High-latitude lakes are quiet workhorses of the carbon cycle: they bury organic carbon efficiently, but how that burial responds to a changing climate has been hard to pin down. A study led by SES PhD student Leah Marshall, published in Arctic, Antarctic, and Alpine Research, tackles the question with a 15,800 year sediment record from Eight Mile Lake in central Alaska.
Working with Darrell Kaufman, Nicholas McKay, and collaborators from six other institutions, Marshall paired the lake core’s physical and biogeochemical properties with soil cores from the surrounding watershed, a combination that let the team compare carbon storage in the lake and on the hillslopes through the same stretch of time.
The record splits into three distinct phases. At the end of the last ice age (15,800 to 11,700 years ago), sediment poured into the lake and organic carbon accumulated at the highest rates in the record, rivaling the organic-rich Holocene soils of the catchment. Through the early and middle Holocene, stable conditions favored carbon from aquatic production. And over the last 5,500 years, carbon burial slowed but became far more variable century to century, as a wetter climate reshuffled erosion and transport while loess and organic-rich soils built up on the hillslopes.
The punchline is a useful asymmetry: the factors that promote carbon storage in permafrost soils, chiefly temperature and geomorphology, are not the ones that control carbon burial in the lakes next door, where sedimentation rate and burial efficiency dominate. For a warming Arctic, that means the fate of lake-stored carbon has to be modeled on its own terms.
The study grew out of long-running SES research on Alaskan lake systems and is part of Marshall’s dissertation work.
Reported by SES Research Highlights for the School of Earth and Sustainability.