Modelling large-scale CO2 leakages in the North Sea

https://doi.org/10.1016/j.ijggc.2014.10.013Get rights and content
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Highlights

  • We simulate large CO2 leakages at two potential sequestration sites in the North Sea.

  • The carbonate system is more sensitive to CO2 additions in stratified regions.

  • Short-term leakages reduce local seawater pH, but impacts are spatially confined.

  • Worst case scenarios cause widespread perturbations to pH across the North Sea.

  • CO2 leakages generally cause weaker acidification than unmitigated CO2 emissions.

Abstract

A three dimensional hydrodynamic model with a coupled carbonate speciation sub-model is used to simulate large additions of CO2 into the North Sea, representing leakages at potential carbon sequestration sites. A range of leakage scenarios are conducted at two distinct release sites, allowing an analysis of the seasonal, inter-annual and spatial variability of impacts to the marine ecosystem.

Seasonally stratified regions are shown to be more vulnerable to CO2 release during the summer as the added CO2 remains trapped beneath the thermocline, preventing outgasing to the atmosphere. On average, CO2 injected into the northern North Sea is shown to reside within the water column twice as long as an equivalent addition in the southern North Sea before reaching the atmosphere.

Short-term leakages of 5000 tonnes CO2 over a single day result in substantial acidification at the release sites (up to -1.92 pH units), with significant perturbations (greater than 0.1 pH units) generally confined to a 10 km radius. Long-term CO2 leakages sustained for a year may result in extensive plumes of acidified seawater, carried by major advective pathways. Whilst such scenarios could be harmful to marine biota over confined spatial scales, continued unmitigated CO2 emissions from fossil fuels are predicted to result in greater and more long-lived perturbations to the carbonate system over the next few decades.

Keywords

Carbon capture and storage
CCS
North Sea
CO2
Shelf sea
pH

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