When It Rains in the Arctic, Rivers Gain Carbon and Lose Nitrate

A summer storm on Alaska's North Slope does something lasting to a river. Dissolved organic carbon rises and nitrate falls — and when the storm passes, the two do not recover together. Nitrate takes longer to come back, so for a while the river carries a different chemical balance than it did before the rain. That lag, measured continuously over five summers, is why the researchers call a storm a biogeochemical disturbance, not just a pulse of water.

An Arctic stream, a tributary of the Akillik River.

Why watch Arctic rivers so closely

The Arctic is among the first places to feel climate change, and its water cycle, seasons and permafrost are already shifting. A river integrates everything happening upstream: what changes across a watershed shows up in the chemistry at its outlet. So measuring carbon and nitrogen in the water is a way to watch a whole tundra landscape respond.

Five thaw seasons of data

• Where: two watersheds in low-gradient tundra typical of the eastern Brooks Range on Alaska's North Slope — the Kuparuk River and Oksrukuyik Creek, both part of the Arctic Long-Term Ecological Research sites.
• When: five consecutive thaw seasons, 2017 through 2021, across a wide range of flows.
• How: high-frequency optical sensors measuring dissolved organic carbon (DOC), nitrate (NO₃⁻) and total dissolved nitrogen (TDN) continuously — capturing individual storm events that occasional sampling misses.

What the storms did

The last row is the surprise. Even in watersheds with relatively high demand for nitrogen, total dissolved nitrogen rose with high flows — a potential "leak" of organic nitrogen, washed out by water, to ecosystems downstream.

Why it matters

Continuous, long-term sensors give a better way to build carbon and nutrient budgets and to track how ecosystems are disturbed and recover over single storms and whole seasons — the timescales on which a changing Arctic will show itself.

Sources

Based on "How Arctic rivers respond to hydrological disturbances," National Park Service, summarizing Shogren, A. J., J. P. Zarnetske, B. W. Abbott, A. L. Grose, A. F. Rec, J. Nipko, C. Song, J. A. O'Donnell and W. B. Bowden, 2024, "Hydrology controls dissolved organic carbon and nitrogen" (as cited by the National Park Service); the National Park Service summary is a work of the United States government in the public domain.