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Holocene warming drove long-term methane increases in lakes across Greenland
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  • Jamie McFarlin,
  • Yarrow Axford,
  • Stephanie Kusch,
  • Andrew Masterson,
  • Gregory Lasher,
  • Magdalena Osburn
Jamie McFarlin
University of Colorado Boulder, University of Colorado Boulder

Corresponding Author:[email protected]

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Yarrow Axford
Northwestern University, Northwestern University
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Stephanie Kusch
University of Cologne, University of Cologne
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Andrew Masterson
Northwestern University, Northwestern University
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Gregory Lasher
University of Pittsburgh, University of Pittsburgh
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Magdalena Osburn
Northwestern University, Northwestern University
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Abstract

Methane (CH4) emissions from Arctic lakes are of global concern in a warming world. Holocene warming provides an opportunity to examine carbon-climate feedbacks that develop over hundreds to thousands of years of warming, but thus far records that document changes in lake CH4 dynamics in the Arctic are limited. Here, we show that Holocene warming led to widespread increases in CH4 in Greenland lakes during the middle Holocene driven by increases in primary production and decreases in oxygen in hypolimnetic water due to stratification. We infer changes in CH4 dynamics using δ2H values of sedimentary moss biomarkers which demonstrate at multiple sites on Greenland a several-thousand-year period during which δ2Hmoss values are consistent with uptake of CH4-derived H, likely via intracellular H2O and NH4+ supplied by endophytic methanotrophic bacteria that dominated in increasingly stratified lakes. These data indicate ongoing warming will promote an enduring shift towards conditions that enhance methanogenesis and increase CH4 in warming Arctic lakes whose geometries are prone to thermal stratification even in lakes where these conditions do not exist today. This work also draws attention to a likely role of common aquatic mosses as an important sink of CH4 in lakes across the Arctic.