22-6 The Evolution of Late Pleistocene Climate Dynamics in Tropical Southeast Africa

Abstract:

The relationship between tropical southeast African climate systems and global climate change remains poorly constrained, and this scientific uncertainty poses significant challenges for human communities and ecological systems in the region under modern anthropogenic forcing. The hydroclimatic sensitivity of tropical southeast Africa to globally warm extremes remains particularly uncertain, as the region is variably sensitive to a wide range of regional and global forcings and feedbacks. To better understand how tropical southeast African temperature and precipitation regimes will respond to abrupt global change, we turn to lacustrine sedimentary archives in the region to reconstruct long-term paleoclimate dynamics during past periods of significant global climate change. Here we present organic geochemical records of temperature and hydroclimate from two cores collected by the 2005 ICDP Lake Malawi Drilling Project (MAL05-1 and MAL05-2A), which together include the past 140,000 years of climate evolution in tropical southeast Africa. We analyze branched and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) to quantify the magnitude of temperature change during two glacial terminations and to refine GDGT-based paleothermometry methods at the site. Our records display strong coherence with global climate fluctuations, capturing peak interglacial warmth during Marine Isotope Stage 5 (130-100 ka), cooling into the Last Glacial Maximum, and early Holocene warming across two basins of the lake. We additionally analyze plant wax deuterium isotopes to reconstruct hydroclimate dynamics at Lake Malawi. Our results suggest that Malawi’s hydroclimate is both sensitive to low-latitude insolation and global climate fluctuations, with a distinct antiphase relationship between our hydroclimate record and similar records from East African sites north of the equator emerging after the Last Glacial Maximum and into the Holocene. These findings better constrain the relationship between regional temperature, hydroclimate, and their overlapping sensitivities to low-latitude forcings and global climate dynamics throughout the past 140,000 years, ultimately lending critical insight into how tropical southeast Africa responds to abrupt global climate change.

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