New faunal and isotopic evidence on the late Weichselian—Holocene oceanographic changes in the Norwegian Sea

Downcore studies of planktonic and benthonic foraminifera and δ¹⁸O and δ¹³C in the planktonic foraminifer Neogloboquadrina pachyderma (sin.) in two piston cores from the southern part of the Norwegian Sea suggest large changes in the oceanic circulation pattern at the end of oxygenisotope stage 2 and in the early part of stage 1. Prior to oxygen-isotope Termination IA (16,000–13,000 yr B.P.), an isolated watermass with lower oxygen content and temperature warmer than today existed below a low salinity ice-covered surface layer in the Norwegian Sea. Close to Termination IA, well-oxygenated deep water, probably with positive temperatures, was introduced. This deep water, which must have had physical and/or chemical parameters different from those of present deep water in the Norwegian Sea, could have been introduced from the North Atlantic or been formed within the basin by another mechanism than that which forms the present deep water of the Norwegian Sea. A seasonal ice cover in the southern part of the Norwegian Sea is proposed for the period between Termination IA and the beginning of IB (close to 10,000 yr B.P.). The present situation, with strong influx of warm Atlantic surface-water and deep-water formation by surface cooling, was established at Termination IB.     

A high-resolution diatom record of late-Quaternary sea-surface temperatures and oceanographic conditions from the eastern Norwegian Sea

Core MD95‐2011 was taken from the eastern Vøring Plateau, near the Norwegian coast. The section between 250 and 750 cm covers the time period from 13 000 to 2700 cal. yr BP (the Lateglacial and much of the Holocene). Samples at 5 cm intervals were analysed for fossil diatoms. A data‐set of 139 modern sea‐surface diatom samples was related to contemporary sea‐surface temperatures (SSTs) using two different numerical methods. The resulting transfer functions were used to reconstruct past sea‐surface temperatures from the fossil diatom assemblages. After the cold Younger Dryas with summer SSTs about 6°C, temperatures warmed rapidly to about 13°C. One of the fluctuations in the earliest Holocene can be related to the Pre‐Boreal Oscillation, but SSTs were generally unstable until about 9700 cal. yr BP. Evidence from diatom concentration and magnetic susceptibility suggests a change and stabilization of water currents associated with the final melting of the Scandinavian Ice Sheet at c. 8100 cal. yr BP. A period of maximum warmth between 9700 and 6700 cal. yr BP had SSTs 3–5°C warmer than at present. Temperatures cooled gradually until c. 3000 cal. yr BP, and then rose slightly around 2750 cal. yr BP. The varimax factors derived from the Imbrie & Kipp method for sea‐surface‐temperature reconstructions can be interpreted as water‐masses. They show a dominance of Arctic Waters and Sea Ice during the Younger Dryas. The North Atlantic current increased rapidly in strength during the early Holocene, resulting in warmer conditions than previously. Since about 7250 cal. yr BP, Norwegian Atlantic Water gradually replaced the North Atlantic Water, and this, in combination with decreasing summer insolation, led to a gradual cooling of the sea surface. Terrestrial systems in Norway and Iceland responded to this cooling and the increased supply of moisture by renewed glaciation. Periods of glacial advance can be correlated with cool oscillations in the SST reconstructions. By comparison with records of SSTs from other sites in the Norwegian Sea, spatial and temporal changes in patterns of ocean water‐masses are reconstructed, to reveal a complex system of feedbacks and influences on the climate of the North Atlantic and Norway.     

Climatic change during the last 4000 years in the southern Tarim Basin,Xinjiang, northwest China

In this study, a ca. 4000 cal. yr ancient lacustrine (or wetland) sediment record at the southern margin of Tarim Basin is used to reconstruct the history of climate change. Six radiocarbon dates on organic matter were obtained. δ¹⁸O and δ¹³C of carbonate, pollen and sediment particle size were analysed for climate proxies. The proxies indicate that a drier climate prevailed in the area before ca. 1010 BC and during period 1010 BC–AD 500 climate then changed rapidly and continuously from dry to moist, but after about AD 500 climate generally shows dry condition. Several centennial‐scale climatic events were revealed, with the wettest spell during AD 450–550, and a relatively wetter interval between AD 930–1030. Pollen results show that regional climate may influence human agricultural activities. Spectral analysis of mean grain size (MGS) proxy reveals statistically pronounced cyclic signals, such as ca. 200 yr, ca. 120 yr, ca. 90 yr, ca. 45 yr and ca. 33 or 30 yr, which may be associated with solar activities, implying that solar variability plays an important role in the decadal‐ and centennial‐scale climate variations in the study area. Copyright © 2007 John Wiley & Sons, Ltd.     

Late Quaternary changes in surface productivity and oxygen minimum zone (OMZ) in the northwestern Arabian Sea: Micropaleontologic and sedimentary record at ODP site 728A

Changes in the abundance of selected planktic foraminiferal species and some sedimentological parameters at ODP site 728A were examined to understand the fluctuations in the surface productivity and deep sea oxygenation in the NW Arabian Sea during last ∼540 kyr. The increased relative abundances of high fertility taxa, i.e., Globigerinita glutinata and Globigerina bulloides mainly during interglacial intervals indicate intense upwelling. Strong SW summer monsoon probably increased the upwelling in the western Arabian Sea during interglacial intervals and caused high surface productivities due to the lateral transport of eutrophic waters. Most of the glacial periods (i.e., MIS 2, 4, 6, 8 and 12) are characterized by higher relative abundances of Neogloboquadrina pachyderma and Neogloboquadrina dutertrei associated with Globigerinoides ruber. The more stratified condition and deep mixed layer due to increased NE winter monsoon are mainly responsible for the higher relative abundances of N. pachyderma during glacial periods. Some of the glacial intervals (i.e., MIS 6 and 8) are also characterized by pteropod spikes reflecting deepening of aragonite compensation depth (ACD) and relatively less intense oxygen minimum zone (OMZ) in this region due to deep sea mixing and thermocline ventilation, and relatively less intense surface productivity during winter monsoon. The interglacial periods are largely devoid of pteropod shells indicating more aragonite dissolution due to increased intensity of OMZ in the northwestern Arabian Sea.     

Did the Indo‐Asian summer monsoon decrease during the Holocene following insolation?

A few studies from the western Arabian Sea indicate that the Indian summer (or southwest) monsoon (ISM), after attaining its maximum intensity at ca. 9 ka, declined during the Holocene, as did insolation. In contrast, earlier and later observations from both the eastern and the western Arabian Sea do not support this inference. Analysis of multiple proxies of productivity in a new sediment core from the western Arabian Sea fails to confirm the earlier, single‐proxy (e.g. abundance of Globigerina bulloides) based, inference of the Holocene weakening of ISM, following insolation. The reason for the observed decreasing trend in foraminiferal abundance – the basis for the earlier inference – could be the favouring of silicate rather than carbonate productivity by the increased ISM wind strength. Although ISM exhibits several multi‐millennial scale fluctuations, there is no evidence from several multi‐proxy data to conclude that it declined during the Holocene; this is consistent with the phase lag analysis of longer time series of monsoon proxies. Thus, on sub‐Milankovitch timescales, ISM did not follow insolation, highlighting the importance of internal feedbacks. A comparison with East Asian summer monsoon (EASM) records suggests that both ISM and EASM varied in unison, implying common forcing factors on such longer timescales. Copyright © 2010 John Wiley & Sons, Ltd.     

Sea‐surface conditions in northernmost Baffin Bay during the Holocene: palynological evidence

The analysis of cores collected in northernmost Baffin Bay, from within the area of the North Water Polynya, permits definition of a composite sedimentary sequence ca. 12 m thick spanning the last 10 000 ¹⁴C yr, with only a few discontinuities. Palynological analyses were performed in order to reconstruct changes in surface water conditions and biogenic production. Transfer functions, using dinocyst assemblages, were applied to estimate sea‐surface temperature (SST) and salinity, as well as the seasonal duration of sea ice cover. At the base of the record, prior to 9300 ¹⁴C yr BP, dinocysts and organic linings of benthic foraminifers are sparse, indicating harsh conditions and low productivity. After ca. 9300 ¹⁴C yr BP, the increased concentration of benthic foraminifers (up to 10³ linings cm^?3) and dinocyst fluxes (10²–10³ cysts cm^?2 yr^?1) reveals high biological productivity related to open‐water conditions. The early to middle Holocene, from ca. 9000 to ca. 3600 ¹⁴C yr BP, is marked by relatively high species diversity in dinocyst assemblages and the significant occurrence of autotrophic taxa such as Spiniferites elongatus, Pentapharsodinium dalei and Impagidinium pallidum. This assemblage suggests conditions at least as warm as at present. From ca. 6400 to ca. 3600 ¹⁴C yr BP, transfer functions indicate warmer conditions than at present, with SST in August fluctuating up to 5.5°C. After 3600 ¹⁴C yr BP, the dinocyst record suggests a trend of decreasing temperature toward modern values, marked by recurrent cooling events. Copyright © 2001 John Wiley & Sons, Ltd.     

Quantitative assessment of precipitation seasonality and summer surface wetness using ombrotrophic sediments from an Arctic Norwegian peatland

Seasonality of precipitation is an important yet elusive climate parameter in paleoclimatological reconstructions. This parameter can be inferred qualitatively from pollen and other paleoecological methods, but is difficult to assess quantitatively. Here, we have assessed seasonality of precipitation and summer surface wetness using compound specific hydrogen and carbon isotope ratios of vascular plant leaf waxes and Sphagnum biomarkers extracted from the sediments of an ombrotrophic peatland, Bøstad Bog, Nordland, Norway. Our reconstructed precipitation seasonality and surface wetness are consistent with regional vegetation reconstructions. During the early Holocene, 11.5–7.5 ka, Fennoscandia experienced a cool, moist climate. The middle Holocene, 7.5–5.5 ka, was warm and dry, transitioning towards cooler and wetter conditions from the mid-Holocene to the present. Changes in seasonality of precipitation during the Holocene show significant coherence with changes in sea surface temperature in the Norwegian Sea, with higher SST corresponding to greater percentage of winter precipitation. Both high SST in the Norwegian Sea and increased moisture delivery to northern Europe during winter are correlated with a strong gradient between the subpolar low and subtropical high over the North Atlantic (positive North Atlantic Oscillation).     

North Atlantic climate variability since AD 1350 recorded in δ 18O and skeletal density of Bermuda corals

The reconstruction of the climatic history during the past several hundred years requires a sufficient geographical coverage of combined climate proxy series. Especially in order to identify causal connections between the atmosphere and the ocean, inclusion of marine records into composite climate time series is of fundamental importance. We present two skeletal δ ¹⁸O chronologies of coral skeletons of Diploria labyrinthiformis from Bermuda fore-reef sites covering periods in the nineteenth and twentieth centuries and compare them with instrumental temperature data. Both time series are demonstrated to display sea-surface temperature (SST) variability on inter-annual to decadal time scales. On the basis of a specific modern δ ¹⁸O vs instrumental SST calibration we reconstruct a time series of SST anomalies between AD 1350 and 1630 covering periods during the Little Ice Age. The application of the coral δ ¹⁸O vs temperature relationship leads to estimates of past SST variability which are comparable to the magnitude of modern variations. Parallel to δ ¹⁸O chronologies we present time series of skeletal bulk density. Coral δ ¹⁸O and skeletal density reveal a strong similarity during Little Ice Age, confirming the reliability of both proxy climate indicators. The past coral records, presented in this study, share features with a previously published climate proxy record from Bermuda and a composite time series of reconstructed Northern Hemisphere summer temperatures. The coral proxy data presented here represent a valuable contribution to elucidate northern Atlantic subtropical climate variation during the past several centuries. Received: 9 November 1998 / Accepted: 13 September 1999     

A high-resolution diatom-inferred palaeoconductivity and lake level record of the Aral Sea for the last 1600 yr

Formerly the world's fourth largest lake by area, the Aral Sea is presently undergoing extreme desiccation due to large-scale irrigation strategies implemented in the Soviet era. As part of the INTAS-funded CLIMAN project into Holocene climatic variability and the evolution of human settlement in the Aral Sea basin, fossil diatom assemblages contained within a sediment core obtained from the Aral Sea have been applied to a diatom-based inference model of conductivity (r² = 0.767, RMSEP = 0.469 log₁₀ μS cm^− 1). This has provided a high-resolution record of conductivity and lake level change over the last ca. 1600 yr. Three severe episodes of lake level regression are indicated at ca. AD 400, AD 1195–1355 and ca. AD 1780 to the present day. The first two regressions may be linked to the natural diversion of the Amu Darya away from the Aral Sea and the failure of cyclones formed in the Mediterranean to penetrate more continental regions. Human activity, however, and in particular the destruction of irrigation facilities are synchronous with these early regressions and contributed to the severity of the observed low stands.     

Short-term climate changes during the Last Glacial–Holocene transition: comparison between Mediterranean records and the GRIP event stratigraphy

This paper presents biostratigraphical and stable isotope data obtained from core CM92–43, which was recovered from the central Adriatic as part of a comprehensive investigation of the palaeoenvironmental history of the basin. The data span the period of the Last Glacial–Holocene (LG–H) transition (ca. 18000 to 8000 GRIP ice-core yr BP). Regional biozones are defined on the basis of characteristic assemblages of planktic Foraminifera, and these are compared with other foraminiferal biostratigraphical schemes from the southern Adriatic and the Tyrrhenian Sea. Variations in relative abundance of selected planktic Foraminifera and in selected pollen types are shown alongside variations in δ¹⁸O and δ¹³C obtained from Globigerina bulloides and relative abundance of Globigerinoides ex. gr. ruber. The data are compared with the GRIP ice-core record and the event stratigraphy scheme based on this record, and it is concluded that the climate forcing mechanisms that controlled climate variations in the North Atlantic region during the LG–H transition also extended their influence into the Mediterranean region over the same period. Copyright © 1999 John Wiley & Sons, Ltd.     

Seasonality in the North Sea during the Allerød and Late Medieval Climate Optimum using bivalve sclerochronology

Seasonal temperature patterns may have changed through time in response to current global warming. However, the temporal resolution of available proxy records is not sufficient to quantify paleotemperature seasonality prior to anthropogenic forcing of the climate. In the present study, we reconstructed seasonal and inter-annual temperature patterns of the North Sea during the last 140 years, the Allerød Interglacial and the Late Medieval Climate Optimum using sclerochronological and δ¹⁸O_aragonite data from bivalve shells, Arctica islandica. On average, the climate during 1278–1353 AD was ca. 1.1°C colder and seasonality was ca. 60% less than today. During the Allerød, long-term temperatures remained about 3.2°C below present values, and absolute summer and winter anomalies were ca. ?4 and ?2.7°C, respectively. However, seasonality was statistically indistinguishable from today. Long-term average temperatures compare well with existing data for the Late Medieval and Allerød, but detailed information on seasonality during the studied time intervals has never been presented before. Our data also demonstrated that annual instrumental and δ¹⁸O_aragonite-derived temperatures did not always match. This difference is explained by (1) NAO-driven salinity changes, which influence the temperature estimation from δ¹⁸O_aragonite and (2) food-driven changes in growth rates; portions of the shell that formed more rapidly are overrepresented in carbonate samples. Our study indicated that individual bivalve shells can open discrete, near-century long, ultra-high-resolution windows into the climate past. Such information can be vital for testing and verifying numerical climate models.     

A 1000-yr record of environmental change in NE China indicated by diatom assemblages from maar lake Erlongwan

Past environmental changes based on diatom relative abundances have been inferred from the maar Lake Erlongwan in northeast China. The limnology of Lake Erlongwan is affected by the strongly seasonal regional climate. The composition of diatom assemblages, in turn, responds to changes in the seasonal duration of ice cover in winter, water-column turnover in spring and autumn, and thermal stratification in summer. Statistical analysis of the sedimentary diatom assemblages reveals three significant stratigraphic zones over the past 1000 yr. The highest abundance of the planktonic species Discostella species occurs between AD 1050 and 1400 and suggests an annual ice-free period of long duration and well-developed summer stratification of the water column. This planktonic diatom peak between ca. AD 1150 and 1200 suggests that this period was the warmest over the past 1000 yr. The interval between AD 1400 and 1800 is marked by a decline in planktonic diatoms and suggests shorter duration of the ice-free season, weaker water stratification and possibly generally cold conditions. After AD 1800 relative abundances of planktonic diatoms, including Puncticulata praetermissa and Asterionella formosa, increase again, which indicates lengthening of the duration of the annual ice-free period and a stronger overturn of the water column. All these data imply that the pattern of the seasons is different between the MWP and the 20th century.     

Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.     

Oceanography in northwestern Europe during the last interglacial from intrashell δO ranges in Littorina littorea gastropods

Coastal sea-surface temperature (SST) and sea-surface salinity (SSS), including seasonality, in northwest (NW) Europe during the early phase of the Eemian interglacial ca. 125 ka ago were reconstructed from Littorina littorea (common periwinkle) gastropods. The results were based on intra-annual δ¹⁸O analyses in recent and fossil shells, mainly originating from the sea of Kattegat (Sweden) and the English Channel (United Kingdom), and confined to intertidal settings. The Eemian L. littorea shells indicated annual SSTs in the range 8–18°C for the English Channel and 8–26°C for Kattegat. All specimens from the Eemian sites experienced summer SSTs of ca. 1–3°C above recent conditions. The estimated winter SST in the English Channel during the Eemian was comparable to modern measurements of ca. 8°C. However, the Kattegat region displayed Eemian winter SST approximately 8°C warmer than today, and similar to conditions in the western English Channel. The recent-fossil isotope analogue approach indicated high SSS above 35 practical salinity units (psu) for a channel south of England in full contact with the North Atlantic Ocean during the last interglacial. In addition, the Kattegat shells indicated a SSS of ca. 29 psu, which points out a North Sea affinity for this region during the Eemian.     

Control of wind strength and frequency in the Aral Sea basin during the late Holocene

Changing content of detrital input in laminated sediments traced by XRF scanning and microfacies analyses reflect prominent variations in sedimentation processes in the Aral Sea. A high-resolution record of titanium from a core retrieved in the northwestern Large Aral Sea allows a continuous reconstruction of wind strength and frequency in western Central Asia for the past 1500 yr. During AD 450–700, AD 1210–1265, AD 1350–1750 and AD 1800–1975, detrital inputs (bearing titanium) are high, documenting an enhanced early spring atmospheric circulation associated with an increase in intensity of the Siberian High pressure system over Central Asia. In contrast, lower titanium content during AD 1750–1800 and AD 1980–1985 reflects a diminished influence of the Siberian High during early spring with a reduced atmospheric circulation. A moderate circulation characterizes the time period AD 700–1150. Unprecedented weakened atmospheric circulation over western Central Asia are inferred during ca. AD 1180–1210 and AD 1265–1310 with a considerable decrease in dust storm frequency, sedimentation rates, lamination thickness and detrital inputs (screened at 40-μm resolution). Our results are concurrent with changes in the intensity of the Siberian High during the past 1400 yr as reported in the GISP2 Ice Core from Greenland.     

北京顺义早更新世有孔虫动物群的古生态及古环境

1975年我们报道了泥河湾盆地怀来及蔚县境内发现半咸水有孔虫化石,当时认为它们的层位可能属第四系上部,后来进一步工作证实应是泥河湾组上部沉积。1977年我们对华北平原第四纪海进海退现象作了初步报道,认为华北平原在早更新世时发生过海进(渤海海进),并引用陈方吉在北京东南发现海相介形虫资料,说明早更新世渤海海进时海水曾经到达这一地区。1978年李鼎容等在北京市顺义县早更新世地层中发现大量有孔虫化石。进一步证实北京地区早更新世确曾发生过海进,使我们解释怀来及蔚县所发现的半咸水有孔虫来源,有更多证据。这一发现,对于北京地区第四纪地层划分对比、新构造运动判别和古地理恢复有重大意义。     

Biostratigraphic Evidence of the Allerød-Younger Dryas-Preboreal Oscillation in Northern Iceland

Basal sediments of Lake Torfadalsvatn, northern Iceland, record changes in terrestrial and limnic environments in the period 11,300-9000 ¹⁴C yr B.P. These changes were probably forced by climate and connected with displacements of the marine polar front and sea-ice margin. Pollen, spores, green algae (Pediastrum), saturation isothermal remanent magnetization, and carbon content of the basal sediments provide the first detailed biostratigraphic record of the last glacial-interglacial transition in Iceland. During the first pioneer phase, beginning at ca. 11,300 ¹⁴C yr B.P., grasses and fell-field herbs became established, and lake productivity was very low. At ca. 10,900 ¹⁴C yr B.P., climatic and soil conditions became favorable for shrubs and dwarf shrubs. This change, together with increased limnic productivity, clearly indicates long seasons without ice-cover in the sea immediately north of Iceland. A return to a colder climate (Younger Dryas), probably in connection with a southward displacement of the marine polar front, occurred by 10,600 ¹⁴C yr B.P. Shrub and dwarf-shrub vegetation disappeared, and limnic productivity diminished. A second pioneer vegetation phase, dominated by Oxyria/Rumex and grasses, was initiated by a change to longer seasons without sea ice at ca. 9900 ¹⁴C yr B.P. This warming is also evident as a contemporaneous increase in lake productivity. After ca. 9400 ¹⁴C yr B.P. the reestablishment of dwarf-shrub heaths and very high limnic productivity indicate further warming.     

A High-Resolution Sea-Surface Temperature Record from the Tropical South China Sea (16,500–3000 yr B.P.)

The timing and magnitude of sea-surface temperature (SST) changes in the tropical southern South China Sea (SCS) during the last 16,500 years have been reconstructed on a high-resolution, ¹⁴C-dated sediment core using three different foraminiferal transfer functions (SIMMAX28, RAM, FP-12E) and geochemical (U^k′₃₇) SST estimates. In agreement with CLIMAP reconstructions, both the FP-12E and the U^k′₃₇ SST estimates show an average late glacial–interglacial SST difference of 2.0°C, whereas the RAM and SIMMAX28 foraminiferal transfer functions show only a minor (0.6°C) or no consistent late glacial–interglacial SST change, respectively. Both the U^k′₃₇ and the FP-12E SST estimates, as well as the planktonic foraminiferal δ¹⁸O values, indicate an abrupt warming (ca. 1°C in <200 yr) at the end of the last glaciation, synchronous (within dating uncertainties) with the Bølling transition as recorded in the Greenland Ice Sheet Project 2 (GISP2) ice core, whereas the RAM-derived deglacial SST increase appears to lag during this event by ca. 500 yr. The similarity in abruptness and timing of the warming associated with the Bølling transition in Greenland and the southern SCS suggest a true synchrony of the Northern Hemisphere warming at the end of the last glaciation. In contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the Younger Dryas (YD) climate event in the tropical SCS, the U^k′₃₇ SST estimates show a cooling of ca. 0.2–0.6°C compared to the Bølling–Allerød period. These U^k′₃₇ SST estimates from the southern SCS argue in favor of a Northern Hemisphere-wide, synchronous cooling during the YD period.     

Sea-level estimates during the last deglaciation based on δO and accelerator mass spectrometry C ages measured in Globigerina bulloides

Coupled measurements of δ¹⁸O and accelerator mass spectrometry (AMS) ¹⁴C in a particular species of planktonic foraminifera may be used to calculate sea-level estimates for the last deglaciation. Of critical importance for this type of study is a knowledge of the seasonality of foraminiferal growth, which can be provided by δ¹⁸O measurements of modern shells (core tops, plankton tows). Isotopic (δ¹⁸O, AMS-¹⁴C dating) and faunal records (transfer function sea surface temperature) were obtained from two cores in the North Atlantic at about 37°N. The locations were chosen to obtain high sedimentation rate records removed from the major ice-melt discharge areas of the last deglaciation. Based upon Globigerina bulloides data, four δ¹⁸O-based sea-level estimates were calculated: −67 ± 7 m at 12,200 yr B.P. and −24 ± 8 m at about 8200 yr B.P. for core SU 81-18; −83 ± 10 m at 12,200 yr B.P. and −13 ± 11 m at about 8500 yr B.P. for core SU 81-14. Using a second working hypothesis concerning the seasonability of G. bulloides growth, it is suggested that the sea-level rose by about 40 m during the millennium which followed 14,500 yr B.P.     

Climate variability in the Aral Sea basin (Central Asia) during the late Holocene based on vegetation changes

High-resolution pollen analyses ( 50 yr) from sediment cores retrieved at Chernyshov Bay in the NW Large Aral Sea record shifts in vegetational development from subdesertic to steppe vegetation in the Aral Sea basin during the late Holocene. Using pollen data to quantify climatic parameters, we reconstruct and date for the first time significant changes in moisture conditions in Central Asia during the past 2000 yr. Cold and arid conditions prevailed between ca. AD 0 and 400, AD 900 and 1150, and AD 1500 and 1650 with the extension of xeric vegetation dominated by steppe elements. These intervals are characterized by low winter and summer mean temperatures and low mean annual precipitation (P_mm < 250 mm/yr). Conversely, the most suitable climate conditions occurred between ca. AD 400 and 900, and AD 1150 and 1450, when steppe vegetation was enriched by plants requiring moister conditions (P_mm  250–500 mm/yr) and some trees developed. Our results are fairly consistent with other late Holocene records from the eastern Mediterranean region and the Middle East, showing that regional rainfall in Central Asia is predominantly controlled by the eastern Mediterranean cyclonic system when the North Atlantic Oscillation (NAO) is in a negative phase.