Geoscience Reference
In-Depth Information
Table 4 Changes to precipita-
tion (P) and discharge (Q) from
1961-1991 to 1991-2002 for 13
major Arctic basins (mm/year)
Basin
DP
DQ
DQ - DP
Churchill
-49.8
-69.7
-19.9
Indigirka
-38.3
-3.0
35.3
Kolyma
-13.9
-8.8
5.2
Lena
-7.6
0.9
8.5
Mackenzie
-32.1
-3.4
28.7
Nelson
-1.0
0.1
1.1
Ob
18.3
9.6
-8.7
Olenek
-2.7
80.7
83.4
Pechora
23.8
47.3
23.5
S Dvina
5.9
26.9
21.0
Yana
-34.2
0.0
34.2
Yenisey
9.7
19.7
9.9
Yukon
-26.7
16.6
43.3
Average basin value
-11.4
9.0
20.4
Positive values in the last column
indicate excess discharge, in
relation to precipitation
Area-weighted pan-Arctic average
-3.7
7.5
11.1
precipitation deviation; that is, after the 1961-1990 climate period, discharge has increased
more (or decreased less) than precipitation within each basin. These disagreements
between precipitation and discharge deviations are in some cases large. At the same time,
temperature has increased in the basins, which should lead to increased evapotranspiration
and therefore less runoff, not more. Previous studies have indeed indicated that Arctic
evapotranspiration has increased (Serreze et al.
2002
; Park et al.
2008
; Rawlins et al.
2010
). Therefore, an essential question for forthcoming investigation is: where does the
extra discharge water come from?
In the present synthesis, we note that the same question also arises from an integrated
assessment of freshwater inflow to the Arctic Ocean (Dyurgerov et al.
2010
). This
assessment is in line with other studies, which also indicate an increase in freshwater
inflow to the Arctic Ocean. However, the Dyurgerov et al. (
2010
) analysis further high-
lights that the magnitude of the increase in total flows from the 1961-1992 to the
1993-2006 period is similar for the Arctic river contributions (87 km
3
/year) as for the
Arctic glacier contributions (56 km
3
/year). Figure
6
shows a main implication of that
result for sea-level rise, underlining the importance of also accounting for river discharge
changes that are not related to glacial mass balance changes as a possible contributing
source for sea-level rise and freshening of the Arctic Ocean. However, determining
whether also the eustatic components of these increases are of similar magnitude requires
further and more refined analysis and modeling.
5 Results for Pan-Arctic Drainage Basin Monitoring
The earlier comprehensive analysis of pan-Arctic hydrological and hydrochemical moni-
toring by Bring and Destouni (
2009
) has shown a considerable difference between
accessible water chemistry monitoring and discharge monitoring. This difference concerns
both the total extent and the characteristics of the data. In general, discharge data are
