University of New Hampshire, Durham, NH
There is an increasing trend in river discharge to the Arctic Ocean from both Eurasia (over 1936-2008) and North America (over 1970-2008).
Annual river discharge to the Arctic Ocean from the major Russian rivers in 2008 was 2078 km3 (Fig. R1). In general, river discharge shows an increasing trend over 1936-2008 with a rate of annual change of 2.9 ± 0.4 km3/year. An especially intensive increase in river discharge to the ocean was observed during last 20 years when sea ice extent in the Arctic Ocean began decreasing (Fig. R1). Interestingly, the correlation between Eurasian river discharge and sea ice extent over 1979-2008 is R = -0.72, or greater than the correlation between precipitation (Willmot et al., 1996) and runoff in these Eurasian drainage basins (R= 0.54). This suggests that both rivers and sea ice were responding to changes in large-scale hemispheric climate patterns (Shiklomanov and Lammers, 2009).
There is also an increasing tendency in river discharge to the Arctic Ocean from North America (Fig. R1). The mean annual discharge to the ocean over 2000-2008 from the 4 large North American Arctic rivers was 6% (31 km3) greater than the long-term mean from 1970-1999.
Official river discharge data are usually processed and published with some delay. This gap is related to discharge calculation techniques that take into account diverse flow conditions and ambiguous relationships between measured water stage (water level) and estimated river discharge. Cold regions, with long periods of ice cover, present the most difficult conditions for reliable discharge estimates in near real-time (Shiklomanov et al., 2006). However, in cooperation with Russian partners, we developed a method to estimate river discharge from the most important Russian monitoring sites in near real-time using provisional stage measurements and river ice data (http://RIMS.unh.edu). Provisional estimates for the 2009 annual river discharge to the Arctic Ocean from the six Russian rivers was greater than the long-term mean over 1936-2008 but much smaller than discharge in 2007 and 2008 (Fig. R1). Taking into account that the provisional estimates over 2003-2007 show a tendency to underestimate the annual observed values within an error of ± 2-4%, we anticipate the total discharge of six largest Eurasian rivers in 2009 being in the range 1930-1970 km3.
Peterson B. J., Holmes R., McClelland J., Vörösmarty C., Lammers R. B., Shiklomanov A., Shiklomanov I., and Rahmstorf S., 2002: Increasing Arctic river discharge: responses and feedbacks to global climate change. Science, 298, 2171-3.
Shiklomanov A. I., and Lammers R. B., 2009: Record Russian river discharge in 2007 and the limits of analysis. Environmental Research Letters, 4, 045015 (9 pp.) doi: 10.1088/1748-9326/4/4/045015.
Shiklomanov A. I., T. I. Yakovleva , R. B. Lammers, I. Ph. Karasev, C. J. Vörösmarty, and E. Linder, 2006: Cold Region River Discharge Uncertainty - Estimates from Large Russian Rivers. Journal of Hydrology, 326 (2006), p. 231–256.
Willmott, C. J., S. M. Robeson, and M. J. Janis, 1996: Comparison of Approaches for Estimating Time-Averaged Precipitation Using Data from the USA. International Journal of Climatology, 16: 1103-111.