A synthesis of tropical American proxy records of hydroclimate variability over the last millennium
Abstract
We present a principal component (PC) and correlation analysis of 30 tropical American hydroclimate records from lake and ocean sediment, ice, and speleothems spanning the last millennium. The results, which account for both age model and analytical uncertainty, provide insight on past spatiotemporal patterns of precipitation/evaporation balance driven by variability in ocean-atmosphere processes such as the Inter-tropical Convergence Zone (ITCZ) and the South American monsoon (SAM). In general, records from the tropical Americas do not correlate with one another. The average number of significant, positive correlations among records from each hemisphere is less than 1.5, a result that is roughly consistent with random chance (given p = 0.05). Notable records such as the Cariaco Basin Ti and Quelccaya ice cap oxygen isotope datasets do not significantly correlate with any other records from their respective hemispheres. Nevertheless, the Monte Carlo based PC analysis indicates a broad pattern of hydroclimate anti-phasing, with a drier Northern Hemisphere and wetter Southern Hemisphere during the Little Ice Age (LIA, ~1450-1850 CE), as indicated by PC1. In general, the northern tropical records demonstrate a gradual transition toward drier conditions while the southern records exhibit a markedly wetter LIA (and hence a strengthened SAM at that time). If the analysis is restricted to precipitation oxygen isotope datasets (e.g. from speleothems), however, a coherent temporal pattern emerges wherein the timing of the LIA hydroclimate transitions in each hemisphere are consistent. PC analyses of annual precipitation amounts in last millennium simulations from global climate models demonstrate a spatial pattern (in the loading values) of north-south anti-phasing that is approximately consistent with that of the proxy data. These results support explanations for common era hydroclimate variability that rely primarily upon changes in the position of the ITCZ, as such changes would be expected to produce anti-phased north-south responses with similar timing in each hemisphere. They additionally demonstrate that local climatic effects, and/or synoptic scale processes that are not strongly related to ITCZ position have the potential to overwhelm regional scale signals in some proxy types and locations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP24B..02S
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGE;
- 4943 Paleolimnology;
- LIMNOLOGY;
- 4914 Continental climate records;
- PALEOCEANOGRAPHY;
- 4954 Sea surface temperature;
- PALEOCEANOGRAPHY