New evidence on the sequence of deglacial warming in the tropical Indian Ocean

The transition from the Last Glacial Maximum to the Holocene was an internal of climate variability that was characterised by large spatial and temporal variations. Here we show that deglaciation warming in the northern Indian Ocean was initiated ca. 19 ka, which is contemporary with deglaciation warming in the Antarctica and Southern Ocean. A gradual warming occurred during the glacial/Holocene transition in the northern Indian Ocean, unlike the two‐step warming seen in Greenland and the North Atlantic. Synchronous deglacial warming ca. 19 ka in Antarctica and the northern Indian Ocean suggests a strong connection in the propagation of climate signals between Antarctica and the Indian Ocean, probably through the Indonesian Throughflow and/or Subantarctic Mode Water. Copyright © 2010 John Wiley & Sons, Ltd.     

Record of a Mid-Pleistocene depositional anomaly in West Antarctic continental margin sediments: an indicator for ice-sheet collapse?

Modern global warming is likely to cause future melting of Earth's polar ice sheets that may result in dramatic sea-level rise. A possible collapse of the West Antarctic Ice Sheet (WAIS) alone, which is considered highly vulnerable as it is mainly based below sea level, may raise global sea level by up to 5–6 m. Despite the importance of the WAIS for changes in global sea level, its response to the glacial–interglacial cycles of the Quaternary is poorly constrained. Moreover, the geological evidence for the disintegration of the WAIS at some time within the last ca. 750 kyr, possibly during Marine Isotope Stage (MIS) 11 (424–374 ka), is ambiguous. Here we present physical properties, palaeomagnetic, geochemical and clay mineralogical data from a glaciomarine sedimentary sequence that was recovered from the West Antarctic continental margin in the Amundsen Sea and spans more than the last 1 Myr. Within the sedimentary sequence, proxies for biological productivity (such as biogenic opal and the barium/aluminum ratio) and the supply of lithogenic detritus from the West Antarctic hinterland (such as ice-rafted debris and clay minerals) exhibit cyclic fluctuations in accordance with the glacial–interglacial cycles of the Quaternary. A prominent depositional anomaly spans MIS 15–MIS 13 (621–478 ka). The proxies for biological productivity and lithogenic sediment supply indicate that this interval has the characteristics of a single, prolonged interglacial period. Even though no proxy suggests environmental conditions much different from today, we conclude that, if the WAIS collapsed during the last 800 kyr, then MIS 15–MIS 13 was the most likely time period. Apparently, the duration rather than the strength of interglacial conditions was the crucial factor for the WAIS drawdown. A comparison with various marine and terrestrial climate archives from around the world corroborates that unusual environmental conditions prevailed throughout MIS 15–MIS 13. Some of these anomalies are observed in the pelagic Southern Ocean and the South Atlantic and might originate in major ice-sheet drawdown in Antarctica, but further research is required to test this hypothesis.     

Precessional forcing of tropical vegetation carbon storage

Since the Mid Pleistocene Revolution, which occurred about one million years ago, global temperatures have fluctuated with a quasi‐periodicity of ca. 100 ka. The pattern of past change in the extent of woodlands, and therefore by inference vegetation carbon storage, has been demonstrated to have a strong positive link with this global temperature change at high and mid latitudes. However, understanding of climate systems and ecosystem function indicates that the pattern of woodland change at low latitudes may follow a fundamentally different pattern. We present output from the intermediate complexity model GENIE‐1, comprising a single transient simulation over the last 800 ka and a 174‐member ensemble of 130 ka transient simulations over the last glacial cycle. These simulations suggest that while vegetation carbon storage in mid–high northern latitudes robustly follows the characteristic ca. 100 ka cycle, this signal is not a robust feature of tropical vegetation, which is subject to stronger direct forcing by the precessional (21 ka) orbital cycle (albeit with a highly uncertain response). We conclude that the correlation of palaeoenvironmental records from low latitudes with global temperature change must be done with caution. Copyright © 2011 John Wiley & Sons, Ltd.     

末次冰消期滇西地区气候突变事件:湖泊孢粉记录

在末次冰消期总体持续增温的过程中,全球气候经历了一系列以"快速增温/降温"为主要特征的千-数十年尺度的突变事件.由于这些气候突变事件具有明显的高频特性,需要在全球范围不同地区开展更多高分辨率的古气候研究,用于进行突变事件的对比和机制的探讨.本研究对比滇西南腾冲青海湖、滇西北泸沽湖和高山湖泊天才湖约2万以来的孢粉、炭屑记录,揭示了中国滇西地区末次冰消期的植被演替与气候变化历史,探讨了末次冰消期存在的气候突变事件.结果表明,滇西地区末次冰消期开始转暖发生在约19 ka(1 ka=1000 cal. a B. P.);冰消期开始以后,滇西地区气候普遍依次在 17. 5±0. 5~15. 2±0. 1 ka期间、 15. 2±0. 1~14. 3±0. 1 ka期间、 14. 3± 0. 1~12. 9±0. 1 ka期间和12. 9±0. 1~11. 7±0. 2 ka期间存在冷干-逐渐变暖变湿-明显更暖湿-温度湿度略有下降等这几个突变事件,它们在时间上分别对应于H1冷事件、波令前增暖期、 B/A暖期和YD冷事件;滇西地区比较一致地在 11. 7±0. 2 ka进入全新世.除此之外,滇西北地区在约17. 7~17. 0 ka期间可能还存在一次短暂的较明显的暖湿期.对末次冰消期气候变化机制的探讨认为,末次冰消期开始转暖及以后逐渐增温的趋势主要受夏季太阳辐射量从约20 ka逐渐增加,到11 ka左右达到峰值的控制;而末次冰消期发生的气候突变事件如H1冷事件、波令前增暖期、 B/A暖期和YD冷事件主要是受大西洋温盐环流的影响,同时温室气体浓度的变化也起了重要的调制作用.     

Last Deglaciation Climatic Fluctuation Record by the Palaeo-Daocheng Ice Cap,Southeastern Qinghai-Tibetan Plateau

The last deglaciation, a key period for understanding present and future climate changes, has long been the hot topic for palaeoclimatological study. The Qinghai-Tibetan Plateau(QTP) is often a target study area for understanding hemispheric, or even global environment changes. The glacial landforms on the QTP provide a unique perspective for its climate change. In order to investigate the onset of the last deglaciation at the QTP and its regional correlation, the terrestrial cosmogenic nuclides(TCN) 10 Be and 26 Al surface exposure dating was chosen to date the roche moutonnée, the polished surface and the moraine debris located at the palaeo-Daocheng Ice Cap(pDIC), southeastern QTP. Our results show that the onset of the last deglaciation is at about 19 ka, followed by another warming event occurring around 15 ka in the p-DIC area. These timings agree well with other records, e.g. equivalent with a rapid sea level rise at 19 ka and the onset of B?lling warming event at about 15 ka. Thus, our new data can provide good reveal constraint on the climate evolution at the QTP.     

Does the Agulhas Current amplify global temperatures during super‐interglacials?

Future projections of climate suggest our planet is moving into a ‘super‐interglacial’. Here we report a global synthesis of ice, marine and terrestrial data from a recent palaeoclimate equivalent, the Last Interglacial (ca. 130–116 ka ago). Our analysis suggests global temperatures were on average ～1.5°C higher than today (relative to the AD 1961–1990 period). Intriguingly, we identify several Indian Ocean Last Interglacial sequences that suggest persistent early warming, consistent with leakage of warm, saline waters from the Agulhas Current into the Atlantic, intensifying meridional ocean circulation and increasing global temperatures. This mechanism may have played a significant positive feedback role during super‐interglacials and could become increasingly important in the future. These results provide an important insight into a future 2°C climate stabilisation scenario. Copyright © 2010 John Wiley & Sons, Ltd.     

The last deglaciation in the Picos de Europa National Park (Cantabrian Mountains,northern Spain)

A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd.     

西藏纳木错地区约120kaBP以来的古植被、古气候与湖面变化

西藏纳木错湖相沉积的U系和^11C测年结果表明，湖泊沿岸的6级湖岸阶地及拔湖约48～139．2m的高位湖相沉积形成于约120ka BP以来的晚第四纪。本文根据该套湖相层的发育和其中的孢粉组合特征对纳木错地区约120ka BP以来的湖面变化与古植被、古气候变迁进行了探讨。结果表明，纳木错地区晚更新世以来经历了频繁的湖面波动、气候的冷暖与干湿变化以及森林—草原与草原植被的交替演化。其总体特征是：约115．9ka BP时，纳木错湖面最高。在116～78ka BP期间，该区气候温和凉爽或温和偏湿，植被以疏林草原与森林草原或森林的交替出现为特征，湖面经历了较大幅度的波动，但基本保持在拔湖140～88m之间。在78～53ka BP期间，该区气候干冷，植被以疏林草原为主，湖面大幅度下降，并在拔湖约36～48m之间波动。约53～32ka BP期间，气候转为温暖偏湿或温暖湿润，湖面波动于拔湖约15～28m之间，波动较为频繁。与阶地的发育相对应，该时期内包含了3次明显的暖期和湖面波动过程，区域植被主要以松、蒿、桦为主，为含一定量的冷杉的森林。其中36ka BP左右气候最温暖湿润，区域内可能出现针叶林或针阔混交林。约32～12ka BP期间，该区气候最为干冷，古植被以草原和疏林草原为主，湖面再次发生较大幅度的下降，最低可至拔湖约8m处，但通常维持在拔湖约12～17m之间。约11．8～4．2ka BP期间，气候整体较为暖湿，其中在约8．4～4．2ka BP期间气候最温暖湿润，该区可能发育针叶林或针阔混交林，湖面波动于拔湖2～9m之间，整体波动幅度较小，但波动最为频繁。区域气候对比发现，纳木错地区的冷、暖气候变化过程与整个青藏高原乃至北半球的气候变化基本是一致的，特别是阶地下切所反映的湖面退缩过程与北大西洋的Henrich冷事件之间具有很好的对应关系。     

Holocene alpine glaciation inferred from lacustrine sediments on northeastern Baffin Island,Arctic Canada

With accelerated melting of alpine glaciers, understanding the future state of the cryosphere is critical. Because the observational record of glacier response to climate change is short, palaeo‐records of glacier change are needed. Using proglacial lake sediments, which contain continuous and datable records of past glacier activity, we investigate Holocene glacier fluctuations on northeastern Baffin Island. Basal radiocarbon ages from three lakes constrain Laurentide Ice Sheet retreat by ca. 10.5 ka. High sedimentation rates (0.03 cm a^?1) and continuous minerogenic sedimentation throughout the Holocene in proglacial lakes, in contrast to organic‐rich sediments and low sedimentation rates (0.005 cm a^?1) in neighbouring non‐glacial lakes, suggest that glaciers may have persisted in proglacial lake catchments since regional deglaciation. The presence of varves and relatively high magnetic susceptibility from 10 to 6 ka and since 2 ka in one proglacial lake suggest minimum Holocene glacier extent ca. 6–2 ka. Moraine evidence and proglacial and threshold lake sediments indicate that the maximum Holocene glacier extent occurred during the Little Ice Age. The finding that glaciers likely persisted through the Holocene is surprising, given that regional proxy records reveal summer temperatures several degrees warmer than today, and may be due to shorter ablation seasons and greater accumulation‐season precipitation. Copyright © 2009 John Wiley & Sons, Ltd.     

Paleogeography of the Laptev Sea eastern shelf in the first half of Holocene based on faunal and palynological evidence

The Holocene paleogeography of the Laptev Sea eastern shelf is reconstructed based on mollusks, foraminifers, ostracodes, spores and pollen found for the first time. Environmental changes in the course of the postglacial (Holocene) transgression are detectable from quantitative analysis of three ostracod assemblages. Three phases of the transgression are established based on ostracode assemblages from the AMS ¹⁴C-dated core from the ancient valley of Yana River, central part of the Laptev Sea eastern shelf. After the first phase of coastal brackish-water environment (11.3–11.1 ka), shallow-water marine taxa appeared in the transitional phase (11.1–10.3 ka), and the third phase of modern sea conditions commenced 10.3 ka ago. Spore and pollen assemblages from the core indicate that the early Holocene land vegetation was dominated by tundra plant communities adapted to climatic conditions not warmer than at present. In the interval of 9.3–8.0 ka, climate was increasingly humid and warm, and forest-tundra vegetation occupied more favorable zones of the region.     

Quantitative inter‐annual and decadal June–July–August temperature variability ca. 570 BC to AD 120 (Iron Age–Roman Period) reconstructed from the varved sediments of Lake Silvaplana,Switzerland

Annually resolved June–July–August (JJA) temperatures from ca. 570 BC to AD 120 (±100 a; approximately 690 varve years) were quantified from biogenic silica and chironomids (Type II regression; Standard Major Axis calibration‐in‐time) preserved in the varved sediments of Lake Silvaplana, Switzerland. Using 30 a (climatology) moving averages and detrended standard deviations (mean–variability change, MVC), moving linear trends, change points and wavelets, reconstructed temperatures were partitioned into a warmer (+0.3°C; ca. 570–351 BC), cooler (?0.2°C; ca. 350–16 BC) and moderate period (+0.1°C; ca. 15 BC to AD 120) relative to the reconstruction average (10.9°C; reference AD 1950–2000 = 9.8°C). Warm and variable JJA temperatures at the Late Iron Age–Roman Period transition (approximately 50 BC to AD 100 in this region) and a cold anomaly around 470 BC (Early–Late Iron Age) were inferred. Inter‐annual and decadal temperature variability was greater from ca. 570 BC to AD 120 than the last millennium, whereas multi‐decadal and lower‐frequency temperature variability were comparable, as evident in wavelet plots. Using MVC plots of reconstructed JJA temperatures from ca. 570 BC to AD 120, we verified current trends and European climate model outputs for the 21st century, which suggest increased inter‐annual summer temperature variability and extremes in a generally warmer climate (heteroscedasticity; hotspot of variability). We compared these results to MVC plots of instrumental and reconstructed temperatures (from the same sediment core and proxies but a different study) from AD 1177 to AD 2000. Our reconstructed JJA temperatures from ca. 570 BC to AD 120 showed that inter‐annual JJA temperature variability increased rapidly above a threshold of ～10°C mean JJA temperature. This increase accelerated with continued warming up to >11.5°C. We suggest that the Roman Period serves with respect to inter‐annual variability as an analogue for warmer 21st‐century JJA temperatures in the Alps. Copyright © 2011 John Wiley & Sons, Ltd.     

Ice‐rafting patterns on the western Svalbard slope 74–0 ka: interplay between ice‐sheet activity,climate and ocean circulation

The distribution of ice‐rafted detritus (IRD) is studied in three cores from the western Svalbard slope (1130–1880 m water depth, 76–78°N) covering the period 74–0 ka. The aim was to provide new insight into the dynamics of the Svalbard–Barents Sea Ice Sheet during Marine Isotope Stages (MIS) 4–1 to get a better understanding of ice‐sheet interactions with changes in ocean circulation and climate on orbital and millennial (Dansgaard–Oeschger events of stadial–interstadial) time scales. The results show that concentration, flux, composition and grain‐size of IRD vary with climate and ocean temperature on both orbital and millennial time scales. The IRD consists mainly of fragments of siltstones and mono‐crystalline transparent quartz (referred to as ‘quartz’). IRD dominated by siltstones has a local Svalbard–Barents Sea source, while IRD dominated by quartz is from distant sources. Local siltstone‐rich IRD predominates in warmer climatic phases (interstadials), while the proportion of allochthonous quartz‐rich IRD increases in cold phases (glacials and stadials/Heinrich events). During the Last Glacial Maximum and early deglaciation at 24–16.1 ka, the quartz content reached up to >90%. In warm climate, local iceberg calving apparently increased and the warmer ocean surface caused faster melting. During the glacial maxima (MIS 4 and MIS 2) and during cold stadials and Heinrich events, the local ice‐sheets must have been relatively stable with low ablation. During ice retreat phases of the MIS 4/3 and MIS 2/1 transitions, maxima in IRD deposition were dominated by local coarse‐grained IRD. These maxima correlate with episodes of climate warming, indicating a rapid, stepwise retreat of the Svalbard–Barents Sea Ice Sheet in phase with millennial‐scale climate oscillations.     

OSL chronology of sand deposits and climate change of last 18 ka in Gurbantunggut Desert,northwest China

The development of the Gurbantunggut Desert is mainly controlled by the Westerly wind, and at present has little influence from Indian and Southeast Asian monsoons. A combined study using optically stimulated luminescence (OSL) dating, ground‐penetrating radar (GPR) surveys and climatic proxies analysis was carried out in the southern part of the desert. The chronology extends back to 18 ka and is constructed based on 16 OSL ages from boreholes in the linear dune body and the inter‐dune area. The chronology suggests that sand deposition in the last 18 ka experienced two rapid accumulation phases at 11 and 2.5 ka ago which were also evident from the GPR surveys. These periods relate to increased aridity in the region. Five climate phases are identified from the last 18 ka, based on the OSL chronology and climatic proxy analysis with grain size and magnetic susceptibility measurements. The deglacial period (18.3–10.4 ka) is characterized by climate instability and possible glacial melting events. The Holocene Optimum peaked 8.5 ka and terminated 3.6 ka ago, when the regional climate became arid. OSL samples from the dune body cluster around 2.5 ka, which indicates rapid advance/extension of dune bodies at this time. Copyright © 2011 John Wiley & Sons, Ltd.     

Hässeldala – a key site for Last Termination climate events in northern Europe

The Last Termination (19 000–11 000 a BP) with its rapid and distinct climate shifts provides a perfect laboratory to study the nature and regional impact of climate variability. The sedimentary succession from the ancient lake at Hässeldala Port in southern Sweden with its distinct Lateglacial/early Holocene stratigraphy (>14.1–9.5 cal. ka BP) is one of the few chronologically well‐constrained, multi‐proxy sites in Europe that capture a variety of local and regional climatic and environmental signals. Here we present Hässeldala's multi‐proxy records (lithology, geochemistry, pollen, diatoms, chironomids, biomarkers, hydrogen isotopes) in a refined age model and place the observed changes in lake status, catchment vegetation, summer temperatures and hydroclimate in a wider regional context. Reconstructed mean July temperatures increased between c. 14.1 and c. 13.1 cal. ka BP and subsequently declined. This latter cooling coincided with drier hydroclimatic conditions that were probably associated with a freshening of the Nordic Seas and started a few hundred years before the onset of Greenland Stadial 1 (c. 12.9 cal. ka BP). Our proxies suggest a further shift towards colder and drier conditions as late as c. 12.7 cal. ka BP, which was followed by the establishment of a stadial climate regime (c. 12.5–11.8 cal. ka BP). The onset of warmer and wetter conditions preceded the Holocene warming over Greenland by c. 200 years. Hässeldala's proxies thus highlight the complexity of environmental and hydrological responses across abrupt climate transitions in northern Europe.     

毛乌素沙漠东南缘全新世剖面光释光年代及古气候意义

在毛乌素沙漠东南缘锦界地区发现的具有3层深棕色至黑色古土壤的全新世剖面,记录了至少3次大型沙地固定与活化的交替演化.在锦界剖面厚约5m的全新世地层中采集了10个光释光样品,利用石英光释光测年单片再生法(SAR),建立了锦界剖面全新世(>7.5-0.2ka)年代格架.结合粒度、磁化率气候变化代用指标和光释光年龄序列,得到...     

Insight into the Last Glacial Maximum climate and environments of the Baikal region

This study presents a multi‐proxy record from Lake Kotokel in the Baikal region at decadal‐to‐multidecadal resolution and provides a reconstruction of terrestrial and aquatic environments in the area during a 2000‐year interval of globally harsh climate often referred to as the Last Glacial Maximum (LGM). The studied lake is situated near the eastern shoreline of Lake Baikal, in a climatically sensitive zone that hosts boreal taiga and cold deciduous forests, cold steppe associations typical for northern Mongolia, and mountain tundra vegetation. The results provide a detailed picture of the period in focus, indicating (i) a driest phase (c. 24.0–23.4 cal. ka BP) with low precipitation, high summer evaporation, and low lake levels, (ii) a transitional interval of unstable conditions (c. 23.4–22.6 cal. ka BP), and (iii) a phase (c. 22.6–22.0 cal. ka BP) of relatively high precipitation (and moisture availability) and relatively high lake levels. One hotly debated issue in late Quaternary research is regional summer thermal conditions during the LGM. Our chironomid‐based reconstruction suggests at least 3.5 °C higher than present summer temperatures between c. 22.6 and 22.0 cal. ka BP, which are well in line with warmer and wetter conditions in the North Atlantic region inferred from Greenland ice‐cores. Overall, it appears that environments in central Eurasia during the LGM were affected by much colder than present winter temperatures and higher than present summer temperatures, although the effects of temperature oscillations were strongly influenced by changes in humidity.     

Glacial and environmental changes over the last 60 000 years in the Polar Ural Mountains,Arctic Russia,inferred from a high‐resolution lake record and other observations from adjacent areas

Our knowledge about the glaciation history in the Russian Arctic has to a large extent been based on geomorphological mapping supplemented by studies of short stratigraphical sequences found in exposed sections. Here we present new geochronological data from the Polar Ural Mountains along with a high‐resolution sediment record from Bolshoye Shchuchye, the largest and deepest lake in the mountain range. Seismic profiles show that the lake contains a 160‐m‐thick sequence of unconsolidated lacustrine sediments. A well‐dated 24‐m‐long core from the southern end of the lake spans the last 24 cal. ka. From downward extrapolation of sedimentation rates we estimate that sedimentation started about 50–60 ka ago, most likely just after a large glacier had eroded older sediments from the basin. Terrestrial cosmogenic nuclide (TCN) exposure dating (¹⁰Be) of boulders and Optically Stimulated Luminescence (OSL) dating of sediments indicate that this part of the Ural Mountains was last covered by a coherent ice‐field complex during Marine Isotope Stage (MIS) 4. A regrowth of the glaciers took place during a late stage of MIS 3, but the central valleys remained ice free until the present. The presence of small‐ and medium‐sized glaciers during MIS 2 is reflected by a sequence of glacial varves and a high sedimentation rate in the lake basin and likewise from ¹⁰Be dating of glacial boulders. The maximum extent of the mountain glaciers during MIS 2 was attained prior to 24 cal. ka BP. Some small present‐day glaciers, which are now disappearing completely due to climate warming, were only slightly larger during the Last Glacial Maximum (LGM) as compared to AD 1953. A marked decrease in sedimentation rate around 18–17 cal. ka BP indicates that the glaciers then became smaller and probably disappeared altogether around 15–14 cal. ka BP.     

New age estimates and climatostratigraphic correlations for the Borrobol and Penifiler Tephras: evidence from Abernethy Forest,Scotland

The emerging tephrostratigraphy of NW Europe spanning the last termination (ca. 15–9 ka) provides the potential for synchronizing marine, ice‐core and terrestrial records, but is currently compromised by stratigraphic complications, geochemical ambiguity and imprecise age estimates for some layers. Here we present new tephrostratigraphic, radiocarbon and chironomid‐based palaeotemperature data from Abernethy Forest, Scotland, that refine the ages and stratigraphic positions of the Borrobol and Penifiler tephras. The Borrobol Tephra (14.14–13.95 cal ka BP) was deposited in a relatively warm period equated with Greenland Interstadial sub‐stage GI‐1e. The younger Penifiler Tephra (14.09–13.65 cal ka BP) is closely associated with a cold oscillation equated with GI‐1d. We also present evidence for a previously undescribed tephra layer that has a major‐element chemical signature identical to the Vedde Ash. It is associated with the warming trend at the end of the Younger Dryas, and dates between 11.79 and 11.20 cal ka BP. Copyright © 2011 John Wiley & Sons, Ltd.     

Mid-Wisconsin seasonal temperatures reconstructed from fossil beetle assemblages in eastern North America: comparisons with other proxy records from the Northern Hemisphere

Mutual climatic range (MCR) analysis was applied to 15 North American beetle assemblages spanning the interval from > 52 000 to 17 200 yr BP, bracketing a Mid-Wisconsin interstadial interval. The analyses yielded estimates of mean July (TMAX) and mean January (TMIN) temperatures. The oldest assemblage (> 52 ka) yielded TMAX values 7.5–8°C lower than present and TMIN values 15–18°C lower than present. A Mid-Wisconsin interstadial warming dating from 43.5–39 ka was rapid and intense. At the peak of the warming event, about 42 ka, TMAX values were only 1–2°C lower than modern. This level of amelioration apparently lasted only about 2000–3000 yr. By 23.7 ka, TMAX values declined to 11.5–10°C lower than modern, but another, small-scale amelioration is indicated by assemblages dating from 20.5 to 19.7 ka. The interstadial event recorded from the site at Titusville, Pennsylvania closely matches the timing and intensity of the climate change estimated from British beetle faunas in the Upton Warren interstadial. Another warm interval (ca. 31–32.5 ka) has been documented from fossil beetle assemblages in Europe and North America. Copyright © 1999 John Wiley & Sons, Ltd.     

Climatic changes since the last deglaciation inferred from a lacustrine sedimentary sequence in the eastern Nanling Mountains,south China

Two sediment cores recovered from Dahu Swamp, which is located in eastern Nanling Mountains in south China, were selected for investigation of palaeoclimatic changes. Multi‐proxy records of the two cores including lithological variation, organic carbon isotope ratio, dry bulk density, organic matter content, magnetic susceptibility, humification degree, median grain size and geochemical proxies reveal that during the last deglaciation three drier phases correspond to the Oldest, Older and Younger Dryas cooling events, and the intercalated two wetter phases synchronise with the Bølling and Allerød warming events. The Holocene Optimum, which was resulted from a strengthening of the East Asian (EA) summer monsoon, occurred in the early and mid Holocene (ca. 10–6 cal. ka BP). In the mid and late Holocene (ca. 6–3 cal. ka BP), a prevailing dry climate suggested a weakening of the EA summer monsoon. The general trend of Holocene climatic changes in this study agrees with the 25° N summer solar insolation, suggesting that orbitally induced insolation may have played an important role in the Holocene climate in the study region. Copyright © 2010 John Wiley & Sons, Ltd.