Abstract
AbstractOxygen isotope ratios in tree rings (δ18OTR) from northern Bolivia record local precipitation δ18O and correlate strongly with Amazon basin‐wide rainfall. While this is encouraging evidence that δ18OTR can be used for paleoclimate reconstructions, it remains unclear whether variation in δ18OTR is truly driven by within‐basin processes, thus recording Amazon climate directly, or if the isotope signal may already be imprinted on incoming vapor, perhaps reflecting a pan‐tropical climate signal. We use atmospheric back trajectories combined with satellite observations of precipitation, together with water vapor transport analysis to show that δ18OTR in Bolivia are indeed controlled by basin‐intrinsic processes, with rainout over the basin the most important factor. Furthermore, interannual variation in basin‐wide precipitation and atmospheric circulation are both shown to affect δ18OTR. These findings suggest δ18OTR can be reliably used to reconstruct Amazon precipitation and have implications for the interpretation of other paleoproxy records from the Amazon basin.
Highlights
Correlate strongly with Amazon basin-wide rainfall. While this is encouraging evidence that δ18OTR can be used for paleoclimate reconstructions, it remains unclear whether variation in δ18OTR is truly driven by within-basin processes, recording Amazon climate directly, or if the isotope signal may already be imprinted on incoming vapor, perhaps reflecting a pan-tropical climate signal
We use atmospheric back trajectories combined with satellite observations of precipitation, together with water vapor transport analysis to show that δ18OTR in Bolivia are controlled by basin-intrinsic processes, with rainout over the basin the most important factor
Relationships between oxygen isotopes (δ18O) and environmental variables have often been the basis for paleoclimate reconstructions, but relying on empirical correlations alone without an understanding of the underlying mechanisms may lead to misinterpretations of proxy records [McCarroll and Loader, 2004]
Summary
Relationships between oxygen isotopes (δ18O) and environmental variables have often been the basis for paleoclimate reconstructions, but relying on empirical correlations alone without an understanding of the underlying mechanisms may lead to misinterpretations of proxy records [McCarroll and Loader, 2004]. Similar relationships with ENSO have been reported for δ18OTR records elsewhere in the tropics, including Ecuador [Volland et al, 2016], Central America [Anchukaitis and Evans, 2010], northern Australia [Boysen et al, 2014], and several sites in Southeast Asia [Poussart et al, 2004; Sano et al, 2012; Schollaen et al, 2014; Xu et al, 2011, 2013, 2015] This leaves some doubt over the extent to which interannual variation in δ18OTR in Bolivia is driven by processes within the Amazon basin or is more representative of processes occurring at the pan-tropical scale. This is important to clarify if such isotope data are to be reliably used to reconstruct climate and potentially validate output from general circulation models (GCMs) in the Amazon [Henderson-Sellers et al, 2002]
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