Holmes, R. M.

McClelland, James W.

Shiklomanov, Alexander I.

Tank, Suzanne E.

Tretiakov, M.

English

University of New Hampshire

University of New Hampshire
University of New Hampshire Scholars' Repository
Faculty Publications
8-31-2016
River Discharge: In State of the Climate in 2015.
R. M. Holmes
Woods Hole Research Center
Alexander I. Shiklomanov
University of New Hampshire, Durham, alex.shiklomanov@unh.edu
Suzanne E. Tank
University of Alberta
James W. McClelland
University of Texas at Austin
M. Tretiakov
Arctic and Antarctic Research Institute
Follow this and additional works at: https://scholars.unh.edu/faculty_pubs
This Report is brought to you for free and open access by University of New Hampshire Scholars' Repository. It has been accepted for inclusion in
Faculty Publications by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact
nicole.hentz@unh.edu.
Recommended Citation
Holmes, R.M., A.I. Shiklomanov, S.E. Tank, J.W. McClelland and M. Tretiakov. 2016. River Discharge. In State of the Climate in 2015.
Bulletin of the American Meteorological Society. 97: S147–S149.
h. River discharge—R. M. Holmes, A. I. Shiklomanov, S. E. Tank, 
J. W. McClelland, and M. Tretiakov
River discharge integrates hydrologic processes 
occurring throughout the surrounding landscape. 
Consequently, changes in the discharge of large rivers 
can be a sensitive indicator of widespread changes in 
watersheds (Rawlins et al. 2010; Holmes et al. 2013). 
Changes in river discharge also impact coastal and 
ocean chemistry, biology, and circulation. This inter-
action is particularly strong in the Arctic, given the 
relative volume of river discharge to ocean volume. 
Rivers in this region transport >10% of the global river 
discharge into the Arctic Ocean, which represents 
only ~1% of the global ocean volume (Aagaard and 
Carmack 1989; McClelland et al. 2012).  
In this section, annual river discharge values since 
2011 are presented for the eight largest Arctic rivers, 
and recent observations are compared to a 1980–89 
reference period (the first decade with data from all 
eight rivers). Six of the rivers lie in Eurasia and two 
are in North America. Together, the watersheds of 
these rivers cover 70% of the 16.8 × 106 km2 pan-
Arctic drainage area and, as such, account for the 
majority of riverine freshwater inputs to the Arctic 
Ocean (Fig. 5.18). Discharge data for the six Eurasian 
rivers are analyzed through 2015, whereas data from 
the Yukon and Mackenzie Rivers in North America 
are only available through 2014. Most of these data 
are now available through the Arctic Great Rivers 
Observatory (www.arcticgreatrivers.org). 
A long-term increase in Arctic river discharge 
has been well documented and may be linked to 
increasing precipitation associated with global warm-
ing (Peterson et al. 2002; McClelland et al. 2006; 
Shiklomanov and Lammers 2009; Overeem and 
Syvitski 2010; Rawlins et al. 2010). The long-term 
discharge trend is greatest for rivers of the Eurasian 
Arctic and constitutes the strongest evidence of in-
tensification of the Arctic freshwater cycle (Rawlins 
et al. 2010). 
In 2015, the combined discharge of 2051 km3 for 
the six largest Eurasian Arctic rivers was 15% greater 
than the 1980–89 average (Fig. 5.19; Table 5.2), and 
the peak discharge occurred earlier than the average 
over the same period (Fig. 5.20). This is the fourth 
highest combined discharge value since measure-
ments began in 1936. The four highest values have 
Fig. 5.17. Snow depth anomaly (% of 1999–2010 average) from the CMC snow depth analysis for (a) Apr, (b) 
May, and (c) Jun 2015.
Fig. 5.18.  Map showing the watersheds of the eight riv-
ers featured in this section. The blue dots show the lo-
cation of the discharge monitoring stations and the red 
line shows the boundary of the pan-Arctic watershed.
AUGUST 2016STATE OF THE CLIMATE IN 2015 | S147
all occurred in the past 14 years. Overall, the most 
recent data indicate a continuing long-term increase 
in Eurasian Arctic river discharge, at a rate of 3.5% 
± 2.1% decade−1 since 1976. Looking more closely at 
recent years, Eurasian Arctic river discharge generally 
declined between 2007 and 2012 and then began to 
increase again in 2013. Values for 2012 (1702 km3), 
2013 (1759 km3), and 2014 (1989 km3) were 5% less, 
1% less, and 2% greater than the 1980–89 period, 
respectively. The short-term variability in Eurasian 
Arctic river discharge is consistent with previous 
increases and decreases over 4–6 year intervals in 
the past (Fig. 5.19). 
For the North American Arctic rivers consid-
ered here (Yukon and Mackenzie), the combined 
discharge declined each year from 2012 (538 km3) 
to 2014 (499 km3), yet in each of those years the 
combined discharge was greater than the long-term 
average (493 km3 year−1; Fig. 5.19; Table 5.2). Thus, as 
discussed for Eurasian rivers, these most recent data 
indicate a longer-term pattern of increasing river 
discharge (Fig. 5.19). At a rate of 2.6% ± 1.7% decade−1 
since 1976, the overall trends of increasing discharge 
are remarkably similar for the North American 
and Eurasian rivers. (Increases per decade follow a 
Mann – Kendall trend analysis; error bounds are 95% 
confidence intervals for the trend.)
Fig. 5.19. Long-term trends in annual discharge for 
Eurasian and North American Arctic rivers. The 
Eurasian rivers are Severnaya Dvina, Pechora, Ob’, 
Yenisey, Lena, and Kolyma. The North American riv-
ers are Yukon and Mackenzie. Note the different scales 
for the Eurasian and North American river discharge; 
discharge from the former is 3–4 times greater than 
the latter.  Reference lines show long-term means for 
the Eurasian (1812 km3 yr−1, 1936–2015) and North 
American (493 km3 yr−1, 1976–2014) rivers. 
Table 5.2. Annual discharge for 2012, 2013, and 2014 for the eight largest Arctic rivers, compared to long-term and 
decadal averages back to the start of observations. Values for 2015 are provided for the six Eurasian rivers. Red values 
indicate provisional data, which are subject to modification before official data are released.
Discharge (km3 yr−1)
Yukon Mackenzie Pechora S. Dvina Ob’ Yenisey Lena Kolyma Sum
2015 123 80 527 654 585 82
2014 227 272 116 91 448 640 607 86 2487
2013 213 311 82 97 372 527 600 80 2282
2012 232 306 103 117 300 458 665 59 2240
Average 
2010–15
212 293 108 93 409 594 583 75 2366
Average 
2000–09
207 305 124 103 415 640 603 78 2475
Average 
1990–99
217 275 117 111 405 613 532 68 2338
Average 
1980–89
206 273 108 100 376 582 549 68 2262
Average 
1970–79
184 292 108 94 441 591 529 65 2304
Average 
1960–69
273 112 98 376 546 535 73
Average 
1950–59
110 108 380 566 511 74
Average 
1940–49
102 100 424 578 498 72
Average for 
Period of  
Record
206 286 111 100 401 589 540 71 2305
AUGUST 2016|S148
Considering the eight Eurasian and North Ameri-
can Arctic rivers together, their combined discharge 
in 2014 (2487 km3) was 10% greater than the average 
discharge for 1980–89. Comparing 2014 to 2012, the 
combined discharge of these eight rivers was almost 
250 km3 greater in 2014. For perspective, 250 km3 is 
approximately 14 times the annual discharge of the 
Hudson River, the largest river on the east coast of 
the United States.
i. Terrestrial permafrost—V. E. Romanovsky, S. L. Smith, 
K. Isaksen, N. I. Shiklomanov, D. A. Streletskiy, A. L. Kholodov, 
H. H. Christiansen, D. S. Drozdov, G. V. Malkova, and S. S. Marchenko
Permafrost is defined as soil, rock, and any other 
subsurface earth material that exists at or below 0°C 
continuously for two or more consecutive years. On 
top of permafrost is the active layer, which thaws 
during the summer and freezes again the following 
winter. The mean annual temperature of permafrost 
and the active layer thickness (ALT) are good indica-
tors of changing climate and therefore designated as 
essential climate variables (Smith and Brown 2009; 
Biskaborn et al. 2015) by the Global Climate Observ-
ing System Program of the World Meteorological 
Organization. Changes in permafrost temperatures 
and ALT at undisturbed locations in Alaska, Canada, 
Russia, and the Nordic region (Fig. 5.21) are reported 
here. Regional variability in permafrost temperature 
records, described below, indicates more substantial 
permafrost warming since 2000 in higher latitudes 
than in the subarctic. This is in general agreement 
with the pattern of average air temperature anomalies.
In 2015, record high temperatures at 20-m depth 
were measured at all permafrost observatories on the 
North Slope of Alaska (Barrow, West Dock, Franklin 
Bluffs, Happy Valley, and Galbraith Lake in Fig. 5.22a; 
Romanovsky et al. 2015). The permafrost temperature 
increase in 2015 was substantial and comparable to 
the highest rate of warming observed in this region 
so far, which occurred during the period 1995–2000; 
20-m depth temperatures in 2015 were from 0.10°C 
to 0.17°C higher than those in 2014 (Fig. 5.22a) 
on the North Slope. Since 2000, temperature at 
20-m depth in this region has increased between 
0.21°C and 0.66°C decade−1 (Fig. 5.22a; Table 5.3). 
Permafrost temperatures in Interior Alaska were 
higher in 2015 than 2014 at all sites (Old Man, 
College Peat, Birch Lake, Gulkana, and Healy 
in Fig. 5.22b), except for Coldfoot. Notably, this 
warming followed slight cooling of 2007–13 (Fig. 
5.22b). However, the recent warming in the interior 
(see section 5b; Fig. 5.2) was not strong enough to 
bring permafrost temperatures back to the record 
highs observed between the mid-1990s and the mid-
2000s except at Gulkana (Fig. 5.22b; Table 5.3). 
In northwestern Canada, temperatures in warm 
permafrost of the central Mackenzie Valley (Nor-
man Wells and Wrigley in Fig. 5.22b) were similar 
in 2014/15 to those observed the previous year. 
Fig. 5.20. Combined daily discharge for the six Eurasian 
Arctic rivers in 2015 compared to the 1980–89 average.
Fig. 5.21. Location of the permafrost monitoring 
sites shown in Fig. 5.22 superimposed on average air 
temperature anomalies during 2000–14 (with respect 
to the 1971–2000 mean) from the NCEP–NCAR re-
analysis (Kalnay et al. 1996) (Source: NOAA/ESRL.) 
Sites shown in Fig. 5.22 are (a) Barrow (Ba), West 
Dock (WD), KC-07 (KC), Deadhorse (De), Franklin 
Bluffs (FB), Galbraith Lake (GL), Happy Valley (HV), 
Norris Ck (No); (b) College Peat (CP), Old Man (OM), 
Chandalar Shelf (CS), Birch Lake (BL), Coldfoot (Co), 
Norman Wells (NW), Wrigley 2 (Wr), Healy (He), 
Gulakana (Gu), Wrigley 1 (Wr); (c) Eureka EUK4 (Eu), 
Alert BH2 (Al), Alert BH5 (Al), Resolute (Re), Alert 
BH1 (Al), Arctic Bay (AB), Pond Inlet (PI), Pangnirtung 
(Pa); (d) Janssonhaugen (Ja), Urengoy #15-10 (Ur), Juv-
vasshøe (Ju), Tarfalaryggen (Ta), Bolvansky #59 (Bo), 
Bolvansky #65 (Bo), Urengoy #15-06 (Ur), Bolvansky 
#56 (Bo), Iskoras Is-B-2 (Is).
AUGUST 2016STATE OF THE CLIMATE IN 2015 | S149


River Discharge: In State of the Climate in 2015.

UNH Scholars' Repository

University of New HampshireUniversity of New Hampshire Scholars' RepositoryFaculty Publications8-31-2016River Discharge: In State of the Climate in 2015.R. M. HolmesWoods Hole Research CenterAlexander I. ShiklomanovUniversity of New Hampshire, Durham, alex.shiklomanov@unh.eduSuzanne E. TankUniversity of AlbertaJames W. McClellandUniversity of Texas at AustinM. TretiakovArctic and Antarctic Research InstituteFollow this and additional works at: https://scholars.unh.edu/faculty_pubsThis Report is brought to you for free and open access by University of New Hampshire Scholars' Repository. It has been accepted for inclusion inFaculty Publications by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contactnicole.hentz@unh.edu.Recommended CitationHolmes, R.M., A.I. Shiklomanov, S.E. Tank, J.W. McClelland and M. Tretiakov. 2016. River Discharge. In State of the Climate in 2015.Bulletin of the American Meteorological Society. 97: S147–S149.h. River discharge—R. M. Holmes, A. I. Shiklomanov, S. E. Tank, J. W. McClelland, and M. TretiakovRiver discharge integrates hydrologic processes occurring throughout the surrounding landscape. Consequently, changes in the discharge of large rivers can be a sensitive indicator of widespread changes in watersheds (Rawlins et al. 2010; Holmes et al. 2013). Changes in river discharge also impact coastal and ocean chemistry, biology, and circulation. This inter-action is particularly strong in the Arctic, given the relative volume of river discharge to ocean volume. Rivers in this region transport >10% of the global river discharge into the Arctic Ocean, which represents only ~1% of the global ocean volume (Aagaard and Carmack 1989; McClelland et al. 2012).  In this section, annual river discharge values since 2011 are presented for the eight largest Arctic rivers, and recent observations are compared to a 1980–89 reference period (the first decade with data from all eight rivers). Six of the rivers lie in Eurasia and two are in North America. Together, the watersheds of these rivers cover 70% of the 16.8 × 106 km2 pan-Arctic drainage area and, as such, account for the majority of riverine freshwater inputs to the Arctic Ocean (Fig. 5.18). Discharge data for the six Eurasian rivers are analyzed through 2015, whereas data from the Yukon and Mackenzie Rivers in North America are only available through 2014. Most of these data are now available through the Arctic Great Rivers Observatory (www.arcticgreatrivers.org). A long-term increase in Arctic river discharge has been well documented and may be linked to increasing precipitation associated with global warm-ing (Peterson et al. 2002; McClelland et al. 2006; Shiklomanov and Lammers 2009; Overeem and Syvitski 2010; Rawlins et al. 2010). The long-term discharge trend is greatest for rivers of the Eurasian Arctic and constitutes the strongest evidence of in-tensification of the Arctic freshwater cycle (Rawlins et al. 2010). In 2015, the combined discharge of 2051 km3 for the six largest Eurasian Arctic rivers was 15% greater than the 1980–89 average (Fig. 5.19; Table 5.2), and the peak discharge occurred earlier than the average over the same period (Fig. 5.20). This is the fourth highest combined discharge value since measure-ments began in 1936. The four highest values have Fig. 5.17. Snow depth anomaly (% of 1999–2010 average) from the CMC snow depth analysis for (a) Apr, (b) May, and (c) Jun 2015.Fig. 5.18.  Map showing the watersheds of the eight riv-ers featured in this section. The blue dots show the lo-cation of the discharge monitoring stations and the red line shows the boundary of the pan-Arctic watershed.AUGUST 2016STATE OF THE CLIMATE IN 2015 | S147all occurred in the past 14 years. Overall, the most recent data indicate a continuing long-term increase in Eurasian Arctic river discharge, at a rate of 3.5% ± 2.1% decade−1 since 1976. Looking more closely at recent years, Eurasian Arctic river discharge generally declined between 2007 and 2012 and then began to increase again in 2013. Values for 2012 (1702 km3), 2013 (1759 km3), and 2014 (1989 km3) were 5% less, 1% less, and 2% greater than the 1980–89 period, respectively. The short-term variability in Eurasian Arctic river discharge is consistent with previous increases and decreases over 4–6 year intervals in the past (Fig. 5.19). For the North American Arctic rivers consid-ered here (Yukon and Mackenzie), the combined discharge declined each year from 2012 (538 km3) to 2014 (499 km3), yet in each of those years the combined discharge was greater than the long-term average (493 km3 year−1; Fig. 5.19; Table 5.2). Thus, as discussed for Eurasian rivers, these most recent data indicate a longer-term pattern of increasing river discharge (Fig. 5.19). At a rate of 2.6% ± 1.7% decade−1 since 1976, the overall trends of increasing discharge are remarkably similar for the North American and Eurasian rivers. (Increases per decade follow a Mann – Kendall trend analysis; error bounds are 95% confidence intervals for the trend.)Fig. 5.19. Long-term trends in annual discharge for Eurasian and North American Arctic rivers. The Eurasian rivers are Severnaya Dvina, Pechora, Ob’, Yenisey, Lena, and Kolyma. The North American riv-ers are Yukon and Mackenzie. Note the different scales for the Eurasian and North American river discharge; discharge from the former is 3–4 times greater than the latter.  Reference lines show long-term means for the Eurasian (1812 km3 yr−1, 1936–2015) and North American (493 km3 yr−1, 1976–2014) rivers. Table 5.2. Annual discharge for 2012, 2013, and 2014 for the eight largest Arctic rivers, compared to long-term and decadal averages back to the start of observations. Values for 2015 are provided for the six Eurasian rivers. Red values indicate provisional data, which are subject to modification before official data are released.Discharge (km3 yr−1)Yukon Mackenzie Pechora S. Dvina Ob’ Yenisey Lena Kolyma Sum2015 123 80 527 654 585 822014 227 272 116 91 448 640 607 86 24872013 213 311 82 97 372 527 600 80 22822012 232 306 103 117 300 458 665 59 2240Average 2010–15212 293 108 93 409 594 583 75 2366Average 2000–09207 305 124 103 415 640 603 78 2475Average 1990–99217 275 117 111 405 613 532 68 2338Average 1980–89206 273 108 100 376 582 549 68 2262Average 1970–79184 292 108 94 441 591 529 65 2304Average 1960–69273 112 98 376 546 535 73Average 1950–59110 108 380 566 511 74Average 1940–49102 100 424 578 498 72Average for Period of  Record206 286 111 100 401 589 540 71 2305AUGUST 2016|S148Considering the eight Eurasian and North Ameri-can Arctic rivers together, their combined discharge in 2014 (2487 km3) was 10% greater than the average discharge for 1980–89. Comparing 2014 to 2012, the combined discharge of these eight rivers was almost 250 km3 greater in 2014. For perspective, 250 km3 is approximately 14 times the annual discharge of the Hudson River, the largest river on the east coast of the United States.i. Terrestrial permafrost—V. E. Romanovsky, S. L. Smith, K. Isaksen, N. I. Shiklomanov, D. A. Streletskiy, A. L. Kholodov, H. H. Christiansen, D. S. Drozdov, G. V. Malkova, and S. S. MarchenkoPermafrost is defined as soil, rock, and any other subsurface earth material that exists at or below 0°C continuously for two or more consecutive years. On top of permafrost is the active layer, which thaws during the summer and freezes again the following winter. The mean annual temperature of permafrost and the active layer thickness (ALT) are good indica-tors of changing climate and therefore designated as essential climate variables (Smith and Brown 2009; Biskaborn et al. 2015) by the Global Climate Observ-ing System Program of the World Meteorological Organization. Changes in permafrost temperatures and ALT at undisturbed locations in Alaska, Canada, Russia, and the Nordic region (Fig. 5.21) are reported here. Regional variability in permafrost temperature records, described below, indicates more substantial permafrost warming since 2000 in higher latitudes than in the subarctic. This is in general agreement with the pattern of average air temperature anomalies.In 2015, record high temperatures at 20-m depth were measured at all permafrost observatories on the North Slope of Alaska (Barrow, West Dock, Franklin Bluffs, Happy Valley, and Galbraith Lake in Fig. 5.22a; Romanovsky et al. 2015). The permafrost temperature increase in 2015 was substantial and comparable to the highest rate of warming observed in this region so far, which occurred during the period 1995–2000; 20-m depth temperatures in 2015 were from 0.10°C to 0.17°C higher than those in 2014 (Fig. 5.22a) on the North Slope. Since 2000, temperature at 20-m depth in this region has increased between 0.21°C and 0.66°C decade−1 (Fig. 5.22a; Table 5.3). Permafrost temperatures in Interior Alaska were higher in 2015 than 2014 at all sites (Old Man, College Peat, Birch Lake, Gulkana, and Healy in Fig. 5.22b), except for Coldfoot. Notably, this warming followed slight cooling of 2007–13 (Fig. 5.22b). However, the recent warming in the interior (see section 5b; Fig. 5.2) was not strong enough to bring permafrost temperatures back to the record highs observed between the mid-1990s and the mid-2000s except at Gulkana (Fig. 5.22b; Table 5.3). In northwestern Canada, temperatures in warm permafrost of the central Mackenzie Valley (Nor-man Wells and Wrigley in Fig. 5.22b) were similar in 2014/15 to those observed the previous year. Fig. 5.20. Combined daily discharge for the six Eurasian Arctic rivers in 2015 compared to the 1980–89 average.Fig. 5.21. Location of the permafrost monitoring sites shown in Fig. 5.22 superimposed on average air temperature anomalies during 2000–14 (with respect to the 1971–2000 mean) from the NCEP–NCAR re-analysis (Kalnay et al. 1996) (Source: NOAA/ESRL.) Sites shown in Fig. 5.22 are (a) Barrow (Ba), West Dock (WD), KC-07 (KC), Deadhorse (De), Franklin Bluffs (FB), Galbraith Lake (GL), Happy Valley (HV), Norris Ck (No); (b) College Peat (CP), Old Man (OM), Chandalar Shelf (CS), Birch Lake (BL), Coldfoot (Co), Norman Wells (NW), Wrigley 2 (Wr), Healy (He), Gulakana (Gu), Wrigley 1 (Wr); (c) Eureka EUK4 (Eu), Alert BH2 (Al), Alert BH5 (Al), Resolute (Re), Alert BH1 (Al), Arctic Bay (AB), Pond Inlet (PI), Pangnirtung (Pa); (d) Janssonhaugen (Ja), Urengoy #15-10 (Ur), Juv-vasshøe (Ju), Tarfalaryggen (Ta), Bolvansky #59 (Bo), Bolvansky #65 (Bo), Urengoy #15-06 (Ur), Bolvansky #56 (Bo), Iskoras Is-B-2 (Is).AUGUST 2016STATE OF THE CLIMATE IN 2015 | S149

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River Discharge: In State of the Climate in 2015.

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