The first palaeoclimate time-series based on compound specific analyses of fatty acid biomarkers from a speleothem.
Abstract
Models predict a large range in atmospheric carbon dioxide (CO2) concentrations (for any given emissions pathway), mainly because of uncertainties in the response of the terrestrial carbon cycle (including respiration) to any future temperature increase. Therefore, gaining new insights into the feedback mechanisms between terrestrial ecosystems and warmer climates is a prerequisite for reliable future climate predictions. Pre-industrial and Holocene, records of temperature-driven CO2changes are needed to provide a critical baseline for constraining such carbon cycle feedbacks at global scales. However, the response of terrestrial carbon cycle feedbacks during the earlier 'warm analogue' episodes of the early Holocene Climate Optimum (HCO) and Medieval Warm Period (MWP) are poorly constrained due to a lack of proxies (and thus available data). Here we present the first palaeoclimaticapplication of compound-specific δ13C measurements on n-fatty acid biomarkers extracted from a stalagmite. The δ13C of the higher plant-derived C24fatty acid records changes in C3and C4vegetation biomass in the stalagmite catchment in response to changing climate (and monsoon strength) during the Holocene. Furthermore, we explore methods to deconvolve the signal of heterotrophic consumption of higher plant substrates, from lower molecular weight (LMW) fatty acids (compounds produced by both microbes and higher plants). We argue that the residual δ13C signal is most parsimoniously explained by greater soil heterotrophic respiration (Rh) and decomposition rates, in response to a warmer and wetter local climate, driven by a stronger Asian summer monsoon during the HCO and MWP. This attribution of LMW fatty acids is uniquely applicable to speleothems, because compared to lake and marine sediments there is minimal contribution from algae. Our results provide the most detailed palaeoclimate records based on compound-specific analyses of lipid biomarkers from a speleothem. Moreover, we gain new insights into the link between East Asian temperature and hydroclimate, and terrestrial ecosystem respiration feedbacks during the Holocene.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP31D1697B
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHYDE: 4924 Geochemical tracers;
- PALEOCEANOGRAPHY