We don’t know enough about the amounts of methane stored under the sea floor. CAGE is going on a summer drilling campaign to make better calculations on quantities of this potent greenhouse gas in the form of ice – so called hydrate.
Text: Maja Sojtaric
Estimates on how much of the greenhouse gas methane is stored beneath the seabed of the Arctic in the form of methane ice differ substantially. The most cited global estimate is 10,000 gigatonnes (Gt). A gigatonne is a billion tons.
But a recent calculation suggests that we rather should be talking about a global estimate of 74 000 Gt methane stored as hydrates.
– The quantification of these deposits is important for climate and environmental research. When they are stable these hydrates keep large quantities of methane gas in check. But methods to predict the stability of these hydrates, especially in the Arctic, is also quite uncertain. And if they melt, they may release large amounts of the powerful greenhouse gas and can alter the marine environment, says CAGE director Jürgen Mienert.
Drilling in the ocean floor at 1200 meter depth
To make more precise calculations researchers must use advanced drilling technology. In July, CAGE will undertake an expedition to the ocean ridge Vestnesa offshore Svalbard, where they will drill for gas hydrates at water depths down to 1,200 meters. Vestnesa is a part of the ridge system of the oceans, which are undersea mountain chains formed by tectonic movement and stretching around the globe.
The expedition is a collaboration with MARUM in Germany, and their mobile drilling rig MeBo will be used to acquire the samples.
The aim is to see how much hydrates exist in the area. But the scientists also want to see how methane hydrates are formed, whether it is by the decomposition of organic matter or whether it comes from chemical reactions in the Earth’s crust, deep under the ocean floor.
– If the methane is mainly abiotic, ie not created by the decomposition of organic matter, we will assume that there are larger amounts of gas than previously calculated along the thousands of kilometers of the ocean ridges, states Mienert.
Planning for more drilling operations in the Arctic
In the long term CAGE plans more drilling in the Arctic and will apply to join the Integrated Ocean Discovery Program (IODP). The hope is to use the Japanese ship Chikyu, which recently drilled gas hydrates outside India. They carried out the largest expedition for mapping of gas hydrates ever, with great success. Several other vessels may also be relevant. India, Japan, China and Canada are countries where gas hydrates are increasingly mapped with a perspective of future extraction and energy production.
– We hope that we can use this expertise in the Arctic areas also, for research on environmental and climate impact of methane emissions from gas hydrates, stresses CAGE director Jürgen Mienert.
