The linked reference presents new findings that the retreat of the Barents Sea Ice Sheet at the end of the last ice age resulted in the explosive release of methane from Arctic seafloor hydrates as overpressure from the ice sheet disappeared. The researchers findings serve as a good past analogy of what may likely happen in the near-term future if the WAIS were to collapse, and/or if marine terminating glaciers in Greenland were to retreat rapidly. As methane has a GWP100 of about 35 such explosive releases of methane could have a significant impact on global warming this century, which has not been considered in either AR5 or CMIP5:
K. Andreassen, A. Hubbard, M. Winsborrow, H. Patton, S. Vadakkepuliyambatta, A. Plaza-Faverola, E. Gudlaugsson, P. Serov, A. Deryabin, R. Mattingsdal, J. Mienert & S. Bünz (02 Jun 2017), "Massive blow-out craters formed by hydrate-controlled methane expulsion from the Arctic seafloor",Science, Vol. 356, Issue 6341, pp. 948-953, DOI: 10.1126/science.aal4500
http://science.sciencemag.org/content/356/6341/948Abstract: "Widespread methane release from thawing Arctic gas hydrates is a major concern, yet the processes, sources, and fluxes involved remain unconstrained. We present geophysical data documenting a cluster of kilometer-wide craters and mounds from the Barents Sea floor associated with large-scale methane expulsion. Combined with ice sheet/gas hydrate modeling, our results indicate that during glaciation, natural gas migrated from underlying hydrocarbon reservoirs and was sequestered extensively as subglacial gas hydrates. Upon ice sheet retreat, methane from this hydrate reservoir concentrated in massive mounds before being abruptly released to form craters. We propose that these processes were likely widespread across past glaciated petroleum provinces and that they also provide an analog for the potential future destabilization of subglacial gas hydrate reservoirs beneath contemporary ice sheets."
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Methane takes the quick way outAccounting for all the sources and sinks of methane is important for determining its concentration in the atmosphere. Andreassen et al. found evidence of large craters embedded within methane-leaking subglacial sediments in the Barents Sea, Norway. They propose that the thinning of the ice sheet at the end of recent glacial cycles decreased the pressure on pockets of hydrates buried in the seafloor, resulting in explosive blow-outs. This created the giant craters and released large quantities of methane into the water above."
See also:
http://gizmodo.com/hundreds-of-giant-seafloor-craters-produced-by-explosiv-1795721166Extract: "The explosive release of methane gas from subglacial sediments produced massive craters on the seafloor. During a recent expedition to the area, Andreassen’s team documented well over a hundred of these craters, which measured between 300 and 1,000 meters (980 to 3,280 feet) wide. Hundreds of smaller craters measuring less than 300 meters wide were also observed, and the researchers identified more than 600 methane flares in-and-around the craters that are still spewing the gas, though at rates far lower than what transpired during the explosive phase. Some of these craters were identified in the 1990s, but new scanning techniques allowed the researchers to survey the seafloor comprehensively.
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Importantly, Andreassen said similar blowouts could happen in the near future on account of climate change. Areas in front of retreating ice sheets in Greenland and West Antarctica could host underlying hydrocarbon reservoirs. These blowouts don’t happen very often, but their environmental impacts could be greater than the impacts of slow and gradual methane seepage, explained Andreassen."
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https://phys.org/news/2017-06-massive-craters-methane-blow-outs-arctic.htmlExtract: ""Our study provides the scientific community with a good past analogue for what may happen to future methane releases in front of contemporary, retreating ice sheets" concludes Andreassen."