Melting Arctic glaciers reveal new source of greenhouse gas emissions

Alanna Madden

(CN) — Human-made climate change may occur a bit faster than anticipated, researchers announced on Thursday through a study revealing that melting Arctic glaciers expose groundwater springs that could release an underestimated source of greenhouse gas into the atmosphere.

The findings come from a study published in Nature Geoscience, where researchers from the University of Cambridge and the University Centre in Svalbard, Norway, discovered large stocks of methane gas leaking from groundwater springs once trapped under Arctic glaciers — a source of methane gas overlooked until now.

“The observed pace of warming in the Arctic has far exceeded climate model predictions, probably due to many feedback loops within the Arctic that the models fail to capture,” the study authors wrote. “Our findings present a regionally important feedback loop related to climate-driven glacier melt that is currently not considered in the Arctic methane budget, where rapid glacial retreat is opening new pathways from methane escape.”

The researcher’s discovery adds a new and considerable source of methane emissions to those already found leaking from melting ice and frozen ground in the Arctic — a discovery they fear could exacerbate human-caused global warming.

“These springs are a considerable, and potentially growing, source of methane emissions — one that has been missing from our estimations of the global methane budget until now,” said lead author Gabrielle Kleber of Cambridge’s Department of Earth Sciences in a statement.

To encounter the grim discovery, Kleber spent nearly three years monitoring the water chemistry of 123 discrete groundwater springs from 78 melted glacier areas across Svalbard — an archipelago roughly 580 miles north of the city of Tromsø on the northern Norwegian coast. It is in Svalbard, researchers say, that annual air temperatures have risen five to seven times faster than the global average and twice as fast as anywhere else in the Arctic — leading to a 30% volume loss of glaciers since 1936 and a decrease in glacial coverage by about 10.4%.

It is also a region that Kleber says will serve as a preview of the potential methane release that could happen at a larger scale across the region, as her team’s monitoring revealed that all but one water sample indicated they came from supersaturated, methane-rich groundwater springs with concentrations more than 600,000 times greater than those in equilibrium with the atmosphere.

“Living in Svalbard exposes you to the front line of Arctic climate change,” said co-author Andrew Hodson of the University Centre in Svalbard in a statement. “I can’t think of anything more stark than the sight of methane outgassing in the immediate forefield of a retreating glacier.”

Researchers discovered how the springs in question are fed by a plumbing system beneath most glaciers that tap into large groundwater reserves within underlying sediments and surrounding bedrock. Once glaciers melt and retreat, the springs appear where the groundwater network protrudes to the surface.

To find these methane-rich water sources, Kleber used satellite images to zoom in on areas exposed by glacier melt, homing in on blue trickles of ice where groundwater had leaked to the surface and froze.

After analyzing samples of groundwater where the ice blistered due to pressurized water and gas build-up, the team concluded that methane emissions from glacial groundwater springs across Svalbard could exceed 2,000 metric tons over a year, equating to roughly 10% of methane emissions from Norway’s annual oil and gas industry.

“If global warming continues unchecked then methane release from glacial groundwater springs will probably become more extensive,” Kleber said.

During the course of the study, researchers also found localized hotspots of methane emissions closely related to the type of rock from which groundwater emerges. For reference, rocks like shale and coal contain natural gases, including methane, all produced by the breakdown of organic matter during rock formation. When these rocks fracture, researchers say, methane could move upwards into the groundwater.

“In Svalbard we are beginning to understand the complex and cascading feedbacks triggered by glacier melt — it seems likely that there are more outcomes like this which we have yet to uncover,” Kleber said.

Hodson stated that the amount of methane trapped below existing glaciers would likely dwarf the amount of methane leaking from the springs they measured.

“That means we urgently need to establish the risk of a sudden increase in methane leakage because glaciers will only continue to retreat whilst we struggle to curb climate change,” Hodson said.