Logo Universitat Bremen
Page path:

Changes in ice volume control seabed methane emissions

Aug 7, 2019
New publication in Science Advances
The seep-carbonate team was able to drill into deeper strata with the sea floor drill rig MARUM-MeBo70. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; G. Bohrmann
The seep-carbonate team was able to drill into deeper strata with the sea floor drill rig MARUM-MeBo70. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; G. Bohrmann

The changing volumes of ice in the Arctic are shown to be directly related to methane emissions from the seafloor west of Spitsbergen (Norway). The thickness of the ice cover on land controls when methane seeps out of the ocean floor. A study on this topic, which also involved researchers at MARUM - Center for Marine Environmental Sciences at the University of Bremen, has now been published in Science Advances.

The research vessel MARIA S. MERIAN in the coal harbor of Longyearbyen on Spitsbergen. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; T. Klein
The research vessel MARIA S. MERIAN in the coal harbor of Longyearbyen on Spitsbergen. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; T. Klein

Large ice movements activate faults in the Earth's crust and thus contribute to methane leakage on the seafloor along the continental margin west of Spitsbergen. “Our results indicate a relationship between changing amounts of continental ice and deep-sea methane emissions in the Arctic,” says first author Dr. Tobias Himmler of the Geological Survey of Norway (NGU).

Researchers from the NGU and the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) at the Arctic University of Norway (Tromsø) took several seafloor limestone samples, called seep carbonates, from active methane seeps at the Vestnesa Ridge in 1200 meters of water. Seep carbonates are formed through a microbial process in which methane generated in the sediments reacts with seawater sulfate close to the seafloor. These carbonates are therefore a very clear indication that methane has risen up through the sediments below. Detailed analyses of the seep carbonates have now shown that methane has been repeatedly emitted since the last glacial maximum 23,000 years ago.

In cooperation with scientists from MARUM, and using the sea floor drill rig MARUM-MeBo70 on an expedition with the research vessel MARIA S. MERIAN, the Norwegian researchers were able to retrieve seep carbonates from deeper layers in the sediment. Based on dates obtained from the drilled seep carbonates, using the natural radioactive isotopes uranium and thorium, the team was able to identify two additional episodes of methane leakage: one between 160,000 and 133,000 and another between 50,000 and 40,000 years ago. The drill cores that were retrieved contained records of active methane emissions at the Vestnesa Ridge at these times. These two periods are characterized by cold climate conditions, during which the ice volumes in the Barents Sea and on Spitsbergen increased significantly. The Earth's crust was depressed by the massive load of the ice cover. To compensate for this, the seafloor beyond the ice cover at Vestnesa Ridge rose. This led to movements along existing faults in the Earth's crust and allowed methane to rise from greater depths.

Over the past 23,000 years the ice has melted and the underlying land masses have been rebounding again. This, in turn, has led to subsidence at the Vestnesa Ridge due to isostatic compensation. The results obtained by the team indicate that methane was primarily emitted when the fault zones were activated by ice-sheet motions.

“Seep carbonates are geological archives for methane emissions at the seafloor. We are very pleased that we were able to drill these archives for the first time at the Vestnesa Ridge with the sea floor drill rig MARUM-MeBo,” reports Gerhard Bohrmann, chief scientist of the expedition. “Methane emissions are documented both during the build-up of ice on land as well as during its retreat.”

The MeBo drilling was carried out with financial support of the German Research Foundation (DFG – Deutsche Forschungsgemeinschaft) in cooperation with CAGE. The further investigations were financed by the Research Council of Norway under the project “Norwegian margin fluid systems and methane-derived carbonate crusts” (NORCRUST).

Contact: 

Prof. Dr. Gerhard Bohrmann
General Geology – Marine Geology
Phone: 0421 218 65050
Email: [Bitte aktivieren Sie Javascript]

 

MARUM produces fundamental scientific knowledge about the role of the ocean and the ocean floor in the total Earth system. The dynamics of the ocean and the ocean floor significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These influence both the climate and the global carbon cycle, and create unique biological systems. MARUM is committed to fundamental and unbiased research in the interests of society and the marine environment, and in accordance with the Sustainable Development Goals of the United Nations. It publishes its quality-assured scientific data and makes it publicly available. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through its dialogue with society. MARUM cooperates with commercial and industrial partners in accordance with its goal of protecting the marine environment.

The eastern foothills of the ice cap on Greenland seen from the plane. Photo: Hannes Grobe, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
The eastern foothills of the ice cap on Greenland seen from the plane. Photo: Hannes Grobe, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research

 

Original publication

Tobias Himmler, Diana Sahy, Tõnu Martma, Gerhard Bohrmann, Andreia Plaza-Faverola, Stefan Bünz, Daniel J. Condon, Jochen Knies, and Aivo Lepland: A 160,000-year-old history of tectonically controlled methane seepage in the Arctic. Science Advances 2019
DOI: 10.1126/sciadv.aaw1450

More informationen on Expedition MSM 57 

More informationen on Sea Floor Drill Rig MARUM-MeBo 70

 

Segment of one of the MeBo drill cores from the Vestnesa Ridge with clearly visible seep carbonates. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen
Segment of one of the MeBo drill cores from the Vestnesa Ridge with clearly visible seep carbonates.
Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen
With the help of the remotely operated submersible vehicle Ægir 6000, geologists collect seep-carbonate samples from the seafloor at a water depth of 1200 m on the Vestnesa Ridge west of Svalbard. Photo: NORCRUST
With the help of the remotely operated submersible vehicle Ægir 6000, geologists collect seep-carbonate samples from the seafloor at a water depth of 1200 m on the Vestnesa Ridge west of Svalbard. Photo: NORCRUST

 

Participating Institutions: 

Geological Survey of Norway, Trondheim (Norwegen)

MARUM - Zentrum für Marine Umweltwissenschaften, Universität Bremen

British Geological Survey, Nottingham (Großbritannien)

Department of Geology, Tallinn University of Technology (Estland)

Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT–The Arctic University of Norway, Tromsø (Norwegen)