Precipitation-dependent vegetation distribution in northern South America during MIS 5e and MIS 1
Abstract
The Cariaco Basin, located off the Venezuelan coast in northern South America, is a sensitive recorder of tropical Atlantic climate variability. For example, analyses of stable carbon isotopic compositions of individual vascular plant leaf waxes preserved in Cariaco Basin sediments have revealed precipitation-driven vegetation shifts during the last glacial period and deglaciation. The record shows a direct correlation with the millennial scale temperature fluctuations recorded at high northern latitudes. Expansions of arid vegetation types are typically associated with the high northern latitude stadials while increases in humid vegetation correlate with interstadials. The amount of rainfall in northern South America is controlled by the position of the Intertropical Convergence Zone (ITCZ). During the last glacial period, abrupt cooling at high northern latitudes changed the meridional temperature gradient, deflecting the ITCZ southwards away from the Cariaco region. Abrupt high latitude warming, on the other hand, resulted in increased precipitation over northern South America as the ITCZ and its convective belt moved further north. While precipitation changes in the tropical Atlantic appear to be a distinct feature with a strong link to northern Atlantic climate during the last glacial period, we are now exploring precipitation patterns during interglacial intervals. Interglacial climate is generally considered as more stable in comparison to glacial climate conditions. Several studies have however reported millennial-scale abrupt events, although weaker in amplitude than the dramatic oscillations during the last glacial interval, during both the previous (MIS 5e) as well as the present (MIS 1) interglacial period. MIS 5e is also suggested to have had a more variable climate than MIS 1. Information on abrupt climate change during interglacials older than MIS 5e is rather limited, partly due to the low number of well-resolved records available from these periods. We are currently generating a high-resolution record of precipitation-dependent vegetation distribution for the Cariaco region during the five most recent interglacials to investigate what role the tropical Atlantic played during interglacial abrupt climate change. Here we present results from MIS 5e and MIS 1 at centennial resolution, suitable to capture millennial variability, while future work will investigate MIS 7, 9 and 11. Additional aspects to be discussed include differences in interglacial peak conditions and patterns of change across earlier deglaciations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMPP44A..06A
- Keywords:
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- 0473 BIOGEOSCIENCES / Paleoclimatology and paleoceanography