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Glacial-interglacial transitions and abrupt millennial-scale events are the most prominent features in many paleoclimate records. Understanding these oscillations requires high-resolution time series from multiple locations to constrain the latitudinal response to forcings. Few high-resolution records exist from the Southern Hemisphere tropics that predate the last two glaciations. We present a high-resolution speleothem oxygen and carbon isotope record from Huagapo Cave in the Central Peruvian Andes covering Marine Isotope Stage (MIS) 8 glacial and MIS 9 interglacial (339 to 249 ka). Uranium-series dates on three stalagmites (n=18) with small age uncertainty ±1% allows us to resolve abrupt climate events similar in structure and duration to Dansgaard-Oescchger and Heinrich events. The South American Summer Monsoon (SASM) controls modern hydroclimate variability in the Andes, and previous records from Huagapo Cave have provided records of past SASM variability. Termination three (T-III) in our record has a steep increase in δ18O values of 5‰, punctuated by two stadial event decreases of ~3‰ (S8.1 and S8.2). This pattern is mirrored in the δ13C record, indicating that these millennial-scale events record hydroclimate and vegetation productivity changes. The same structure as our T-III record is found in other records globally, where they are noted to be Heinrich-like events. Frequency analysis indicates that the occurrence of these abrupt events changes between glacial cycles. Precession is weakly expressed in the δ18O record during MIS 8; similar to speleothem records from the region dating to the Last Glacial Maximum (LGM). Global ice cover and sea levels were similar in the LGM and MIS 8, but the Milankovitch insolation forcing differed. This change in SASM behavior is not observed in the East Asian monsoon, where the precession signal is dominant throughout. Interglacial precessional control is apparent during the latter half of MIS 9 and during Huagapo Cave intervals dating to MIS 6 and 7. These data indicate that the response to high-latitude forcing in the Southern Hemisphere tropics fluctuates through time, and potential explanations for low-latitude sensitivity to forcing factors are further explored.
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Tropical vegetation productivity and atmospheric methane over the last 40,000 years from model simulations and stalagmites in Sulawesi, Indonesia
Recent research has shown the potential of speleothem δ13C to record a range of environmental processes. Here, we report on 230Th-dated stalagmite δ13C records for southwest Sulawesi, Indonesia, over the last 40,000 yr to investigate the relationship between tropical vegetation productivity and atmospheric methane concentrations. We demonstrate that the Sulawesi stalagmite δ13C record is driven by changes in vegetation productivity and soil respiration and explore the link between soil respiration and tropical methane emissions using HadCM3 and the Sheffield Dynamic Global Vegetation Model. The model indicates that changes in soil respiration are primarily driven by changes in temperature and CO2, in line with our interpretation of stalagmite δ13C. In turn, modelled methane emissions are driven by soil respiration, providing a mechanism that links methane to stalagmite δ13C. This relationship is particularly strong during the last glaciation, indicating a key role for the tropics in controlling atmospheric methane when emissions from high-latitude boreal wetlands were suppressed. With further investigation, the link between δ13C in stalagmites and tropical methane could provide a low-latitude proxy complementary to polar ice core records to improve our understanding of the glacial–interglacial methane budget.
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- Award ID(s):
- 2202913
- PAR ID:
- 10537425
- Publisher / Repository:
- Cambridge University Press
- Date Published:
- Journal Name:
- Quaternary Research
- ISSN:
- 0033-5894
- Page Range / eLocation ID:
- 1 to 16
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1017/qua.2023.75
