Ship wake-induced water column mixing and meter-scale seabed erosion in the Baltic Sea

TL;DR

This study shows that ship traffic in the Baltic Sea causes seafloor erosion and stirs up water layers, which could affect marine ecosystems and chemical balances.

Contribution

The study reveals how ship wakes cause seafloor erosion and water column mixing in the Baltic Sea, linking these effects to long-term vessel traffic.

Findings

Up to 1.5 meters of seafloor erosion over 10 years is linked to vessel traffic in the Bay of Kiel.

Wake turbulence from ships disrupts stratified water layers and may generate internal waves.

The increased mixing of oxygen, nutrients, and greenhouse gases could impact marine ecosystems and element budgets.

Abstract

Commercial shipping is a cornerstone of global trade. Its impact on the marine environment, however, remains underexplored. This study combines hydroacoustic data, sediment samples, propeller-induced shear stress calculations and vessel tracking information to assess the effects of shipping in one of the busiest maritime regions in the Baltic Sea, the Bay of Kiel. We unveil substantial seafloor erosion, including up to 1.5 m variation in water depths, over 10 years that clearly relates to vessel traffic. By imaging water column disturbance behind passing ships, we trace wake turbulence to the seafloor and show the breakdown of a strongly stratified water column and a possible excitement of internal waves, likely increasing the mixing of oxygen, nutrients, and greenhouse gases. While the environmental consequences of this anthropogenic stressor are unquantified, our findings leave little doubt that they include modifications to marine ecosystems and element budgets on a Baltic-wide scale.

The study shows how ship traffic in the Baltic Sea modifies seafloor morphology and disrupts water layers, thereby increasing the mixing of oxygen, nutrients and greenhouse gases, suggesting broad impacts on Baltic marine ecosystems.

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