Nord Stream methane leaks case: ICON-ART model simulation versus observations at various ICOS stations

Methane is emitted during the production and transportation of fossil fuels. Methane emissions result also from intensive livestock farming and agricultural practices as well as by the decay of organic waste. The leakage throughout the extraction, processing and transportation of natural gas releases methane straight into the atmosphere. Due to the damage to the Nord Stream gas pipelines on 26 September 2022 leaks have appeared close to the Danish island of Bornholm in the Baltic Sea, which releases large amounts of methane in the pipeline into the atmosphere within just a few days. In our study, we simulated the transport of methane plume in Nord Stream case by using DWD’s regional Icosahedral Nonhydrostatic (ICON) model with its transport scheme ART (Aerosols and Reactive Trace gases) extension.

The model is run for Limited Area Mode (LAM) with a horizontal spatial resolution of 6.5 km and 60 model levels. As source strength of methane emissions were used the estimates which were calculated by the German Federal Environmental Agency (Umwelt Bundesamt). An assumption, that a constant 700 kg/s of gas had been leaking since September 26 was used for the hourly model run to simulate the methane plume between September 26 and October 1 2022.

The model results had been compared to the potential methane signals of Nord Stream leaks detected at Integrated Carbon Observation System (ICOS) stations. According to our simulations, we found a good fit with respect to ICOS observations for the stations Hyltemossa, Birkenes and Norunda. Further analysis has been conducted to look at vertical profiles at different heights and also into correlation coefficients between the model and observations.

In this Nord Stream case, our simulation demonstrates modelling capabilities of the ICON-ART model and its associated quantitative assessment of methane emissions.

This work has been funded by the German Federal Ministry for Digital and Transport programme for Development and Implementation of Copernicus services for public needs within the HoTC project.