) Correlation -0.2 -0.2 -0.4 -0.4 -15 -10 -5 0 Air Temperature, C 0 5 10 15 20 Discontinuous Permafrost, % Annual Air Temperature/Stream Flow Correlation COLD: no T control on Q THRESHOLD: T control through permafrost melt WARM: T control through Evapotranspiration

  25. 100% 100% 0% 0% can be explained by Observed Precipitation can be explained by Reanalysis Precipitation cannot be explained by any Precipitation Product Stream Flow/Precipitation Trend Compatibility Lena Yenisey Ob’ Gauged Frequency of Periods Reconstructed

  26. Ground Ice Conditions

  27. High Quality Precipitation Stations High Quality Temperature Stations

  28. Lena Yenisey Ob’ Lena Yenisey Ob’

  29. Modeling Framework

  30. Arctic river network: 100 km grid system

  31. Simulated Naturalized Observed Hydrologic Simulations Lena • VIC land surface hydrology model – complete water and energy balance • Controls handled: (1)Precipitation: YES (2)Temperature on evaporation: YES (3)Temperature on Permafrost: SOON (4) Reservoirs: NO Yenisey Annual Stream Flow, 103 m3/s Ob’

  32. Lena: X Ob’: Ob’(head): ~ S. Dvina: Observed/Simulated Stream Flow Trends Gauged Recon. Observed Trend, mm/yr Gauged Simulated Trend, mm/yr

  33. Trend Analysis • Selection of trend test: * Sensitive to seasonal differences in trend • Varying periods between 1936 and 1998 • Test for 99% significance, two-tailed • Calculate trends for stream flow (gauged and reconstructed (McClelland et al. 2004)), precipitation, and temperature

  34. Lena • Reservoir • Precipitation • Permafrost? • ET? Yenisey • Permafrost • Reservoir • Precipitation? Ob’ • Precipitation • ET • Reservoir? Aldan (Lena) • Permafrost • Precipitation? Severnaya Dvina (1)Precipitation (2)ET? Stream Flow Trend, mm/yr Lena (head) (1)Precipitation Precipitation Trend, mm/yr Stream Flow/Precipitation Trends Gauged Recon. Gauged

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