Fluvial sediment flux to the Arctic Ocean

Geomorphology 80 (2006) 94 – 104 www.elsevier.com/locate/geomorph

Fluvial sediment flux to the Arctic Ocean V.V. Gordeev P.P. Shirshov Institute of Oceanology Russian Academy of Sciences, Moscow, Russia Received 1 November 2004; received in revised form 27 September 2005; accepted 27 September 2005 Available online 1 September 2006

Abstract The paper presents an overview of recent publications on the fluvial suspended sediment flux to the Arctic Ocean. The total suspended matter exported from the Russian territory is 102 × 106 t/year and from the Canadian Arctic is 125 × 106 t/year. The total suspended matter (TSM) flux to the Arctic (227 × 106 t/year) is very low, only about 1% of the global flux. Mean concentrations of suspended matter and specific sediment discharge are approximately one order of magnitude lower than the global concentration. An analysis of the trends in the sediment loads based on records of up to 62 years in length shows decreases (Yenisey), increases (Kolyma) and stability (Ob). Among the reasons for the very low concentrations and fluxes of suspended sediment in the Arctic rivers are thin weathering crusts on the Arctic watersheds, low precipitation, extensive permafrost, low temperatures for most of the year, large areas of swamps and lakes and a low level of human activity. A stochastic sediment transport model by Morehead et al. [Morehead, M.D., Syvitski, J.P., Hutton, E.W., Peckham, S.D., 2003. Modeling the temporal variability in the flux of sediment from ungauged river basins. Glob. Planet. Change 39, 95–110] is applied to the Arctic rivers to estimate the sediment load increase should the surface temperature of the drainage basin increase. For every 2 °C of warming a 30% increase in the sediment flux could result and for each 20% increase in water discharge, a 10% increase in sediment load could follow. Based on this model, an increase of the sediment flux of six largest arctic rivers (Yenisey, Lena, Ob, Pechora, Kolyma and Severnaya Dvina) is predicted to range from 30% to 122% by 2100. © 2006 Elsevier B.V. All rights reserved. Keywords: Arctic rivers; Suspended sediment; Sediment flux; Temporal variation

1. Introduction Fluxes of water and suspended sediments from arctic rivers to the ocean are àn integrated expression of processes occurring in their watersheds. Changes in these fluxes are a reflection of the natural and anthropogenic changes in the Arctic. Accurate estimates of fluvial sediment fluxes in the Arctic are fundamental to an understanding of land–ocean linkages, as well as contaminant and nutrient processes. They are also very

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important for detecting possible future natural and anthropogenic change (Holmes et al., 2002). Erosion, transport and fluxes of fluvial sediment are functions of many factors. Among non-anthropogenic factors, the most significant are the size of à drainage basin and the largå-scale relief within the basin (Pinet and Sourian, 1988; Milliman and Syvitski, 1992; Harrison, 1994; Syvitski, 2002). Other factors are local relief, climate, precipitation, runoff, basin geology including the erodibility of the substrate, vegetation, ice cover and lakes, all of these factors have a high correlation with the size of drainage basin or large-scale relief (Fournier, 1960; Douglas, 1967; Ahnert, 1970;

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Wilson, 1973; Jansen and Painter, 1974; Milliman, 1980; Walling, 1987; Milliman and Syvitski, 1992). In the former Soviet Union, sampling programs to measure Arctic river suspended sediments were begun between 1935 and 1966 within the framework of the Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet). The first assessments of sediment fluxes appeared in the 1950s (Shamov, 1949, Lopatin, 1952). Subsequently the suspended sediment studies were carried out by specialists at the State Hydrological Institute, Leningrad (Bobrovitskaya, 1968; Lisitzyna, 1974; Karaushev, 1974), the Arctic and Antarctic Research Institute, Leningrad (Ivanov and Piskun, 1995), the Moscow State University (Alabyan et al., 1995; Mikhailov, 1997; Magritsky, 2001), the P.P. Shirshov Institute of Oceanology, Moscow (Lisitzyn, 1972; Gordeev et al., 1996) and others. The discharge of water and suspended sediment by the largest river of the Canadian Arctic, the Mackenzie River, has been monitored by Environment Canada since the early 1970s and nearly all of the published estimates of sediment flux into the delta rely on the Environment Canada database. Fig. 1 shows the geographical provinces, major river basins and watershed boundaries in the Arctic Ocean.

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The Yukon River (Alaska) which drains into the Pacific Ocean just south of the Bering Straits is also included. The flow of the Yukon influences the freshwater budget of the Arctic Ocean. There are several geographical definitions of the Arctic Ocean boundaries (Prowse and Flegg, 2000) not all of which include the Yukon River in the basin of the Arctic Ocean. The definition of the Arctic Ocean and its drainage basin used in this paper is adopted from the NATO Research Workshop “Arctic Ocean Freshwater Budget”: the “Arctic Ocean River Basin — AORB” (Lewis, 2000). This defines the Arctic Ocean as being bounded by the Russian mainland, a line across Bering strait, the north coast of Alaska and the northernmost limit of the islands in the Canadian Arctic Archipelago, then across Kennedy Channel to Peary Land, across Svalbard, down to the Nordkapp in Norway and back to the Russian coast. The total contributing area for the AORB definition is 15.5 × l06 km2 with a total mean river discharge of 3299km3/ year and a range of 3043 to 3546 km3/year (Prowse and Flegg, 2000). 2. River water and sediment fluxes Mean multi-annual river water and suspended matter discharges for the main rivers of the Arctic are shown in

Fig. 1. Map of the Arctic Ocean showing river basins and watershed boundaries. Rivers: 1 — Onega, 2 — Severnaya Dvina, 3 — Mezen, 4 — Pechora, 5 — Ob, 6 — Pur, 7 — Taz, 8 — Yenisey, 9 — Pyasina, 10 — Khatanga, 11 — Olenjok, 12 — Lena, 13 — Omoloy, 14 — Yana, 15 — Indigirka, 16 — Alazeya, 17 — Kolyma, 18 — Yukon, 19 — Mackenzie (modified from Carmack, 2000).

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Table 1. Data for the Russian Arctic are from the Roshydromet database for the period 1970–1995. Total discharge into the Arctic Ocean from the Russian

territory is 2932km3, and is 367km3 from the Canadian Arctic. Mean specific discharge for the Russian Arctic is 7.3l/s·km2 and 5l/s·km2 for the Canadian Arctic, lower

Table 1 Total river water and suspended matter discharge into the Arctic Ocean (Gordeev et al., 1996; Holmes et al., 2002; Gordeev and Rachold, 2003) River

Area 103 km2

Discharge km3

Total suspended matter m3·s− 1

1·s− 1·km− 2

106 t·y− 1

g·m− 3

t·km− 2·y− 1

Barents and White seas Onega S. Dvina Mezen Pechora Other area Total

57 357 78 324 570 1386

15.9 110 27.2 131 179 463

500 3470 860 4130 5690 14,600

8.8 9.7 11.0 12.7 10.0 10.7

0.3 4.1 0.6 4.4 3.5 17.9

18 37 33 72 19 39

5.2 12.0 7.7 38.0 6.2 12.9

Kara sea Ob Nadym Pyr Taz Yenisei Pyasina Other area Total

2545 64 112 150 2594 182 867 6589

404 18 34.3 44.3 620 86 275 1480

12,760 570 1080 1400 19,600 2730 8690 46,830

5.0 8.9 9.8 9.5 7.6 15 10.0 7.1

15.5 0.4 0.7 0.7 4.7 3.4 5.5 30.9

37 22 18 21 8 39 20 21

6.4 6.2 6.2 4.7 1.9 18.8 6.3 4.7

Laptevs sea Khatanga Anabar Olenjok Lena Omoloy Yana Other area Total

364 100 219 2448 39 225 197 3592

85.3 17.3 32.8 523 7 31.9 40.3 738

2700 550 1040 16,530 220 1010 1280 23,330

7.4 5.5 4.7 6.7 5.7 4.5 6.5 6.5

1.7 0.4 1.1 20.7 0.04 4.0 0.65 28.6

20 24 38 39 18 130 16 39

4.6 4.1 5.1 8.5 1.0 17.8 3.3 8.0

East Siberian sea Indigirka Alazeya Kolyma Other area Total

360 68 647 252 1327

54.2 1.5 122 48.2 233

1710 50 3860 1530 7380

4.7 4.1 6.0 6 5.6

11.1 0.1 10.1 3.85 25.15

207 67 83 80 108

30.8 3.4 19.0 15.3 19

9.2 11.2 20.4

290 2050 2340

9.7 5.5 6.8

0.05 0.65 0.7

6 58 34

1.8 10 7.4

2932

94,480

7.3

102.2

36

7.9

– – 330 37

– – 10,430 1170

– – 5.8 1.6

– – 124 1.1

– – 168 –

367 3299

11,600 106,080

5.0 6.8

125.1 227.3

– 68

Chukchi sea without Alaska Amguema Other area Total Eurasian Arctic basin Total

29.6 64.6 94.2 12,987

Chukchi sea (Alaska) and Beaufort sea Kobuk 24.7 Kuparuk 8.1 Mackenzie 1787 Other area 726 Canadian Arctic basin Total Total Arctic

2513 15,500

– – 74 –

50 14.7

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than the global mean of 11 l/s·km2 (Milliman, 1991). The seasonal variation in water discharge by the largest rivers is shown in Fig. 2. The western rivers (Severnaya Dvina, Mezen, Onega) have a maximum discharge in May and the rivers of the western and eastern Siberia (Ob, Yenisey, Lena, Indigirka etc.) have a June maximum discharge. A comprehensive critical review of the existing data on sediment fluxes of the Arctic rivers was published by Holmes et al. in 2002. The authors established sediment flux estimates for the Yenisey, Lena, Kolyma, Pechora, Severnaya Dvina, Mackenzie and Yukon rivers. These estimates have been used in this paper. The concentration of total river suspended matter (TSM) ranges from 6 to 207 mg/l with a mean of 36 mg/l (Table 1). The Barents, White and Kara sea basin rivers are characterized by lower concentrations compared to the rivers of East Siberia and the Mackenzie River (168 mg/l). The maximum TSM discharges for the western rivers also occur in May and for the eastern rivers in June (Fig. 2). There is à high correlation between the specific water and total suspended matter discharges (Fig. 3). There is also à significant difference between the rivers of the west and east of the Russian Arctic, with the East Siberian rivers (Yànà, Alazeya, Indigirka, Kolyma) being more similar to the rivers of North America than to the rivers of the western Russian Arctic (Gordeev et al., 1996). TSM flux from the Russian territory is 102.2 × 106 t/year, and 125.1 × l06 t/year from the Cana-

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dian Arctic. Total flux to the Arctic Ocean is 227.3 × 106 t/year (Table 1). 3. Recent trends in sediment fluxes The transport of fluvial sediment to the ocean is an important pathway in the global geochemical cycles. An understanding of the effects of anthropogenic activity and climate change on the sediments is important if the human impact and climate changes are to be predicted (Syvitski, 2003; Walling and Fang, 2003). The IGBP Water Sediment Group has been established to consider the problem in details. The findings and recommendations of this group were published in “Global and Planetary Change”, 2003, v.39, N1/2. The Group identifies the Arctic as a particularly sensitive area in relation to sediment discharge. Syvitski (2003) believes that the Arctic may be the only terrestrial region where the effect of climate change may be greater than the anthropogenic effect. However, detailed examination of the recent trends in sediment yields of the Arctic rivers shows that “changes in suspended sediment yield depend more on man's activity than on climate change” (Bobrovitskaya et al., 2003). In an analysis of the sediment loads of 145 rivers in the world with records of more than 25 years including the Siberian rivers with records of up to 62 years Bobrovitskaya et al. (2003) indicate that 70 rivers show no evidence of à significant trend, 68 rivers show à

Fig. 2. (A, B) Seasonal variations of water discharge (A) and total suspended matter (TSM) discharge (B) by the largest Eurasian rivers (Gordeev et al., 1996).

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Fig. 3. Mean specific annual TSM export by the largest Arctic rivers versus their respective runoff. 1 — Onega, 2 — Severnaya Dvina, 3 — Mezen, 4 — Pechora, 5 — Ob, 6 — Nadym, 7 — Pyr, 8 — Taz, 9 — Yenisey, 10 — Pyasina, 11 — Khatanga, 12 — Anabar, 13 — Olenjok, 14 — Lena, 15 — Yana, 16 — Indigirka, 17 — Alazeya, 18 — Kolyma, 19 — Mackenzie, 20 — Yukon (Gordeev et al., 1996).

decrease, due mainly to dams, and only 7 rivers show evidence of an increase in sediment load (Walling and Fang, 2003). Fig. 4 shows annual discharges of suspended load and water at six gauging stations on the Yenisey River from 1960 to 1988. Although the annual sediment flux in the Yenisey river was very low before the 1960s (13.2 × 106 t/year; Milliman and Meade, 1983), it has declined to one-third (4.7 × 106 t/year) of that total at the present time (Holmes et al., 2002). In 1967, à very large dam was completed on the Yenisey river near Êrasnoyarsk (the Êrasnoyarsk Dam) and in the 1970s several additional dams were built on the Angara river, à large tributary of the Yenisey. After the construction

of the Êrasnoyarsk Dam, sediment flux at Divnogorsk (Fig. 4) declined from 6.3 to 0.2 × l06 t/year (Lisitzyna, 1974). The discharge of the Kolyma river at Ust-Srednekan from 1941 to 1988 is shown in Fig. 5. It shows no significant trend and can be considered essentially as constant. The sediment flux has, however, clearly increased during this period. A double mass plot of cumulative suspended sediment yield and cumulative annual water discharge (Fig. 5; Walling and Fang, 2003) indicates that the sediment flux has more than doubled since the mid-1960s. Bobrovitskaya et al. (2003) have estimated that the annual sediment yield increased from 1.9 × 106 t/year for the period 1941–1964 to 3.7 × 106 t/

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Fig. 4. (A, B) Annual suspended matter discharge (A) and water discharge (B) at six gauging stations in the Yenisey River basin during period 1960– 1988 (Meade et al., 2000).

year from 1964 to 1988. This could be the result of gold mining in the Kolyma river basin. The water and sediment fluxes in the River Ob at Salekhard (Fig. 6) show no statistically significant trends. A decrease in suspended matter yield has been observed during the last 30 years in the upper basin, reflecting the reservoir effect at Barnaul and Kolpashevo and at Tobolsk on the Irtysh River. At Belogorie, however, about 700 km upstream of Salekhard, there was a positive trend, with annual yields increasing from 19.2 × 106 t/year from 1938 to 1956 to 28.4 × 106 t/year from 1957 to 1990, owing to a significant human activity impact. Bobrovitskaya et al. (2003) consider that one reason for the stable sediment flux at Salekhard is the wide floodplain downstream of Belogorie. A large proportion of the sediments, about 59%, is deposited and exchanged between the river and the flood plain.

Other Siberian rivers, including the Yana at Verkhoyansk, the Indigirka at Vorontsovo and the Viliuy at Ust-Ambardakh have had a constant yield over time. 4. Arctic rivers in global context Table 2 shows river runoff and TSM flux to the Arctic Ocean with global fluxes. Water discharge to the Arctic Ocean is about 10% of the world river discharge and specific water discharge about 60% of the world total but the TSM discharge to the Arctic Ocean is very low, only about 1% of the global flux. The concentration of suspended matter in the Arctic rivers of 68g·m− 3 is approximately one order of magnitude lower than the global concentration of 528 g·m− 3. Specific sediment discharge is only 8% of the world total.

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Fig. 5. Recent changes in the sediment load and annual water discharge of the Kolyma River at Ust-Srednekan during period 1942–1989 (Walling and Fang, 2003).

Within the Arctic basin the values vary. The rivers of the European Russian Arctic and West Siberia differ from the rivers of East Siberia and North America (see Fig. 3). The rivers of western Eurasia are generally similar to other lowland rivers in the world (Milliman and Syvitski, 1992) but the rivers of East Siberia and North America are characterized by higher suspended matter concentrations (Table 1) because they drain areas of active glaciation and tectonics which generate large quantities of fluvial sediments (Holmes et al., 2002). Why do the Arctic rivers have very low rates of transport in spite of the large unconsolidated sedimentary deposits located throughout the Arctic (Syvitski, 2002)? Bobrovitskaya et al. (2003) have suggested that the vast areas of swamps and forests in the Siberian watersheds could explain very low loads of the Russian Arctic rivers. Lisitzyn (1995, 1998) considers that there are several reasons for the very low sediment fluxes in the Arctic. First, there are only thin very low weathering crusts on the surfaces of the large watershed basins and very little sedimentary material is removed from the tundra and taiga. Secondly, low precipitation, extensive permafrost

and low temperatures prevent the soils from weathering during much of the year. The lack of human activity in the region also plays an important role. Gordeev et al. (1996) have shown that there was a significant difference in many of the parameters for the western and eastern rivers of the Russian Arctic. The boundary between the two regions crosses the Laptev Sea basin. This boundary also coincides with the boundary between the Eurasian and North American tectonic plates. More research is needed to understand the significance of this. Syvitski (2002) has recently published a paper in which he presented the results of a model to predict the sediment flux in the arctic and sub-arctic rivers. He suggests that the model could explain why Arctic rivers have low sediment loads. 5. Climatic warming and sediment fluxes Morehead et al. (2003) have developed a stochastic model for simulation of sediment discharge in ungauged rivers. They suggest that basin temperature may influence the sediment load carried by rivers. In this

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Fig. 6. Recent changes in the sediment load and annual water discharge of the Ob River at Salekhard during period 1950–1996 (Walling and Fang, 2003).

model, the long-term mean of the daily sediment discharge Qs is defined as: Qs ¼ aH 3=2 A1=2 ekT ; whereby H is the river basin relief (m), A is river basin area (km2), T is the mean surface temperature of the basin (°C), α and k are dimensionless constants. Table 2 Riverine water and suspended matter fluxes to the Arctic Ocean in global context Parameter

Arctic Whole world

Area, 106 km2 15.5 99.9 Water discharge, 103 km3·y− 1 3.3 35 Specific water discharge, 6.8 11 1·s− 1·km− 2 Average concentration of 68 528 TSM, g·m− 3 TSM discharge, 106 t·y− 1 227 18,500 185 Specific sediment discharge, 14.7 t·km− 2·y− 1

Arctic, % of whole world 15.5 9.4 61.8 12.8 1.2 8

Most of the existing models simulate individual events for a specific time interval but they are not more generally applicable. The model by Morehead et al. (2003) accounts for the inter- and intra-annual variability of the suspended loads of rivers. The authors state that: “The strength of this new model is that the coefficients have strong trends between river basins that can be related to drainage basin parameters. The model accounts for basin wide characteristics through a mean exponent. A variable exponent captures the annual variability and is related to the size of the river basin.” The database of the model includes 48 arctic and subarctic rivers from Russia, the U.S. and Canada. The model is sensitive to drainage basin temperature and can be used to examine the impact of a climatic warming scenario on the loads of high latitude rivers. The model predicts that there will be a 30% increase in sediment load for every 2 °C of warming in the drainage basin (Fig. 7). However, because the main equation is a steady state predictor, the model does not predict the length of the transition period that will be required to reach this increase in sediment load. The

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lack of data for some rivers, the influence of dams, on the Yenisey, for example, and other anthropogenic factors, it is very difficult to make this comparison. It is possible, though, to use the model to estimate flux increase over the next 100 years. The Intergovernmental Panel on Climate Change (IPCC) projects a global rise in SAT of from 1.4 °C to 5.8 °C by 2100. On this basis the discharge of the six largest Eurasian rivers would increase by 315 to 1260 km3/year by 2100 (Peterson et al., 2002), an increase of from 18 to 70% over present conditions. The model by Morehead et al. (2003) estimates that the sediment flux of six arctic rivers will increase in a range from 30% to 122%, or from 17.8 × 106 t/year to 72.6 × 106 t/year, a very significant increase. 6. Conclusions Fig. 7. Predicting of sediment load increase with drainage basin temperature as modeled on the Colville River (Syvitski, 2002).

model also predicts that a 20% increase in discharge will result in a 10% increase in sediment transport. The combination of 2 °C warming with a 20% increase in runoff would increase the sediment load of Arctic rivers by 40%. Mean global surface air temperature (SAT) has increased by 0.6° ± 0.2 °C over the past century (IPCC, 2001). Evidence of increasing runoff in the Arctic had been reported recently (Shiklomanov et al., 2000; Semiletov et al., 2000; Lammers et al., 2001; Peterson et al., 2002). Peterson et al. (2002) have identified long-term trends in discharge from major Eurasian rivers flowing to the Arctic Ocean and have evaluated the possible links to climatic variability. Over the period of observations from 1936 to 1999, aggregate annual discharge from the six largest Eurasian rivers (Yenisey, Lena, Ob, Pechora, Kolyma and Severnaya Dvina) has increased at a mean annual rate of 2.0° ± 0.7° km3, so that today's mean annual discharge is now about 128 km3/year greater than it was when routine measurements of discharge began in the 1930s. This amounts to an increase of about 7%. The increase in discharge also corresponds to the increase in global, pan-arctic and Eurasian arctic SATs. Over the period of the discharge records, pan-arctic SAT increased by 0.6 °C and Eurasian arctic SAT by 0.7 °C (Peterson et al., 2002). It would be interesting to compare the real sediment flux of these six rivers with the flux predicted by the model over the period 1936–1999. The model estimates show an increase in the sediment flux of 14%. Due to

An overview of the available data on the suspended sediment fluxes in the Eurasian and North America Arctic rivers, their recent and future trends is presented in this paper. Predicted warming in the Arctic is expected to affect the extent of the permafrost and icecovered regions, the amount of precipitation and the productivity of terrestrial and aquatic ecosystems which in turn will affect river water and sediment discharges to the Arctic Ocean. All available recent assessments of fluvial sediment fluxes were taken into account (Gordeev et al., 1996; Gordeev, 2000; Meade et al., 2000; Magritsky, 2001; Holmes et al., 2002; Gordeev and Rachold, 2003). At present, all arctic rivers deliver 227.3 × 106 t/year of suspended sediment to the Arctic Ocean, of which the Eurasian rivers supply 102.2 × 106 t/year and Canadian rivers 125.1 × 106 t/year (Table 1). This forms only 1.2% of the total global flux. The mean concentration of suspended matter in arctic rivers and their specific sediment discharge is about one order of magnitude less than the global means. Bobrovitskaya et al. (2003) and Walling and Fang (2003) have published a detailed analysis of sediment flux in the Eurasian, Siberian and world's rivers showing trends based on long observational records of up to 62 years. Walling and Fang (2003) examined the time trends in the sediment flux of 145 major rivers. They showed that the dominant trends were either stability or declining, with almost the same number of rivers in each category. Only seven rivers showed evidence of an increase in sediment flux over time. The authors conclude that reservoir construction currently represents the most important influence on land–ocean sediment fluxes and evidence of the impacts of climate change is limited.

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Three Siberian rivers, the Ob, Yenisey and Kolyma, are examples of different trends. Construction of large reservoirs in the upper reaches of the Ob and Yenisey rivers has resulted in a decreased sediment yield. The sediment yield in the Yenisey river at Igarka after the construction of reservoirs declined to one-third from 13.2 × 106 t/year before 1960s to 4.7 × 106 t/year at present. The sediment yield regime in the lower reaches of the Ob is stable (Bobrovitskaya et al., 2003), probably because of the wide floodplain downstream at Belogorie (700 km upstream of Salekhard) where about half the sediment transported by the river is deposited. The Kolyma river at Ust-Srednekan shows a double sediment increase which is due to the human impact resulting from the mining of gold in the basin (Bobrovitskaya et al., 2003). It should be noted that it is the sediment flux in the downstream reaches of the arctic rivers that has been evaluated. The estuarine or the river/sea mixing zone is the marginal filter (Lisitzyn, 1995) which retains up to 90–95% of the sediment flux in the estuaries and deltas and on the broad shelf of the Arctic Ocean. There are several reasons for the concentration of the suspended sediment and the sediment fluxes in arctic rivers to be very low. They include the thin weathering crust and absence of removal by wash of sediment from tundra and taiga surfaces, low precipitation, large areas of permafrost, low temperatures for most of the year and little human activity (Lisitzyn, 1995, 1998). A stochastic sediment transport model for predicting the sediment flux (Morehead et al., 2003) explains why arctic rivers have a low sediment load when compared with global rivers. Because it is sensitive to drainage basin temperature, the model is used to estimate the impact of a climate-warming scenario on the loads of highlatitude rivers. A 30% increase in the flux carried is estimated for every 2 °C of warming and a 10% increase for every 20% increase in discharge. The Intergovernmental Panel on Climate Change projects a global surface air temperature increase of between 1.4 and 5.8 °C by 2100. Peterson et al. (2002) consider that on this basis the discharge of the six largest Eurasian arctic rivers (Yenisey, Lena, Ob, Pechora, Kolyma and Severnaya Dvina) would increase by 18–70% by 2100 which would mean that the sediment flux of the six arctic rivers would increase from 30 to 122% by 2100. Acknowledgments The preparation of this paper was initiated by the Steering Committee of the Sedimentary Source-to-SinkFluxes in Cold Environments (SEDIFLUX) project. The

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comments of two anonymous reviewers were very helpful in improving the manuscript. Author is especially appreciated to Prof. Frank Ahnert and Bridget Ahnert for their improvements in English translation. References Ahnert, F., 1970. Functional relationships between denudation, relief, and uplifting in large mid-latitude drainage basins. Am. J. Sci. 268, 243–263. Alabyan, A.M., Chalov, R.S., Korotaev, V.N., Sidorchuk, A.Y., Zaitsev, A.A., 1995. Natural and technogenic water and sediment supply to the Laptev sea. Rep. Polar Res., Bremerhaven, Germany, vol. 176, pp. 265–271. Bobrovitskaya, N.N., 1968. Determination of the normal annual discharge of suspended sediments and its cycling fluctuations. Sov. Hydrol. Select Pap. 7, 447–462 (in Russian). Bobrovitskaya, N.N., Kokorev, A.V., Lemeshko, N.A., 2003. Regional patterns in recent trends in sediment yields of Eurasian and Siberian rivers. Glob. Planet. Change 39, 127–146. Carmack, E.C., 2000. The Arctic Ocean's freshwater budget: sources, storage and export. In: Lewis, E.L. (Ed.), The Freshwater Budget of the Arctic Ocean. Kluwer Acad.Publ., Dordrecht, pp. 91–126. Douglas, J., 1967. Man, vegetation and the sediment yield of rivers. Nature 215, 925–928. Fournier, F., 1960. Climat et Erosion. Presses Universitaires de France, Paris. 201 pp. Gordeev, V.V., 2000. River input of water, sediment, major ions, nutrients and trace metals from Russian territory to the Arctic Ocean. In: Lewis, E.L. (Ed.), The Freshwater Budget of the Arctic Ocean. Kluwer Acad. Publ., Dordrecht, pp. 297–322. Gordeev, V.V., Rachold, V., 2003. River input. In: Stein, R., Macdonald, R. (Eds.), Organic Carbon Cycle in the Arctic Ocean: Present and Past. Springer Verlag, Berlin, pp. 78–87. Gordeev, V.V., Martin, J.-M., Sidorov, I.S., Sidorova, M.N., 1996. A reassessment of the Eurasian water, sediment, major ions, and nutrients to the Arctic Ocean. Am. J. Sci. 296, 664–691. Harrison, C.G., 1994. Rates of continental erosion and mountain building. Geol. Rundsch. 83, 431–447. Holmes, R.M., McClelland, J.W., Peterson, B.J., Shiklomanov, I.A., Shiklomanov, A.I., Zhulidov, A.V., Gordeev, V.V., Bobrovitskaya, N.N., 2002. A circumpolar perspective on fluvial sediment flux to the Arctic Ocean. Glob. Biogeochem. Cycles 16, 1849–1862. Intergovernmental Panel on Climate Change (IPCC), 2001. Climate change 2001. In: Houghton, J.T., et al. (Ed.), The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the IPCC. Cambridge Univ. Press, Cambridge. Ivanov, V.V., Piskun, A.A., 1995. Distribution of river water and suspended sediment loads in the deltas of rivers in the basin of the Laptev and East-Siberian seas. In: Kassens, H.M., Bauch, H.A., Dmitrenko, I.A., Eicken, H., Hubberten, H.W., Melles, M., Thiede, J., Timokhov, L.A. (Eds.), Land–Ocean Systems in the Siberian Arctic: Dynamics and History. Springer, New York, pp. 239–250. Jansen, J.M., Painter, R.B., 1974. Predicting sediment yield from climate and topography. J. Hydrol. 21, 371–380. Karaushev, A.V. (Ed.), 1974. Sediment Yield and Its Geographic Distribution. Gidrometeoizdat, Leningrad. 240 pp. (in Russian). Lammers, R.B., Shiklomanov, A.I., Vorosmarty, C.J., Peterson, B.J., 2001. Assessment of contemporary arctic river runoff based on observational discharge records. J. Geophys. Res. 106, 3321–3341.

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