A study of ancient plant wax has revealed how global warming affects methane in Arctic lakes. This shows that warming has led to an intensified methane cycle, lasting thousands of years. This is based upon the novel use of plant biomarkers preserved in sediment to reconstruct methane cycling over the past 10,000 years.
The study comes from Northwestern University and University of Wyoming researchers who are gaining a better understanding of how methane produced in Arctic lakes might affect, and be affected by, climate change.
As the planet has warmed due to slow changes in Earth’s orbit, lakes have produced increased amounts of methane, a potent greenhouse gas. The study shows how we can look to these signs from the past to predict our future.
Specifically, the researchers have examined the waxy coatings of leaves preserved as organic molecules within sediment from the early-to-middle Holocene, a period of intense warming that occurred due to slow changes in Earth’s orbit 11,700 to 4,200 years ago.
These wax biomarkers, once a part of common aquatic brown mosses, were preserved in sediment buried beneath four lakes in Greenland. The analysis indicates that past warming during the middle Holocene caused lakes across a wide range of Greenland’s climates to generate methane.
Since methane is a more potent greenhouse gas than carbon dioxide, any changes in methane production with warming are important to understand. It appears that warming potentially could lead to a previously under-appreciated flux in methane emissions from lakes.
The researchers produced new data at two lakes (Wax Lips Lake and Trifna Sø) and reviewed published data from two additional lakes on Greenland (Lake N3 and Pluto Lake). The focus was with comparing the hydrogen isotopic composition of aquatic plant waxes within the sediment to biomarkers from terrestrial plants and other sources.
These data show increased periods of methane cycling during past warm periods. This is the basis for considering signs from the past to help predict our future. Lakes act as significant natural sources of methane, but exactly how much methane production will change with ongoing warming within Arctic lakes is not fully quantified.
The highlights that vast swaths of Arctic lakes are vulnerable to climate-driven changes in methane cycling. This is another way that rapid warming in the Arctic could affect global climate.
The research appears in the journal Science Advances. It is titled “Aquatic plant wax hydrogen and carbon isotopes in Greenland lakes record shifts in methane cycling during past Holocene warming.”
