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Author Topic: Antarctic Methane Concentrations  (Read 57769 times)

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #100 on: January 13, 2016, 03:49:02 PM »
While 99 showed acceleration, that seems well after the 97/98 El Nino whereas this seems before current El Nino reached its peak so it seems hard to attribute it to just an El Nino effect.

Even so short term fluctuation or long term trend turning point?

Poles showing increases but Mauna Loa not

I would guess it seems more likely to be regional sources becoming more active rather than local or global as there isn't likely to be much local sources or sinks near south pole.

Certainly concerning if it continues.

I generally agree with your observations, and I note that a local source of methane near the South Pole seems particularly disturbing to me, if true, as any significant methane emissions from the Southern Ocean are most certainly not in any climate model forecasts for 2015.

Robert Scribbler just made the following relevant post about methane (with a GWP10 of 130) and carbon dioxide.  When looking a Scribbler's data indicates local Arctic methane concentrations approaching 3,000 ppb, and the South Pole data showing high local methane concentrations; taken at face value such data would indicate that Polar Amplification is triggering methane emissions from these polar regions faster than natural emissions from other parts of the global.  That said, I am concerned that when the next La Nina induced rainforest floods come they will submerge much of the dead vegetation killed by the current drought, which would then produce methane emissions spikes from tropical rainforests.

http://robertscribbler.com/2016/01/12/the-ominous-greenhouse-gas-accumulation-continues-peak-methane-approaches-3000-parts-per-billion-as-co2-growth-rate-jumps-higher/

Extract: "But the very pertinent question must be asked — are we waking up fast enough? And the still rapidly growing concentrations of gasses that heat the Earth’s atmosphere would seem to supply the answer in the form of a resounding, thunderous — “NO!”"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #101 on: December 04, 2017, 09:59:39 PM »
The linked reference discusses how gas hydrates in the bed sediment beneath marine glaciers can cause 'sticky spots' that can regulate ice stream flow rates:

Winsborrow, M., K. Andreassen, A. Hubbard, A. Plaza-Faverola, E. Gudlaugsson and H. Patton (2016). "Regulation of ice stream flow through subglacial formation of gas hydrates." Nature Geosci 9(5): 370-374, DOI: 10.1038/NGEO2696

https://www.nature.com/articles/ngeo2696
&
http://www.nature.com/articles/ngeo2696.epdf?referrer_access_token=IHHHsNRUI3lD2eFpTMWvl9RgN0jAjWel9jnR3ZoTv0N6H6twa9eus1zouX_OVF0HHps81v4XTc0_11DCSpeGLDxz98tw1yul2mr16lbVJL4uOjHYggNVEvnorXQDpPb-4F8Dx03N10vp8xTpF1OSQUCQuGQbrx_agiKHwJMiE0Vb3p9RlZE1kgUDa_7CPZDbIHfa0-zC2RtwAc1-HEOzfwPw5ovCnEJWlCwr6K4nmQjxYGctlb4MLBBjUrGaOUBg&tracking_referrer=austhrutime.com

 Abstract: "Variations in the flow of ice streams and outlet glaciers are a primary control on ice sheet stability, yet comprehensive understanding of the key processes operating at the ice–bed interface remains elusive. Basal resistance is critical, especially sticky spots—localized zones of high basal traction—for maintaining force balance in an otherwise well-lubricated/high-slip subglacial environment. Here we consider the influence of subglacial gas-hydrate formation on ice stream dynamics, and its potential to initiate and maintain sticky spots. Geophysical data document the geologic footprint of a major palaeo-ice-stream that drained the Barents Sea–Fennoscandian ice sheet approximately 20,000 years ago. Our results reveal a ∼250 km sticky spot that coincided with subsurface shallow gas accumulations, seafloor fluid expulsion and a fault complex associated with deep hydrocarbon reservoirs. We propose that gas migrating from these reservoirs formed hydrates under high-pressure, low-temperature subglacial conditions. The gas hydrate desiccated, stiffened and thereby strengthened the subglacial sediments, promoting high traction—a sticky spot— that regulated ice stream flow. Deep hydrocarbon reservoirs are common beneath past and contemporary glaciated areas, implying that gas-hydrate regulation of subglacial dynamics could be a widespread phenomenon."

Also see:

Title: "Regulation of Ice Stream Flow Through Subglacial Formation of Gas Hydrates"

http://austhrutime.com/ice_stram_flow_regulation_subglacial_gas_hydrates.htm

Extract: "Based on the presence of extensive sedimentary basins and modelling studies (Wadham et al., 2012; Wallmann et al., 2012) it is proposed that abundant gas hydrate accumulations are present beneath the ice sheets of Greenland and Antarctica. Also, gas hydrates have been identified in ice core samples obtained from above the subglacial Lake Vostok in East Antarctica (Uchida et al., 1994). The role of potentially widespread gas hydrate reservoirs in the modification of the thermomechanical regime at the base of contemporary ice sheets, which makes them critically sensitive, as well as their impact on ice steam force balance and dynamics has, so far, not been recognised. This control that was previously unforeseen, given the current lack of knowledge with regard to the distribution of gas hydrate, represents a significant unknown in attempts to model the current and future discharge and evolution of contemporary ice sheets, as well as their contribution to rising global sea levels."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson