Palaeogeography, Palaeoclimatology, Palaeoecology 386 (2013) 408–414

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Palaeogeography, Palaeoclimatology, Palaeoecology

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Climatic variability during the last interglacial inferred from geochemicalproxies in the Lake El'gygytgyn sediment record

Laura Cunningham a,⁎, Hendrik Vogel b,c, Norbert Nowaczyk d, Volker Wennrich b, Olaf Juschus b,Per Persson e, Peter Rosén a

a Climate Impacts Research Centre (CIRC), Umeå University, SE-98107 Abisko, Swedenb University of Cologne, Institute of Geology and Mineralogy, Zuelpicher Str. 49a, D-50674 Cologne, Germanyc University of Bern, Institute of Geological Sciences and Oeschger Centre for Climate Change Research, Baltzerstr, 1+3, CH-3012 Bern, Switzerlandd GeoForschungsZentrum Potsdam, Section 3.3, Telegrafenberg, D-14473 Potsdam, Germanye Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden

⁎ Corresponding author at: Department of GeograpBuckingham Building, Lion Terrace, Portsmouth PO1+44 23 9284 2513; fax: +44 23 9284 2512.

E-mail address: laura.cunningham@port.ac.uk (L. Cu

0031-0182/$ – see front matter © 2013 Elsevier B.V. Allhttp://dx.doi.org/10.1016/j.palaeo.2013.06.009

a b s t r a c t

a r t i c l e i n f o

Article history:Received 4 October 2012Received in revised form 7 June 2013Accepted 8 June 2013Available online 15 June 2013

Keywords:PalaeolimnologyClimate changeFar-eastern Arctic RussiaPrimary productivityGlacial terminationLast interglacial period

The Last Interglacial Period (LIP) is often regarded as a good analogue for potential climatic conditions underpredicted global warming scenarios. Despite this, there is still debate over the nature, duration and frequencyof climatic changes during this period. One particularly contentious issue has been the apparent evidence ofclimatic instability identified in many marine cores but seemingly lacking from many terrestrial archives, es-pecially within the Arctic, a key region for global climate change research. In this paper, geochemical recordsfrom Lake El'gygytgyn, north-eastern Russia, are used to infer past climatic changes during the LIP from with-in the high Arctic. With a sampling resolution of ~20–~90 years, these records offer the potential for detailed,high-resolution palaeoclimate reconstruction. This study shows that the LIP commenced in central Chukotka~129 thousand years ago (ka), with the warmest climatic conditions occurring between ~128 and 127 ka be-fore being interrupted by a short-lived cold reversal. Mild climatic conditions then persisted until ~122 kawhen a marked reduction in the sedimentation rate suggests a decrease in precipitation. A further climaticdeterioration at ~118 ka marks the return to glacial conditions. This study highlights the value of incorporat-ing several geochemical proxies when inferring past climatic conditions, thus providing the potential to iden-tify signals related to environmental change within the catchment. We also demonstrate the importance ofconsidering how changes in sedimentation rate influence proxy records, in order to develop robustpalaeoenvironmental reconstructions.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

Rapid warming observed within the latter part of the 20th centuryraised many questions regarding the rate at which global climate canchange (Kelts, 1992). In answer to this, palaeoclimatic data from a va-riety of proxies have demonstrated multiple, rapid shifts from full gla-cial conditions to milder interglacial conditions (e.g. Petit et al., 1999).For example, the isotopic composition of ice-cores from Greenlandsuggests a 10 °C increase in temperature occurred within a decade(Alley, 2000; Steffensen et al., 2008). Furthermore, episodes of abruptclimatic change occur repeatedly within the past 100 thousand years(kyr), as evidenced by both terrestrial and marine palaeoclimate re-cords (Dansgaard et al., 1993; Genty et al., 2003). Since polar regionshave been glaciated for most of this time, it is often argued that large,

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abrupt changes in climate could not occur without high volumes ofice present in the northern and southern hemispheres (Denton,2000). Abrupt, large scale, climatic changes have been reported dur-ing the Holocene (the present interglacial period) from many differ-ent geographical regions (Rohling et al., 2002; Moros et al., 2004),however, there is still limited evidence for abrupt climate changesduring the Last Interglacial Period (LIP) when ice volumes wereeven lower than today (Chapman and Shackleton, 1999; Karabanovet al., 2000).

The higher number of palaeoclimate records available for the LIP,relative to earlier interglacials, means that the LIP is often used asan analogue for the Holocene and to infer potential impacts of contin-ued global warming under reduced ice conditions (Rioual et al., 2001;McManus et al., 2002; Tzedakis, 2003). These research efforts have,however, increased uncertainty as to the temporal and spatial extentof climatic changes during this period, partly due to contradictory re-sults produced by different proxy records. To help address this issue,and to understand the rate, extent, and mechanisms of climatechange, several palaeoclimate records covering the last glacial–

409L. Cunningham et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 386 (2013) 408–414

interglacial cycle have been generated, with the highest density of re-cords for the North Atlantic and adjacent continental regions (e.g.,Tzedakis et al., 2003; Martrat et al., 2004; Oppo et al., 2006; Braueret al., 2007). Within the Arctic, recent low-resolution records indicatea significant climatic shift during the LIP (e.g. Chapligin et al., 2012;Snyder et al., 2012). Despite this, high-resolution records extendingbeyond the last interglacial are extremely scarce from the Arctic. Tostudy the rate and extent of climate change, as well as the role ofcomplex feedback mechanisms as contributors to past climate change(Holland and Bitz, 2003; Serreze and Francis, 2006), it is essential toinvestigate long and continuous palaeoclimate records from this keyregion of global climate change, in high resolution.

El'gygytgyn Crater Lake hosts the longest terrestrial record of cli-mate change from the Arctic (Brigham-Grette et al., 2007) with a con-tinuous sediment record spanning the last 3.6 Ma (Melles et al.,2012). Variations in the composition of these sediments reflectclimate-induced changes in the catchment and water column of LakeEl'gygytgyn (Nowaczyk et al., 2002, 2007; Asikainen et al., 2007;Lozhkin et al., 2007;Melles et al., 2007, 2012;Minyuk et al., 2007). Geo-chemical proxies such as biogenic silica (BSi), total organic carbon(TOC), magnetic susceptibility (MS) and the elemental ratios of silicato titanium (Si/Ti) and iron tomanganese (Mn/Fe) can provide valuableinformation about past climatic and environmental conditions at thissite (Melles et al., 2012; Cunningham et al., 2013). For example, BSi re-flects the productivity of silica producing organisms,which are predom-inantly diatoms in Lake El'gygytgyn (Cremer and Wagner, 2003;Cherapanova et al., 2007). At this location, the productivity of diatomcommunities is strongly affected by climate. Warmer climates lead toreduced ice and snow cover both on the lake andwithin the catchment,thus increasing light availability and nutrient supply, respectively andthus stimulating productivity (Melles et al., 2012; Cunningham et al.,2013). Thus diatoms are not responding solely to increased air temper-atures or precipitation, but also to environmental changes driven bythese climatic variables. The same is true of the geochemical proxiesincorporated within this study thus the inclusion of multiple proxiesenables a more complete interpretation. The selected geochemical pa-rameters are ideal for high resolution studies as they can be rapidlyand cost-effectively quantified using methods such as FTIRS or XRFcore-scanning. Consequently a high-resolution study was undertakenusing these geochemical proxies to assess both the amplitude and ra-pidity of climatic changes during the LIP and thus contribute to our un-derstanding of climate change during interglacial periods.

2. Site description

Lake El'gygytgyn (67°30′N, 172°05′E) is situated in a 3.6 Ma old,18 km wide meteorite impact crater located in the Far East RussianArctic (Fig. 1). The 12 km wide lake is bowl shaped with steep slopes,a flat and extensive bottom, and a maximum water depth of 170 m(Melles et al., 2012). Lake El'gygytgyn is a monomicitic, oligotrophiclake (Nolan and Brigham-Grette, 2007), with a water residence timeof ~100 years (Fedorov et al., 2012).

The region surrounding Lake El'gygytgyn has a cold Arctic climate,with a mean annual temperature of −10.2 °C recorded in 2002(Nolan and Brigham-Grette, 2007). The cold conditions and limitedprecipitation result in well-developed permafrost in the catchment,which can be up to 300 m thick (Nolan and Brigham-Grette, 2007).Almost all material eroded from the catchment is deposited into thelake, predominantly by fluvial action during the period of snow-melt (Fedorov et al., 2012). The harsh climate also affects the lake it-self, which remains ice covered for at least nine months of the year.Given the extreme Arctic climate, it is not surprising that vegetationwithin the area is sparse and consists predominantly of lichen andherbaceous taxa (Lozhkin et al., 2007). In more sheltered areas,small shrub forms of Salix and Betula are occasionally present.

3. Methods

In May 2003 a 16.6 m composite core (Lz1024) was recoveredfrom the central part of Lake El'gygytgyn, where a seismic survey in-dicated horizontal bedding and parallel reflectors (Niessen et al.,2007). The surface sediments and deeper sediments of core Lz1024were collected using a 0.6 m gravity corer and a 3 m long percussionpiston corer, respectively (both UWITEC Co.). Prior to subsampling,the cores were split lengthwise into halves. One of the core halveswas used for high-resolution X-ray fluorescence (XRF) and MS mea-surements, as described in Cunningham et al. (2013). The Mn/Feratio was calculated from the raw counts per second (cps) dataobtained from the XRF scanning. As Si is a light element, the intensi-ties derived from XRF analysis are particularly susceptible to the ef-fects of the sediment matrix. Consequently matrix corrected Si/Tidata, derived from a longer composite core from Lake El'gygytgyn(Melles et al., 2012), has been utilised within this study. To facilitatecomparisons between datasets, interpolation and block averagingwere used to match these higher resolution series (XRF and MS) tothe sample resolution of the biogenic proxies (BSi and TOC), whichwere analysed every 0.25 cm. The amount of BSi and TOC withinthe sediments was quantified using FTIRS. Sample preparation andanalysis followed Rosén et al. (2011) with existing calibration models(Vogel et al., 2008; Melles et al., 2012) applied to the data.

As described in Melles et al. (2012), the age model for LakeEl'gygytgyn is primarily based on palaeomagnetic data and tuningof the proxy record to insolation at 67.5°N and the global marineoxygen isotope stack. First order tie points are provided by themagnetostratigraphic results, with fourteen polarity reversalsclearly defined in the El'gygytgyn lake sediment record (Melleset al., 2012). Nine of these could be dated using the ages ascribedby Lisiecki and Raymo (2005) to major reversals of the Earth'smagnetic dipole field within their benthic oxygen isotope (δ18O)stack.

As described in Nowaczyk et al. (2013), 2nd and 3rd order tiepoints were derived from synchronously tuning an additional ninesedimentary parameters to the δ18O stack (Lisiecki and Raymo,2005), or to Northern Hemisphere summer insolation values calculat-ed by Laskar et al. (2004), respectively. Elemental concentrations,spectral colour, grain-size, biogenic silica and pollen concentrationswere used to derive the 2nd order tie points whilst fluctuations ofMS and TOC were used for 3rd order tie points. The error associatedwith these correlations must be at least that inherent in the correlateddata series, estimated as 4 ka (Lisiecki and Raymo, 2005) and 0.5 ka(Laskar et al., 2004), respectively. Using this approach, over 600tie-points, spanning the last 3.6 Ma, were used to develop a robust,high-resolution age-model (Nowaczyk et al., 2013). Additionally, sev-eral ages within the uppermost sediments were confirmed by radio-carbon and infrared stimulated luminescence (IRSL) dating(Nowaczyk et al., 2013). As the section of the core discussed in thispaper is essentially based on tuning of the proxy record to insolation,the ages given may not be accurate in terms of absolute ages. The ac-curacy of the chronology should be relatively consistent within thetime period presented here, with a potential error of ~500 years(Nowaczyk et al., 2013).

Based on the age model (Melles et al., 2012; Nowaczyk et al., 2013),the section of the core between 500 and 625 cm covers the time periodfrom ~114 to ~135 kyr, thus extending slightly either side of the LIP.The temporal resolution of samples varied with the stratigraphic posi-tion reflecting systematic changes in the sedimentation rate (Fig. 2).Temporal resolution was highest for the middle section of the core seg-ment analysed here, with a resolution of ~20–30 years per 0.25 cmsample interval. The uppermost section had the lowest temporal reso-lution (~90 years per 0.25 cm sample interval). Bioturbation withinthe sedimentwould, however, have distorted the signal thus degradingthe apparent temporal resolution slightly.

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Fig. 1. Map showing the location of Lake El'gytgytn within the Arctic region (Cunningham et al., 2013).

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To assess the impact of sediment accumulation rates on the proxyrecords, we present the datasets both in their original units andstandardised by the time period over which the sediments accumu-lated (hereafter indicated by the subtextadj). The latter was achievedby dividing each value by the number of years that it took for thesample to accumulate. Thus if a sample had 25% BSi and represented100 years of sedimentation, the adjusted value was calculated by di-viding 25 by 100 thereby providing a rough approximation of fluxto the sediment.

4. Results and discussion

4.1. The proxy records

Distinct changes are observed in the proxy records during the LIP(Fig. 2). The MSSI data shows the most abrupt changes, possibly indi-cating thresholds within the oxygenation state of the lake (i.e. suddenchanges from anoxic to oxic). For example, a change from a perma-nently ice covered lake to seasonally open lake could result from a

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Fig. 2. (A) Sediment derived records of the Last Interglacial Period (LIP) from Lake El'gygytgyn showing the original data series (black lines; inner y-axis) and series adjusted for thetime period which each sample took to accumulate (grey lines; outer y-axis) (see text for details). Climate-related proxy records and temperature reconstructions from Lake Baikal(B) are shown for comparison, namely a pollen derived temperature index and pine pollen % from core CON01-603-2 (Granoszewski et al., 2005) as well as diatom biovolume ac-cumulation rates (Rioual and Mackay, 2005), and BSi% records from sediment cores BDP-98, BDP-96-2 (Prokopenko et al., 2002) and BDP-96-SP (Prokopenko et al., 2006).

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gradual warming; however, the disruption of stratified layers mightbe expressed more abruptly. The Mn/Fecps shows a relatively similarprofile as the MSSI, suggesting intense dissolution of both Fe and Mnmineral phases under anoxic conditions in glacial times but withsedimentation rates sufficiently high to preserve the catchment-derived signal (Snowball, 1993) during the interglacial period. Thisis consistent with previous interpretations of these proxies at LakeEl'gygytgyn (e.g. Melles et al., 2012). Despite the strong initial simi-larity between these two proxies, some periods of marked disparityare observed later within the LIP (e.g. ~124–119 ka) indicating rela-tively complex interactions between these proxies. A greater consis-tency is observed between the records once they have beenadjusted to account for the changing sedimentation rates (Fig. 2).Only minor variations are observed between ~122–114 ka and~135–129 ka, reflecting the low sedimentation rates observed duringthese periods.

Sediment accumulation rates have a major influence on patterns ofvariation observedwithin the proxy records, as evidenced by a compar-ison of the original data-serieswith the adjusted series (Fig. 2). TOCpro-vides the most dramatic demonstration of this; TOC% data indicate thatthe highest concentrations (1.9%) occur around 115 ka, during a glaciat-ed period, however, the TOCadj data show peak values at approximately128 ka. This discrepancy can be attributed to different sources of sedi-ment input. During glaciated periods, there is minimal input of sedi-ment from the catchment, thus the autochthonous componentdominates. This amplifies the increases in TOC that result from betterpreservation of organicmatter under sub-oxic/hypoxic conditionswith-in the glacial period. In contrast, the autochthonous signal is dilutedwhen sediment enter the lake from the catchment. This process is

equally applicable to other proxies that reflect in-lake conditions includ-ing BSi and, to a lesser extent, Si/Ti. Consideration of the approximaterates of sediment accumulation therefore enables distinction betweenactual flux and apparent changes in concentration associated withchanging sedimentation processes (Peinerud, 2000). Proxies related tothe dissolution ofmagneticminerals are also influenced by sediment ac-cumulation rates as faster burial of sediments reduces the time duringwhich these minerals are exposed to dissolution (Snowball, 1993;Granina et al., 2004).

Although the adjusted series allow for the varying input of alloch-thonous and autochthonous material, they are also highly dependenton the age-depth model. Any uncertainties or errors in the age-depthmodel would be propagated into the adjusted proxy records. Further-more, the constraints of age-depth models (including the use oftie-points) often result in more distinct, stepwise changes to the sed-iment accumulation rates than would occur naturally. This can subse-quently result in sharper, more abrupt changes in the proxy recordsand could potentially account for the abruptness observed withinthe adjusted series (Fig. 2). Finally, large changes in sediment accu-mulation could either amplify or dilute the climatic signal withinthe proxy records, especially if both are driven by the same climaticparameter. Consequently we suggest that both the original and ad-justed series should be considered in order to develop the most reli-able interpretation.

4.2. Interpretation of past conditions

The early part of the record (~135–129 ka) represents glacial con-ditions during MIS 6. TOC levels initially are relatively high which

412 L. Cunningham et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 386 (2013) 408–414

could reflect either stratification within the water column or strongeroxygen uptake during decomposition of organic matter in surfacesediments thus leading to better preservation. TOC values decreasefrom ~135 ka to 132 ka when the lowest values (0.6%) within the re-cord are observed (Fig. 2). This coincides with minimum BSi% values(6%; Table 1) whilst a less pronounced decrease is also observed inthe Mn/Fe values. These data suggest a slight intensification of theglacial conditions, potentially including an increase of snow coveron the lake ice, thereby reducing light availability for photosyntheticorganisms such as diatoms. This is consistent with total diatomconcentrations which suggest low productivity under a permanentice-cover at 135 ka decreasing to minimum values at ~132 ka(Snyder et al., 2012).

The period between ~129 and 128 ka clearly represents the transi-tion into the LIP with warm, ice-free conditions established within~1 kyr. An additional step-like improvement in climatic conditionsoccurs at ~128 ka, persisting for ~1 kyr. BSi values are approximatelydouble those seen during the preceding glacial period, consistent witha doubling of total diatom concentrations during MIS5e (Snyder et al.,2012). Additional support for optimal climatic conditions at this timeis derived from the oxygen isotope composition of biogenic silica,which reaches maximum values at ~127 ka (Chapligin et al., 2012).The peak values seen in the BSiadj data are probably magnified bythe higher sedimentation rates seen at this time. Pollen-based recon-structions indicate that precipitation remains relatively low at thistime (Melles et al., 2012) thus the increased sediment input can bestbe explained by melting of perennial snow fields in the catchment ofthe lake and deepening of the permafrost active layer which wouldpromote increased erosion of formerly frozen soils.

During the sharp increase in BSi values between ~128 and 127 ka,a sudden decrease is observed in MS values, probably reflecting dilu-tion of minerogenic sediments due to high biological production. Thisis, however, followed by an abrupt decrease in all the other proxieswithin the next 100 years. Mn/Feadj and Si/Tiadj records decrease tovalues similar to those observed within the early LIP whilst BSi, TOCand MS revert to values well below those values previously observedduring the LIP. This period of low values within all the proxy recordsis interpreted as an intense, cold reversal, potentially similar to theYounger Dryas event. It is hypothesised that this cold reversalresulted in extended ice cover on the lake, possibly accompanied byincreased snow cover, thus causing a decrease in primary productionand anoxic bottom waters as evidenced by the BSi and TOC records.This event has not previously been detected at Lake El'gygytgyn, pre-sumably due to its short duration (only a few hundred years) and themillenial resolution of prior studies (e.g. Cherapanova et al., 2007;Melles et al., 2007; Minyuk et al., 2007).

After this brief reversal, values quickly increase again. The adjust-ed series suggest values similar to those seen within the early LIPwhilst, with the exception of MSSI, the unadjusted values are higherthan those previously observed within the LIP (Fig. 2). ModerateMSSI values (900–1400 SI) during this time potentially reflect dilu-tion of minerogenic sediments due to the increased production ofautochthonous organic material. A pronounced decrease in Si/Ti is

Table 1(a) Maximum and (b) minimum values of the unadjusted geochemical data-series.

(a) (b)

Value Sample age(ka)

Value Sample age(ka)

MS 2118.5 SI 128.6 MS 55.5 SI 134.8BSi 25.4% 124.6 BSi 6.0% 132.3TOC 1.9% 113.9 TOC 0.6% 132.6Si/Ti 0.46 cps 125.7 Si/Ti 0.21 cps 114.9Mn/Fe 14.6 cps 119.3 Mn/Fe 6.7 cps 132

observed between ~126 and 125 ka, a period when BSi values remainrelatively high, but variable (~12–20%). The decrease in Si/Ti may beassociated with an increased rate of chemical weathering of sourcematerial within the catchment. Silica is more mobile and has a higherdissolution rate than Ti (Nesbitt and Wilson, 1992) thus silica isquickly lost from soils during weathering (Egli et al., 2001). Conse-quently, one would expect higher Si/Ticps values when relativelyunweathered soils are entering the lake (as would occur immediatelyafter de-glaciation) with lower Si/Ti occurring once the soils havebeen weathered and thus contain relatively little Si. This suggestionis consistent with higher precipitation and temperatures inferredfrom pollen records for this period (Melles et al., 2012), as a warmand wet climate would promote chemical weathering. The moregradual decrease observed in the Si/Tiadj data further supports thissupposition as it demonstrates that the marked decrease seen in theSi/Ticps values is influenced by the relatively high sedimentationrate and the associated terrigenous input. This example highlightsthe importance of multiple geochemical studies to enable distinctionsbetween catchment and climatic influences.

The Mn/Fecps values decrease at ~124 ka, however, the Mn/Feadjseries shows a very minor increase. This suggests a slight increase inthe input of weathered material from the catchment as the relativestability of MS values precludes changes to redox conditions. BSivalues (both % and adj) show a gradually decrease from maximalvalues at ~124 ka until ~122 ka, although values remain higherthan those seen in the preceding glacial. In contrast, TOC values(both % and adj) remain high during this period, suggesting either de-creased decomposition of organic material, increased production orincreased catchment input.

MSSI show a marked decrease at ~122 ka, a time when the sedi-mentation rate becomes markedly slower. The lower sedimentationrate is reflected in the adjusted records which all show a decreasein values at this time. A moderate increase in Mn/Fecps, MSSI andBSi% values is subsequently observed at ~119 ka; suggesting a returnto slightly milder climatic conditions before glacial conditions re-established at ~118 ka. Due to the low accumulation rates, this fea-ture is much less pronounced in the adjusted series. The occurrenceof this brief climatic amelioration is supported by the total diatomconcentrations which show a similar pattern at around this time(Snyder et al., 2012), however, the low resolution of the latter pre-cludes more detailed comparisons. Similarly, total diatom concentra-tions begin to increase once more at ~115 ka, in good agreement withboth the BSi and TOC % data presented here, thereby suggesting algalproductivity under a permanent ice-cover.

4.3. Comparisons with other proxies records from Lake El'gygytgyn

Detailed comparisons between the results presented here andother proxy records from Lake El'gygytgyn are hampered by the lowresolution of most other data series. For example, the oxygen isotoperecord contains less than 10 data points for this time period(Chapligin et al., 2012) whilst the pollen record consists of 12 datapoints (Lozhkin and Anderson, 2013). Thus only general features,such as the approximate time at which maximum values are reached,can be compared, as per Section 4.2. Despite a lower temporal resolu-tion, the record of diatom abundances (Snyder et al., 2012) provides agood confirmation of the BSi record presented here, with regards toboth the timing and magnitude of observed changes.

4.4. Comparisons with Lake Baikal

Like Lake El'gygytgn, Lake Baikal offers the potential for continu-ous, high resolution climatic reconstructions over many glacial–inter-glacial cycles (Mackay, 2007). Under modern conditions, both lakesundergo complete mixing of the water column each year (Mackay,2007; Nolan and Brigham-Grette, 2007). Situated in a climatically

413L. Cunningham et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 386 (2013) 408–414

sensitive area in south-eastern Siberia, Lake Baikal provides impor-tant records of past climatic changes with records of diatom abun-dance and biogenic silica being particularly valuable (Prokopenko etal., 2001; Rioual and Mackay, 2005; Mackay, 2007). Comparisonswith these records may therefore contribute a greater understandingof regional climate.

When comparing the BSi records from the LIP, Lake Baikal obvi-ously shows much higher concentrations than those seen at LakeEl'gygytgyn. This may partly be attributable to higher inputs of catch-ment material at Lake El'gygytn diluting the BSi signal, a scenario alsosuggested by Mackay (2007) to explain the differences in concentra-tion observed between different basins at Lake Baikal. Climatic differ-ences between the two regions may also contribute to thisdiscrepancy as the more southerly location of Lake Baikal would re-sult in warmer temperatures than those seen at Lake El'gygytgyn,thus resulting in more productive diatom communities. This sugges-tion is supported by the high values of BSi (b40%) seen during“super-interglacials” at Lake El'gygytgyn (Melles et al., 2012).

Comparisons of the BSi records from these lakes suggest that theLIP commenced ~1000 years earlier at Lake El'gygytgyn than at LakeBaikal (Prokopenko et al., 2002; Rioual and Mackay, 2005) althoughProkopenko et al. (2006) suggest a more contemporaneous initiation(Fig. 2C), reflecting differences within the age-model used. Such chro-nological uncertainty within the Lake Baikal record prevents a moredefinitive statement on the relative timing of this event. Similarly, re-cords from Lake Baikal variously suggest that optimal climatic condi-tions either occurred simultaneously with those at Lake El'gygytgyn(Prokopenko et al., 2006; Tarasov et al., 2007), or ~2–3 ka later(Rioual and Mackay, 2005).

There is no evidence of a cold reversal within the early warmingphase at Lake Baikal. The low temporal resolution and the short dura-tion of this event probably preclude its detection at Lake Baikal andhighlight the value of high resolution records for improving our un-derstanding of past climatic changes. Similar events have, however,been previously reported from a number of proxy records includingdiatom-based sea surface temperatures (SSTs) from the SouthernOcean (Bianchi and Gersonde, 2002), alkenone derived SSTs fromthe Mediterranean (Martrat et al., 2004), oxygen isotopes from theSanta Barbara Basin (Cannariato and Kennett, 2005), pollen recordsfrom the Iberian margin (Sánchez Gońi et al., 1999) and SSTs inferredfrom foraminifera in the South China Sea (Tu et al., 2001). There isstill insufficient data to determine whether this event was expressedon a global scale, although the above records suggest a cooling inmost oceans at this time. Higher resolution studies at Lake Baikalcould prove instrumental in determining whether this event wasalso expressed in continental regions, or restricted to areas potential-ly influenced by ocean dynamics.

Several proxies indicate changes to both catchment input andweathering regimes at Lake El'gygytgyn between ~124 and 120 ka,which agrees well with the warm, moist climate inferred for LakeBaikal at this time (Rioual and Mackay, 2005). The SAR suggests anearlier change in precipitation regimes at ~122 ka, which corre-sponds to a pollen-inferred climatic deterioration at Lake Baikal(Granoszewski et al., 2005). The cessation of the LIP occurs contem-poraneously in the unadjusted El'gygytgyn data (~118–117 ka) andseveral proxy records from Lake Baikal (Rioual and Mackay, 2005;Grygar et al., 2006). This suggests that the low sedimentation rate ob-served after 122 ka masks any climate signal within the adjusted re-cords and emphasises the importance of considering the sedimentaccumulation rate in palaeolimnological reconstructions.

5. Conclusions

The climatic reconstruction presented here shows a good generalagreement with palaeoclimate reconstructions from Lake Baikal,although there is some suggestion that climatic changes may have

occurred slightly earlier at Lake El'gygytgyn. This paper demonstratesthe occurrence of several important climatic features within theArctic immediately prior to, during, and after the LIP including:

• a ‘Younger Dryas’ like cold reversal during Termination II;• high frequency climatic variability during the interglacial period;• the occurrence of a mid-LIP cool period, albeit with a more gradualtransition back to minimum values than is commonly reported.

As such, it is hoped that this paper may help stimulate discussion asto the mechanisms by which these climatic events are caused or trans-mitted to different locations globally. Thus, both similarities and differ-ences between different records and regions can be important.

For example, are Arctic regions likely to experience a higher de-gree of climatic variability than mid or low latitude regions and, ifso, what are the implications of this in regard to future climatechanges? Clearly, further high-resolution studies from terrestrial set-tings in the Arctic are required to address such issues.

Acknowledgements

The authors would like to thank the participants on the springcampaign of the Lake El'gygytgyn expedition 2003 for the recoveryof the sediment core Lz1024 used in this study. They also gratefullyacknowledge the expertise and leadership provided by Martin Mellesand Julie Brigham-Grette, without which this project wouldn't havebeen possible. We would also like to thank Annika Holmgren, JanÅberg, Carin Olofsson and Thomas Westin for laboratory assistance.Funding was provided by the German Federal Ministry for Educationand Research (BMBF; grant no. 03G0586A, B), the German ResearchFoundation (DFG, JU 465/2-1), Vetenskapsrådet and FORMAS. Thisresearch was also supported by the Climate Impacts Research Centre(Umeå University) who provided salary to Laura Cunningham andPeter Rosén.

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