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 important for detecting possible future natural and anthropogenic change (Holmes et al., 2002). Fluxes of water and suspended sediments from arctic Erosion, transport and fluxes of fluvial sediment are rivers to the ocean are àn integrated expression of functions of many factors. Among non-anthropogenic processes occurring in their watersheds. Changes in factors, the most significant are the size of à drainage these fluxes are a reflection of the natural and basin and the largå-scale relief within the basin (Pinet anthropogenic changes in the Arctic. Accurate estimates and Sourian, 1988; Milliman and Syvitski, 1992; of fluvial sediment fluxes in the Arctic are fundamental Harrison, 1994; Syvitski, 2002). Other factors are to an understanding of land–ocean linkages, as well as local relief, climate, precipitation, runoff, basin geology contaminant and nutrient processes. They are also very 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 E-mail address: [email protected]. relief (Fournier, 1960; Douglas, 1967; Ahnert, 1970;

Wilson, 1973; Jansen and Painter, 1974; Milliman, The Yukon River (Alaska) which drains into the Pacific 1980; Walling, 1987; Milliman and Syvitski, 1992). Ocean just south of the Bering Straits is also included. In the former Soviet Union, sampling programs to The flow of the Yukon influences the freshwater budget measure Arctic river suspended sediments were begun of the Arctic Ocean. There are several geographical between 1935 and 1966 within the framework of the definitions of the Arctic Ocean boundaries (Prowse and Russian Federal Service for Hydrometeorology and Flegg, 2000) not all of which include the Yukon River in Environmental Monitoring (Roshydromet). The first the basin of the Arctic Ocean. The definition of the assessments of sediment fluxes appeared in the 1950s Arctic Ocean and its drainage basin used in this paper is (Shamov, 1949, Lopatin, 1952). Subsequently the adopted from the NATO Research Workshop “Arctic suspended sediment studies were carried out by Ocean Freshwater Budget”: the “Arctic Ocean River specialists at the State Hydrological Institute, Leningrad Basin — AORB” (Lewis, 2000). This defines the Arctic (Bobrovitskaya, 1968; Lisitzyna, 1974; Karaushev, Ocean as being bounded by the Russian mainland, a line 1974), the Arctic and Antarctic Research Institute, across Bering strait, the north coast of Alaska and the Leningrad (Ivanov and Piskun, 1995), the Moscow State northernmost limit of the islands in the Canadian Arctic University (Alabyan et al., 1995; Mikhailov, 1997; Archipelago, then across Kennedy Channel to Peary Magritsky, 2001), the P.P. Shirshov Institute of Ocean- Land, across Svalbard, down to the Nordkapp in ology, Moscow (Lisitzyn, 1972; Gordeev et al., 1996) Norway and back to the Russian coast. The total and others. contributing area for the AORB definition is 15.5× The discharge of water and suspended sediment by l06 km2 with a total mean river discharge of 3299km3/ the largest river of the Canadian Arctic, the Mackenzie year and a range of 3043 to 3546km3/year (Prowse and River, has been monitored by Environment Canada Flegg, 2000). since the early 1970s and nearly all of the published estimates of sediment flux into the delta rely on the 2. River water and sediment fluxes Environment Canada database. Fig. 1 shows the geographical provinces, major river Mean multi-annual river water and suspended matter basins and watershed boundaries in the Arctic Ocean. 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). 96 V.V. Gordeev / Geomorphology 80 (2006) 94–104

Table 1. Data for the Russian Arctic are from the territory is 2932km3, and is 367km3 from the Canadian Roshydromet database for the period 1970–1995. Total Arctic. Mean specific discharge for the Russian Arctic is discharge into the Arctic Ocean from the Russian 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 Discharge Total suspended matter 3 2 10 km − − − − − − − km3 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 57 15.9 500 8.8 0.3 18 5.2 S. Dvina 357 110 3470 9.7 4.1 37 12.0 Mezen 78 27.2 860 11.0 0.6 33 7.7 Pechora 324 131 4130 12.7 4.4 72 38.0 Other area 570 179 5690 10.0 3.5 19 6.2 Total 1386 463 14,600 10.7 17.9 39 12.9

Kara sea Ob 2545 404 12,760 5.0 15.5 37 6.4 Nadym 64 18 570 8.9 0.4 22 6.2 Pyr 112 34.3 1080 9.8 0.7 18 6.2 Taz 150 44.3 1400 9.5 0.7 21 4.7 Yenisei 2594 620 19,600 7.6 4.7 8 1.9 Pyasina 182 86 2730 15 3.4 39 18.8 Other area 867 275 8690 10.0 5.5 20 6.3 Total 6589 1480 46,830 7.1 30.9 21 4.7

Laptevs sea Khatanga 364 85.3 2700 7.4 1.7 20 4.6 Anabar 100 17.3 550 5.5 0.4 24 4.1 Olenjok 219 32.8 1040 4.7 1.1 38 5.1 Lena 2448 523 16,530 6.7 20.7 39 8.5 Omoloy 39 7 220 5.7 0.04 18 1.0 Yana 225 31.9 1010 4.5 4.0 130 17.8 Other area 197 40.3 1280 6.5 0.65 16 3.3 Total 3592 738 23,330 6.5 28.6 39 8.0

East Siberian sea Indigirka 360 54.2 1710 4.7 11.1 207 30.8 Alazeya 68 1.5 50 4.1 0.1 67 3.4 Kolyma 647 122 3860 6.0 10.1 83 19.0 Other area 252 48.2 1530 6 3.85 80 15.3 Total 1327 233 7380 5.6 25.15 108 19

Chukchi sea without Alaska Amguema 29.6 9.2 290 9.7 0.05 6 1.8 Other area 64.6 11.2 2050 5.5 0.65 58 10 Total 94.2 20.4 2340 6.8 0.7 34 7.4 Eurasian Arctic basin Total 12,987 2932 94,480 7.3 102.2 36 7.9

Chukchi sea (Alaska) and Beaufort sea Kobuk 24.7 –––––– Kuparuk 8.1 –––––– Mackenzie 1787 330 10,430 5.8 124 168 74 Other area 726 37 1170 1.6 1.1 ––

Canadian Arctic basin Total 2513 367 11,600 5.0 125.1 – 50 Total Arctic 15,500 3299 106,080 6.8 227.3 68 14.7 V.V. Gordeev / Geomorphology 80 (2006) 94–104 97 than the global mean of 11l/s·km2 (Milliman, 1991). dian Arctic. Total flux to the Arctic Ocean is The seasonal variation in water discharge by the largest 227.3×106 t/year (Table 1). rivers is shown in Fig. 2. The western rivers (Severnaya Dvina, Mezen, Onega) have a maximum discharge in 3. Recent trends in sediment fluxes May and the rivers of the western and eastern Siberia (Ob, Yenisey, Lena, Indigirka etc.) have a June The transport of fluvial sediment to the ocean is an maximum discharge. important pathway in the global geochemical cycles. An A comprehensive critical review of the existing data understanding of the effects of anthropogenic activity on sediment fluxes of the Arctic rivers was published by and climate change on the sediments is important if the Holmes et al. in 2002. The authors established sediment human impact and climate changes are to be predicted flux estimates for the Yenisey, Lena, Kolyma, Pechora, (Syvitski, 2003; Walling and Fang, 2003). The IGBP Severnaya Dvina, Mackenzie and Yukon rivers. These Water Sediment Group has been established to consider estimates have been used in this paper. the problem in details. The findings and recommenda- The concentration of total river suspended matter tions of this group were published in “Global and (TSM) ranges from 6 to 207mg/l with a mean of Planetary Change”, 2003, v.39, N1/2. 36mg/l (Table 1). The Barents, White and Kara sea The Group identifies the Arctic as a particularly basin rivers are characterized by lower concentrations sensitive area in relation to sediment discharge. Syvitski compared to the rivers of East Siberia and the (2003) believes that the Arctic may be the only Mackenzie River (168mg/l). terrestrial region where the effect of climate change The maximum TSM discharges for the western rivers may be greater than the anthropogenic effect. However, also occur in May and for the eastern rivers in June (Fig. detailed examination of the recent trends in sediment 2). There is à high correlation between the specific water yields of the Arctic rivers shows that “changes in and total suspended matter discharges (Fig. 3). There is suspended sediment yield depend more on man's also à significant difference between the rivers of the activity than on climate change” (Bobrovitskaya et al., west and east of the Russian Arctic, with the East 2003). Siberian rivers (Yànà, Alazeya, Indigirka, Kolyma) In an analysis of the sediment loads of 145 rivers in being more similar to the rivers of North America than the world with records of more than 25 years including to the rivers of the western Russian Arctic (Gordeev et the Siberian rivers with records of up to 62 years al., 1996). TSM flux from the Russian territory is Bobrovitskaya et al. (2003) indicate that 70 rivers show 102.2×106 t/year, and 125.1×l06 t/year from the Cana- 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). 98 V.V. Gordeev / Geomorphology 80 (2006) 94–104

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 of the Êrasnoyarsk Dam, sediment flux at Divnogorsk evidence of an increase in sediment load (Walling and (Fig. 4) declined from 6.3 to 0.2×l06 t/year (Lisitzyna, Fang, 2003). 1974). Fig. 4 shows annual discharges of suspended load The discharge of the Kolyma river at Ust-Srednekan and water at six gauging stations on the Yenisey River from 1941 to 1988 is shown in Fig. 5. It shows no from 1960 to 1988. Although the annual sediment flux significant trend and can be considered essentially as in the Yenisey river was very low before the 1960s constant. The sediment flux has, however, clearly (13.2×106 t/year; Milliman and Meade, 1983), it has increased during this period. A double mass plot of declined to one-third (4.7×106 t/year) of that total at cumulative suspended sediment yield and cumulative the present time (Holmes et al., 2002). In 1967, à very annual water discharge (Fig. 5; Walling and Fang, 2003) large dam was completed on the Yenisey river near indicates that the sediment flux has more than doubled Êrasnoyarsk (the Êrasnoyarsk Dam) and in the 1970s since the mid-1960s. Bobrovitskaya et al. (2003) have several additional dams were built on the Angara river, estimated that the annual sediment yield increased from à large tributary of the Yenisey. After the construction 1.9×106 t/year for the period 1941–1964 to 3.7×106 t/ V.V. Gordeev / Geomorphology 80 (2006) 94–104 99

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 Other Siberian rivers, including the Yana at Ver- mining in the Kolyma river basin. khoyansk, the Indigirka at Vorontsovo and the Viliuy The water and sediment fluxes in the River Ob at at Ust-Ambardakh have had a constant yield over Salekhard (Fig. 6) show no statistically significant time. trends. A decrease in suspended matter yield has been observed during the last 30 years in the upper basin, 4. Arctic rivers in global context reflecting the reservoir effect at Barnaul and Kolpashevo and at Tobolsk on the Irtysh River. At Belogorie, Table 2 shows river runoff and TSM flux to the however, about 700km upstream of Salekhard, there was Arctic Ocean with global fluxes. Water discharge to the a positive trend, with annual yields increasing from Arctic Ocean is about 10% of the world river discharge 19.2×106 t/year from 1938 to 1956 to 28.4×106 t/year and specific water discharge about 60% of the world from 1957 to 1990, owing to a significant human activity total but the TSM discharge to the Arctic Ocean is very impact. Bobrovitskaya et al. (2003) consider that one low, only about 1% of the global flux. The concentration reason for the stable sediment flux at Salekhard is the of suspended matter in the Arctic rivers of 68g·m− 3 is wide floodplain downstream of Belogorie. A large approximately one order of magnitude lower than the proportion of the sediments, about 59%, is deposited global concentration of 528g·m− 3. Specific sediment and exchanged between the river and the flood plain. discharge is only 8% of the world total. 100 V.V. Gordeev / Geomorphology 80 (2006) 94–104

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 and low temperatures prevent the soils from weathering the European Russian Arctic and West Siberia differ during much of the year. The lack of human activity in from the rivers of East Siberia and North America (see the region also plays an important role. Fig. 3). The rivers of western Eurasia are generally Gordeev et al. (1996) have shown that there was a similar to other lowland rivers in the world (Milliman significant difference in many of the parameters for the and Syvitski, 1992) but the rivers of East Siberia and western and eastern rivers of the Russian Arctic. The North America are characterized by higher suspended boundary between the two regions crosses the Laptev matter concentrations (Table 1) because they drain areas Sea basin. This boundary also coincides with the of active glaciation and tectonics which generate large boundary between the Eurasian and North American quantities of fluvial sediments (Holmes et al., 2002). tectonic plates. More research is needed to understand Why do the Arctic rivers have very low rates of the significance of this. transport in spite of the large unconsolidated sedimen- Syvitski (2002) has recently published a paper in tary deposits located throughout the Arctic (Syvitski, which he presented the results of a model to predict the 2002)? Bobrovitskaya et al. (2003) have suggested that sediment flux in the arctic and sub-arctic rivers. He the vast areas of swamps and forests in the Siberian suggests that the model could explain why Arctic rivers watersheds could explain very low loads of the Russian have low sediment loads. Arctic rivers. Lisitzyn (1995, 1998) considers that there are several 5. Climatic warming and sediment fluxes reasons for the very low sediment fluxes in the Arctic. First, there are only thin very low weathering crusts on Morehead et al. (2003) have developed a stochastic the surfaces of the large watershed basins and very little model for simulation of sediment discharge in ungauged sedimentary material is removed from the tundra and rivers. They suggest that basin temperature may taiga. Secondly, low precipitation, extensive permafrost influence the sediment load carried by rivers. In this V.V. Gordeev / Geomorphology 80 (2006) 94–104 101

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 Most of the existing models simulate individual discharge Qs is defined as: events for a specific time interval but they are not more generally applicable. The model by Morehead et al. ¼ a 3=2 1=2 kT ; Qs H A e (2003) accounts for the inter- and intra-annual variabil- whereby H is the river basin relief (m), A is river basin ity of the suspended loads of rivers. The authors state “ area (km2), T is the mean surface temperature of the that: The strength of this new model is that the basin (°C), α and k are dimensionless constants. 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 Table 2 exponent. A variable exponent captures the annual Riverine water and suspended matter fluxes to the Arctic Ocean in variability and is related to the size of the river basin.” global context The database of the model includes 48 arctic and sub- Parameter Arctic Whole Arctic, % of whole arctic rivers from Russia, the U.S. and Canada. The world world model is sensitive to drainage basin temperature and can Area, 106 km2 15.5 99.9 15.5 be used to examine the impact of a climatic warming − Water discharge, 103 km3·y 1 3.3 35 9.4 scenario on the loads of high latitude rivers. Specific water discharge, 6.8 11 61.8 − − The model predicts that there will be a 30% increase 1·s 1·km 2 Average concentration of 68 528 12.8 in sediment load for every 2 °C of warming in the TSM, g·m− 3 drainage basin (Fig. 7). However, because the main TSM discharge, 106 t·y−1 227 18,500 1.2 equation is a steady state predictor, the model does not Specific sediment discharge, 14.7 185 8 predict the length of the transition period that will be −2 −1 t·km ·y required to reach this increase in sediment load. The 102 V.V. Gordeev / Geomorphology 80 (2006) 94–104

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 1260km3/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 An overview of the available data on the suspended temperature as modeled on the Colville River (Syvitski, 2002). sediment fluxes in the Eurasian and North America Arctic rivers, their recent and future trends is presented model also predicts that a 20% increase in discharge will in this paper. Predicted warming in the Arctic is result in a 10% increase in sediment transport. The expected to affect the extent of the permafrost and ice- combination of 2 °C warming with a 20% increase in covered regions, the amount of precipitation and the runoff would increase the sediment load of Arctic rivers productivity of terrestrial and aquatic ecosystems which by 40%. in turn will affect river water and sediment discharges to Mean global surface air temperature (SAT) has the Arctic Ocean. increased by 0.6°±0.2 °C over the past century All available recent assessments of fluvial sediment (IPCC, 2001). Evidence of increasing runoff in the fluxes were taken into account (Gordeev et al., 1996; Arctic had been reported recently (Shiklomanov et al., Gordeev, 2000; Meade et al., 2000; Magritsky, 2001; 2000; Semiletov et al., 2000; Lammers et al., 2001; Holmes et al., 2002; Gordeev and Rachold, 2003). At Peterson et al., 2002). Peterson et al. (2002) have present, all arctic rivers deliver 227.3×106 t/year of identified long-term trends in discharge from major suspended sediment to the Arctic Ocean, of which the Eurasian rivers flowing to the Arctic Ocean and have Eurasian rivers supply 102.2×106 t/year and Canadian evaluated the possible links to climatic variability. Over rivers 125.1×106 t/year (Table 1). This forms only 1.2% the period of observations from 1936 to 1999, aggregate of the total global flux. The mean concentration of annual discharge from the six largest Eurasian rivers suspended matter in arctic rivers and their specific (Yenisey, Lena, Ob, Pechora, Kolyma and Severnaya sediment discharge is about one order of magnitude less Dvina) has increased at a mean annual rate of than the global means. Bobrovitskaya et al. (2003) and 2.0°±0.7°km3, so that today's mean annual discharge Walling and Fang (2003) have published a detailed is now about 128km3/year greater than it was when analysis of sediment flux in the Eurasian, Siberian and routine measurements of discharge began in the 1930s. world's rivers showing trends based on long observa- This amounts to an increase of about 7%. The increase tional records of up to 62 years. in discharge also corresponds to the increase in global, Walling and Fang (2003) examined the time trends in pan-arctic and Eurasian arctic SATs. Over the period of the sediment flux of 145 major rivers. They showed that the discharge records, pan-arctic SAT increased by 0.6 the dominant trends were either stability or declining, °C and Eurasian arctic SAT by 0.7 °C (Peterson et al., with almost the same number of rivers in each category. 2002). Only seven rivers showed evidence of an increase in It would be interesting to compare the real sediment sediment flux over time. The authors conclude that flux of these six rivers with the flux predicted by the reservoir construction currently represents the most model over the period 1936–1999. The model estimates important influence on land–ocean sediment fluxes and show an increase in the sediment flux of 14%. Due to evidence of the impacts of climate change is limited. V.V. Gordeev / Geomorphology 80 (2006) 94–104 103

Three Siberian rivers, the Ob, Yenisey and Kolyma, comments of two anonymous reviewers were very are examples of different trends. Construction of large helpful in improving the manuscript. Author is espe- reservoirs in the upper reaches of the Ob and Yenisey cially appreciated to Prof. Frank Ahnert and Bridget rivers has resulted in a decreased sediment yield. The Ahnert for their improvements in English translation. sediment yield in the Yenisey river at Igarka after the construction of reservoirs declined to one-third from References 13.2×106 t/year before 1960s to 4.7×106 t/year at present. The sediment yield regime in the lower reaches Ahnert, F., 1970. Functional relationships between denudation, relief, of the Ob is stable (Bobrovitskaya et al., 2003), probably and uplifting in large mid-latitude drainage basins. Am. J. 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