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1. Biomarker Evidence for an MIS M2 Glacial‐Pluvial in the Mojave Desert Before Warming and Drying in the Late Pliocene

   https://doi.org/10.1029/2023PA004687  

   Peaple, Mark D.; Bhattacharya, Tripti; Tierney, Jessica E.; Knott, Jeffrey R.; Lowenstein, Tim K.; Feakins, Sarah J. (January 2024, Paleoceanography and Paleoclimatology)

   Abstract Ancient lake deposits in the Mojave Desert indicate that the water cycle in this currently dry place was radically different under past climates. Here we revisit a 700 m core drilled 55 years ago from Searles Valley, California, that recovered evidence for a lacustrine phase during the late Pliocene. We update the paleomagnetic age model and extract new biomarker evidence for climatic conditions from lacustrine deposits (3.373–2.706 Ma). The MBT′_5Metemperature proxy detects present‐day conditions (21 ± 3°C,n = 2) initially, followed by warmer‐than‐present conditions (25 ± 3°C,n = 17) starting at 3.268 and ending at 2.734 Ma. Bacterial and archeal biomarkers reveal lake salinity increased after 3.268 Ma likely reflecting increased evaporation in response to higher temperatures. The δ¹³C values of plant waxes (−30.7 ± 1.4‰,n = 28) are consistent with local C₃taxa, likely expanded conifer woodlands during the pluvial with less C₄than the Pleistocene. δD values (−174 ± 5‰,n = 25) of plant waxes indicate precipitation δD values (−89 ± 5‰,n = 25) in the late Pliocene are within the same range as the late Pleistocene precipitation δD. Microbial biomarkers identify a deep, freshwater lake and a cooling that corresponds to the onset of major Northern Hemisphere glaciation at marine isotope stage marine isotope stages M2 (3.3 Ma). A more saline lake persisted for ∼0.6 Ma across the subsequent warmth of the late Pliocene (3.268–2.734 Ma) before the lake desiccated at the Pleistocene intensification of Northern Hemisphere Glaciation. 

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2. Clyde Foreland Lake, Nunavut CO2 Concentration and d14C Data over the past 12.5 kiloannum

   https://doi.org/10.18739/A2HQ3S13M  

   Lindberg, Kurt; Thomas, Elizabeth K (April 2025, NSF Arctic Data Center)

   Recent anthropogenic warming in the Arctic has caused accelerated permafrost thaw, leading to the export of relict organic carbon (OC) to the atmosphere and surrounding depositional environments. Past episodes of warmth exceeding pre-industrial temperatures, such as the Holocene Thermal Maximum (HTM; 11 to 8 kiloannum (ka) at our study site), may serve as an analogue for how the Arctic carbon cycle responds to ongoing warming. We reconstructed accumulation rates of three OC endmembers (contemporaneous aquatic biomass, postglacial soil, and MIS 5 soil) at Lake CF8, northeastern Baffin Island, during the 12.4 kyr (kiloyear) since local deglaciation. We characterized OC endmembers and downcore sediment mixtures using Ramped Pyrolysis/Oxidation (RPO), radiocarbon (14C) age offsets between bulk sediment and macrofossils, and stable carbon isotopes (δ13C). We modeled endmember contributions to the lake sediment using the Bayesian mixing framework, MixSIAR. RPO revealed similar patterns between OC volatilization and pyrolysis temperature indicating minimal OC degradation between source and sink. Endmember OC accumulation rates, accounting for MixSIAR results, sedimentation, and total OC content, showed that mean postglacial soil inputs to Lake CF8 were greatest between 11.9 and 9.0 ka, 1.5 times greater than the rest of the record. This period coincided with regional peak Holocene summer temperatures (up to 5 °C (celsius) warmer than the pre industrial average), despite having low 14C age-offsets. Since modern Arctic temperatures have already warmed by 2-3 °C, similar to the HTM, regional permafrost may be mobilized at the same rates that we estimate for the early Holocene. 

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3. Modelling climate constraints on the formation of pluvial Lake Bonneville in the Great Basin, United States

   https://doi.org/10.1002/jqs.3394  

   Belanger, Bryce K.; Amidon, William H.; Laabs, Benjamin J. C.; Munroe, Jeffrey S.; Quirk, Brendon J. (November 2021, Journal of Quaternary Science)

   ABSTRACT This study uses a hydrologic‐balance model to evaluate the range of precipitation and temperature (P‐T) conditions required to sustain Lake Bonneville at two lake levels during the late Pleistocene. Intersection with a second set of P‐T curves determined from glacial modelling in the nearby Wasatch Mountains places tighter climatic constraints that suggest gradually increasing wetness from ~21 to 15 ka. Specifically, during the latter part of the Last Glacial Maximum (LGM) (~21–20 ka), Lake Bonneville approached its highest level under conditions roughly 9.5°C colder but only 7% wetter than modern. As the lake reached its pre‐flood Bonneville level (~18.2–17.5 ka), climate conditions were ~16% wetter and ~9°C colder than modern. Byca. 15–14.8 ka, Lake Bonneville abandoned the overflowing Provo level under conditions that were ~21% wetter and ~7°C cooler. These results suggest that regional LGM highstands were not caused by large increases in precipitation, but rather by a climatic optimum in which moderate wetness combined with depressed temperatures to create a positive hydrologic budget. Later highstands during Heinrich I from 17 to 15 ka were likely achieved under gradual increases in precipitation, prior to a transition to drier conditions after 15 ka. 

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4. An abrupt temperature and hydroclimate transition in eastern Africa during Termination V

   Ramirez, B.; Castañeda, I.S.; Salacup, J.M.; Johnson, T.C. (July 2023, XXI INQUA Congress)

   Over the last few million years, Africa’s climate exhibits a long-term drying trend with episodes of high climate variability coinciding with the intensification of glacial-interglacial cycles. Of particular interest, is a shift to drier and more variable conditions noted in the Olorgesailie Formation (Kenya) between 500 and 300 thousand years ago (ka) in which Potts et al. (2018) observed a turnover of ~85% of large-body mammalian fauna to smaller-body related taxa and suggested that the shift was an evolutionary response to better adapt to the changing climate. However, an erosional gap in the Olorgesailie record during this time interval means that the cause of this faunal shift is still an outstanding question. To understand East African climate variability during the Mid-Pleistocene, we analyze Lake Malawi drill core MAL 05–1 (~11ºS, 34ºE) to investigate if a specific climatic event stands out as a possible driver of the dramatic change observed in the East African mammal community. We use organic geochemical proxies including branched glycerol diaklyl glycerol tetraethers (brGDGTs; the MBT′5ME index) andleaf wax carbon and deuterium isotopes to develop high-resolution temperature, vegetation, and precipitation records, respectively, between 600 and 200 ka. Results show an abrupt temperature increase of ~9°C occurring in less than 3000 years during Glacial Termination V, which is the Marine Isotope Stage (MIS) 12 to MIS 11 transition at ~330 ka. Preliminary leaf wax deuterium isotopic values show an enrichment that coincides with deglacial warmings suggesting a shift to more arid conditions during interglacial than in glacial periods. This change from a cold/wet glacial to a warm/dry interglacial contrast with the cool/dry pattern of the Last Glacial Maximum (LGM) in East Africa which transitioned to a warm/wet Holocene. Leaf wax carbon isotopes are presently being analyzed to understand past shifts in C3 vs C4 vegetation type, which can be related to climatic conditions. We propose that the major warming and drying during Termination V in East Africa represents a significant abrupt change in the climate of eastern Africa and was a likely driver of the major faunal turnover noted in the region. 

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5. Palaeoenvironmental data indicate late quaternary anthropogenic impacts on vegetation and landscapes in Mzimba, northern Malawi

   https://doi.org/10.3389/fearc.2023.1250871  

   Wright, David K.; Ivory, Sarah J.; Birk, Jago J.; Choi, Jeong-Heon; Davies, Benjamin; Fiedler, Sabine; Davis, Jacob; Kaliba, Potiphar; Thompson, Jessica C. (January 2024, Frontiers in Environmental Archaeology)

   Landscapes are formed by long-term interactions between the underlying geology and climatic, edaphic and biotic factors, including human activity. The Kasitu Valley in the Mzimba District of northern Malawi includes the Kasitu River and its adjacent floodplains and uplands, and it has been a location of sustained human occupation since at least 16 thousand years ago (ka) based on archaeological excavations from rockshelters. We trace the changing ecology and geomorphology of the region through soil stable isotopes (δ¹³C, δ¹⁵N), microcharcoal and fossil pollen analysed from alluvial terraces dated by Optically Stimulated Luminescence, and wetland auger cores and archaeological sites dated by radiocarbon. Our results suggest that the region was primarily covered in mosaic forest at ca. 22.5 ka. Middle and Late Holocene samples (6.0–0.5 ka) show an increasingly open, herbaceous landscape over time with an inflection toward more abundant C4 vegetation after 2 ka. Significant upland erosion and terrace formation is also evidenced since 2 ka alongside high concentrations of microcharcoal, suggesting more intensive use of fire. Faecal biomarkers simultaneously indicate higher numbers of humans living adjacent to the archaeological site of Hora 1, which may be indicative of an overall population increase associated with the arrival of Iron Age agropastoralists. More recently, the introduction of exogenous commercial taxa such asPinussp. are correlated with regional afforestation in our proxy record. These results show increasing stepwise human impacts on the local environment, with deforestation and maintenance of open landscapes correlated with the regional introduction and intensification of agriculture during the Late Holocene. 

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