Decade–centenary resolution records of climate changes in East Siberia from elements in the bottom sediments of lake Baikal for the last 150 kyr

Decade–centenary resolution records of climate changes in East Siberia from elements in the bottom sediments of lake Baikal for the last 150 kyr

ARTICLE IN PRESS Nuclear Instruments and Methods in Physics Research A 575 (2007) 193–195 www.elsevier.com/locate/nima Decade–centenary resolution r...

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ARTICLE IN PRESS

Nuclear Instruments and Methods in Physics Research A 575 (2007) 193–195 www.elsevier.com/locate/nima

Decade–centenary resolution records of climate changes in East Siberia from elements in the bottom sediments of lake Baikal for the last 150 kyr E.L. Goldberga,, M.A. Phedorina, E.P. Chebykina, K.B Zolotarevb, N.A. Zhuchenkoa a

b

Limnological Institute of the SB RAS, 664033 Irkutsk, Russia Budker Institute of Nuclear Physics of SB RAS, Lavrentyev prospect -11, 630090 Novosibirsk, Russia Available online 19 January 2007

Abstract High-resolution scanning Synchrotron Radiation X-ray Fluorescence Analysis (SRXFA) was applied to investigate the downcore distribution of elements in the sediments from Lake Baikal (East Siberia). The obtained multi-element time series reveal the presence of abrupt climate shifts in East Siberia which were synchronous with the abrupt warming events in the North Atlantic and Greenland (Dansgaard–Oeschges events (D/O) during the last ice age 24–75 kyr BP. We show here the set of climatic indicators reveals all globally known climate changes from dry and cool or glacial climates to humid and warm ones, which were recorded in Northern Atlantic and East Siberia both on the orbital and millennial time scales during the last 150 kyr. r 2007 Elsevier B.V. All rights reserved. PACS: 07.85.Qe; 92.70.Gt; 92.40.Fb; 91.65.Dt Keywords: Synchrotron Radiation; Lake baikal; Global climate change; Elemental records; Millennial scale oscillations; Dansgaard–Oeschger events

1. Introduction This paper represents the continuation of our investigations cycle devoted to paleoclimate reconstructions with the use of Synchrotron Radiation X-ray Fluorescence Analysis (SXRFA). Earlier it has been shown that downcore distribution of elements concentrations in the sediments of the Siberian lakes can be used for reconstruction of climate changes, both on an orbital scale and on millennial scale [1–3]. The objective of this study was to obtain the records of change of a climate and an environment with the decade resolution from the sediments of Lake Baikal for the period of the last 150 kyr. 2. Methods and samples We measured the concentrations of U, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Br, I, Rb, Sr, Y, Zr, Nb, Mo, Pb, Th, Sn, Sb, Cs, Ba, La, Ce and some other elements in the sedimentary core st2—PC-GC-1999 which was retrieved Corresponding author. Tel.: +7 3832 325229; fax: +7 3832 34 3321.

E-mail address: [email protected] (E.L. Goldberg). 0168-9002/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2007.01.065

from Akademichesky Ridge (Lake Baikal) [4] and new core st2-PC-2001 taken in the same site. Both cores are overlapping ones. Core st2-PC-GC-1999 covered the period from the modern age up to ca.150 ky and ages of the core st2-PC-2001 are from 60 up to 150 kyr. The samples used for investigation presented 6–8-mmthick slices which were cut out from wet sediment along the core axis and placed into aluminum trays. Lengths of the slices varied from 15 up to 29 cm. The tray was moved vertically under horizontal 1 mm high SR beam, which was collimated by a cross–slit system. The spectra were collected in a scanning mode with 23 and 45 keV beams from the VEPP-3 storage ring at the ‘‘Baikal’’ SRXFA station in the Institute of Nuclear Physics, Novosibirsk [1,2]. The spectral responses with obtaining absolute concentrations of elements from their fluorescent peaks were processed using the algorithm of fundamental parameters to overcome the problems caused by water content variability in nearly saturated wet sediments. The processing algorithm of spectra from thick slices of wet sediments is reported in Ref. [5]. The isotopes of 238U, 232Th, 234U and 230Th have been measured in the sediments investigated by ICP-MS [4]

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method and few horizons of the core st2-PC-GC-1999 related with warm climates have been dated by direct U–Th method [4,6]. The depth-age model for the core st2-PC2001 was received by correlations of water contents (WC) and diatom abundances profiles in both cores over the overlapping interval. The scanning procedure was applied to the core st2-PC-GC-1999 over interval 0–100 kyr and for the core st2-PC-2001 over ca. 85–150 kyr. All results during the interval from modern to 150 kyr are presented here for the composite core which consisted of these both cores. 3. Results and discussion We used everywhere the records after their normalization (X-Xaverage)/STD. K-like behaviors have been found for the set of terrigenous elements such as Ti, Rb, Nb, Zr, Y,Ba and Ce. The correlations between these elements are 0.78–0.92. Other group of elements, which anticorrelated with the elements of the first group, is presented by U, Br, I, Sr/Rb, Ca/K and few other. Two time series for typical representatives of both groups (Br and K) are shown in Fig. 1 for composite core. Good adjustment between both cores over interval of their overlapping is obvious. The stack [3] of terrigenous elements (K, Ti, Rb, Nb) is presented in Fig. 2 together with the profile of diatom abundance in the sediment investigated and d18O in benthos ocean’s foraminifers. Diatom shells in the sediments from Lake Baikal are proxy 0

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K, a.u

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age, kyr Fig. 1. The time series for Br and K for the composite core from Lake Baikal. Y-axis for K is inverse one. Peaks on the both records correspond to warm and wet climates. The resolution of the records is ca. 20 years.

Fig. 2. The time series for the terrigenous stack (K, Ti, Rb, Nb), diatom abundance in the sediments investigated and d18O in benthic ocean foraminifers [9]. Last is proxy of global ice volume. The gray bars mark warm periods in East Siberia, which were synchronous the global ones. Arrows show millennial scale climate shifts in East Siberia which were simultaneous with some known world events. B/A—Bolling-Alerod, D/O 17,18, 19—Dansgaard–Oeschger events, Q—short cooling episode in Europe during the middle of MIS5.1; H 7 and 11—Heidrich events; MECP—Middle Eom Cooling Period in Europe. The resolution of the records is ca. 20 years.

of humid and warm climates [7]. d18O in benthos ocean’s foraminifers is proxy of global ice volume [8,9]. We can see in Fig. 2 obvious correlations between inputs of terrigenous elements and climate changes. Low concentrations of terrigenous elements in Lake Baikal correspond to more warm and humid climates and on the contrary. The main reason of such correlation is an intensification of different sources of terrigenous particles during the alternative climatic periods [1–3]. During the ice ages, terrigenous particles were delivered from glaciers situated on the mountains surrounding lake (‘‘glacier milk’’). In contrast, over the warm periods terrigenous particles entered in the lake with riverine waters from the lowlands [1–3]. Thus, elemental composition of the sediments in the lake Baikal reflects climate changes in the region investigated (East Siberia). Not only the long-time climate changes are obvious here, but the millennial scale climate shifts are clearly indicated on the data presented in Figs. 1 and 2. As

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[10,11] over the last ice age (14–74 kyr) synchronously appeared in East Siberia.

Sr/Rb

Acknowledgments 2.5

We thank E.G. Miginsky and V.M. Tsukanov for maintainance of the SRXFA scanning station. We are grateful to academicians G.N. Kulipanov and M.A. Grachev for overall support and concern in our work. This work was supported by RFBR grants 04-05-64395, 06-05-91576-JR, and the program of the Russian Academy of Sciences 16.8.

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Fig. 3. Sr/Rb ratio in Lake Baikal sediments (proxy of warm and humid climates in East Siberia) and d18O in Greenland ice (proxy of air temperature). All abrupt and short climate shifts (D/O events) took place in Greenland and East Siberia simultaneously. Both d18O and Sr/Rb ratio are drawn using their own depth-age models. The resolution of the records is ca. 20 years.

we have shown in most prominent proxy of climate shifts on millennial scale in the Lake Baikal sediments is Sr/Rb (and/or Ca/K) ratio [2,3]. The trend of Sr/Rb ratio in the sediments of Lake Baikal is compared in Fig. 3 with d18O in the ice sheets, which is the proxy of temperatures in the Greenland [10,11]. The positive pikes in the trend of Sr/Rb ratio (Fig. 3) reveal humid and warm periods and episodes in the watershed of Lake Baikal [3]. In the limit of U–Th dating errors, all abrupt and short warm episodes (Dansgaard–Oeschger events) discovered in Greenland

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