Potential Methane Reservoirs Beneath Antarctica

Source Aug. 29, 2012 — The Antarctic Ice Sheet could be an overlooked but important source of methane, a potent greenhouse gas, according to research published August 29 in Nature and conducted by an international team led by Professor Jemma Wadham from the University of Bristol’s School of Geographical Sciences. Team leader, Professor Wadham said: “This is an immense amount of organic carbon, more than ten times the size of carbon stocks in northern permafrost regions. Our laboratory experiments tell us that these sub-ice environments are also biologically active, meaning that this organic carbon is probably being metabolised to carbon dioxide and methane gas by microbes.”

The researchers then numerically simulated the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model. They found that sub-ice conditions favour the accumulation of methane hydrate (that is, methane trapped within a structure of water molecules, forming a solid similar to regular ice).

They also calculated that the potential amount of methane hydrate and free methane gas beneath the Antarctic Ice Sheet could be up to 400 billion tonnes (that is, 400 Pg of carbon), a similar order of magnitude to some estimates made for Arctic permafrost. The predicted shallow depth of these potential reserves also makes them more susceptible to climate forcing than other methane hydrate reserves on Earth.

Dr Sandra Arndt, a NERC fellow at the University of Bristol who conducted the numerical modelling, said: “It’s not surprising that you might expect to find significant amounts of methane hydrate trapped beneath the ice sheet. Just like in sub-seafloor sediments, it is cold and pressures are high which are important conditions for methane hydrate formation.”

Related: Microbial life in extreme subglacial antarctic lake environments: Lake Vostok

Identification and control of subglacial water networks under Dome A, Antarctica

Wolovick, Michael J.; Bell, Robin E.; Creyts, Timothy T.; Frearson, Nicholas | Source

Abstract

Subglacial water in continental Antarctica forms by melting of basal ice due to geothermal or frictional heating. Subglacial networks transport the water from melting areas and can facilitate sliding by the ice sheet over its bed. Subglacial water flow is driven mainly by gradients in overburden pressure and bed elevation. We identify small (median 850 m) water bodies within the Gamburtsev Subglacial Mountains in East Antarctica organized into long (20-103 km) coherent drainage networks using a dense (5 km) grid of airborne radar data. The individual water bodies are smaller on average than the water bodies contained in existing inventories of Antarctic subglacial water and most are smaller than the mean ice thickness of 2.5 km, reflecting a focusing of basal water by rugged topography. The water system in the Gamburtsev Subglacial Mountains reoccupies a system of alpine overdeepenings created by valley glaciers in the early growth phase of the East Antarctic Ice Sheet. The networks follow valley floors either uphill or downhill depending on the gradient of the ice sheet surface. In cases where the networks follow valley floors uphill they terminate in or near plumes of freeze-on ice, indicating source to sink transport within the basal hydrologic system. Because the ice surface determines drainage direction within the bed-constrained network, the system is bed-routed but surface-directed. Along-flow variability in the structure of the freeze-on plumes suggests variability in the networks on long (10s of ka) timescales, possibly indicating changes in the basal thermal state.

Supplemental

Crustal uplifting rate associated with late-Holocene glacial-isostatic rebound at Skallen and Skarvsnes, Lützow-Holm Bay, East Antarctica: evidence of a synchrony in sedimentary and biological facies on the geological setting

• GPS measurement of isostatic rebound and tectonic deformation in Marie Byrd Land, West Antarctica
• Postglacial rebound
• Asthenosphere is a portion of the upper layer of the mantle just below the lithosphere that is involved in plate tectonic movement and isostatic adjustments.

Related

• Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers
• Migration of methane sulphonate in Antarctic firn and ice
• Coastal Antarctic Permafrost Melting Faster Than Expected
• Atmospheric Methane and Nitrous Oxide of the Late Pleistocene from Antarctic Ice Cores
• What Do Methane Deposits In The Antarctic And Arctic Mean For The Climate?
• Antarctic Tectonics
• Reaction of Ozone and Climate to Increasing Stratospheric Water Vapor
• Antarctic bottom water disappearing
• Antarctic ice volume measured
• 1250now.org