A new publication in ocean science connects cutting-edge technology to developments in our understanding of the environment and climate, highlighting and limiting uncertainties in current estimates of methane from Arctic methane seepage sites.
At the forefront of ocean observation technologies, the K-Lander, an innovative ocean observatory equipped with numerous ocean sensors, designed in collaboration between the CAGE water column group led by Bénédicte Ferré and Kongsberg Maritime. This observatory was designed to monitor the release of methane from the sea floor to the water column in harsh environments, providing invaluable information on the temporal and spatial variability of natural release of methane that can potentially reach the atmosphere.
A new study published in Ocean Science led by CAGE PhD candidate Knut Ola Dølven and co-authors presents time-series data from two methane seep sites off western Svalbard in the Arctic. These unique results show high variability on both hourly and seasonal timescales and describe the interconnectivity between methane seepage and the ocean.
“The length and location are what make these time series unique, as they answer old questions and raise new questions related to this variability and how we can best constrain it in future emissions estimates.” Says Knut Ola Dølven, Dølven, who conducted this study as part of his doctorate. at CAGE.
Areas of intense methane seepage
In 2015 and 2016, two K-Lander observatories were deployed at separate sites of intensive methane infiltration west of Prins Karls Forland, where thousands of streams of gas bubbles from the seabed were observed.
Although methane seep sites are known to likely experience great temporal and spatial variability, our understanding of the quantity, distribution, and release of methane in the Arctic Ocean is largely based on studies that were undertaken from late spring to early fall due to better ice and weather conditions. Until now.
Long-term continuous monitoring of methane releases
Using data from the K-Lander, Dølven and his co-authors processed a single long time series that spanned 10 months, measuring methane, carbon dioxide and physical parameters at each site. These measurements provided important information on short-term and seasonal variations in methane emissions and concentrations.
“It was interesting to observe that, despite the very high short-term variability in methane release, the source of methane release appeared to be relatively unchanged throughout the 10-month deployment. This has strong implications for the future interpretations of methane concentration in seep areas. Dolven said.
There is also an increased potential for methane release to the atmosphere during fall and winter, if seepage persists, due to weaker stratification of the water column (increased mixing of layers in the ocean ).
Although seabed seepage is considered a minor natural source of atmospheric methane, there are large uncertainties associated with current and projected emission estimates. Dølven and his co-authors were therefore able to highlight and limit uncertainties related to the variability of methane inventory estimates from seabed methane seepage.
K-Lander technology in future research applications
This work has highlighted the successful cooperation between maritime industry and research teams, providing cutting-edge technology for methane monitoring to help explain questions about ocean greenhouse gas emissions. This is the first long-term dataset providing exceptional multi-sensor data on methane releases and other physical and chemical ocean conditions in the Arctic.
“This infrastructure will play a major role in understanding the factors controlling methane emissions not only in the Arctic, as this study highlights, but also in other places around the world. Methane seepage data combined with d “Other parameters measured by the K-Lander will help to estimate current and future global budgets for methane in our oceans”, says Bénédicte Ferré, team leader of WP4 “Gas in the water column” and EMAN7, and responsible for the development, acquisition and analysis of data related to the K-Lander.