Carbon sources in the North Sea evaluated by means of carbon isotope tracers, supplement to: Burt, William J; Thomas, H; Hagens, Mathilde; Pätsch, J; Clargo, N M; Salt, L A; Winde, Vera; Böttcher, Michael E (2016): Carbon sources in the North Sea evaluated by means of radium and stable carbon isotope tracers. Limnology and Oceanography, 61(2), 666-683

• Main Authors: Böttcher, Michael E, Winde, Vera
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2016
• Subjects: Event label; DATE/TIME; LATITUDE; LONGITUDE; DEPTH, water; Alkalinity, total; Salinity; δ13C, dissolved inorganic carbon; Water sample; Potentiometric titration; Tetra Con 325 salinity and temperature probe; Isotope ratio monitoring IRM mass spectrometry; Biological Impacts of Ocean Acidification BIOACID; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.858134; https://doi.pangaea.de/10.1594/PANGAEA.858134

A multitracer approach is applied to assess the impact of boundary fluxes (e.g., benthic input from sedi- ments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the d13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indi- cates the presence of an external carbon source, which is traced to the European continental coastline using naturally occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of meta- bolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e., unbuffered) release of metabolic DIC. Finally, long- term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.