Changes in Freeze-Thaw and Permafrost Dynamics and Their Hydrological Implication over the Russian Arctic Drainage Basin Tingjun Zhang and R. G. Barry National Snow and Ice Data Center University of Colorado at Boulder Freshwater Investigators Meeting Boulder, Feb , 2003 NSF OPP

Problems: Zhang and Barry, 2003, NSIDC Combined annual discharge from six largest Eurasian arctic rivers for the period from 1936 to 1999 has increased at a rate of about 2.0 km 3 /year (Peterson et al., Science, 2002). It has been reported (Yang et al., JGR, 2002; Serreze et al., JGR, 2002) that runoff has increased about 25% to 90% during cold season (October to April) over the Russian Arctic drainage basin in the past several decades. QUESTION : What causes the increase in discharge over the Eurasian arctic rivers, especially during the winter months?

Objective: to investigate the response of soil thermal, freeze-thaw, and permafrost dynamics to climatic change and their impact on the hydrologic cycle in the Russian arctic drainage basin over the past 50 years ( ). Specifically, we will: Investigate the impact of changes in freeze-thaw and permafrost dynamics on the arctic hydrological cycle Collect, rescue, and synthesize soil temperature, freeze-thaw cycle, and permafrost data from 400 stations over the Russian arctic drainage basin Zhang and Barry, 2003, NSIDC

Hypothesis: Climatic Warming Increasing length of thaw season Delaying active layer freeze-up Thickening the active layer Increase ground water storage capacity More ground water storage Increasing PF temperature and PF thawing Increasing in melt water of excess ground ice Increasing winter river runoff Increasing river runoff Zhang and Barry, 2003, NSIDC

Data Sets Needed: Existing Data Sets: IPA permafrost map (1:10,000,000) (Brown et al., 1997; Zhang et al., 1999) Gridded air temperature and precipitation (Jones et al., 1995) River runoff, precipitation, etc. (Legates and Willmott, 1990; Groisman, 1991; Lammers et al., 2001) New Data Sets from this study: Digital Russian permafrost map (1:1,000,000) by Yershov et al. (1998). Soil and permafrost temperature Active layer thickness Thawing index of air temperature Length of thaw season Zhang and Barry, 2003, NSIDC

1.240 stations (red dots): up to 1990; update to new stations (blue dots) to new stations (green dots) up to new stations from Mongolia up to 2002 (not shown). Zhang and Barry, 2003, NSIDC

Soil temperature increase at each river basin ( ): Ob: 1.2 o C Yenisey: 0.8 o C Lena: 1.5 o C Increase in soil temperature basin-wide leads to thickening the active layer and thawing of permafrost. Zhang and Barry, 2003, NSIDC

Active Layer: Variations of active layer thickness from 11 stations from Lena river basin. Variation of the thawing index estimated from mean monthly air temperature for each basin. Ground-based measurements indicate that active layer thickness increased about 30 cm from late 1960 to 1985 over Lena river basin. Thawing index has increased significantly from late 1960s to the late 1990s, implying thickening of the active layer basin-wide. Zhang and Barry, 2003, NSIDC

Impacts to Runoff (Discharge): Change in active layer thickness (cm) Yenisey ( ) ( ) ( ) Lena ( ) ( ) ( ) Ob ( ) ( ) ( ) These values are estimated using ground ice data from IPA permafrost map. Runoff is in mm over the period from 1965 to 1985 and discharge in km 3 /yr. Zhang and Barry, 2003, NSIDC

Impact to Runoff (Discharge) During the period from 1965 through 1985, discharge equivalent due to the melting of excess ground ice over the Ob, Yenisey, and Lena river basins: Active Layer Thickness Increase Discharge Equivalent 10 cm 2.1 to 2.9 km 3 /year 20 cm 4.2 to 5.8 km 3 /year 30 cm 6.3 to 8.7 km 3 /year Possible water sources contributing to: 1.Evaporation 2.Wetland and thaw lake contribution 3.River discharge Zhang and Barry, 2003, NSIDC

Impact on winter runoff Lateral thawing of permafrost contributes to winter runoff. Active layer thickness is positively correlated with winter runoff. Zhang and Barry, 2003, NSIDC

Acknowledgments: This study is supported by: NSF Office of Polar Program Thank You!