Increasing Nutrient Fluxes and Mixing Regime Changes in the Eastern Arctic Ocean

Primary productivity in the Arctic Ocean is experiencing dramatic changes linked to the receding sea ice cover. The vertical transport of nutrients from deeper water layers is the limiting factor for primary production. Here, we compare coincident profiles of turbulence and nutrients from the Siberian Seas in 2007, 2008, and 2018. In all years, the water column structure in the upstream region of the Arctic Boundary Current promotes upward nutrient transport, in contrast to the regions further downstream, and there are first indications for an eastward progression of these conditions. In summer 2018, strongly enhanced vertical nitrate flux and primary production above the continental slope were observed, likely related to a remote storm. The estimated contribution of these elevated fluxes above the slope to the Pan-Arctic vertical nitrate supply is comparable with the basin-wide transport, and is predicted to increase with declining sea ice cover in the future.

Automated summary

Primary productivity in the Arctic Ocean is undergoing significant changes due to the reduction in sea ice cover. The vertical transport of nutrients from deeper water layers is a limiting factor for primary production. Comparing data from the Siberian Seas in different years, it was found that the upstream region of the Arctic Boundary Current promotes upward nutrient transport, while the downstream regions do not. In summer 2018, there was a strong vertical nitrate flux and primary production above the continental slope, possibly due to a remote storm. The estimated contribution of these elevated fluxes to the overall vertical nitrate supply in the Arctic is similar to basin-wide transport and is expected to increase with declining sea ice cover.