A plot of [DON] versus salinity for stations occupying the eastern Arctic is shown in Fig. 4a. Mixing between two end-members is evident: DON-enriched river water at low salinities and lower DON marine water at high salinity. The impact of a third potential end member in Arctic summer from sea ice melt is both reduced in this
cytochrome c fragment (93-10 cool region (Fig. 2c) and likely to be negligible for reasons of its [DON] (detailed below in Section 5.5). Regression analysis reveals an apparent [DON] within the river water fraction of 9.1 ± 1.0 μM N (Model II regression, ± standard error of intercept), taken from the y-intercept (salinity = 0) in Fig. 4a. This apparent river end-member [DON] can be compared to estimates of the [DON] in the Siberian rivers draining to the region from (Holmes et al., 2012). The calculated annual mean flow weighted [DON] within the four Siberian rivers (Ob, Yenisey, Lena, and Kolyma) is 15.2 ± 0.8 μM N. The [DON] found within the river water fraction from the regression observed over the Makarov and Eurasian Basins is reduced relative to
B memory cells measured in the regional riverine sources, indicating a net loss of 6.1 ± 1.3 μM tDON over the Siberian Arctic shelves. If the annual flow weighted [DON] for the more local eastern Siberian Lena and Kolyma Rivers is employed instead (15.7 ± 0.9 μM N), the net loss of tDON is 6.6 ± 1.3 μM.
