Ice Cover Enhances Methane Consumption in Alaskan Thermokarst Lakes
Abstract
Rapid warming in the Arctic provides one of the clearest examples of climate change occurring today, with a potential positive feedback to methane generation and emission from arctic lakes and wetlands. To develop a predictive capacity for feedback between climate and methane, a fundamental understanding of systematic controls on methane production and consumption within these environments is required. Here we present a comparison of methane consumption (methanotrophy) rates between ice-cover and ice-free seasons in waters from three shallow thermokarst lakes in arctic Alaska. At all three lakes, under-ice methane concentrations were high, and turnover times were rapid; 1-3 orders of magnitude greater than measurements made in the ice-free season, even under conditions of under-ice oxygen limitation. Rates measured with a radiotracer method are supported by stable isotopic and microbiological evidence. This observation is contrary to the prevailing assumption that under-ice methane consumption becomes oxygen limited early in the season, and that the ice-free season is the primary period for active methanotrophy in these lakes. Further, our results suggest that the seasonal process of ice formation plays a role in modulating rates of methanotrophy in thermokarst lakes, suggesting a link between methanotrophic efficacy and changing climate. Moreover, the observed rates imply that significantly more methane is produced during the ice-cover season than is accounted for by measuring late winter storage and spring flux. Together, these results call for a re-evaluation of our understanding of the full potential of arctic lakes as an atmospheric methane sources.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMGC51J..03H
- Keywords:
-
- 0458 BIOGEOSCIENCES / Limnology;
- 0475 BIOGEOSCIENCES / Permafrost;
- cryosphere;
- and high-latitude processes;
- 0497 BIOGEOSCIENCES / Wetlands;
- 0708 CRYOSPHERE / Thermokarst