Last Glacial Interglacial Transition Research Articles

Modelled sensitivity of Monte San Lorenzo ice cap, Patagonian Andes, to past and present climate

Sparse measurements of glacier mass balance, velocity and ice thickness in Patagonia challenge our ability to understand glacier sensitivity to climate change and relate past glacier fluctuations to palaeoclimate change. Small ice caps, such as Monte San Lorenzo, have short response times and high climate sensitivity, making well-dated moraines in their glacier foregrounds an important tool for exploring glacier response to rapid changes in palaeoclimate. Here, the Parallel Ice Sheet Model (PISM) is used to model ice flow across a domain centred on the Monte San Lorenzo ice cap. Ice-flow parameters are calibrated to match present-day ice extent, velocity and thickness. Our aim is, firstly, to quantify present-day physical glacier properties, and ice cap dynamics and sensitivities, and secondarily, to evaluate the controls on the deglaciation of the ice cap within the context of the Southern Hemisphere palaeoclimate system during the Last Glacial-Interglacial Transition (LGIT). The simulated present-day ice cap shows high surface mass flux, with ablation at outlet glacier tongues up to 18 m w. e. a−1, accumulation at the highest elevations of up to 5.5 m w. e. a−1 and a simulated Equilibrium Line Altitude (ELA) of 1750–2000 m asl. The ice cap is more sensitive to changes in precipitation relative to changes in temperature. We provide envelopes with likely ranges of palaeotemperature and palaeoprecipitation for glacial advances to moraines formed during the Last Glacial-Interglacial Transition and Holocene. Our numerical model predicts that cooling and an increase in precipitation is required to force glacial advance to mapped moraine limits at 12.1 ka (2°C cooler, 50% more precipitation), 5.6 ka (0°C cooler, 50% more precipitation) and 0.2 ka (1°C cooler, 25% more precipitation). Our modelling results thus provide insights into the present-day mass balance, thermal regime and velocity of the ice cap, explores the sensitivities of this ice cap to various model and climatic parameters, and provide palaeoclimatic envelopes for readvances during the LGIT and Holocene in Patagonia.

Volcanism and the Greenland ice cores: A new tephrochronological framework for the last glacial-interglacial transition (LGIT) based on cryptotephra deposits in three ice cores

Chemical profiles from Greenland ice cores show that the frequency of volcanism was higher during the last glacial-interglacial transition (LGIT) and early Holocene, (17–9 ka b2k) than in any other period during the last 110 kyr. This increased frequency has partly been linked to climate-driven melting of the Icelandic ice sheet during the last deglaciation, with regional isostatic changes thought to alter mantle viscosity and lead to more eruptions. Our study is the first to construct a comprehensive tephrochronological framework from Greenland ice cores over the LGIT to aid in the reconstruction of volcanic activity over this period. The framework is based on extensive high-resolution sampling of three Greenland ice cores between 17.4 and 11.6 ka b2k and comprises a total of 64 cryptotephra deposits from the NGRIP, GRIP and NEEM ice cores. We show that many of these tephras are preserved within the core without an associated chemical signature in the ice, which implies that reconstructions of volcanism based solely on glacio-chemical indicators might underestimate the number of events. Single glass shards from each deposit were geochemically characterised to trace the volcanic source and many of these deposits could be correlated between cores. We show that the 64 deposits represent tephra deposits from 42 separate volcanic events, and of these, 39 are from Iceland, two from the north Pacific region (Japan and USA) and one has an unknown source. Six deposits can be correlated to terrestrial and/or marine tephra deposits in the Northern Hemisphere and the remaining 36 are unreported in other archives. We did not locate tephra from the compositionally distinctive Laacher See eruption (∼13 ka b2k) in our records. Combining our new discoveries with the previously published tephra framework, raises the number of individual tephra horizons found in Greenland ice over this interval to 50. This significantly improves the regional tephrochronological framework, our knowledge of the eruptive history of Iceland during the LGIT and provides new tephra constraints over key LGIT climate events. Consequentially, this framework can guide sampling strategies of future tephra studies in the terrestrial and marine realms aiming to link these records to the Greenland ice cores to assess regional climate synchroneity.

Continuous vegetation record of the Greater Cape Floristic Region (South Africa) covering the past 300 000 years (IODP U1479)

Abstract. The Greater Cape Floristic Region (GCFR) of South Africa is a biodiversity hotspot of global significance, and its archeological record has substantially contributed to the understanding of modern human origins. For both reasons, the climate and vegetation history of southwestern South Africa is of interest to numerous fields. Currently known paleoenvironmental records cover the Holocene, the last glacial–interglacial transition and parts of the last glaciation but do not encompass a full glacial–interglacial cycle. To obtain a continuous vegetation record of the last Pleistocene glacial–interglacial cycles, we studied pollen, spores and micro-charcoal of deep-sea sediments from IODP Site U1479 retrieved from SW of Cape Town. We compare our palynological results of the Pleistocene with previously published results of Pliocene material from the same site. We find that the vegetation of the GCFR, in particular fynbos and afrotemperate forest, responds to precessional forcing of climate. The micro-charcoal record confirms the importance of fires in the fynbos vegetation. Ericaceae-rich and Asteraceae-rich types of fynbos could extend on the western part of the Paleo-Agulhas Plain (PAP), which emerged during periods of low sea level of the Pleistocene.

Environmental changes in the late Allerød and early Younger Dryas in the Netherlands: a multiproxy high-resolution record from a site with two Pinus sylvestris populations

In the Netherlands, several proxies of climate change during the Last Glacial-Interglacial Transition (LGIT) (c. 14,700 to 11,700 b2k) have been investigated in detail over the last few decades. The present paper presents two tree-ring chronologies LETR-A (n = 16, timespan 106 rings) and LETR-B (n = 24, timespan 201 rings) from in situ subfossil pine remains (Pinus sylvestris) discovered at Leusden-Den Treek in the Netherlands that date from the Bølling-Allerød interstadial (GI-1). Using a multiproxy approach (both abiotic and biotic), it was possible to study local woodland development in detail as part of long-term environmental change. Moreover, the trees opened up possibilities for dendrochronological and dendroclimatological research. The tree-ring series show the occurrence of two successive phases of pine woodland development, which were 14C dated with high precision and calibrated using the recent IntCal20 14C calibration curve: 13,450–13,396 to 13,370–13,316 calBP (series LETR-A) and 12,952–12,937 to 12,754–12,739 calBP (series LETR-B). At the north-western boundary of its ecotone, Pinus was highly sensitive to climate change during the latter part of GI-1 and the transition to GS-1. The inability to set fruit and the disappearance of the pine woodland within decades before and after c. 12,745 calBP is interpreted as the vegetational response to abrupt climate deterioration at the start of the Younger Dryas (12,807 ± 12 cal BP).

Stratigraphy and vegetation signals from an upland, landslide-dammed, paleolake during the Last Glacial-Interglacial Transition, Waipaoa Sedimentary System, Hikurangi Margin, eastern North Island, New Zealand

ABSTRACT A recently discovered upland paleolake (Redpath Lake) provides evidence of the expansion of lowland podocarp temperate forest to higher elevations within the tectonically active Waipaoa Sedimentary System (WSS), eastern North Island, New Zealand, during the Last Glacial-Holocene Transition. Interpreted as a localised landslide-dammed lake, lithofacies analyses indicate deposition and preservation in a low energy, sub-aqueous, lacustrine environment. Robust Bayesian-derived age-depth models constrained by key tephra fall beds and independent 14C dating (n = 7) indicate storm-bed frequency of c. 226 yrs on average. The absence of extensive soft-sediment deformation or lake-bed tilting implies that seismic shaking was insignificant during the Lake’s c. 12 ka yr (17.3–5.5 cal ka BP) existence. Pollen spectra extracted from lacustrine deposits include a mix of montane shrubland and lowland podocarp species spanning a well-dated c. 2200-year (c. 16.3–14.1 cal ka BP) period coeval with a phase of significant climate amelioration (late NZCe–5/NZce-4 mild episode), based on biotic proxies during the latter part of the climatically variable Last Glacial-Interglacial Transition (LGIT) (c. 18.2–11.8 cal ka BP). These pollen spectra represent the first New Zealand record of replacement of montane shrublands in terrestrial uplands of the WSS were replaced by lowland podocarp forest.

Duelling narratives of chironomids and pollen explain climate enigmas during The Last Glacial-Interglacial transition in North Island New Zealand

The Last Glacial-Interglacial Transition (LGIT) was a dynamic stage of Earth's history, and the difficulty of reconstructing this complex interval may be compounded by divergent proxy records, often collected from the same archive. To overcome this obstacle, we exploit the contrasting biological preferences of chironomids to both summer temperature and degree days (positive) and pollen to both the length of the growing season (positive) and winter duration (negative), recorded by a small lake in the central North Island of New Zealand. The climate proxy records are anchored to shifting zonal boundaries (e.g., southern westerly wind belt) via the hydrogen isotope ratios of leaf wax n-alkanes (δDwax). These results enable us to interrogate the structure of the LGIT and address two fundamental questions: 1) Is there evidence for Holocene-like temperatures during the early deglacial? and 2) Were early Holocene summers cool?Lake sediment δDwax values indicate a poleward retreat of the westerlies around 18,000 calibrated years before present (cal kyr BP), signalling the onset of climate amelioration for the region. Remarkably, the independently derived summer and mean annual temperature reconstructions are anti-phased. Chironomid-inferred summer temperatures surpass modern values by 17.5 cal kyr BP, whereas pollen-inferred mean annual temperatures remain supressed. Summers cool from 17.5 to 11 cal kyr BP, when they reach a minimum for the record, while winter and mean annual temperatures simultaneously warm to a maximum. The chironomid record generally traces regional insolation, although an Antarctic template imprints on this trend with declining summer temperatures during the Antarctic Cold Reversal (ACR) and warming during the Younger Dryas (YD). Forest development during the early LGIT, on the other hand, is supressed by cool, dry winters, punctuated by severe frosts, despite being set against a backdrop of overall warming; the successional pattern is best explained by a latitudinal retreat of the westerlies. Our findings underscore the complementarity of multiple bioproxy responses and reveal the importance of seasonal heat and energy distribution during the LGIT.

Complexity and asynchrony of climatic drivers and environmental responses during the Last Glacial-Interglacial Transition (LGIT) in north-west Europe

The Last Glacial-Interglacial Transition (ca 16–8 ka BP) in north-west Europe is an important period of climatic change where millennial-scale climatic evolution led to environmental reorganisation. Imprinted upon these long-term changes are a series of short-lived, centennial-scale events that appear to be spatially and temporally complex across Europe. The complexity of environmental change in response to these climatic events is poorly understood because of a paucity of paired investigations that provide evidence of both driver and response variables. We present a high-resolution palynological, charcoal and stable isotopic record alongside chironomid-inferred temperature data from Tirinie, south-east Grampian Highlands, Scotland. The record is stratigraphically and chronologically constrained using tephra and radiocarbon dating. The isotopic and chironomid data reveal centennial-scale climatic deteriorations at ca 14.0; 13.2 and 11.4 cal ka BP. In response to these cooling events, vegetation became more open, fire frequency increased and landscape erosion was common. The reconstruction of both climate and environment reveals asynchrony in the phasing of annual and summer temperature variability, vegetation change and fire for each climatic event. Whilst responses appear strongest following the convergence of annual and summer temperature variability across all events, the ca 13.2 ka BP event reveals a two-stage environmental and fire response to climatic change, and the ca 11.4 ka BP event exhibits environmental change in the absence of summer temperature variability. The data further suggests that fire is an integral component of abrupt climatic change in this part of north-west Europe.

Environmental variability in response to abrupt climatic change during the Last Glacial–Interglacial Transition (16–8 cal ka BP): evidence from Mainland, Orkney

The Last Glacial–Interglacial Transition (LGIT) is a period of climatic complexity where millennial-scale climatic reorganization led to changes in ecosystems. Alongside millennial-scale changes, centennial-scale climatic events have been observed within records from Greenland and continental Europe. The effects of these abrupt events on landscapes and environments are difficult to discern at present. This, in part, relates to low temporal resolutions attained by many studies and the sensitivity of palaeoenvironmental proxies to abrupt change. We present a high-resolution palynological and charcoal study of Quoyloo Meadow, Orkney and use the Principal Curve statistical method to assist in revealing biostratigraphic change. The LGIT vegetation succession on Orkney is presented as open grassland and Empetrum heath during the Windermere Interstadial and early Holocene, and open grassland with Artemisia during the Loch Lomond Stadial. However, a further three phases of ecological change, characterized by expansions of open ground flora, are dated to 14.05–13.63, 10.94–10.8 and 10.2 cal ka BP. The timing of these changes is constrained by cryptotephra of known age. The paper concludes by comparing Quoyloo Meadow with Crudale Meadow, Orkney, and suggests that both Windermere Interstadial records are incomplete and that fire is an important landscape control during the early Holocene.Supplementary material: All raw data associated with this publication: raw pollen counts, charcoal data, Principal Curve and Rate of Change outputs and the age-model output are available at https://doi.org/10.6084/m9.figshare.c.4725269Thematic collection: This article is part of the ‘Early Career Research’ available at: https://www.lyellcollection.org/cc/SJG-early-career-research

The Final Palaeolithic Hunter-Gatherer Colonisation of Lithuania in Light of Recent Palaeoenvironmental Research

This paper critically reviews the culture-historical framework for the re-colonisation of Lithuania during the Final Palaeolithic in the light of recent palaeoclimatic and palaeoenvironmental data. We argue that the existing chronology of the Final Palaeolithic in Lithuania suffers from an undue western European orientation grounded in research history, and that it likely requires reconsideration. The lack of well-constrained excavations, the paucity of both radiocarbon dates and of palaeoenvironmental data pertinent to the Last Glacial-Interglacial Transition (LGIT) lead us to be cautious with regard to the existing chronology. In reviewing the typological classification of the relevant lithic material, we argue in particular that there is a lack of reliable evidence not only for Hamburgian occupation but also for any substantive Federmessergruppen, Brommean and Ahrensburgian presence. Whilst Swiderian sites are better represented, a large majority of these may date to the early Holocene. In light of the current evidence, we question the usefulness of existing archaeological taxonomies for this period and favour a model of punctuated colonisation for the Lithuanian territory, where periodic and ephemeral forager presences are interspersed with longer periods of depopulation. In closing, we outline avenues for future research in the region.

Evidence for a bi-partition of the Younger Dryas Stadial in East Asia associated with inversed climate characteristics compared to Europe

The Younger Dryas Stadial (YDS) was an episode of northern hemispheric cooling which occurred within the Last Glacial Interglacial Transition (LGIT). A major driver for the YDS climate was a weakening of the Atlantic Meridional Overturning Circulation (AMOC). It has been inferred that the AMOC began to strengthen mid-YDS, producing a bipartite structure of the YDS in records from continental Europe. These records imply that the polar front and westerlies shifted northward, producing a warmer second phase of the YDS in Europe. Here we present multi-proxy data from the sediments of Lake Suigetsu (Japan), as evidence that a related bi-partition of the YDS also occurred in East Asia. Besides showing for the first time that the bi-partition was not limited to the North Atlantic/European region, the data also imply a climatic dipole between Europe and East Asia since the cold-warm characteristics are reversed at Lake Suigetsu. We suggest that changes in eastward moisture transport from the North Atlantic are the primary mechanism by which the teleconnection can be explained.

The last maximum ice extent and subsequent deglaciation of the Pyrenees: an overview of recent research

This paper reviews data currently available on the glacial fluctuations that occurred in the Pyrenees between the Würmian Maximum Ice Extent (MIE) and the beginning of the Holocene. It puts the studies published since the end of the 19th century in a historical perspective and focuses on how the methods of investigation used by successive generations of authors led them to paleogeographic and chronologic conclusions that for a time were antagonistic and later became complementary. The inventory and mapping of the ice-marginal deposits has allowed several glacial stades to be identified, and the successive ice boundaries to be outlined. Meanwhile, the weathering grade of moraines and glaciofluvial deposits has allowed Würmian glacial deposits to be distinguished from pre-Würmian ones, and has thus allowed the Würmian Maximum Ice Extent (MIE) –i.e. the starting point of the last deglaciation– to be clearly located. During the 1980s, 14C dating of glaciolacustrine sequences began to indirectly document the timing of the glacial stades responsible for the adjacent frontal or lateral moraines. Over the last decade, in situ-produced cosmogenic nuclides (10Be and 36Cl) have been documenting the deglaciation process more directly because the data are obtained from glacial landforms or deposits such as boulders embedded in frontal or lateral moraines, or ice-polished rock surfaces. On that basis, it is now accepted that (i) the Würmian MIE occurred in the Pyrenees during MIS 4 and not the Global LGM; and that (ii) a major glacial readvance took place during the Global LGM. This ice readvance reached a position close to the MIS 4 icefield boundary in the Eastern part of the range, but apparently not in the west. (iii) Soon after the Global LGM, the Pyrenean ice margin went into major and rapid recession. Even before the beginning of the Lateglacial, the main trunk glaciers had already retreated to the upper parts of the valleys. (iv) The paleogeography of the Pyrenean icefield during the Last Glacial-Interglacial Transition (LGIT) is still partially unknown but all available data indicate that glaciers during the Oldest Dryas (GS-2a) were substantially smaller than during the Global LGM. During the Bølling-Allerød interstadial, the Pyrenean ice margins retreated substantially, and glaciers locally vanished definitively. The Younger Dryas cooling event generated either a short readvance of existing cirque glaciers or the development of rock glaciers.

A second tephra isochron for the Younger Dryas period in northern Europe: The Abernethy Tephra

Visible and non-visible (cryptotephra) volcanic ash layers are increasingly being used to underpin the chronology and high-precision correlation of sequences dating to the last glacial–interglacial transition (LGIT). As the number of sediment records analysed for tephra content rises, and methodological developments permit the detection, extraction and chemical analysis of increasingly scantily represented glass shard concentrations, greater complexity in shard count profiles is revealed. Here we present new evidence from sites in Scotland, and review published evidence from sites elsewhere in NW Europe, that indicate complexity in the eruptive history of Katla volcano during the mid-Younger Dryas and Early Holocene. We propose evidence for a previously-overlooked tephra isochron, here named the Abernethy Tephra, which is consistently found to lie close to the Younger Dryas/Holocene transition. It has a major-element chemical composition indistinguishable from that of the Vedde Ash, which was erupted from the Katla volcano at 12,121 ± 114 cal a BP. The new data suggest that Katla may have erupted again between 11,720–11,230 cal a BP and the subsequent ash fall increases the potential to assess environmental response to Holocene warming across north and west Europe.

The evolution of Palaeolake Flixton and the environmental context of Star Carr, NE. Yorkshire: stratigraphy and sedimentology of the Last Glacial-Interglacial Transition (LGIT) lacustrine sequences

The basal topography and sediments recording the Last Glacial-Interglacial Transition (LGIT) from Palaeolake Flixton, North Yorkshire have been reinvestigated by a detailed auger and borehole survey. The data presented here, from the area to the north of Flixton Island and the River Hertford, suggests the basal topography of Palaeolake Flixton is irregular with deep and areally small basins interspersed within a gravel surface ca. 21m OD. At its shallowest the gravel surface is ca. 2m below current land surface and the deeper, steep-sided basins are up to 9m in depth. Examination of the sediment sequences indicates the deeper basins accumulate sediments from the Dimlington Stadial (DS), Windermere Interstadial (WI), Loch Lomond Stadial (LLS) and the Holocene, whilst the shallower sequences only record the Holocene. The configuration of the deposits in the basins suggest that lake levels declined during the WI from 24 to 23m OD and then fell further during the LLS to ca. 20.90m OD. The lake water levels then rose slowly during the Holocene to a height of between 23 and 24m OD. These fluctuations in lake water level at the transition from the LLS to Holocene perhaps indicate that the configuration of the water body during the resettlement of the area in the Mesolithic was different to previous reconstructions, with lower water levels and a greater area of land exposed for habitation. This highlights the potential for additional preservation of archaeological assemblages in the area of the former lake. Moreover the complex basal stratigraphy suggests that a systematic analyses of the Palaeolake Flixton sedimentary archive is required to resolve high-resolution palaeoclimate data from this lake sequence.

Tracing long‐term tropical montane ecosystem change in the Eastern Arc Mountains of Tanzania

ABSTRACTPollen, charcoal, stable carbon and nitrogen isotope, and radiocarbon analyses are used to reconstruct a palaeoenvironmental record from the Eastern Arc Mountains (EAM), Tanzania, dating back >45 000 years. A sedimentary hiatus covering the last glacial‐interglacial transition (LGIT) and early to mid Holocene follows the lead up to the Last Glacial Maximum (LGM) period. A late Holocene portion of the record is included as a modern analogue. Before 45 000 cal a BP, very low regional pollen counts imply open vegetation surrounding the site. Subsequently, the development of extensive montane forest characterizes a relatively mesic pre‐LGM. The transition into the LGM witnessed a marked shift from C3‐ to C4‐dominated biomass, representing an expansion of open forest dominated by grasses. These changes may be attributed to a combination of enhanced moisture stress and CO2 limitation, factors that may have been exacerbated by an intensive fire regime, as evident from the charcoal record. This is supported by a decrease in montane forest taxa, coupled with an associated expansion of C4 graminoids and ericaceous heathland to form a montane grassland mosaic similar to that previously recorded on other East African mountains around the time of the LGM but not, to date, having been shown in the Eastern Arc Mountains.

The taphonomy of Last Glacial–Interglacial Transition (LGIT) distal volcanic ash in small Scottish lakes

Pyne-O’Donnell, S. 2010: The taphonomy of Last Glacial–Interglacial Transition (LGIT) distal volcanic ash insmall Scottish lakes. Boreas, 10.1111/j.1502-3885.2010.00154.x. ISSN 0300-9483.An extensive micro-tephrostratigraphic survey of three small lakes in the Scottish Inner Hebrides was conductedencompassing the Last Glacial–Interglacial Transition (LGIT). The lakes are highly contrasting in terms of lakearea to catchment ratio, the presence or absence of stream inlets draining the catchment, and in the complexity ofthe catchment drainage network. A suite of distal Icelandic volcanic ashes was consistently detected in all threelakes, with three, namely Penifiler Tephra, Vedde Ash and Ashik Tephra, being common to all the lakes. Theseashes were chosen to examine the taphonomic intercomparability of ash location and concentration among thelakes. Findings reveal that the part played by catchment inlets in determining ash concentration and within-basinlocationappliestomicrotephra layersasmuchasitdoesinstudiesofmacrotephra layerthickness. ThepositionofashconcentrationmaximaisalsoshowntovarysignificantlyfordifferentLGITperiodsandmaybeaconsequenceof lake-level changes, especially during the early Holocene. High-resolution stratigraphic analysis through theVedde Ash visible macrotephra at Loch Ashik reveals a high degree of complexity in taphonomic behaviour be-tween the different geochemical components, with possible implications for the correct interpretation of the iso-chron position. The detection of multiple intact ash isochrons and the taphonomic processes responsible for theirdeposition should prove useful in future tephrostratigraphic surveys, as well as having applications within otherpalaeolimnological disciplines.Sean Pyne-O’Donnell (e-mail: Sean.Pyne-Odonnell@geo.uib.no), Centre for Quaternary Research, Department ofGeography, Royal Holloway, University of London, Egham TW20 0EX, UK; present address: Department of EarthScience, University of Bergen, Alle´gaten 41, N-5007 Bergen, Norway; received 5th November 2009, accepted 19thFebruary 2010.

The stratigraphic context of ultra-distal tephrochron-ology in the last Glacial-Interglacial Transition (LGIT) of Europe

The stratigraphic context of ultra-distal tephrochron-ology in the last Glacial-Interglacial Transition (LGIT) of Europe

A late glacial Antarctic climate teleconnection and variable Holocene seasonality at Lake Pupuke, Auckland, New Zealand

We present the first continuous paleolimnological reconstruction from the North Island of New Zealand (37°S) that spans the last 48.2 cal kyr. A tephra- and radiocarbon-based chronology was developed to infer the timing of marked paleolimnological changes in Lake Pupuke, Auckland, New Zealand, identified using sedimentology, magnetic susceptibility, grain size and geochemistry (carbon, nitrogen and sulphur concentrations and fluxes, carbon and nitrogen stable isotopes). Variable erosional influx, biomass and benthic REDOX conditions are linked to changing effective precipitation and seasonality within three inferred broad intervals of climatic change: (1) the Last Glacial Coldest Phase (LGCP) of reduced effective precipitation and cooler temperatures, from 28.8 to 18.0 cal kyr BP, (2) the Last Glacial Interglacial Transition (LGIT) of increasing effective precipitation and warmer conditions, from 18.0 to 10.2 cal kyr BP, and (3) a Holocene interval of high effective precipitation, beginning with a warm period of limited seasonality from 10.2 cal kyr BP and followed by increasing seasonality from 7.6 cal kyr BP. The LGCP and LGIT also contain millennial-scale climate events, including the coldest inferred glacial conditions during the LGCP from 27.8 to 26.0 and 22.0–19.0 cal kyr BP, and a climate reversal in the LGIT associated with lower lake level, from 14.5 to 13.8 cal kyr BP, coeval with the Antarctic Cold Reversal. The onset of seasonal thermal stratification occurred at 5.7 cal kyr BP and was linked to natural eutrophication of Lake Pupuke, which produced enhanced organic sedimentation.

Changes in fire regimes on the Chinese Loess Plateau since the last glacial maximum and implications for linkages to paleoclimate and past human activity

A high-resolution black carbon (BC) record from 27.5 kyr BP to present was reconstructed using a chemical oxidation method on loess and paleosol samples from the Lijiayuan section of the Chinese Loess Plateau. The black carbon mass sedimentation rates (BCMSR) and carbon isotopic record reveal a paleofire history and its relationship with climate and vegetation changes at the study site. The BCMSR record was decomposed into two components: background BCMSR and the BCMSR peaks. The background BCMSR represents regional fires and shows high fire activities occurred contemporaneous with the Younger Dryas, Older Dryas, Heinrich events and Greenland stadials as registered in the loess grain size record. This suggests a rapid response of regional fires on the Loess Plateau to abrupt climate changes. Spectral analysis of background BCMSR showed two meaningful periodicities of 1620 and 1040 years, close to the cyclicity of the East Asian monsoon as recorded in the stalagmite δ 18O record in Central China. This indicates a tight control of millennial scale wet–dry changes in the monsoonal climate on regional fires on the Loess Plateau. By contrast, the BCMSR peaks are considered to reflect local fire episodes. The occurrences of local fires were more frequent during the last glacial period, with a maximum frequency of ~ 6 episodes/1000 years during the Last Glacial Maximum (LGM) (22.3 to 14.6 kyr BP), when the climate was drier and more continuous grassy fuels existed on the landscape. During the last glacial–interglacial transition (LGIT) period (14.6 to 11.0 kyr BP), fire frequency was largely reduced due to an increase in precipitation and more woody vegetation. If the LGIT period is taken as an analog for the projected near future, then future global warming alone may not produce large wildfires in northwestern China. Wildfires remained infrequent during the early-to-middle Holocene. Biomass burning increased after 4.0 kyr BP, when the climate became drier and land-use was more intensive. BC carbon isotope ratios may well reflect changes in the vegetation being burnt (i.e., grasses versus trees), yielding results consistent with the associated pollen data in the region.

Paleoclimatic and archeological implications of Pleistocene and Holocene environments in Azraq, Jordan

Wetlands are a key archive for paleoclimatic and archeological work, particularly in arid regions, as they provide a focus for human occupation and preserve environmental information. The sedimentary record from 'Ayn Qasiyya, a spring site on the edge of the Azraq Qa, provides a well-dated sequence through the last glacial–interglacial transition (LGIT) allowing environmental changes in the present-day Jordanian desert to be investigated robustly through this time period for the first time. Results show that the wettest period at the site preceded the last glacial maximum, which itself was characterised by marsh formation and a significant Early Epipaleolithic occupation. A sedimentary hiatus between 16 and 10.5 ka suggests a period of drought in the region although seasonal rains and surface waters still allowed seasonal occupation of the Azraq region. Archeological evidence suggests that conditions had improved by the Late Epipaleolithic, about the time of the North Atlantic Younger Dryas. The changes between wet and dry conditions at the site show similarities to patterns in the eastern Mediterranean and in Arabia suggesting the Jordan interior was influenced by changes in both these regions through the LGIT climatic transition.

A 19.5 kyr vegetation history from the central Cederberg Mountains, South Africa: Palynological evidence from rock hyrax middens

In arid and semi-arid areas such as southern Africa, rock hyrax ( Procavia capensis) middens represent an exceptionally valuable source of late Quaternary palaeoenvironmental information. Pollen and stable isotope data derived from two rock hyrax middens extracted from De Rif in the Cederberg Mountains of the southwestern Cape, casts new light on climatic changes that occurred across the Last Glacial–Interglacial Transition (LGIT) and the Holocene (19.5–0.7 cal kBP) and how the region's vegetation responded to these changes. Significant changes in vegetation community composition would be expected in response to environmental changes characteristic of the contrast between ‘glacial’ and ‘interglacial’ climates. However, the pollen assemblages in general indicate that mountain fynbos remained dominant throughout the record and that most of the pollen taxa exhibited only muted frequency variations. This finding could be considered to be inconsistent with indications of marked climatic variations recorded in the stable isotope records for the same midden. An analysis of the geological setting and the bioclimatic affinities of the taxa suggest that the explanation for this inconsistency may lie in the dominating influence of sandstone substrates and the relative resilience of mountain fynbos vegetation to climate change.