Impacts of climate warming and permafrost thaw on the riverine transport of nitrogen and phosphorus to the Kara Sea

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Abstract

[1] Measurements of nitrogen and phosphorus (N and P) concentrations from previously unstudied streams and rivers throughout west Siberia suggest that climate warming and/or associated permafrost thaw will likely amplify the transport of N and P to the Kara Sea and adjacent Arctic Ocean. We present concentrations of dissolved organic nitrogen (DON), ammonium (NH4-N), nitrate (NO3-N), total dissolved nitrogen (TDN), and total dissolved phosphorus (TDP) from 96 streams and rivers within the Ob'-Irtysh, Nadym, and Pur river drainage basins. The sampled sites span ∼106 km2, a large climatic gradient (∼55°N–68°N), and include 41 cold, permafrost-influenced and 55 warm, permafrost-free watersheds. Concentrations for all measured watersheds average 765 μg L−1 (DON), 19.3 μg L−1 (NH4-N), 36.7 μg L−1 (NO3-N), 821 μg L−1 (TDN), and 104 μg L−1 (TDP). Our results show no statistically significant difference in dissolved inorganic N (NH4-N and NO3-N) between permafrost-influenced and permafrost-free watersheds. However, we do find significantly higher concentrations of DON, TDN, and TDP in permafrost-free watersheds (increasing as a function of watershed peatland coverage) than in permafrost-influenced watersheds. When combined with climate model simulations, these relationships enable a simple “space-for-time” substitution to estimate possible increases in N and P release from west Siberia by the year 2100. Results suggest that predicted climate warming in west Siberia will be associated with ∼32–53% increases in DON concentrations, ∼30–50% increases in TDN concentrations, and 29–47% increases in TDP concentrations as averaged across the region. While such increases in N and P are unlikely to significantly influence primary production in the Kara Sea as a whole, they will likely have large local impacts in the Ob' and Yenisey bays and nearshore environments.

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