Recent sedimentation and organic carbon burial in a shelf sea: the North Sea

Abstract

To obtain a carbon budget of the North Sea, recent sedimentation rates and organic carbon and nitrogen concentrations were determined on 27 box cores from the shallow North Sea (with a water depth < 200 m and a surface area of 500 × 10 3 km 2). The sedimentation rates in these box cores range from 5 to 35 cm · 100 year −1, C org concentrations are < 0.05 − 1%. Based on these numbers and published data the total amount of C org buried in the shallow North Sea is calculated as ~ 1 × 10 5 tons · year −1. In large parts of the shallow North Sea recent sedimentation is (nearly) absent. Reworking of relict deposits and partial mixing of these deposits with small amounts of recent fine grained sediments by biological and physical processes and human activities (beam trawl fishery) result in apparent sedimentation rates which are likely to exceed the real net sedimentation rates considerably. The results of this study suggest that the majority of the organic matter is exported from the shelf over the shelf edge into the Norwegian Sea and into inner shelf deeps (Skagerrak and Norwegian Channel). Coarse grained shelf sediments are only of minor significance for the preservation of organic matter.