The most extensive sampling of subglacial methane from the Greenland Ice Sheet provides the first evidence of its consistent and widespread release of the potent greenhouse gas. The research by an international team of scientists gives us insight into changes to the ice sheet extent in recent times.
The new study was led by Dr Jade Hatton, a landscape biogeochemist at the UK Centre for Ecology & Hydrology as part of her research within the Cryoeco Group, at Charles University, Prague.
The study, published in Nature Geoscience, involved the sampling and analysis of 26 meltwater streams, across the entire Western margin of the Greenland Ice Sheet, over three summer melt seasons.
It has shed new light on the timing of methane released from the Greenland Ice Sheet, which is linked to glacier margin fluctuations. This highlights the likely accumulation of organic material during the Holocene – the current geographical period that followed the last major ice age 11,700 years ago - in areas now covered by the ice sheet.
Dr Hatton explained: “The findings show widespread, pervasive methane release, produced under the ice by methanogens converting organic matter to methane.
"The methane was found to be sourced from carbon aged between 1,500-4,500 years old, which suggests the ice sheet retreated inside its present margins during the Holocene.”
During ice-free periods, Tundra vegetation grew and organic matter accumulated in the newly exposed areas, which was subsequently overridden by the readvancing ice in the following colder period.
Dr Hatton said: “The results support the hypothesis of dynamic sensitivity of the Greenland Ice Sheet to climate warming – something which is not yet fully understood or realised in current ice sheet models.
“Increased melting could lead to greater emissions of methane in the future – not just under the Greenland Ice Sheet, but also the Antarctic Ice Sheet, where organic matter reserves are much larger.