Methane dissolved in the water was discovered by scientists collecting meltwater streams near Greenland’s glacier borders for several years. The flows of this methane appeared to be tiny, localised, and reliant on the conditions at any particular site, thus it hardly registered as a global problem.
An multinational team made the decision to simultaneously test that image throughout the entire western boundary. The age of the gas they recovered indicated that the ice had previously retreated much more than anyone had thought.
Finding the source of the gas
The gas is methane, which is a stronger greenhouse gas than carbon dioxide. It had previously been observed by researchers oozing from glacier fronts at several locations worldwide. Methane gushing out of one Greenland vent was also confirmed in a previous study.
But no one had checked whether this was one strange site or something happening along the entire edge of an ice sheet. Jade Hatton worked with a multinational team at Charles University in Prague to address that topic.
Taking a sample of the ice edge
From far northwest Greenland to the southwest, the transect covered an area of more than 1,200 miles. The researchers sought dissolved subglacial methane and chemical traces of its origin in each stream of meltwater that emerged from beneath the ice.
To get to the bed, field workers dug over 3,900 feet through the ice, retrieving water samples and sediment cores. The oxygen runs out quickly down there. Whatever microorganisms inhabit that murky sludge will have to do without it.
An old signature
The scientists conducted two primary tests back in the lab. To ascertain whether the gas originated from deep geological sources or bacteria, they first examined the gas’s chemical signature. They then determined its age using radiocarbon dating. Microbes were directly indicated by the isotopes.
Methane does not seep up from deep rock formations; rather, it is produced by anaerobic bacteria chewing through decomposing plant matter in oxygen-starved sediments. The unexpected part was the radiocarbon results. These samples were found to be between 1,500 and 4,400 years old.
The story of that age is reversed. The radiocarbon clock suggests that organic debris buried beneath the ice has been used by bacteria to produce the gas. Vegetation must have once grown on the now-covered ground for that to have occurred.
What the evidence points to
A recognised warm period in Earth’s recent past is indicated by the maths. The Holocene Thermal Maximum, which occurred between 11,000 and 5,000 years ago when the Arctic was warmer than For plants to flourish during that warm time, Greenland’s ice sheet had to be thinner. Even smaller than it is currently.
According to the findings, tundra and boreal woodland may have infiltrated that open area. Every year, plants took root, perished, and left carbon-rich material in the silt. The weather then cooled once more. That open ground was overrun by ice as it proceeded again.
Thousands of feet of frozen weight sealed the remains of the plant. Centuries after centuries, microorganisms continued to erode the buried carbon underground.
A self-sustaining loop
That earlier turn is being repeated in the current glacial retreat. Today, the methane produced by those long-buried bacteria is flushed out by meltwater that finds new routes through the bed as the ice border retreats.
Approximately 790 tonnes of dissolved methane are being released annually by the land-based glaciers in Western Greenland. The flow could continue for at least another 200 years thanks to the buried organic stuff.
A review is being prepared. More routes beneath the ice open as Greenland melts. Methane leaks out. The warming action of such gas has the potential to accelerate the melting.
Antarctica is more prominent.
On a far larger scale, the same configuration probably exists at the opposite pole.
An earlier study raised the prospect of enormous methane reservoirs beneath Antarctica, where the amount of buried organic matter is significantly higher than that of Greenland. The same type of delayed methane transport could intensify and dwarf Greenland’s if Antarctic ice continues to shrink and its bed becomes more connected by meltwater.
The total flux may be higher than anticipated because the survey only covered the western edge of Greenland, leaving the eastern and northern parts unexplored. Additionally, the 200-year projection has a large uncertainty range and is based on a degradation model rather than direct measurement.
The ultimate irony
Methane had never been measured along an ice sheet’s whole edge prior to this experiment. Greenland’s last major retreat may now be precisely dated thanks to the gas’s age, which links it to a particular historical environment.
This dynamism is not yet captured by current ice sheet models. According to different research, Greenland is already committed to a sea level rise of about one foot. The floor is too low, according to the methane research. Greenland’s ice has demonstrated that it may swing farther than the models predict, and as it retreats, it contributes to the heat that causes more retreat.
Alun Hubbard, a professor at the University of Oulu and co-author of the study, stated, “The ultimate irony is that as it retreats, the ice sheet itself further contributes to those methane emissions.”