Bottom-up estimates of CH4 emissions from northern thaw lakes: modern and paleo- perspectives
Abstract
Here we describe and quantify an important source of atmospheric methane (CH4)— ebullition (bubbling) from northern lakes— that has not been incorporated in previous regional or global CH4 budgets. Using multiple bottom-up approaches we (1) Introduce a new method to quantify the patchiness of ebullition by direct measurement of bubbling point sources and hotspots, thereby increasing previous estimates of CH4 flux from lakes 5-fold in Siberia and 2.5- to 14-fold in Alaska; (2) Weight stable and radiocarbon isotope signatures of different types of ebullition (maximum 14CCH4 age of hotspots 43,000 yrs; whole lake average 16,500 yrs) demonstrating that ebullition patchiness influences estimates of regional isofluxes and that Pleistocene-age organic matter released from thawing permafrost fuels methanogenesis; (3) Use an independent mass-balance approach based on carbon lost from permafrost that thawed beneath lakes to confirm the measured flux estimate in Siberia; and (4) Verify the magnitude of lake CH4 emissions based on CH4 production potentials of organic matter from Pleistocene-aged frozen sediments. Furthermore, we apply these techniques together with a compilation of thaw lake basal ages to show that thaw lake development, a previously unrecognized source, contributed up to 70% of the rapid increase in northern sources of atmospheric CH4 recorded in ice cores during deglaciation. Given the large amount of carbon still present in Siberian permafrost (500 Gt), we predict that tens of thousands of Tg of CH4 will be released in the future from thaw lakes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.B32A..04W
- Keywords:
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- 0475 Permafrost;
- cryosphere;
- and high-latitude processes (0702;
- 0716);
- 0490 Trace gases;
- 0497 Wetlands (1890);
- 0746 Lakes (9345);
- 3344 Paleoclimatology (0473;
- 4900)