Frazil ice changes winter biogeochemical processes in the Lena River.

The ice-covered period of large Arctic rivers is shortening. To what extent will this affect biogeochemical processing of nutrients? Here we reveal, with silicon isotopes (δSi), a key winter pathway for nutrients under river ice. During colder winter phases in the Lena River catchment, conditions are met for frazil ice accumulation, which creates microzones.

Seasonal nitrogen fluxes of the Lena River Delta.

The Arctic is nutrient limited, particularly by nitrogen, and is impacted by anthropogenic global warming which occurs approximately twice as fast compared to the global average. Arctic warming intensifies thawing of permafrost-affected soils releasing their large organic nitrogen reservoir. This organic nitrogen reaches hydrological systems, is remineralized to reactive inorganic nitrogen, and is transported to the Arctic Ocean via large rivers.

Degrading permafrost river catchments and their impact on Arctic Ocean nearshore processes.

Arctic warming is causing ancient perennially frozen ground (permafrost) to thaw, resulting in ground collapse, and reshaping of landscapes. This threatens Arctic peoples' infrastructure, cultural sites, and land-based natural resources. Terrestrial permafrost thaw and ongoing intensification of hydrological cycles also enhance the amount and alter the type of organic carbon (OC) delivered from land to Arctic nearshore environments.

Toward understanding the contribution of waterbodies to the methane emissions of a permafrost landscape on a regional scale-A case study from the Mackenzie Delta, Canada.

Waterbodies in the arctic permafrost zone are considered a major source of the greenhouse gas methane (CH ) in addition to CH emissions from arctic wetlands. However, the spatio-temporal variability of CH fluxes from waterbodies complicates spatial extrapolation of CH measurements from single waterbodies. Therefore, their contribution to the CH budget of the arctic permafrost zone is not yet well understood.