Paleoclimate papers (Titles and Abstracts only please)

[pmokeefe]

Thread for Paleoclimate papers with implications for Human Evolution and Culture (Titles and Abstracts only please).

Changes in the cyclicity and variability of the eastern African paleoclimate over the last 620 kyrs
Walter Duesing, Stefanie Kaboth-Bahr, Asfawossen Asrat, Andrew S.Cohen, Verena Foerster, Henry F. Lamb, Frank Schaebitz, Martin H. Trauth, Finn Viehberg
https://doi.org/10.1016/j.quascirev.2021.107219

Highlights
•Orbitally controlled variation in insolation have caused wet-dry climate cycles in the CHB over the las 620 kyrs.
•The climate of the CHB was characterized by a long term drying trend coinciding with an increase in variability.
•Short term increases of variability correspond to changes in eccentricity translating into fast climate transitions.
•During the transition from Acheulean to MSA technologies the climate of the CHB was highly variable.

Abstract
There is ongoing debate concerning whether or not changes in the eastern African climate, both long-term and short-term, affected the evolution, dispersal, cultural development, and technological innovations of Homo sapiens – and if so, in what way. We present the wavelet spectral analysis results of a ∼620 kyr record of environmental change from the Chew Bahir (CHB ) basin in the southern Ethiopian rift, approximately 120 km from the Omo-Kibish fossil locality, which boasts one of the oldest documented appearances of H. sapiens. Our results indicate that the long-term wet-dry changes in the eastern African climate recorded in the CHB sediments were mainly caused by changes in orbital eccentricity, with relatively dry but variable climates occurring during eccentricity minima within the 400 kyr eccentricity cycle, and increased precipitation, interspersed with distinctly dryer phases associated with orbital precession, during eccentricity maxima. Such insolation-forced precipitation changes would have affected the habitat of H. sapiens in the region; the transition from Acheulean to Middle Stone Age (MSA) documented in the Olorgesailie Basin of southern Kenya coincides with a distinct eccentricity minimum with reduced precipitation and repeated abrupt climatic transitions. In contrast, at the time of the subsequent, first documented occurrence of H. sapiens in eastern Africa the climate was distinctly wetter and less variable.

Did increased flooding during the African Humid Period force migration of modern humans from the Nile Valley?
Abdallah S.Zak i, Georgina E. King, Negar Haghipour, Robert Giegengack, Stephen E. Watkins, Sanjeev Gupta, Mathieu Schuster, Hossam Khairy, Salah Ahmed, Mostafa El-Wakil, Saleh A. Eltayeb, Frédéric Herman, Sébastien Castelltort
https://doi.org/10.1016/j.quascirev.2021.107200

Highlights
•A chronological and palaeohydrological approach has been applied to six fossil rivers.
•Our chronological constraints cluster within the AHP (13–5.2 ka BP).
•Average rainfall intensity of 55–80 mm/h during channel sediment transport events occurred up to 3–4 times more frequently during the AHP.
•Human migration from the Nile Valley may have been driven by increased flooding for ca. 3000 years.

Abstract
During the Quaternary period, the eastern Sahara's hydroclimate oscillated between wet and dry intervals. These oscillations caused drastic changes in precipitation rates, often associated with ancient human migrations. In particular, significant migration of riparian populations from the Nile Valley to the west and northwestward of the Sahara occurred during the African Humid Period (AHP), an episode of increased monsoons, which characterized North Africa in response to increasing insolation. Several fossil rivers, now preserved as ridges throughout southern Egypt due to their floodplains' deflation, contain archeological artifacts and thus represent a potentially important record of fluvial activity during this episode of past human dynamics and environmental change. Here we present 14C and Optically Stimulated Luminescence (OSL) ages of sediments preserved in these palaeorivers, which cluster within the AHP and are thus consistent with increased fluvial activity during this distinct humid period. Palaeohydraulic reconstructions based on grain size, channel geometry, and drainage area suggest typical precipitation intensities of 55–80 mm/h during sediment transport events. Given previous annual rainfall estimates, these hydrologic conditions may have lasted, or occurred, during the AHP up to 3–4 times more frequently than before and after this period. Such intense fluvial activity is consistent with monsoon intensification and may have rendered the area inhospitable for human settlements, congruent with population migration out of the Nile Valley during the AHP. These findings highlight links between past human ecodynamics and environmental signals, providing a concrete narrative of human population response to warming with potential echo in the current situation.

[pmokeefe]

A global environmental crisis 42,000 years ago
ALAN COOPER, CHRIS S. M. TURNEY, JONATHAN PALMER, ALAN HOGG, MATT MCGLONE, JANET WILMSHURST, ANDREW M. LORREY , TIMOTHY J. HEATON, JAMES M. RUSSELL ... ROLAND ZECH

Reversing the field
Do terrestrial geomagnetic field reversals have an effect on Earth's climate? Cooper et al. created a precisely dated radiocarbon record around the time of the Laschamps geomagnetic reversal about 41,000 years ago from the rings of New Zealand swamp kauri trees. This record reveals a substantial increase in the carbon-14 content of the atmosphere culminating during the period of weakening magnetic field strength preceding the polarity switch. The authors modeled the consequences of this event and concluded that the geomagnetic field minimum caused substantial changes in atmospheric ozone concentration that drove synchronous global climate and environmental shifts.

Abstract
Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.




Comment on “A global environmental crisis 42,000 years ago”
ANDREA PICIN, STEFANO BENAZZI, RUTH BLASCO, MATEJA HAJDINJAK, KRISTOFER M. HELGEN, JEAN-JACQUES HUBLIN, JORDI ROSELL, PONTUS SKOGLUND, CHRIS STRINGER, AND SAHRA TALAMO
SCIENCE 18 Nov 2021
DOI: 10.1126/science.abi8330

Abstract
Cooper et al. (Research Articles, 19 February 2021, p. 811) propose that the Laschamps geomagnetic inversion ~42,000 years ago drove global climatic shifts, causing major behavioral changes within prehistoric groups, as well as events of human and megafaunal extinction. Other scientific studies indicate that this proposition is unproven from the current archaeological, paleoanthropological, and genetic records.

[jose luis]

The spatio-temporal structure of the Lateglacial to early Holocene transition reconstructed from the pollen record of Lake Suigetsu and its precise correlation with other key global archives: Implications for palaeoclimatology and archaeology
Takeshi Nakagawa, Pavel Tarasov, Richard Staff, Christopher Bronk Ramsey, Michael Marshall, Gordon Schlolauth, Charlotte Bryant, Achim Brauerh, Henry Lamb...
July 2021

Abstract

Leads, lags, or synchronies in climatic events among different regions are key to understanding mechanisms of climate change, as they provide insights into the causal linkages among components of the climate system. The well-studied transition from the Lateglacial to early Holocene (ca. 16–10 ka) contains several abrupt climatic shifts, making this period ideal for assessing the spatio-temporal structure of climate change. However, comparisons of timings of past climatic events among regions often remain hypothetical because site-specific age scales are not necessarily synchronised to each other. Here we present new pollen data (n = 510) and mean annual temperature reconstruction from the annually laminated sediments of Lake Suigetsu, Japan. Suigetsu's 14C dataset is an integral component of the IntCal20 radiocarbon calibration model, in which the absolute age scale is established to the highest standard. Its exceptionally high-precision chronology, along with recent advances in cosmogenic isotope studies of ice cores, enables temporally coherent comparisons among Suigetsu, Greenland, and other key proxy records across regions.

We show that the onsets of the Lateglacial cold reversal (equivalent to GS-1/Younger Dryas) and the Holocene were synchronous between East Asia and the North Atlantic, whereas the Lateglacial interstadial (equivalent to GI-1/Bølling-Allerød) started ca. two centuries earlier in East Asia than in the North Atlantic. Bimodal migration (or ‘jump’) of the westerly jet between north and south of the Tibetan plateau and Himalayas may have operated as a threshold system responsible for the abruptness of the change in East and South (and possibly also West) Asia. That threshold in Asia and another major threshold in the North Atlantic, associated with switching on/off of the Atlantic meridional overturning circulation (AMOC), were crossed at different times, producing a multi-centennial asynchrony of abrupt changes, as well as a disparity of climatic modes among regions during the transitional phases. Such disparity may have disturbed zonal circulation and generated unstable climate during transitions. The intervening periods with stable climate, on the other hand, coincided with the beginnings of sedentary life and agriculture, implying that these new lifestyles and technologies were not rational unless climate was stable and thus, to a certain extent, predictable.
https://www.sciencedirect.com/scienc...21818121000783

[pmokeefe]

A climatic evaluation of the southern dispersal route during MIS 5e
Samuel Luke Nicholson, Rob Hosfield, Huw S. Groucutt, Alistair W.G. Pike, Stephen J. Burns, Albert Matter, Dominik Fleitmann
https://doi.org/10.1016/j.quascirev.2022.107378

Highlights
• Timing of MIS 5e monsoon intensification in Southern Arabia (SAHP 4) confined to 127.7-121.1 ka BP.
•SAHP 4 represents the most substantial increase of rainfall in the last 130 ka BP.
• The onset of monsoon intensification lagged sea-level rise.


Abstract
Homo sapiens dispersals out of Africa are often linked to intensifications of the African and Indian Summer Monsoons. Current models advocate that dispersals along the “southern-route” into Arabia occurred during Glacial Termination-II (T-II), when lower sea-level and reduced Bab-al-Mandab width increased the likelihood of crossing. The precise phasing between sea-level and monsoon precipitation is thus key to assess the likelihood of a successful crossing or the behavioural and technological capacities that facilitated crossing. Based on a precisely-dated stalagmite record from Yemen, we reveal a distinct phase-lag of several thousand years between sea-level rise and major monsoon intensification. Pluvial conditions in Southern Arabia during MIS 5e lasted from ∼127.7 to ∼121.1 ka BP and occurred when sea-levels were already higher than at present. Based on our observations, we propose three models for the dispersal of H. sapiens which all have pertinent implications for our understanding of human technological and behavioural capacities during MIS 5e.

[pmokeefe]

Did a mega drought topple empires 4,200 years ago?
Nature NEWS FEATURE 26 January 2022
People abandoned thriving cities in Mesopotamia, the Indus Valley and farther afield at about the same time as a decades-long drought gripped parts of the planet.
Michael Marshall

[pmokeefe]

Radiocarbon dating from Yuzhniy Oleniy Ostrov cemetery reveals complex human responses to socio-ecological stress during the 8.2 ka cooling event
Rick J. Schulting, Kristiina Mannermaa, Pavel E. Tarasov, Thomas Higham, Christopher Bronk Ramsey, Valeri Khartanovich, Vyacheslav Moiseyev, Dmitriy Gerasimov, John O’Shea & Andrzej Weber
Nature Ecology & Evolution (2022)


Abstract
Yuzhniy Oleniy Ostrov in Karelia, northwest Russia, is one of the largest Early Holocene cemeteries in northern Eurasia, with 177 burials recovered in excavations in the 1930s; originally, more than 400 graves may have been present. A new radiocarbon dating programme, taking into account a correction for freshwater reservoir effects, suggests that the main use of the cemetery spanned only some 100–300 years, centring on ca. 8250 to 8000 cal BP. This coincides remarkably closely with the 8.2 ka cooling event, the most dramatic climatic downturn in the Holocene in the northern hemisphere, inviting an interpretation in terms of human response to a climate-driven environmental change. Rather than suggesting a simple deterministic relationship, we draw on a body of anthropological and archaeological theory to argue that the burial of the dead at this location served to demarcate and negotiate rights of access to a favoured locality with particularly rich and resilient fish and game stocks during a period of regional resource depression. This resulted in increased social stress in human communities that exceeded and subverted the ‘normal’ commitment of many hunter-gatherers to egalitarianism and widespread resource sharing, and gave rise to greater mortuary complexity. However, this seems to have lasted only for the duration of the climate downturn. Our results have implications for understanding the context of the emergence—and dissolution—of socio-economic inequality and territoriality under conditions of socio-ecological stress.

[pmokeefe]

Multiple phases of human occupation in Southeast Arabia between 210,000 and 120,000 years ago
K. Bretzke, F. Preusser, S. Jasim, C. Miller, G. Preston, K. Raith, S. J. Underdown, A. Parton & A. G. Parker
Scientific Reports volume 12, Article number: 1600 (2022)


Abstract
Changing climatic conditions are thought to be a major control of human presence in Arabia during the Paleolithic. Whilst the Pleistocene archaeological record shows that periods of increased monsoon rainfall attracted human occupation and led to increased population densities, the impact of arid conditions on human populations in Arabia remains largely speculative. Here, we present data from Jebel Faya in Southeast (SE) Arabia, which document four periods of human occupation between c. 210,000 and 120,000 years ago. The Jebel Faya record indicates that human occupation of SE Arabia was more regular and not exclusively linked to major humid periods. Our data show that brief phases of increased rainfall additionally enabled human settlement in the Faya region. These results imply that the mosaic environments in SE Arabia have likely formed a population refugia at the end of the Middle and the beginning of the Late Pleistocene.

[pmokeefe]

The unexpectedly short Holocene Humid Period in Northern Arabia
Ina Neugebauer, Michèle Dinies, Birgit Plessen, Nadine Dräger, Achim Brauer, Helmut Brückner, Peter Frenzel, Gerd Gleixner, Philipp Hoelzmann, Kim J. Krahn, Anna Pint, Valérie F. Schwab, Anja Schwarz, Rik Tjallingii & Max Engel
Communications Earth & Environment volume 3, Article number: 47 (2022)


Abstract
The early to middle Holocene Humid Period led to a greening of today’s arid Saharo-Arabian desert belt. While this phase is well defined in North Africa and the Southern Arabian Peninsula, robust evidence from Northern Arabia is lacking. Here we fill this gap with unprecedented annually to sub-decadally resolved proxy data from Tayma, the only known varved lake sediments in Northern Arabia. Based on stable isotopes, micro-facies analyses and varve and radiocarbon dating, we distinguish five phases of lake development and show that the wet phase in Northern Arabia from 8800–7900 years BP is considerably shorter than the commonly defined Holocene Humid Period (~11,000–5500 years BP). Moreover, we find a two century-long peak humidity at times when a centennial-scale dry anomaly around 8200 years BP interrupted the Holocene Humid Period in adjacent regions. The short humid phase possibly favoured Neolithic migrations into Northern Arabia representing a strong human response to environmental changes.

[pmokeefe]

ESR dating of the Hougou Paleolithic site in the Nihewan Basin, North China, using both additive and regenerative dose methods
HaoJi, Chunru Liu, Gongming Yin, Chuanyi Wei, Weijuan Song
https://doi.org/10.1016/j.quaint.2021.10.001
Abstract
The Nihewan Basin is one of the most important areas for the study of early human evolution and land mammals in East Asia. More than 100 Paleolithic sites have been discovered in the basin, spanning the Early Pleistocene to the Late Pleistocene. The chronological framework for the Early Pleistocene sites is well established using magnetostratigraphy. However, few independent ages are associated with Middle Pleistocene sites; one such example is the Hougou Paleolithic site, where interpolated magnetostratigraphic ages are not precise and accurate enough, owing to the artifact layer of the site is far relative to the Matuyama/Brunhens (M/ boundary. In this study, we use the ESR signals of Al and Ti–Li centers in quartz to date the Hougou site. The advantages of the regenerative dose method over the additive dose method were discussed. Our ESR results indicate that the age of the Hougou Paleolithic site is between 436 ± 30 and 416 ± 42 ka, approximately with an average of 426 ± 36 ka, which corresponds to Marine Isotope Stage (MIS) 12 or loess layer L5. In addition, the disappearance time of the eastern part of the Nihewan paleolake may be approximately 430 ka.

[pmokeefe]

The age of the opening of the Ice-Free Corridor and implications for the peopling of the Americas
Jorie Clark, Anders E. Carlson, Alberto V. Reyes, Elizabeth C. B. Carlson, Louise Guillaume, Glenn A. Milne, Lev Tarasov, Marc Caffee, Klaus Wilcken, and Dylan H. Rood
March 21, 2022 https://doi.org/10.1073/pnas.2118558119

Significance
The Ice-Free Corridor (IFC) has long played a key role in hypotheses about the peopling of the Americas. Earlier assessments of its age suggested that the IFC was available for a Clovis-first migration, but subsequent developments now suggest a pre-Clovis occupation of the Americas that occurred before the opening of the IFC, thus supporting a Pacific coastal migration route instead. However, large uncertainties in existing ages from the IFC cannot preclude its availability as a route for the first migrations. Resolving this debate over migration route is important for addressing the questions of when and how the first Americans arrived. We report cosmogenic nuclide exposure ages that show that the final opening of the IFC occurred well after pre-Clovis occupation.

Abstract
The Clovis-first model for the peopling of the Americas by ∼13.4 ka has long invoked the Ice-Free Corridor (IFC) between the retreating margins of the Cordilleran and Laurentide ice sheets as the migration route from Alaska and the Yukon down to the Great Plains. Evidence from archaeology and ancient genomics, however, now suggests that pre-Clovis migrations occurred by at least ∼15.5 to 16.0 ka or earlier than most recent assessments of the age of IFC opening at ∼14 to 15 ka, lending support to the use of a Pacific coast migration route instead. Uncertainties in ages from the IFC used in these assessments, however, allow for an earlier IFC opening which would be consistent with the availability of the IFC as a migration route by ∼15.5 to 16.0 ka. Here, we use 64 cosmogenic (10Be) exposure ages to closely date the age of the full opening of the IFC at 13.8 ± 0.5 ka. Our results thus clearly establish that the IFC was not available for the first peopling of the Americas after the Last Glacial Maximum, whereas extensive geochronological data from the Pacific coast support its earlier availability as a coastal migration route.