Pollen-inferred Late-Glacial and Holocene climate in southern Balkans (Lake Maliq)

High-temporal resolution analysis of pollen records from Lake Maliq (Albania) provides quantitative estimates of monthly temperature and precipitation changes since the last deglaciation. The climate parameters were estimated using the best modern analogue technique with an updated modern pollen-climate database composed of 2748 surface samples. The record shows two main cooling phases in the Maliq area (the Oldest and Younger Dryas) and a cooling event around 8200 years, which suggests that the forcing factors driving climate variations in the North Atlantic area since the Last Glacial period also extended their influence into the Mediterranean area. The Oldest and Younger Dryas are also characterized by an arid climate and a change in the seasonality of precipitation: the summer precipitation tends to be greater during the cooling phases than during the temperate periods. The Holocene climate is relatively stable and the values of each parameter reach their modern levels, except for an arid event between 8300 and 8100 cal BP.     

Postglacial climate and vegetation history, north-central Kola Peninsula, Russia: pollen and diatom records from Lake Yarnyshnoe-3

A sediment core from Lake Yarnyshnoe-3 (69°04'N; 36°04'E), an emerged coastal lake from the tundra of the north-central Kola Peninsula, has been analyzed for fossil pollen and diatoms. The pollen record shows the Younger Dryas event marked by increasing Artemisia coupled with decreases in Poaceae, Cyperaceae and Salix at c. 10 700 to 10 000 BP. This core provides the first well-defined palynological record of the Younger Dryas event on the Kola Peninsula. Stomates from Pinus were recovered from the core interval between 8000 and 6000 BP. The stomates, coupled with elevated values of pine pollen, indicate that Pinus sylvestris grew near the arctic coastline of the central Kola Peninsula in the middle Holocene. However, the small number of stomates suggests that pines were not plentiful. The diatom record from the core reflects basin isolation from the sea and indicates additional limnological changes during the climate transition between c. 5000 and 4000 BP. The broadly similar climate and vegetation history on the north-central Kola Peninsula and in Fennoscandia demonstrates the propagation of late glacial and Holocene climate events from the North Atlantic region into the Eurasian Arctic.     

Climatic oscillations in central Italy during the Last Glacial–Holocene transition: the record from Lake Accesa

This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake‐level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial–early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north‐central Italy). On the basis of an age–depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas–Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700–11 650 cal. yr BP. Four sub‐millennial scale cooling phases were recognised from pollen data at ca. 14 300–14 200, 13 900–13 700, 13 400–13 100 and 11 350–11 150 cal. yr BP. The last three may be Mediterranean equivalents to the Older Dryas (GI‐1d), Intra‐Allerød (GI‐1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice‐core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra‐Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake‐level record shows that the sub‐millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2 ka cold reversal. Copyright © 2006 John Wiley & Sons, Ltd.     

Extent, timing, and climatic implications of glacier advances Mount Rainier, Washington, U.S.A., at the pleistocene/holocene transition

The North Atlantic Younger Dryas climatic reversal did not cause a glacier advance on Mount Rainier. The glaciers on Mount Rainier seem to have advanced in response to regional or local shifts in climate. However, the Younger Dryas climatic reversal may have affected the Mount Rainier area, causing a cold, but dry, climate unfavorable to glacier advances. Glaciers in the vicinity of Mount Rainier advanced twice during late glacial/early Holocene time. Radiocarbon dates obtained from lake sediments adjacent to the corresponding moraines are concordant, indicating that the ages for the advances are closely limiting. The first advance occurred before 11,300 ¹⁴C yr BP (13,200 cal yr BP). During the North Atlantic Younger Dryas event, between 11,000 and 10,000 ¹⁴C yr BP (12,900 and 11,600 cal yr BP), glaciers retreated on Mount Rainier, probably due to a lack of available moisture, but conditions may have remained cold. The onset of warmer conditions on Mount Rainier occurred around 10,000 ¹⁴C yr BP (11,600 cal yr BP). Organic sedimentation lasted for at least 700 years before glaciers readvanced between 9800 and 8950 ¹⁴C yr BP (10,900 and 9950 cal yr BP).     

Contrasting patterns of hydrological changes in Europe in response to Holocene climate cooling phases

The quantitative reconstruction of climatic parameters from pollen and lake-level data obtained at Saint-Jorioz, Lake Annecy (eastern France), gives evidence for cooler and wetter conditions during the 8.2 ka cold event. A comparison of these regional data with other hydrological records reconstructed in Europe for the same period suggests, as a working hypothesis, that mid-latitudes between ca 50° and 43° underwent wetter conditions in response to the cooling, whereas northern and southern Europe were marked by drier climate, in the latter case leading to an interruption of the sapropel 1 formation in the Mediterranean. A similar hydrological tri-partition of Europe can be observed during other Holocene cooling phases associated with North Atlantic IRD events. Data indicate, that the middle zone characterised by wetter climate conditions could have had a more extended latitudinal amplitude during phases of climate cooling weaker than the 8.2 ka event. The differences in expansion of the wet mid-European zone depending on Holocene climate cooling phases could reflect variations in the strength of the Atlantic Westerly Jet in relation with the thermal gradient between high and low latitudes.     

Connection between South Mediterranean climate and North African atmospheric circulation during the last 50,000 yr BP North Atlantic cold events

High-resolution clay mineralogical analyses were performed on sediment deposited during the last 50,000 yr in the Alboran sea (ODP Site 976). The clay mineral record is compared with pollen assemblages and with annual precipitation (Pann) and mean temperatures of the coldest month (MTCO) reconstructed with the modern analog technique (MAT). Enhanced contribution of palygorskite, a typical wind-blown clay mineral, characterizes the North Atlantic cold climatic events. Coeval development of the semi-arid vegetation (Artemisia rich) associated with a drastic fall of reconstructed precipitations and temperatures, suggest cold and arid continental conditions in the West Mediterranean area during North Atlantic cold events. The clay mineral association, especially the palygorskite content and the illite-to-kaolinite ratio, indicate western Morocco as one of the major source of the clay-size fraction during the North Atlantic cold events. The maximum abundance of Artemisia associated with the presence of Argania pollen both indicate Morocco as the main origin for pollen during these cold periods. The comparison of these pollen and clay mineral-specific features allows us to pinpoint western Morocco as the dominant source of wind-blown particles during North Atlantic cold events. These specific mineralogical composition and palynological assemblages reveal enhanced aridity over North Africa and intensification of winds favouring dust erosion and transport from North Africa toward the Alboran Sea during the North Atlantic cold events. According to atmospheric models, such a meridian transport (1) likely results from the development of strong and stable anticyclonic conditions over the tropical Atlantic and North Africa, similar to today's summer meteorological configuration and (2) implies a northward position of the westerly winds during North Atlantic cold events. Finally the synoptic situation over the West Mediterranean during the North Atlantic cold events is compared with the North Atlantic Oscillation (NAO), suggesting that during the cold Atlantic events, weather regimes over Europe and North Africa may have been systematically shifted towards a positive NAO situation.     

Lake Torfadalsvatn: a high resolution record of the North Atlantic ash zone I and the last glacial-interglacial environmental changes in Iceland

High resolution environmental records with a refined chronology are essential to understand, reconstruct and model the climate dynamics of the last glacial-interglacial transition. Sediments from Lake Torfadalsvatn in northern Iceland contain at least four primary volcanic tephras that belong to ash zone I in the North Atlantic deep-sea cores. We chemically define these basaltic/rhyolitic tephras and the high resolution allows us to date them to about 10,800, 10,600, 9300 and 8900 BP. This detailed tephrostratigraphy will act as a refined dating and correlation tool in the North Atlantic region and enable calibration between different absolute chronologies. The pollen stratigraphy of the sediments suggests that by 10,400 ¹⁴C years BP plant colonization of coastal north Iceland had begun. The pollen stratigraphy shows a succession of pioneer plants, from open tundra vegetation towards birch-juniper woodland, which probably also reflects a transition from a cool climate at 10,400 BP to conditions similar to today's sub-polar oceanic climate around 9200 BP. Diatom data largely concur with the climatic information from pollen, indicating gradually increasing productivity in the lake.     

早全新世降温事件的湖泊沉积证据

我国华北干旱－半干旱区封闭湖泊流域化学风化历史记录了全新世以来次级的气候环境波动过程。高精度的沉积物地球化学、物理及生物参数变化表明，在全新世早－中期过渡阶段存在一次强降温气候事件，具体表现为流域化学风化减弱（高Rb/Sr比）、湖泊产生力减弱（低有机碳）以及湖泊水位下降。虽然该事件的寒冷程度比Younger Dryas弱，但是其与来自湖沼（包括北极、非洲、北美、西欧、青藏高原、祁连山等）、海洋（比北大西洋、地中海、加勒比海等）、欧－美大陆生物组合、极地冰芯等在内的环境记录的冷事件发生时间基本一致，集中发生于8.0-8.5ka B.P.之间。     

The multiple chronological techniques applied to the Lake Suigetsu SG06 sediment core,central Japan

The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range).     

Fingerprinting the 8.2 ka event climate response in a coupled climate model

Using results from coupled climate model simulations of the 8.2 ka climate event that produced a cold period over Greenland in agreement with the reconstructed cooling from ice cores, we investigate the typical pattern of climate anomalies (fingerprint) to provide a framework for the interpretation of global proxy data for the 8.2 ka climate event. For this purpose we developed an analysis method that isolates the forced temperature response and provides information on spatial variations in magnitude, timing and duration that characterise the detectable climate event in proxy archives. Our analysis shows that delays in the temperature response to the freshwater forcing are present, mostly in the order of decades (30 a over central Greenland). The North Atlantic Ocean initially cools in response to the freshwater perturbation, followed in certain parts by a warm response. This delay, occurring more than 200 a after the freshwater pulse, hints at an overshoot in the recovery from the freshwater perturbation. The South Atlantic and the Southern Ocean show a warm response reflecting the bipolar seesaw effect. The duration of the simulated event varies for different areas, and the highest probability of recording the event in proxy archives is in the North Atlantic Ocean area north of 40° N. Our results may facilitate the interpretation of proxy archives recording the 8.2 ka event, as they show that timing and duration cannot be assumed to correspond with the timing and duration of the event as recorded in Greenland ice cores. Copyright © 2011 John Wiley & Sons, Ltd.     

Changing palynological methods and their role in three successive interpretations of the late-glacial environments at Bucyrus Bog, Ohio, USA

The pollen stratigraphy of Bucyrus Bog records the major shifts in the spruce ecotone of the mid-western North American late-glacial. The site has been studied three times: in 1930 by Paul Sears, in 1958 by Johannes Iversen, and in 1986–88 by my self. This paper examines these data sets from a historical perspective. The pollen record is basically consistent; all investigators interpret it to show the classic late-glacial warming plus a subsequent, more controversial climate reversal. Sears saw a progressive shift from cold/moist to warm/ dry climate, with a moisture reversal near the top of the record. Iversen and I both correlate the record with the European Late-Glacial climatic sequence, including an AUerød/Younger Dryas reversal. Iversen's interpretation depends on exclusion of thermophilous deciduous pollen taxa, placing the cold reversal during the spruce decline. I include the deciduous taxa, placing the cold reversal at the time of a spruce recurrence above the expansion of deciduous types. All interpretations are strongly influenced by current technology and prevailing thinking at the time of the investigation.     

东亚中高纬Heinrich 1事件的表现特征:呼伦湖孢粉记录

Heinrich 1事件是发生于末次冰消期的极端气候突变事件之一,对全球大气环流和陆地生态格局产生了深刻影响.基于对东亚夏季风边缘区最北端呼伦湖 HL08 孔5. 75 m 以上沉积岩芯的 AMS 14C定年技术和 415~275 cm段140个样品的孢粉分析,重建了东亚中高纬地区呼伦湖21500~13000 cal. a B. P.高分辨率植被变化历史,在此基础上揭示了Heinrich 1事件期间呼伦湖区植被响应过程,明确了Heinrich 1事件在东亚中高纬地区的表现特征.结果显示:呼伦湖区Heinrich 1事件发生于16500~15400 cal. a B. P.,以剧烈降温和显著干旱化为表现特征;事件发生期间湖区周围山地发育亚高山草甸,森林植被稀疏;湖盆区域以藜科为主的荒漠草原显著扩张,区域植被盖度降低、生态环境明显恶化;同时,不同植被类型对Heinrich 1事件的响应存在明显差别,亚高山草甸和蒿属为主的典型草原较藜科为主的荒漠草原和桦属为主的落叶阔叶林响应更为快速、敏感.     

Millennial-scale vegetation changes during the last 40,000 yr based on a pollen record from Lake Biwa, Japan

A high-resolution pollen record covering the last 40,000 yr (BIW95-4) from Lake Biwa, western Japan, shows regional vegetation responses to millennial-scale climate changes. From 40 to 30 ka, Cryptomeria japonica was dominant around the lake among pinaceous conifers and deciduous broad-leaved trees. During this period, fluctuations of C.japonica are correlated with Dansgaard-Oeschger (D-O) cycles recognized from the anhysteretic remanent magnetization (ARM) record. Increases in the abundance of this taxon may have been caused by wetter summer conditions influenced by the East Asian monsoon or increased snowfall on the Sea of Japan side of the Japanese archipelago. Between 29 and 14 ka, pinaceous conifer forests mainly composed of Pinus subgenus Haploxylon, Tsuga, and Picea trees developed. At approximately 23 ka, Picea trees increased in abundance as ARM values decreased. This expansion of Picea trees has been correlated with Heinrich event (HE) 2 in the North Atlantic. At about 14 ka, the distribution of broad-leaved forest (mainly composed of deciduous oaks) began to expand after D-O 1. Evidence of significant vegetation change related to the abrupt Younger Dryas cooling event has not been found.     

Problems with identifying the ‘8200‐year cold event’ in terrestrial records of the Atlantic seaboard: a case study from Dooagh,Achill Island,Ireland

The Northern Hemisphere cooling event 8200 years ago is believed to represent the last known major freshwater pulse into the North Atlantic as a result of the final collapse of the North American Laurentide ice sheet. This pulse of water is generally believed to have occurred independently of orbital variations and provides an analogue for predicted increases in high‐latitude precipitation and ice melt as a result of anthropogenically driven future climate change. The precise timing, duration and magnitude of this event, however, are uncertain, with suggestions that the 100‐yr meltwater cooling formed part of a longer‐term cold period in the early Holocene. Here we undertook a multiproxy, high‐resolution investigation of a peat sequence at Dooagh, Achill Island, on the west coast of Ireland, to determine whether the 8200‐year cold event impacted upon the terrestrial vegetation immediately ‘downwind’ of the proposed changes in the North Atlantic. We find clear evidence for an oscillation in the early Holocene using various measures of pollen, indicating a disruption in the vegetation leading to a grassland‐dominated landscape, most probably driven by changes in precipitation rather than temperature. Radiocarbon dating was extremely problematic, however, with bulk peat samples systematically too young for the North Atlantic event, suggesting significant contamination from downward root penetration. The sustained disruption to vegetation over hundreds of years at Dooagh indicates the landscape was impacted by a long‐term cooling event in the early Holocene, and not the single century length 8200‐year meltwater event proposed in many other records in the North Atlantic region. Copyright © 2006 John Wiley & Sons, Ltd.     

Rapid response of forested vegetation to multiple climatic oscillations during the last deglaciation in the northeastern United States

Isotopic and pollen results from a marl lake (White Lake) in the Mid-Atlantic region of USA indicate the coupling of climate and vegetation changes. Oxygen isotopes of calcite from this site show multiple oscillations at millennial and centennial scales, including the Younger Dryas with 3‰ negative shifts in δ¹⁸O at 12.4-11.4 ka (1 ka = 1000 cal yr BP) and three cold events of magnitude 1-2‰ shifts during the Bølling-Allerød warm period (BOA) at 14.3-12.4 ka. Pollen data from the same core show nearly synchronous, close correspondence with isotope-inferred climate shifts, indicating rapid forest response to deglacial climate oscillations in southern New England. A plateau-like BOA is similar to other records around the North Atlantic Ocean.     

Vegetation dynamics during the Younger Dryas-Holocene transition in the extreme northern taiga zone, northeastern European Russia

Vegetation dynamics during the Younger Dryas-Holocene transition in the extreme northern taiga zone of the Usa basin, northeastern European Russia, were reconstructed using plant macrofossil and pollen evidence from a sediment core from Lake Llet-Ti. The pollen stratigraphy during the Younger Dryas (about 12 500-11 500 cal. yr BP) is characterized by pollen types indicative of treeless arctic vegetation, whereas the macrofossil evidence shows the occurrence of scattered spruce and birch trees around the lake. The Younger Dryas-early Holocene transition is characterized by a rapid increase in vegetation density, including an increase in the birch population, followed by the expansion of the spruce population at about 10 000 cal. yr BP. Dense spruce-birch forest dominated until 5000 cal. yr BP. Our results contribute to the debate about the Lateglacial environments in northern Russia, and illustrate the importance of plant macrofossil records in Lateglacial vegetation reconstructions.     

Major and trace element abundances in volcanic glass shards in visible tephras in SG93 and SG06 drillcore samples from Lake Suigetsu,central Japan,obtained using femtosecond LA–ICP–MS

The major and trace element concentrations of volcanic glass shards from visible tephra layers in the SG93 and SG06 cores from Lake Suigetsu, central Japan, were determined by femtosecond laser ablation–inductively coupled plasma–mass spectrometry. The glass-shard analyses, together with the petrographic properties of the tephra samples, allow the Suigetsu tephra layers to be broadly classified into tephras derived from calderas on Kyushu Island, and from Daisen and Sambe volcanoes in the Chugoku district of southwest Japan. The layers correlated with tephras from Kuju caldera and Daisen volcano, and with the younger Sambe tephras, have adakitic elemental features. A Suigetsu tephra sample correlated with the Sambe−Kisuki tephra based on petrographic properties has an elemental pattern similar to that of the Toya tephra from Hokkaido Island, northeast Japan. This match implies that tephras from northeast Japan, as well as Kyushu–Chugoku tephras, are possible correlatives of the Suigetsu tephra layers. Both petrographic properties and major–trace element data of volcanic glass shards are essential for robust tephra correlations, and hierarchical cluster analysis proved additionally useful in statistically evaluating relationships among the tephras.     

Lateglacial and early Holocene climatic fluctuations recorded in the diatom flora of Xiaolongwan maar lake,NE China

A palaeolimnological study of the annually laminated sediment sequence of Lake Xiaolongwan, a small maar lake in northeastern China, revealed distinct diatom responses to Lateglacial and early Holocene climate change between c. 19 700 and c. 10 700 a BP. In addition to analyses of diatom assemblage composition and of the biovolume accumulation rate of planktonic diatoms, geochemical (total nitrogen, total organic carbon) and physical (varve type and thickness) indicators were used to assess past environmental change. The diatom assemblages reveal a complex interplay between direct climate effects on the seasonal lake conditions (timing of ice cover break‐up, water column mixing and thermal stratification), catchment‐mediated effects on the concentrations of nutrients and dissolved organic carbon and, possibly, biotic interactions between the different algal groups present in the phytoplankton of Lake Xiaolongwan (diatoms, Chrysophyceae and Dinophyceae). The most remarkable changes in the aquatic system were: (i) a sharp increase in Asterionella formosa and the collapse of Handmannia balatonis at c. 14 780 a BP, corresponding with the onset of the Bølling – Allerød interstadial; (ii) a sharp rise in Stephanodiscus minutulus at c. 12 840 a BP, marking the start of the Younger Dryas event and (iii) when the lake phytoplankton became dominated by Dinophyceae instead of diatoms at c. 11 170 a BP, after the Pre‐Boreal oscillation. Two diatom assemblage zones characterize the Younger Dryas at Lake Xiaolongwan, suggesting a bipartite division of this stadial event as in several records from eastern Asia and Europe. The quasi‐synchronicity of these events with the oscillations described in the North Atlantic realm demonstrates that during the Lateglacial, North Atlantic dynamics at centennial and millennial time scales had a strong control upon the climate in northeastern China.     

大兴安岭地区新仙女木事件的表现特征

新仙女木事件是末次冰消期期间发生的一次气候转冷事件,该事件对整个北半球的中高纬度地区的气候变化有明显的影响.然而,在该事件造成东亚中高纬地区温度下降的统一认识下,对于其季节性特征仍较为缺乏认识.本文用大兴安岭中部月亮湖末次冰消期多指标记录,揭示了大兴安岭地区在新仙女木事件期间植被中的北方针叶林成分增加、森林发育、冬季温度下降、东亚冬季风明显增强.     

Exploring typhoon variability over the mid-to-late Holocene: evidence of extreme coastal flooding from Kamikoshiki,Japan

Sediment cores from two coastal lakes located on the island of Kamikoshiki in southwestern Japan (Lake Namakoike and Lake Kaiike) provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years. Sub-bottom seismic surveys exhibit acoustically laminated, parallel to subparallel seismic reflectors, intermittently truncated by erosional unconformities. Sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse-grained units, with depths of coarse deposits concurrent with prominent seismic reflectors. The timing of the youngest deposit at Kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 AD. Assuming that this modern deposit provides an analog for identifying past events, paleo-typhoons may be reconstructed from layers exhibiting an increase in grain-size, a break in fine-scale stratigraphy, and elevated Sr concentrations.Periods of barrier breaching are concurrent with an increase in El Niño frequency, indicating that the El Niño/Southern Oscillation has potentially played a key role in governing typhoon variability during the mid-to-late Holocene. An inverse correlation is observed between tropical cyclone reconstructions from the western North Atlantic and the Kamikoshiki site, which may indicate an oscillating pattern in tropical cyclone activity between the western Northern Atlantic and the western North Pacific, or at least between the western Northern Atlantic and regions encompassing southern Japan. The two kamikaze typhoons which contributed to the failed Mongol invasions of Japan in 1274 AD and 1281 AD occur during a period with more frequent marine-sourced deposition at the site, suggesting that the events took place during a period of greater regional typhoon activity.