Quaternary International 91 (2002) 75–99

Climate changes in East Europe and Siberia at theLate glacial–holocene transition

A.A. Velichkoa, N. Cattob,*, A.N. Drenovaa, V.A. Klimanova, K.V. Kremenetskia,V.P. Nechaeva

aLaboratory of Evolutionary Geography, Institute of Geography, Russian Academy of Sciences, Staromonetny lane 29, 109017 Moscow,

Russian FederationbDepartment of Geography, Memorial University of Newfoundland, St. John’s, NF, Canada A1B 3X9

Abstract

The main climatic oscillations of the Lateglacial/Early Holocene (Aller�d, Younger Dryas, and Preboreal) can be distinguished allover Eastern Europe and Siberia. Distribution of the main climatic indices in the Lateglacial/Early Holocene, from west to east in

Northern Eurasia, shows that variations of the mean January temperature ðtoJanÞ were larger, than those of July temperature ðtoJulyÞ:As at present, toJan decreased to the east, while the deviations from the present-day values were greater in the west. During the

Younger Dryas the seasonality of climate increased considerably, especially in the western (European) part of the studied area. The

greatest negative temperature deviations from the present-day values (up to �141C) occurred in the northwestern part of the East

European Plain, near the Scandinavian ice-sheet. It can be explained by a cooling influence from the remaining large ice body.

Accordingly, with degradation of the ice-sheet at the warmer intervals of the Lateglacial and Early Holocene, the regional

differences in temperature deviations became smaller (up to 81C).

On the whole, precipitation (P) decreased in an easterly direction, though its deviations from the modern level varied for different

time-intervals. During the Younger Dryas, P amounted to 60–65% of the present-day values in the East European Plain, 80% in

central West Siberia, and only 50% in central Yakutia. For the entire Northern Eurasia, P did not exceed 300–350mm/yr (in

Yakutia it was only 100mm/yr), levels typical for present-day dry steppe and semidesert zones. Nevertheless, the reconstructed

changes of the main climatic indexes were proportional to the present-day climatic characteristics, so that the general tendencies of

their contemporary distribution in the mid-latitudes were preserved during the entire Lateglacial/Early Holocene interval. This

shows that the general circulation of the atmosphere and geographical distribution of the main Highs and Lows in the studied time-

interval were in essence similar to the present-day ones.

Boundaries of permafrost in Lateglacial and Early Holocene migrated in response to climate changes. The southern limit of

permafrost during the Aller�d was at 601N in East Europe and 551N in West Siberia. During the Younger Dryas it moved south to

50–521N in East Europe, and parabolic sand dunes were formed. r 2002 Elsevier Science Ltd and INQUA. All rights reserved.

1. Introduction

Study of events which took place within the Lategla-cial and Early Holocene enables a better understandingof the process of transition from one essential part of aclimatic cycle to another, that is, from a glacial epoch toan interglacial one. The relatively short duration ofclimatic oscillations along with their substantial ampli-tudes caused a dramatic transformation of landscapesfrom ‘‘almost glacial’’ to ‘‘almost interglacial’’ states.The process was interrupted by a brief return to

periglacial conditions during the Younger Dryas cool-ing. A study of this transitional time-interval gives us apossibility to quantitatively estimate speeds, frequencies,and amplitudes characteristic for climatic oscillationsof such a rank, as well as the landscape changescorresponding to them. Such estimations are importantfor understanding future environmental changes of bothnatural and anthropogenic origin.Within Northern Eurasia, three main climatic regions

can be identified: (1) a West European sub-Atlanticregion, characterised by an oceanic climate; (2) an EastEuropean region with a temperate climate, transitionalfrom oceanic to continental; and (3) a Siberian regionwith a typical continental climate. Reconstructions ofcommon and specific features of major Lateglacial

*Corresponding author. Tel.: +1-709-737-8413; fax: +1-709-737-

3119.

E-mail address: ncatto@mun.ca (N. Catto).

1040-6182/02/$ - see front matter r 2002 Elsevier Science Ltd and INQUA. All rights reserved.

PII: S 1 0 4 0 - 6 1 8 2 ( 0 1 ) 0 0 1 0 4 - 5

climatic events, such as the Aller�d interstadial and theYounger Dryas stadial in each of these regions may helpto understand causes of climatic fluctuations and toestimate the impact of various factors on climate. One ofthe factors, considered to be the most important causeof the Younger Dryas cooling, is an influx of cold freshwater from the melting ice-sheets into the NorthAtlantic (Ruddiman and McIntyre, 1981; Broecker,1994, 1998). In particular, this factor has stronglyaffected the West European region. It is thereforeimportant to trace the reaction of the Siberian regionto the North Atlantic cooling, taking into considerationthe distance from the Atlantic Ocean, and the fact thatthere was no large continental ice-sheet in Siberia at thattime (Velichko et al., 2000). Modelling data suggest apositive feedback between vegetation cover and climate(Renssen and Lautenschlager, 2000).Unfortunately, there are still insufficient data from

Northern Eurasia for a comprehensive study. Primarypaleogeographical data are still scarce for some areas,and their interpretation may be ambiguous. Such adeficiency was partly made up for in West Europe bystudies of Vandenberghe (1991), Isarin (1997), Hoek(1997), Coope et al. (1998) and others. Paleobotanicaldata from the East European and Siberian regionswere discussed in the studies of Grichuk (1982) andKhotinsky (1977). A number of authors discussedvarious aspects of climate and vegetation changes atthe Lateglacial/Early Holocene transition in EastEurope and Siberia in the monograph ‘‘Short-termand Abrupt Landscape and Climatic Oscillations duringthe Last 15,000 yr’’ (Velichko, 1994) and in Quaternary

International 41/42 (1997). The processes of aeoliandune formation at the Lateglacial were studied byDrenova et al. (1997). Palynological studies of theLateglacial deposits were performed in West Siberia byLevina et al. (1983) among others, and in the Siberian

Arctic by Nikol’skaya (1980). The present study aims toanalyse peculiarities of the vegetation and climatechanges for the main time-intervals from Aller�d toBoreal for Eastern Europe and Siberia, based onpaleobotanical data and 14C dates, both published inthe above-mentioned studies and collected recently bythe authors.

2. Vegetation changes in Eastern Europe and Siberia

inferred from Palynological data

In this study, palynological data served as the basisfor both vegetation and climatic reconstructions. Theavailable palynological data, including unpublishedinformation by Zelikson and Borisova (also seeBorisova, 1997; Borisova et al., 1998; Zelikson, 1997)are not uniformly distributed over the study area. Mostsites are located in the East European Plain, with theexception of its southern part. Studied Lateglacialpollen sequences in Siberia are still rather few and farapart (see also Velichko et al., 1997; Velichko, 1999).Nevertheless, the amount of sites and their distributionpermits an attempt to reconstruct the main features ofvegetation and climate changes for Northern Eurasia.A selection of six pollen diagrams for the key-sections

of the Lateglacial and Early Holocene from differentregions of Northern Eurasia is presented in the nextsection. The selected sites are typical for their respectiveregions and dated by means of radiocarbon analysis.Their locations are shown in Fig. 1.

2.1. East European plain

The Ponizovye section (Fig. 2) is situated in thepresent-day zone of mixed broadleaved-coniferousforest and is typical for the west-central region of the

100° 140° 180°60°20°60°

60°

40°

�

�

��

��

Ponizovye

Melekhovo

Buzuluksky Bor

Entarny

Khomustakh

Dolgoe(Kamenistoye)

�Taimyr

Fig. 1. Location of key sites discussed in Fig. 2.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9976

East European Plain. In the Lateglacial deposits non-arboreal pollen (NAP) make about 30% of the total sumof terrestrial pollen and spores. High-percentage valuesof Artemisia are characteristic for this time-interval,while in the Holocene deposits it seldom occurs in this

region. Arboreal pollen (AP) is represented mainly byspruce, pine and birch. Pollen of such Siberiantree species, as Pinus sibirica, Larix, and Abies hasbeen recorded in the interval in small quantities.Complex vegetation of this time-interval combined dark

Hip

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(a) Ponizovye (b) Melekhovo (c) Buzuluksky Bor (d) Entarny (e) Khomustakh (f ) Kamenistoye55 N 31 E 57 N 39 E 53 N 51 E 61 N 79 E 64 N 125 E 72 N 128 Eo oo o o o o o o o oo

Fig. 2. Indicator pollen taxa of the Allerod–Younger Dryas–Preboreal vegetation and climate changes in Northern Eurasia. Simplified pollen

percentage curves for six key-sites are modified from: (a) Borisova (non-published data); (b) Khotinsky et al. (1991); (c) Kremenetski et al. (1999); (d)

Arkhipov et al. (1980); (e) Andreev et al. (1997); (f) Pisaric et al. (2001). All percentages are calculated from the total sum of pollen and spores of

terrestrial plants. Dashed curves show NAP percentages in spectra. Numbers in circles correspond to radiocarbon dates (the ages are quoted in

conventional radiocarbon yr):

Site Number 14C age (yr BP) Site Number 14C age (yr BP)

(a) Ponizovye 1 4960770 6 89787353

2 68807100 7 98977388

3 7720780 8 10,2887435

4 82907130 9 12,00075700

5 10,57171108 (d) Entarny 1 1110730

(b) Melekhovo 1 810745 2 2270745

2 1880740 3 6860750

3 3270760 4 99207120

4 4680760 (e) Khomustakh 1 9730750

5 65807460 2 99807100

6 7140760 3 10,4007600

7 82907480 (f) Dolgoye 1 1630760

8 10,2607300 2 3780770

9 11,9757370 3 5150770

(c) Buzuluksky Bor 1 1191750 4 7250780

2 2716769 5 9830780

3 3253770 6 10,2407120

4 46207126 7 11,5207110

5 69497319

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 77

coniferous forest communities of the West Siberian type,pine and birch forests, and herbaceous associations ofthe periglacial steppe type with xerophytes (Ephedra). Inthe Younger Dryas layer, the percentage of NAP ishigher than in the Aller�d (about 40%), with increasingcontent of shrub birch pollen (Fig. 2).Periglacial forest steppe of the Younger Dryas was

characterised by a larger role for open plant commu-nities with typical heliophytes (Helianthemum). Thewarming at the transition to the Holocene caused arapid spread of forest vegetation, represented mainly bybirch woodlands, and also by mixed birch-coniferouscommunities. AP relative abundance reaches 90% ofspectra at the end of the Preboreal. Important changesalso occurred in the composition of NAP: Artemisia

pollen content became as low as 20% of total herbac-eous pollen.The site Melekhovo is situated in the zone of broad-

leaved-coniferous forest about 125 km northeast ofMoscow. Pollen spectra of the Aller�d interstadial aredominated by AP, mainly that of spruce. Highpercentages of spruce, comparable with those in theSubatlantic, are typical for the Aller�d deposits in thisregion (so-called ‘‘lower maximum of spruce’’). Thecomposition of spectra shows that the surrounding areawas covered by spruce woodland/open forest incombination with periglacial steppe communities. Thepollen spectra of the Younger Dryas are dominated byNAP, mainly that of Artemisia. Chenopodiaceae pollenvalues in this interval are also greater than in the rest ofthe section. Pollen of periglacial steppe plants Kochia

prostrata, Eurotia ceratoides, Artemisia s/g Seriphidium

has been recorded in this zone (Khotinsky et al., 1991).Shrub birch pollen content increases against a dramaticdecrease of spruce pollen, which indicates spread ofherbaceous communities of periglacial steppe type overthe area due to the climate deterioration. In thePreboreal, AP values become greater, which reflects arapid spread of forest vegetation over the area. Thewoodlands were then dominated by birch with increas-ing participation of pine.The section Buzuluksky Bor is situated in the south-

eastern Russian Plain in the herb–grass steppe zone.Pollen spectra here were dominated by NAP not onlyduring the Lateglacial, but also during the entireHolocene. Nevertheless, NAP reached its maximum(about 85%) during the Lateglacial. High proportionsof Artemisia pollen (40–45%) were typical for both theLateglacial and the Preboreal intervals. Such spectrareflect a spread of the periglacial steppe vegetation incold and dry climates. The maximum of the Chenopo-diaceae curve, as well as an increase of Ephedra pollencontent, indicate that the most severe climatic condi-tions existed here during the Younger Dryas stadial. Inthe Preboreal, pine spread rapidly over the area andbecame the dominant species of forest communities at

about 9Kyr BP (Kremenetski et al., 1999). Chenopo-diaceae values decrease, while the diversity of Variatypes increases.

2.2. West Siberia

The section Entarny (Arkhipov et al., 1980) is locatedon the first terrace of the Ob’ River in the middle taigazone (spruce-fir-Siberian pine forest). Pollen spectraduring the Lateglacial/Preboreal interval are dominatedby NAP (mainly Poaceae)Fup to 60%. Such spectrareflect widespread herb–grass communities on thesurrounding territory. A small but distinctive peak ofArtemisia pollen (10% of spectra) corresponds to theYounger Dryas, indicating cold and relatively dryclimatic conditions. Arboreal species played a minorrole in the vegetation. Tree pollen is represented mainlyby birch. Pine pollen (both of Pinus sylvestris and P.

sibirica) occur in small quantities. Picea values graduallyincrease during the Preboreal. The spectra show that thearea was covered mainly by birch forest with spruce,though herbaceous communities were still prominent inthe vegetation.

2.3. East Siberia

Khomustakh Lake (Andreev et al., 1997) is situated incentral Yakutia in the zone of middle taiga (larchforest). Here the Aller�d pollen spectra are characterisedby the predominance of AP (up to 80%), about halfbeing pollen of shrub birch. Pine and larch values in thispollen zone are slightly greater than in the one of theYounger Dryas. Pollen of Alnaus fruticosa, Picea, Salix,and Alnus is registered here in small amounts. In theNAP group Artemisia is the most abundant type,though its content is only 15–20% of the total sum ofpollen and spores of the terrestrial plants. In the pollenspectra of the Younger Dryas NAP values increaseconsiderably (up to 60%), including about 40% ofArtemisia. AP is represented here mainly by tree andshrub species of birch. Climate amelioration during thePreboreal is marked with gradual increase of AP, mainlythat of Betula, and also by a small peak of Larix pollen.

Dolgoye Lake (Pisaric et al., 2001) is situated near theLena River mouth, at the northern limit of open larchforest (northern taiga zone). Coring of lake sedimentsand their study were a part of a collaborative Canadian–Russian project Paleo Arctic Tree Line (PACT). TheLateglacial and the Preboreal layers at this site arecharacterised by high NAP content (up to 70%), mainlythat of Poaceae, Cyperaceae and Artemisia. AP isrepresented by Betula and Salix. In the layer, corre-sponding to the Younger Dryas, pollen curves of allmain herbaceous taxa, including Artemisia, form theirmaximums. Their relative abundance decreases consid-erably at the Lateglacial/Holocene boundary. Larix

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9978

pollen, as well as its stomata, indicating an actualpresence of the larch trees at the site, appears in thesequence only within the Atlantic climatic optimum ofthe Holocene.

Lateglacial plant communities were inherited from theperiglacial steppe vegetation of the Last Glacial max-imum (Grichuk, 1984). Their gradual restructuring tookplace both under a direct influence of the climatechanges (increasing heat and moisture supply, a decreaseof continentality of climate, etc.), and due to an impactof changes in abiotic components of the landscapes inresponse to the warming (e.g. permafrost degradation).These changes in the composition of vegetation occurredon the basis of the same flora, because the Lateglacialwarming did not reach a degree sufficient for a completedisappearance of some taxa from the flora. Introductionof other plants has been limited, by natural speeds ofmigration, which reaches about 1 km/yr for the pioneertree species and 0.3–0.5 km/yr for the broad-leaved trees(Velichko et al., 1991), in addition to the constraintsposed by climate conditions.The Aller�d was the first episode after LGM when a

forest zone, though different from the present-day onein the composition of communities and density ofwoodlands, was formed on the East European Plain.The Younger Dryas was the most recent stage ofperiglacial vegetation re-establishment in EasternEurope. The maximum of Artemisia pollen curve,typical for the Younger Dryas of the Europeandiagrams, is a characteristic feature of the YoungerDryas time-interval all over Northern Eurasia. Itindicates specific cold and dry continental climaticconditions of the stadial.A transition from the Lateglacial to the Holocene was

marked by crucial changes in the composition of floraand vegetation. In the Preboreal, forest vegetationspread rapidly all over the studied area.

3. Quantitative palaeoclimatic reconstruction

3.1. Method

Paleoclimatic reconstruction from pollen data isbased on the correlation between the composition ofrecent pollen spectra (RPS) and present-day climaticconditions. A total of 777 RPS from 220 sites located allover the territory of the former Soviet Union were usedfor this study. Climatic parameters such as mean annualtemperature and mean annual precipitation were de-rived from relationships with the composition of RPS.To determine such relationships, an information-logicalanalysis was used (Puzachenko, 1971).Percentage values for each main arboreal taxon of

pollen spectra (0–100%) and the main groups ofterrestrial plants (AP/NAP/Spores) were subdivided

into two to ten grades, depending on the number ofRPS containing pollen of this taxon and the range of itsvalues. The following main climatic indexes, tradition-ally used to characterise heat and moisture supply, werechosen: mean annual temperature (to), mean January to;mean July to; and mean annual precipitation. Modernclimatic indexes for the RPS sites were taken from theClimatic Atlas (Klimaticheskiy atlas, 1960). For eachmain climatic index, a range of its variation was sub-divided into 9–11 grades. For each main climatic para-meter and for percent values of main taxa, a table showingthe probabilities of their combinations was compiled.Every natural system is characterised by a degree of

uncertainty, for example, the variability of mean Julytemperature at a particular location. In statisticalinformation theory, the uncertainty of a system iscalculated from the Shannon–Weiner formula,

HnðAÞ ¼ �Xn

i¼1

PðaiÞ log2PðaiÞ; ð1Þ

where PðaiÞ is the probability of event ai in system A:The larger the value of Hn; the greater the uncertainty ofthe system. The uncertainty can be reduced if anotherevent in a different system has occurred. For example,climatic variables of a region can be predicted with lessuncertainty if the percentages of particular pollen taxaare known. If the conditional uncertainty of phenom-enon A (in the example, a particular climate variable) iscombined with known state of factor bk(the percentageof the kth pollen taxon), then

HnðA=bkÞ ¼ �Xn

i¼1

Pðai=bkÞ log2Pðai=bkÞ; ð2Þ

where Pðai=bkÞ is the conditional probability of event ai;provided that event bk has occurred. In the calculations,the values of P log2 P are taken from special tables. Ifthe conditional uncertainty HnðA=bkÞ is less than theunconditional value HnðAÞ; then event bk decreases theuncertainty of phenomenon A: The difference of thesequantities is a measure of the extent to which theestimation of A becomes more certain when bk is known,and it is referred to as the information (Y ) on A

contained in bk (Table 1).

Y ðA=bkÞ ¼ HnðAÞ � HnðA=bkÞ: ð3Þ

Each bk carries only part of the informationtransmitted in the two-component system A � B as awhole, with all of the information transmitted deter-mined from the formula

TðA;BÞ ¼Xm

k¼1

PðbkÞY ðA=bkÞ: ð4Þ

In this context, information transmitted means themeasure of uncertainty that can be eliminated. Themagnitude of TðA; BÞ depends not only on the strengthof the relationship between the phenomenon A and the

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 79

factor B but also on the magnitude of their uncertain-ties. The dimensionality of information determined in agiven system is eliminated by means of the normalisedcoefficient of contingency (K):

KðA;BÞ ¼2TðA;BÞ � 1

2Hmin � 1; ð5Þ

where Hmin is the minimum uncertainty of phenomenonA or factor B (Table 2).According to the coefficient KðA; BÞ; the main tree

species can be divided into three groups, of high,medium and minor importance for the climatic recon-struction, the trees with a broad ecological amplitudebeing the least important for the purpose. The higher the

pollen content of the most informative taxa is, the morecertain the climatic reconstructions are.Still another characteristic of relationships between

two systems (climatic data and pollen spectra) is theclassification criterion (C), which is defined as the ratioof the conditional probability of the phenomenon to itsunconditional probability C ¼ ½Pðai=bkÞ�=½PðaiÞ�: WhenC is maximised, the probability of phenomenon ai

having occurred is maximised at state bk (index 100). Inthe example (see Table 1), C; and hence the probabilityof a particular mean July temperature (ai), is maximisedat the location where the particular pollen percentage ofa taxon most definitely related with the particulartemperature interval. As the result of statistical analysisof RPS, 16 tables were compiled (one for each main tree

Table 1

Information (Y ) and classification criterion (C) for selected tree pollen types and mean July temperature

Pollen percentage classes Mean July temperature (1C)

o6 6–10 10–14 14–16 16–18 18–20 20–22 22–24 24–28 >28 Y ðA=bkÞ

Quercus 0.1–5 F F 0 0 1 1 100 1 0 0 0.678

5.1–10 F F 0 F 0 100 1 1 0 F 0.860

10.1–20 F F 0 F F 100 1 0 0 F 0.884

20.1–35 F F 0 F F 1 100 0 0 F 0.992

35.1–55 F F F F F 1 100 0 F F 1.041

55.1–75 F F F F F 1 100 0 F F 1.416

75.1–100 F F F F F 0 100 1 F F 0.953

Tilia 0.1–5 F F 0 0 1 1 100 0 0 0 0.664

5.1–10 F F 0 F 0 100 1 F F F 1.117

10.1–20 F F 0 F F 100 1 F F F 1.370

20.1–35 F F 0 F F 100 F F 0 F 1.443

35.1–50 F F 0 F F 100 F F F F 2.150

>50 F F F F F 100 F F F F 2.742

Carpinus 0 1 1 1 1 1 1 0 0 1 1 0.062

0.1–10 F F F 0 0 1 1 100 F F 0.576

10.1–25 F F F F 0 1 1 100 F 0 0.899

25.1–50 F F F F F 0 0 100 F 0 1.282

>50 F F F F F F F 100 F 0 1.930

Betula 0.1–5 100 1 1 1 0 0 F F F F 1.005

5.1–10 100 1 1 1 0 0 F F F F 1.032

10.1–20 F F 100 1 0 0 F F F F 1.123

20.1–30 F F 100 0 0 0 F F F F 1.490

>30 F F 100 0 F F F F F F 1.820

Picea 0.1–5 0 1 1 1 1 100 1 1 0 F 0.364

5.1–10 0 0 1 1 100 1 0 0 0 F 0.572

10.1–15 0 0 1 100 1 1 0 0 0 F 0.476

15.1–20 F F 0 1 100 0 0 0 F F 1.028

20.1–30 F F 0 1 100 0 0 F F F 0.965

30.1–40 F F 0 100 1 0 F F F F 1.284

40.1–50 F F 0 100 1 0 F F F F 1.443

>50 F F 0 100 1 F F F F F 1.930

Pinus 0.1–10 1 1 1 1 0 0 0 0 1 100 0.048

10.1–20 1 1 100 1 1 1 0 0 1 100 0.254

20.1–30 1 100 1 1 1 1 0 0 1 1 0.236

30.1–40 1 1 100 1 1 1 0 0 0 F 0.580

40.1–60 1 1 0 0 100 1 0 0 0 F 0.377

60.1–80 1 1 0 1 1 1 1 1 100 F 0.116

80.1–100 F 1 0 0 1 1 1 1 100 F 0.148

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9980

species). These tables reveal the structure of relation-ships existing between the percent values of pollen of themain arboreal taxa in RPS and the main climaticparameters.The method of information-logical analysis enables:

(a) estimation of the degree of relationship between theclimatic parameters and composition of RPS, or arelative importance of each tree species for estimating aspecific climatic index, described by a coefficientKðA; BÞ; (b) determination of the coefficient of con-tingency between a percentage of a specific taxon inpollen spectra and a specific climatic index; and (c)assessment of which climatic indexes are characteristicfor certain pollen percentages in the spectra (Table 3).The most probable value of a paleoclimatic variable fora particular pollen spectrum corresponds to the largest

sum of the classification criterion (C) obtained from allthe pollen types in the spectrum. If two climatic classesgive equal summations, the more probable value is theone corresponding to the larger sum of the maximumclassification criterion (the one including more doubleprime units).The reliability and accuracy of the prepared tables for

reconstructing climatic variables were determined byestimating present-day main climatic indexes frommodern pollen spectra. In the reconstruction, 190 RPSwere analysed. An incorrect result was obtained from 39spectra. From 27 spectra out of these 39, the recon-structed and actual climatic values were in adjacentclasses. Such discrepancies are not significant. Appreci-able discrepancies of more than one class were predictedby 12 (6.3%) of the assemblages for mean July

Table 2

Normalized contingency (K) of pollen types with climatic parameters

Pollen Normalized contingency coefficient K

Mean annual temperature Mean July temperature Mean January temperature Total annual precipitation

Total spectra composition

Arboreal pollen 0.047 0.093 0.032 0.050

Non-arboreal pollen 0.052 0.104 0.040 0.043

Spores 0.059 0.052 0.038 0.024

Arboreal pollen types

Abies 0.236 0.067 0.203 0.120

Alnus 0.046 0.050 0.039 0.055

Betula 0.046 0.027 0.039 0.028

Betula nana 0.273 0.164 0.267 0.103

Carpinus 0.251 0.257 0.267 0.207

Fagus 0.384 0.333 0.343 0.314

Larix 0.325 0.124 0.351 0.141

Picea 0.075 0.079 0.029 0.050

Pinus 0.040 0.036 0.042 0.029

Quercus 0.142 0.132 0.117 0.049

Salix 0.105 0.051 0.099 0.046

Tilia 0.142 0.117 0.131 0.088

Ulmus 0.112 0.125 0.087 0.073

Table 3

Example of a reconstruction of mean July temperatures

Pollen types Pollen percentage Mean July temperatures (1C)

o6 6–10 10–14 14–16 16–18 18–20 20–22 22–24 24–28 >28

Arboreal pollen 31 1 100 1 0 0 1 100 0 0 FNon-arboreal pollen 13 0 0 1 100 1 0 0 0 F FSpores 56 F F 1 0 0 0 0 F F FBetula 7 0 0 0 0 0 0 1 1 1 1

Picea 3 0 1 1 1 1 100 1 1 0 FPinus 35 1 1 100 1 1 1 0 0 0 FQuercus 16 F F 0 F F 100 1 0 0 FTilia 37 F F 0 F F 100 F F F FUlmus 2 F F 0 0 0 1 100 F F FSum of classification criteria 2 3 5 3 3 6 5 2 1 1

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 81

temperatures. In the reconstruction of mean annualtemperatures, appreciable discrepancies were 6.7%, formean January temperatures 8.2%, and for total annualprecipitation 7.0%. The mean statistical errors for thereconstruction were 70.61C for mean annual and forJuly temperature, 711C for mean January temperature,and 725mm for total annual precipitation.

3.2. Regional climatic changes

The bar chart in Fig. 3 shows the summarised resultsof quantitative reconstruction of temperatures andannual precipitation for six sections forming a sub-latitudinal profile. In this figure, peculiarities are evidentin the distribution of the main climatic indexes in theLateglacial/Early Holocene from west to east throughNorthern Eurasia.In the central part of the East European Plain

(Melekhovo), the temperature in Aller�d was 11C lowerthan today in July and 21C lower in January. The meanannual precipitation was slightly greater than at present(by 25mm). The mean temperatures in the YoungerDryas were conspicuously lower compared to thepresent-day level: by 81C in January and by 61C inJuly. In contrast to the Aller�d, the annual precipitationwas also lower than at present (by 150mm). At thebeginning of the Preboreal, the temperatures were closeto the present-day ones, the deviations being negligible

for the mean January to and �11 for July to: The meanannual precipitation was then 50mm lower.During the Aller�d, two warmer intervals, separated

by a short cooling, were reconstructed (Figs. 10 and 11)in the southeast East European Plain (Buzuluksky Bor).During the first warming, the mean January to was 31Clower, and that of July 21C lower than at present. Theprecipitation was reduced by 50–75mm compared tomodern values. The second warming was approximately0.5–11C warmer than the first one. During the YoungerDryas the climate was colder and drier than in theAller�d: the mean January to was 61C lower, that of July51C lower, and the precipitation sum 200mm lower thanthe present-day one. Two warm intervals were registeredduring the Preboreal. The warming ca. 98977388 yr BP(14C uncal.) was characterised by the main temperatureindexes close to the modern ones, with the precipitationreduced by 25–50mm. The second warming was similarto the first one. During the cold interval separating thesetwo warm stages, the mean January to was 41C lower,that of July 31C lower, and the mean annual precipita-tion almost 100mm lower than the present-day level.The reconstruction for the Galich site (Velichko et al.,

2001) reveals a similar pattern of temperature andannual precipitation deviations from the modern valuesfor the Aller�d and the Younger Dryas. During thePreboreal DtoJan was 81C lower, DtoJuly was about 61Clower, and precipitation was about 120mm less than atpresent.

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A.A. Velichko et al. / Quaternary International 91 (2002) 75–9982

In Siberia, climate parameters during the warmintervals of the Lateglacial and Early Holocene werecloser to the modern level than those in Eastern Europe.In the Taimyr Peninsula the mean January and July to

were lower than the present-day ones only by 11C. InCentral Yakutia (Khomustakh, Suollakh and Vilyuisites) the mean January to was 31C and mean July to 21Clower than at present. In both of these regions theannual precipitation during the Aller�d was about50mm lower than today. During the Younger Dryasthe deviations of the main climatic indexes from thepresent-day values were larger: DtoJan�41C, DtoJuly�21Cin Taimyr; DtoJan¼ �51C, DtoJuly�61C in the central partof West Siberia (Entarny) and in Central Yakutia. Thedeviations of annual precipitation from the present-dayvalues were �100mm in Taimyr and Central Yakutia,and �150mm in the central part of West Siberia. In thePreboreal, DtoJan and DtoJuly were �21C in Taimyr and�11C in Central Yakutia. In the central part of WestSiberia DtoJan was about �21C, DtoJuly�31C. The meanannual precipitation was generally close to the present-day level: the deviations were +25mm in West Siberiaand �25mm in Central Yakutia.The reconstructions show that variations of the mean

January temperature were generally greater than thoseof the mean July to: As at present, the mean Januarytemperature decreased from the west to the east, whileits deviations from the present-day values were slightlygreater in the East European Plain than in Siberia. Onthe whole, precipitation decreased in the easterndirection, but its deviations from the modern levelvaried for different time-intervals. The reconstructionfor Aller�d show precipitation close to the modern levelfor Melekhovo site (central East European Plain), but inthe other sites precipitation was reduced. During theYounger Dryas, the mean annual precipitationamounted to 60–65% of the present-day values in theEast European Plain, 80% in central West Siberia, andonly 50% in central Yakutia. For the whole studiedarea, the precipitation did not exceed 300–350mm/yr (inYakutia it was only 100mm/yr), that is, the level typicalat present for dry steppe and semidesert zones. Takinginto consideration existing correlation between wintertemperatures and precipitation, one can assume thatsuch a considerable reduction of precipitation during theYounger Dryas was mainly due to the winter precipita-tion decrease.Nevertheless, the reconstructed changes of the main

climatic indexes at all the key-sites were proportional tothe present-day climatic characteristics, so that thegeneral tendencies of their contemporary distributionalong the mid-latitudinal belt were preserved duringentire Lateglacial/Early Holocene interval. This showsthat the main centres of general circulation of theatmosphere in the studied time-interval were in essencesimilar to the present-day ones.

The reconstructions from all these sites show that theYounger Dryas stadial was both the coldest and thedriest period during the Lateglacial/Holocene transition.The decrease of toJan compare to the Aller�d interstadialwas larger than that of toJuly:

3.3. Spatial climatic reconstruction

In spite of the limited number of the studied sites andtheir non-uniform distribution over the research area, itis still possible to reconstruct the main features ofclimate of Northern Eurasia for several time-intervals ofthe Lateglacial and Early Holocene.

3.3.1. Allerød

Reconstruction of the main climatic indexes for theAller�d is based on 31 sites (Table 4).

Mean January temperature (Fig. 4a). Against thegenerally low-temperature background as compared tothe present-day level, two areas with larger negativetemperature deviations are registered: the northwesternpart of the East European Plain, and eastern andsoutheastern Siberia. If the existence of the former onecan be explained by the influence of the Scandinavianice-sheet, that of the latter one is more difficult toexplain. While in East Europe the meridional gradient ofthe mean January temperature was larger than atpresent, it became smaller in Siberia.

Mean July temperature (Fig. 4b). In summer, acooling influence of the Scandinavian ice-sheet can stillbe traced in the northwestern East European Plain. Anarea with relatively large negative deviations of toJuly isalso reconstructed in southern Siberia. An interestingfeature of the summer temperature distribution in theAller�d was an area in eastern Arctic Siberia with a toJulyexceeding the present-day ones. Thus, in the northern-most part of the Yano-Indigirskaya Lowland DtoJuly wereabove +21C. Therefore, the meridional gradient of themean July temperature was greater than at present inEast Europe, close to the present value in West Siberia,and smaller in East Siberia and in northeastern Asia.

Mean annual precipitation (Fig. 4c). Deviations of themean annual precipitation from the modern values werealso not uniform over the studied area. Over the majorpart of Siberia the precipitation was lower than atpresent by approximately 50mm. The deviations werelarger in the northwestern East European Plain, near themargin of the Scandinavian ice-sheet. The southernparts of the study area, in contrast, experienced anincrease of precipitation.

3.3.2. Younger Dryas

The reconstructions of the main climatic indexes forthe Younger Dryas stadial are based on the pollenspectra from 29 sites (Table 5).

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 83

Mean January temperature (Fig. 5a) and mean July

temperature (Fig. 5b). Temperature deviations from thepresent-day values both for the coldest and for thewarmest months were distributed over Northern Eurasiamore uniformly in the Younger Dryas than during theAller�d. The entire East European Plain and Siberiashow negative temperature deviations, which were atleast two times the values reconstructed for the meanJanuary temperature in the Aller�d. As in the Aller�d,one of the areas with the greatest negative temperaturedeviations was the northwestern part of the EastEuropean Plain closest to the Scandinavian ice-sheet.In the East European Plain DtoJan exceeded �141C andDtoJuly �81C. Another region with substantial negativetemperature deviations from the modern values wassituated in southern Siberia. Here, the mean January to

were 121C lower than today, and those of July 81Clower. The meridional temperature gradient in EastEurope reached its maximum for the entire Lateglacialin the Younger Dryas. In Siberia, on the contrary, it wassmaller than at present.

Mean annual precipitation (Fig. 5c). As mentionedabove, the Younger Dryas was the driest interval of the

Lateglacial, though the degree of aridity varied over thearea under investigation. The maximum decrease inprecipitation compared to the present-day level (bymore than 250mm) was reconstructed for the northernpart of the East European Plain. The region is located tothe east of the one with the largest negative temperaturedeviations. It is possible that in the western part of thearea invasions of moisture-bearing air masses from theAtlantic sometimes occurred, while its eastern part wasmore constantly blocked from such invasions by ananticyclone system located above the ice-sheet. Anotherarea with large negative deviations of the mean annualprecipitation from the modern values was reconstructedin the southern Siberia.

3.3.3. Preboreal

Reconstruction of the main climatic indices for thePreboreal is based on the pollen spectra from 30 sites(Table 6).

Mean January temperature (Fig. 6a) and mean July

temperature (Fig. 6b). In the Preboreal, the pattern oftemperature deviations from the modern values wasgenerally similar to the one reconstructed for Aller�d,

Table 4

Climatic reconstructions for Aller�d sites

Site number Latitude, 1N Longitude, 1E Name of the site DtoJan DtoJuly DP Sources of palynological data

1 62 34 Gotnavolok �9 �3 �110 Yelina G.A.a

2 61 34 Dlinnoye �10 �3.5 �100 F3 61 30 Ladoga �7 �3 �100 Delyusina I.V.a

4 67 35 Kun’ok �5.5 �3 �100 Lebedeva R.M.a

5 59 25 Vakharu �7 �1.5 �100 Kayak et al. (1976)

6 58 25 Vizusti �3.5 �1 �60 Pirrus (1971)

7 69 35 Kol’sky Zaliv �7 �3.5 �75 Malyasova (1960)

8 67 35 Solovki �8 �2.5 �75 Manuilov et al. (1981)

9 55 25 Shvyantos �3 �1.5 �50 Stelle (1966)

10 57 26 Dukuldpite �4 �1 �75 F11 56 23 Lielautse �3.5 �1 �50 F12 57 24 Kalitsieas �3 �1 �50 F13 55 22 Binavinyai �3.5 �1 �60 Bartosh (1966)

14 54 27 Chernikhovo �1 �0.5 �30 Zernitskaya et al. (1988)

15 56 28 Naroch �3 �1.5 �25 Makhnach et al. (1971)

16 55 28 Latashi �3.5 �1 �30 Zimenkov and Val’chik (1986)

17 51 25 Starniki �1 �0.5 �30 Bezus’ko L.G.a

18 56 39 Melekhovo �2 �1.5 0 Khotinsky et al. (1991)

19 50 31 Srednee Pridneprov’ye �0.5 �0.5 �10 Kayutkina T.M.a

20 57 31 Sit’ma �3.5 �2 �30 Zimenkov and Val’chik (1986)

21 56 37 Msharovskoye �3 �1.5 �30 Khotinsky (1977)

22 73 100 Balakhnya �0.5 0 F Nikol’skaya M.V.a

23 52 105 Kotokel’ �6 �3 �50 Khotinsky (1977)

24 63 125 Khomustakh �3 �1.5 �60 Andreev et al. (1997)

25 58 125 Suollakh �1 �1 �25 F26 45 137 Kievka �7 �2.5 �50 Shumova and Klimanov (1986)

27 43 133 Partizanskaya �9 �2.5 �50 Golubeva and Karaulova (1983)

28 44 135 Ussuri �9.5 �2 �50 F29 69 170 Chaunskaya 1 �5 5 F Veinbergs et al. (1976)

30 72 170 Chaunskaya 2 �2 3 �20 Ovander et al. (1987)

31 53 83 Suzun �5 �3.5 35 Levina T.P.a

32 53 51 Buzuluksky Bor �3 �4 �65 Kremenetski et al. (1998)

aPersonal communication.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9984

(a)

(b)

Fig. 4. Spatial climatic reconstructions for the Aller�d interstadial (deviations from the present-day values): (A) mean January to; (B) mean July to;and (C) mean annual precipitation. (1) The Scandinavian ice-sheet boundary; (2) the present-day position of the �50m bathymetric contour.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 85

though the deviations (both positive and negative) weresomewhat smaller. Near the Scandinavian ice-sheetDtoJan reached �61C, and DtoJuly �21C. In southernSiberia, both DtoJan and DtoJuly were close to �2C1. Themean temperatures were close to the present-day ones innorthern Siberia, minor positive deviations beingreconstructed for the area.

Mean annual precipitation (Fig. 6c). Along withgenerally lower temperatures than at present, thePreboreal was characterised by lower precipitation(generally by 50mm/yr). The largest negative deviationswere reconstructed for the area adjacent to theScandinavian ice-sheet (by more than 150mm/yr). Insouthern Siberia the mean annual precipitation wasabout 25mm less than the present-day. In contrast, thereconstructed precipitation value in Taimyr is 50mmhigher than the modern one.

4. CryolithozoneFspatial reconstruction

It is well known that there is a definite relationshipbetween recent climatic parameters and those of thecryosphere (Gavrilova, 1981). Frozen ground tempera-ture depends on the mean annual air temperature,

annual air temperature range, as well as on the snowcover thickness and properties (Kudryavtsev, 1959;Washburn, 1979). The soil temperature field forms abasis for subdivision of the permafrost area intoindividual subzones.Some climatic parameters, however, permit identifica-

tion not only variation of thermal characteristics withinthe single permafrost area, but also spatial distributionof its varieties (continuous, discontinuous, sporadicpermafrost). One such example is the relative severityindex, defined as the ratio between the absolute values ofthe temperature of the coldest month (January) and thatof the warmest one (July), expressed in degrees Celsius(Nechaev, 1981). The special convenience of this index isthat all the necessary data on climates are readilyavailable. As well, it permits establishment of thecryolithozone structure when studying large areas.Spatial climatic reconstruction for certain time-inter-

vals, such as appeared in recent decades, opened freshopportunities for detailed studies of the cryolithozonedynamics. On the basis of the principle of uniformity,these relationships and indices can be applied toreconstruction of the cryolithozone and some of itscharacteristics during the chronological intervals underconsideration (the LateglacialFEarly Holocene).

(c)

Fig. 4 (continued).

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9986

4.1. Allerød (Fig. 7a)

At that time, the spatial structure of the cryolithozonein the Eurasian North develops features not unlike tothose of interglacials. The environments, however, werestill more severe as compared with the present day. Thisis especially true of the western segment (west of theYenisei R.) and of the Far East. The southern limit ofsporadic permafrost was near latitude 601N in EasternEurope and close to 551N in West Siberia. In theTransbaikalian region and the Amur drainage basinpermafrost was more widespread than at present. Innortheastern Europe, continuous permafrost expandedsouth of the Arctic Circle, with frozen ground tempera-ture �41C to �51C at the lower reaches of the PechoraRiver. Ground temperatures somewhat below thepresent-day values occurred also in the north of WestSiberia, in the Lower Tunguska River basin, and inCentral Yakutia.The warming was distinct in northeastern Asia. The

lowest frozen ground temperatures reconstructed for theregion are �81C to �101C, that is, close to those oftoday. As suggested by data on the Kolyma–IndigirkaLowland, formation of the loess-ice deposits ended

about 13 ka BP (Gubin, 1997). There are strong reasonsto believe that this was largely due to the Aller�dwarming in the region.Therefore, a certain duality may be noted as typical

for the cryolithozone structure and parameters duringthe Aller�d. On one hand, a stepped configuration of thepermafrost southern boundary and the ground tem-perature field in the Siberian North are similar to thecharacteristics of the recent interglacial (the Holocene).On the other hand, the cryolithozone parameters in theEuropean Northeast and in the Far East are indicativeof more severe conditions than at present.

4.2. Younger Dryas (Fig. 7b)

The Younger Dryas cold stage resulted in an unusualstructure of the cryolithozone. Subzones of continuous,discontinuous and sporadic permafrost replaced eachother from north to south in northern and centralEastern Europe. A peculiar hyperzone of permafrostdominated vast expanses of Asia, from the Urals to thePacific coasts. This area of low-temperature continuouspermafrost joined the alpine permafrost area of the

Table 5

Climatic reconstructions, Younger Dryas sites

Site number Latitude, 1N Longitude, 1E Name of the site DtoJan DtoJuly DP Sources of palynological data

1 62 34 Gotnavolok �15 �5 �150 Yelina G.A.a

2 61 32 Dlinnoye �15.5 �5.5 �150 F3 64 38 Tomitsa �15 �5.5 �150 Koshechkin et al. (1977)

4 64 43 Seb-boloto �14 �6 �225 Yelina G.A.a

5 61 29 Vuoksa �16 �5.5 �200 Ladyshkina et al. (1977)

6 59 25 Kunda �13 �6 �200 Pirrus (1976)

7 56 23 Elgava �13.5 �4.5 �175 Stelle (1966)

8 58 27 Ostrov �15 �6 �175 Malakhovsky et al. (1983)

9 54 27 Kobuzi �6.5 �4 �90 Bogdel I.I.a

10 54 28 Sudoble �6.5 �4 �75 F11 54 27 Chernikhovo �6 �3.5 �75 Zernitskaya et al. (1988)

12 51 26 Stariniki �4 �2 �50 Bezus’ko I.G.a

13 56 39 Melekhovo �10 �5 �200 Khotinsky et al. (1991)

14 59 52 Sit’ma �12.5 �6 �200 Ivanova (1971)

15 62 57 Dutovo �6 �3 �275 Nemkova (1976)

16 61 57 Niz’va �10 �3 �300 F17 57 54 Votkinsk �11 �4.5 �200 F18 55 55 Yevbazy F �5 �225 Nemkova (1976)

19 58 61 Gorbunovo �10.5 �4.5 �150 Khotinsky (1977)

20 61 78 Entarny �7 �5 �150 Klimanov and Levina (1989)

21 53 83 Suzun �13 �11 �125 F22 53 96 Todzha �13 �6 �225 Levina et al. (1983)

23 52 105 Kotokel’ �12 �5 �325 Khotinsky (1977)

24 69 90 Noril’sk F �2 �25 Kind (1974)

25 71 98 Boyarka F �2.5 F Nikol’skaya M.V.a

26 63 118 Markha F �4 F Shofman I.I.a

27 63 120 Vilyui �6.5 �3 �150 Andreev A.A.a

28 45 137 Kiyevka �12 �5.5 �150 Shumova and Klimanov (1986)

29 52 142 Uandi �8 �3 �175 Khotinsky (1977)

30 53 51 Buzuluksky Bor �6 �5 �200 Kremenetski et al. (1998)

aPersonal communication.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 87

(a)

(b)

Fig. 5. Spatial climatic reconstructions for the Younger Dryas (deviations from the present-day values): (A) mean January to; (B) mean July to; and(C) mean annual precipitation. (1) The Scandinavian ice-sheet boundary; (2) the present-day position of the �50m bathymetric contour.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9988

Altai, Sayan, Khentei and Khingan mountain systems.Each of the sectors deserves special consideration.In the north of Eastern Europe (north of latitude

63–641N) a low-temperature permafrost subzone ex-isted, where ground temperatures were less than �71Cto �91C. Such temperatures are reconstructedfor the Kola Peninsula, Karelia, Mezen, and Pechoradrainage basins. The southern boundary of thecontinuous permafrost subzone with ground tempera-tures lower than �21C to �31C was at latitude 601Nnear the Baltic coast, at about 551N in the Kama basin,and sharply advanced towards the south (to 501N) nearthe Ural Mountains. The southern boundary of thesporadic permafrost ran near 521N in the centralportion of the region and at about 501N within theVolga basin. On the whole, in the Younger Dryas thepermafrost boundary shifted southward by at least700–800 km relative to its position in the Aller�d. Inparticular, evidence of active cryogenic processes, suchas frost cracking and small polygon formation near thepermafrost southern limit, are suggested by data on theDesna drainage basin and the northern Caspian region(Velichko et al., 1977; Ivanov and Vasilyev, 1995).As stated above, there was a region of extremely

severe cryogenic conditions beyond the Urals. Thelow-temperature continuous permafrost with ground

temperature less than �61C to �71C occurred north of651N in West Siberia and expanded up to the Altai andSayan foothills in the upper reaches of the Ob andYenisei rivers. The Younger Dryas ice wedge pseudo-morphs found here are comparable in size and distribu-tion to the pseudomorphs dated to the Sartan maximum(Tseitlin, 1979). Similarly, severe conditions have alsobeen reconstructed for the Transbaikalian region andnorthern Far East.Frozen ground temperatures were as low as �101C to

�111C in the central part of East Siberia and �121C to�141C in the northeast of Asia; that is about 31C to 51Cbelow the temperatures during the Aller�d. However,loess-ice complex formation did not resume in theYounger Dryas in spite of the cooling. Conceivably,those syngenetically frozen deposits require much lowertemperatures (�201C to �251C). Unlike the regionsfarther west and south, permafrost characteristics in theSiberian North differed essentially during the YoungerDryas from those typical of the Late Pleistocenemaximum cooling.

4.3. Preboreal (Fig. 7c)

During Preboreal time, the structural pattern of thecryolithozone largely resembled that of the Aller�d. Its

(c)

Fig. 5 (continued).

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 89

western segment (west of the Yenisei) featured cryogenicconditions more severe than at present, while the condi-tions in East Siberia were much like those of today.In the north of Eastern Europe, continuous perma-

frost expanded all over the Malozemelskaya andBolshezemelskaya tundras, but unlike during theAller�d, it was absent from the Kola and Kaninpeninsulas. The southern limit of the sporadic perma-frost occurrence ran somewhere along latitude 621N,about 200–250 km north of its present-day position. Onthe whole, the region under consideration featuredsomewhat less severe conditions than during the Aller�dd warming.Such is not the case for West Siberia; both the thermal

characteristics of the cryolithozone and the location ofsubzones practically coincide with reconstructed cryo-genic features of the Aller�d (southern boundary of thecontinuous permafrost near latitude 651N, that ofsporadic permafrostFnear 551N). A similarity betweenthe cryolithozone structure in the Aller�d and Preborealis also typical for Eastern Siberia; there, however, unlikeWest Siberia, the permafrost characteristics were essen-tially close to modern (that is, interglacial) ones.

5. Discussion

The paleoclimatic reconstructions reveal some pecu-liar features of climate in Northern Eurasia during theLateglacial. During the Aller�d summer temperatures innortheastern Arctic Siberia were 21C higher than thepresent-day ones. Such a pattern of the deviations of themean July temperature from the present-day values canbe explained by the greater distance of the northern EastSiberian sites from the Arctic Ocean compared to thepresent. In agreement with relative sea-level curves (e.g.Chappell and Shackleton, 1986; Bard et al., 1996),during the Aller�d mean sea-level was more than 55mbelow the modern one. A low stage of the World Oceanwould cause major changes in the land–sea distributionin the Siberian Arctic, as the oceanic shelf is veryshallow in this region. The present-day bathymetriccontour of �50m (Atlas Okeanov, 1980) should largelycorrespond to the shoreline position in the Aller�d(Fig. 4). Thus the exposed land extended 500–600 kmfurther northeast of the Taimyr Peninsula, and themodern sub-coastal regions were then situated deepinside the continent.

Table 6

Climatic reconstructions, preboreal sites

Site number Latitude, 1N Longitude, 1E Name of the site DtoJan DtoJuly DP Sources of palynological data

1 62 32 Kivach �6 �2 �155 Yelina G.A.a

2 62 34 Gotnavolok �7 �2 �100 F3 61 30 Ladoga �6 �2.5 �100 Delyusina I.V.a

4 61 31 Suo �3 �1.5 �50 Savel’yeva I.A.a

5 59 31 Shirinsky Mokh �2 �1 �40 F6 60 31 Vishnevskoye �2 �1 �50 F7 64 43 Seb-boloto �5 �3 �150 Yelina G.A.a

8 56 26 Konsu �1.5 �1 �25 Levkovskaya G.M.a

9 57 39 Melekhovo 0 0 �25 Khotinsky et al. (1991)

10 53 51 Buzuluksky Bor 0 0 �40 Kremenetski et al. (1998)

11 50 26 Stoyanov �1.5 �1 �10 Bezus’ko I.G.a

12 54 37 Tulitsa �1.5 �0.5 �50 Klimanov and Serebryannaya (1986)

13 50 23 Krakow �3 �1.5 �150 Szczepanek (1969)

14 54 27 Chernikhovo �1 �1 �25 Zernitskaya et al. (1988)

15 64 71 Nadym-Kazym �1.5 �1 �25 Khotinsky and Klimanov (1985)

16 61 79 Entarny �3 �2 �25 Klimanov and Levina (1989)

17 57 85 Yagodnoye �3 �2.5 �75 Blyakharchuk and Klimanov (1989)

18 55 84 Ust’-Tom’ �2.5 �2.5 �50 Votakh and Klimanov (1994)

19 49 75 Pashennoye �3 �2.5 0 Klimanov et al. (1994)

20 50 80 Ozerki �3 �2 15 Kremenetski K.V.a

21 64 125 Khomustakh �1 �0.5 �25 Andreev et al. (1997)

22 58 125 Suollakh �1.5 �0.5 �25 F23 63 163 Penzhino �0.5 0.5 �25 Borisova Z.K.a

24 45 137 Kiyevka �3 �0.5 �40 Shumova and Klimanov (1986)

25 47 136 Zeva �1 0 �25 Bolikhovskaya N.S.a

26 72 99 Labaz Lake 1.5 1.5 50 Hahnea

27 73 103 Taimyr Lake 1 1.5 40 F28 74 98 Lama Lake 1.5 1.5 50 F29 72 128 Kamenistoye �1 1 0 Pisaric et al. (2001)

30 56 32 Sosvyatskoye �2 �1.5 �50 Gunova V.S.a

aPersonal communication.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9990

(a)

(b)

Fig. 6. Spatial climatic reconstructions for the Preboreal (deviations from the present-day values): (A) mean January to; (B) mean July to; and (C)

mean annual precipitation.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 91

The present-day distribution of the mean Julytemperature near the Arctic Ocean coast shows aconsiderable cooling influence from the ocean. Withina distance of 100–200 km southward from the coast toJanrises by 8–101C, in spite of the decrease of the mean Junesolar radiation values towards the south in these highlatitudes (Fig. 8). The north–south temperature gradientis as sharp as 0.06–0.081C/km at the Arctic coast. Agreater distance from the coastline would be equivalentto a summer ‘‘warming’’ during the Aller�d in the areassituated at present near the coastline.The mean January temperature in Siberia, on the

contrary, decreases from the coastline to the continentalinterior, its distribution being strongly influenced by theSiberian High. During the Aller�d toJan in this region waslower than the present-day one. The COHMAP simula-tion (1988) shows that for Northern Hemisphere withinthe time-interval from 12,000 to 9000 yr BP, solarradiation in June through August was about 8% higherthan at present, while in December through February itwas 8% below the present-day value. According toBerger and Loutre (1991), the positive deviation of the651N July mid-month insolation from the 1950 ADvalue (427W/m2) was 43W/m2 at 10Kyr BP, that is, the

insolation was about 10% higher than at present. Suchchanges can explain to certain extent an increasedseasonality in the high latitudes of Northern Eurasiaduring the Lateglacial, both in the Aller�d and theYounger Dryas.Some features of atmospheric circulation during the

Lateglacial can be derived from the study of aeoliansand dunes, which are described from many localities inthe periglacial zone of the East European Plain since theearly works of Tutkovsky (1910) and Markov (1928).The development of aeolian dunes in interior boreal andtaiga environments is commonly considered as evidence

(c)

Fig. 6 (continued).

–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––"

Fig. 7. Reconstructions of the cryolithozone during the Late Glacial

and the Holocene. (A) Allerod; (B) the Younger Dryas; (C) Preboreal.

(1) Southern limit of the modern permafrost; (2) southern limit of

permafrost during the Late Glacial and Early Holocene; (3) southern

boundary of continuous permafrost at present; (4) southern boundary

of continuous permafrost during the Late Glacial and Early Holocene;

(5) southern boundary of the northern subzone of continuous

permafrost at present; (6) southern boundary of the northern subzone

of continuous permafrost during the Late Glacial and Early Holocene;

(7) mountain regions.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9992

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 93

of climate change. However, determination of the natureof climate change requires analysis of the internalsedimentology of the dune sequences, and considerationof the effects of sediment availability and variablesediment flux on the dune stratigraphy. Dunes devel-oped under climate regimes as different as taiga(Koppen–Geiger Dfc) and high desert (BWk) mayexhibit similar internal sedimentology and stratigraphy,as a result of the interplay of variable sediment supply,sediment flux, and differential rates of retention ofaeolian sediment (Halsey et al. 1990; Catto, 2000; Cattoand Bachhuber, 2000). Conversely, dunes developedunder superficially similar climate regimes may exhibitsignificant geomorphological and sedimentologicaldifferences.At sites in the Eastern European Plain and Fennos-

candia where well-formed parabolic dunes in excess of5m high are preserved, planar tabular and convex-upwards cross-stratified medium-grained sands depos-ited by viscous grain flow form the basal member of thedune sequences (Catto et al., 2000). Overlying thesesediments are planar tabular cross-stratified mediumsands, produced by traction and saltation on slipfacesurfaces, coupled with locally extensive reworking byaeolian deflation, surface rilling, and niveo-aeolianprocesses. Adhesion warts, infilled rain/hail pit struc-tures, and crenulated beds are common. All of thesedunes of late Weichselian to Younger Dryas age displaynumerous niveo-aeolian features. In contrast, youngeradjacent dune sequences, even those developed underboreal and subarctic climate regimes, contain few or noniveo-aeolian structures.At several localities in eastern Europe, buried

palaeosols indicate that the climatic shifts of the latestWeichselian were sufficient to interrupt or change thestyle of aeolian sedimentation. At Beleopesotsk, OkaRiver Basin (see Drenova et al. (1997)), a buriedpalaeosol has been 14C dated at 12,6807512 BP (IG-1051; 14C uncal.), indicating formation during theB .olling Interstadial. A second, locally discontinuous

palaeosol is separated from the first by 1m of underlyingaeolian sediment, attributed to the preceding MiddleDryas event. The upper palaeosol is dated at10,5007170 BP (GIN-9922; 14C uncal.), indicative offormation during the Aller�d. Renewed aeolian sedi-mentation marked the Younger Dryas (Drenova et al.,1997; Catto et al., 2000). These responses to variationsin sediment availability and flux, changes in windregime, and increased vegetation cover are replicatedin many other boreal and steppe aeolian sequences. Incontrast, Younger Dryas aeolian sedimentation wasprecluded in areas marked by extensive permafrostdevelopment, such as coastal Newfoundland (Livermanet al., 2000).The chronological data recorded from Beleopesotsk

correspond well to age determinations for parabolicdunes in western and central Europe (e.g. B .ose, 1991;Koster, 1988; Nowaczik, 1986). Studies on dunedirections in several key-regions of the East EuropeanPlain, in particular, in the Oka River basin (Fig. 9)showed that they were formed by prevailing western andnorthwestern winds. In contrast, the Oka River Basin isdominated by prevailing southwesterly winds today.Aeolian dunes also suggest that sand-transporting windscame from westerly quadrants throughout western andCentral Europe (Isarin et al., 1997; Isarin and Bohncke,1999). Dunes in The Netherlands indicate an averageWSW direction, whereas for central Poland a rangefrom SW to NW directions is suggested with westerlydepositional winds most frequently deduced.The nomogram approach compiled by Borshi and

Novaczik (Nowaczik, 1986) was used to approximatelyestimate the dune-forming wind speed from the mediandiameters of sand grains in the aeolian sediments of theOka River Basin. Although the estimates are necessarilyvery approximate, the values of 6–7m/s are 1.5–2 timesgreater than the present-day speed of prevalent winds inthis region (Fig. 9). However, these values cannot beconsidered to indicate an overall increase in wind speedduring the Middle and Younger Dryas at Beleopesotsk,as the sedimentology suggests that the dunes werestrongly influenced by gusting winds. The peak windspeeds necessary to move the sand grains may have beensubstantially in excess of the modal wind speedthroughout the Middle and Younger Dryas. Thisphenomenon is commonly observed in modern coastaland interior boreal dune fields. The availability of sandfor erosion and transport, due to the drier climate andreduced vegetation cover, was more critical for dunedevelopment than was any increase in wind velocity.The parabolic dunes formed under climates domi-

nated by drier conditions than currently prevail at theirlocalities. All were developed under the influence ofmoderate to strongly gusting winds, with individualhigh-speed wind events having a greater influence thanthe overall wind velocity regime. Periodic snowfall and

100 2000

2

4

6

8

12

10

Julyo

115 Eoo

155 Eo

Distance fromthe coast, km

14

N S

15

14

16

Sola

r ra

diat

ion

(Jun

e)

, CT I,kcal/cm2

Fig. 8. The present-day distribution of the mean July temperature and

mean June solar radiation in the sub-coastal zone of eastern Arctic

Siberia.

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9994

hail events also contributed to development ofthe aeolian sedimentary assemblages. The variabilityin wind regimes recorded in the sediments at mostof the Younger Dryas sites was substantially in excess ofthat characteristic of the modern climates at eachlocality.The aeolian records from north-western and central

Europe suggest that dune formation took place duringthe entire Lateglacial, both under interstadial andstadial conditions (Nowaczik, 1986; Koster, 1988;B .ose, 1991), although the intensity of this process mayhave varied strongly. The most widespread duneformation and remodelling of the existing dunesprobably occurred during the Younger Dryas. A majorshift of the Arctic atmospheric front to the south,suggested by Ruddiman and McIntyre (1981) for theNorthern Atlantic, would bring the Arctic and Polaratmospheric fronts closer to each other, which in its turnwould intensify the atmospheric circulation, particularlywesterly winds.Evidence of cooling found in eastern and northeastern

Siberia in the time-interval corresponding to the Younger

Dryas raises a question regarding the nature of theclimatic mechanism, powerful enough to cause anabrupt and rather strong cooling in these regions soremote from the North Atlantic. Along with thiscooling, the Lateglacial/Preboreal interval containedseveral warming and cooling episodes of shorterduration (200–400 yr), and the warming in earlyPreboreal was in its turn interrupted by a number ofeven shorter cold events (50–100 yr) (Fig. 10). Thisprobably indicates that there is a common hemispheric(global?) mechanism causing such short-term climaticoscillations within the transitional time-interval fromthe glacial to interglacial phase of the climatic rhythm.There is recent supportive evidence for this concept fromthe Southern Hemisphere (Moreno et al., 2001).

6. Conclusions

The main climatic oscillations of the Lateglacial/EarlyHolocene (the Aller�d, the Younger Dryas and thePreboreal) can be distinguished all over Eastern Europeand Siberia. The main trend of climatic changes is ingood agreement with the GISP2 Oxygen isotope curve(Fig. 11). The continental data display similar trends ofhigh-frequency climate oscillation as those evident fromthe ice core data. Both ice core and continental climatereconstruction prove that the main Lateglacial climateevents, such as the Aller�d and Younger Dryas, havecomplex internal structures. The Younger Dryas mayhave been marked by a small warming event in themiddle of that phase. Some cooling was also experiencedin the middle of the Aller�d. There is a pre-Aller�d coldphase, possibly corresponding with the Middle Dryas,which was preceded by a warm phase (in EasternEurope, possibly corresponding with the B .olling).These climatic oscillations are most clearly expressed

in the changes of the mean temperature of the coldestmonth (January) and precipitation (probably mainly thewinter precipitation) (Fig. 3). The amplitude of tem-perature oscillation between maximum Aller�d warming

0

2

4

6

8

Vladimir Kasimov Murom Elatma

January

Modern

July Modern

Reconstructed

(summer)

m/sec

Fig. 9. Summer wind speed in the Oka River basin during Lateglacial aeolian dune formation in comparison with modern values.

100

100

500

300

300

100200 75

50-100

200

8000

9000

10000

11000

12000

13000

14000

C years BP14

PB

YD

AL

-6 -4 -2 0 2 -6 -4 -2 0 2

tJan Ct CJuly

Fig. 10. High-frequency climate fluctuation in the interval 12,000–

9000 radiocarbon yr (Buzuluksky Bor).

A.A. Velichko et al. / Quaternary International 91 (2002) 75–99 95

and minimum Younger Dryas cooling is much higher inthe GISP2 core than in the Buzuluk climate reconstruc-tion curve. Such a difference possibly suggests thattemperature oscillation in Lateglacial was greater in

high than in middle latitudes. For example, the climatereconstruction for the Melekhovo section (which islocated north and west of Buzulukski Bor) provided alarger amplitude of temperature change between the

-43

-41

-39

-37

-35

-33

0 2000 4000 6000 8000 10000 12000 14000 16000 18000

δO18 (GISP2)

-8

-7

-6

-5

-4

-3

-2

-1

0

1

2

0 2000 4000 6000 8000 10000 12000 14000 16000 18000

δTI

-7

-6

-5

-4

-3

-2

-1

0

1

2

0 2000 4000 6000 8000 10000 12000 14000 16000 18000

δTVII

-250

-200

-150

-100

-50

0

50

0 2000 4000 6000 8000 10000 12000 14000 16000 18000

δPyear, mm

Fig. 11. Lateglacial–Holocene climate oscillation (Buzuluksky Bor) and its comparison with GISP2 oxygen isotope data (Stuiver et al., 1995).

A.A. Velichko et al. / Quaternary International 91 (2002) 75–9996

Aller�d and Younger Dryas events (for the meanJanuary temperature 81C and 41C, respectively).There is a certain similarity between the spatial

distributions of the main climatic parameters in theabove-mentioned time-intervals of the Lateglacial/EarlyHolocene and at present. This indicates similar atmo-spheric circulation.One of the peculiar features revealed by the

climatic reconstructions is an area in the northeast ofSiberia with temperatures exceeding the present-dayones in the Aller�d and to a lesser extent also in thePreboreal. This peculiarity can be explained by asubstantial shift of the Arctic coastline to the northdue to the low relative level of the ocean during theLateglacial.During the Younger Dryas, the intra-annual tem-

perature range increased considerably, especially in theEast European Plain (e.g. Melekhovo). This increase ofseasonality was probably connected with changes ininsolation due to the orbital forcing. The decrease inwinter temperatures was accompanied by conspicuousreduction of precipitation. As at present, the meanJanuary temperature decreased from the west to theeast, while its deviations from the present-day valueswere slightly greater in the East European Plain than inSiberia. On the whole, the Younger Dryas stadial wasboth the coldest and the driest period during theLateglacial/Holocene transition.

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