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Contents Supplementary Figures S1-S5 Figure S1 consists of a schematic showing the main findings of the paper; Figure S2 shows the sampling locations; Figure S3 shows radiochronological sediment core data; Figure S4 and S5 show isotopic values for our defined end-members. Supplementary Methods This contains detailed information on the sampling campaigns, bulk elemental and isotope analyses, and sediment flux calculations, followed by a thorough description of the end-members used for dual-carbon isotopic mixing model (including individual description of topsoil-PF, ICD-PF and marine end-members), and the Monte Carlo simulations. The Muostakh Island methods consist of a study area description, sampling description, elemental and isotopic carbon analysis, lipid extraction, fractionation and analysis, and analysis of CO2 fluxes. Supplementary Tables S1-S10 Table S1 and S2 show a summary of bulk geochemical data and sediment flux data, respectively; Tables S3 and S4 contain the data that were used for the end-m values; Table S5 summarizes the relative

ember

contribution of the three defined sources;

Table S6 su mmarizes the coastal an d shelf carb on fluxes; T able S7 and S8 contains data from Muostakh Island; Tables S9

and S10 contain raw bulk geochem ical and

radiochronological data, respectively.

 

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Figure S1 | Coastal erosion fluxes from Ice Complex and subsea permafrost in the ESAS. a, The existing knowledge1-6 on remobilization of coastal OC excludes sub-aerial degradation and acknowledges an unknown fate of this carbon in the coastal ocean. b, The current study on remobilization of coastal OC includes release of greenhouse gases (GHG) on the coastal slopes and details shelf degradation and deposition fluxes. All numbers reported as Tg OC/yr (mean±95% confidence interval).

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Figure S2 | Sampling locations in the East Siberian Arctic Shelf region Map of the Laptev and East Siberian Seas showing all sampling locations for surface sediments (in red) and sediment cores (in blue).

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Figure S3 | Radiochronological data for East Siberian Sea sediment cores. Regression plots of the natural logarithm of excess

210

Pb (LN

210

Pbxs) against core depth (cm) for

sediment cores a, YS-36, b, YS-37 and c, YS-90.

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d13C (‰) -31 200

0

-30

-29

-28

-27

-26

-25

-24

topsoil-PF

-23

-22

-21

-20

marine

Δ 14C-OC (‰)

13C n=30 14C n=18

-200

-400

-600

-800

ICD-PF 13C n=374 14C n=300

-1000

Figure S4 | Isotopic values for topsoil-PF, ICD-PF and marine end-members Isotopic ranges that are used to define the marine, topsoil-PF, and ICD-PF end-members. Central values and references for applied range: marine 13C -24±3.0‰, 14C +60±60‰ (refs 1, 7-17; Fig. S5; these papers report ranges, not individual data points), topsoil-PF 13C -28.2±1.96‰ 14C 126±54‰ (Table S3; refs 18-19, http://arcticgreatrivers.org/data, unpublished data from ISSS-08 and The Polaris Project), ICD-PF 13C -26.3±0.67‰ 14C -940±84‰ (Table S4; refs 20-40). Further explanation can be found in the Supplementary text. Black points refer to surface sediment values in the East Siberian Sea and Laptev Sea.

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Figure S5 | Literature values on 13C signature of marine particulate organic matter and ice algae Reported literature values for 13C on ice algae (grey bars, refs 7-10) and marine particulate organic matter (black bars, refs 1, 7, 9-13). Numbers on bars indicate references.

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Supplementary Methods Sampling campaigns Surface sediments were collected at 83 stations during August/September 2008 as part of the International Siberian Shelf Study 2008 (ISSS-08) onboard the H/V Yakob Smirnitskiy and the smaller ship H/V TB-0012 (Fig. S2). They were collected with a Van Veen grab sampler and a dual gravity corer (GEMAX, Kart Oy, Finland; modified at Stockholm University). The surface layers of the grab samples were retrieved with stainless steel spatulas, transferred into polyethylene containers and frozen until analysis. The sediment cores were sectioned into 1 cm slices with an extruder (Kart Oy, Finland), and likewise transferred into polyethylene containers and frozen until analysis. Further sampling was performed in the Laptev and East Siberian Seas on several separate expeditions using the mid-size hydrographic vessels Ivan Kireev (2003/2004) and Viktor Buynitskiy (2007) (Fig. S2). For 117 stations, surface sediments were collected with a Van Veen grab sampler. The surface layers of the grab samples were retrieved with stainless steel spatulas, transferred into polyethylene containers and frozen until analysis.

Bulk elemental and isotope analyses From the ISSS-08 (n=83) and 2007 (n=20) stations, around 10 mg dried (60°C, 24 h), ground and homogenized sediment was weighed into pre-combusted silver capsules (5 x 9 mm, Säntis Analytical AG, Teufen, Switzerland). The samples were acidified in situ with 50 µl 1M HCl to remove carbonates and dried overnight at 60°C42. Total organic carbon (TOC) and total nitrogen (TN) content, as well as its δ13C signal were measured on triplicate samples using an elemental analyzer (EA) isotope ratio mass spectrometer (Europe Hydra 20/20, University of California, Davis Stable Isotope Facility, USA). Elementary (TOC) and isotopic (δ 13C) composition of bottom sediments (n=97) for the 2003, 2004 and 2007 expeditions were determined by Carlo Erba elemental analyzers and a Finnigan MAT Delta Plus isotope ratio mass spectrometer, respectively, at the International Arctic Research Center, University of Alaska, Fairbanks (USA). Accuracy and reproducibility of the isotope results were within δ13C ±0.1‰. A subset of 30 samples was freeze-dried (Christ Alpha 2-4, LSC with low carbon vacuum hybrid pump, Vacubrand RC-6; Martin Christ, Labex Instrument AB, Sweden) and sent to the U.S. National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility of the Woods Hole Oceanographic Institution (WHOI, Woods Hole, USA). Here the samples were acidified to remove

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carbonates and analyzed for bulk organic 14C content by AMS.

Sediment flux calculations The 210Pbxs activity of the sediment cores IK-105, IK-110, IK-114, IK-118, YS-22, YS-26, and YS93 was derived based on measurements by Stockholm University with a co-axial low-energy gamma spectrometer (EG&G ORTEC) with a High-Purity Germanium (HPGe) detector. The 210Pb and

226

Ra were analyzed in gas-tight containers about three weeks after sealing. Self-absorption

corrections and thus overall counting efficiencies of the 46 keV line from 210Pb were done using an external

210

Pb point source43, which for Stockholm University was a calibrated U-Th series

pitchblende standard (Stackebo, Sweden). The measurements were blank subtracted and decay corrected to date of collection. Cores YS-35, YS-36, YS-37, YS-90, YS-98 and YS-120 were measured at the Radiation Research Division of the Risø National Laboratory for Sustainable Energy (Roskilde, Denmark) using low-energy HPGe detectors with a carbon entrance window. Most cores from these shallow shelves were unable to show a clear age-depth chronology, presumably caused by sediment resuspension, bioturbation and ice scouring effects, yet a few cores may be used for dating (Fig. S3). However, even in the absence of a linear sedimentation rate, it is possible to derive an average (over the mean lifetime of the depth-integrated inventory of excess

210

210

Pb) sediment accumulation flux. Using

Pb (210Pbxs), we were able to estimate annual OC

accumulation rates (e.g., ref. 44). For each core slice (0-1cm, 1-2cm, 2-3cm, etc.), the excess 210Pb can be calculated according to: 210

Pbxs [Bq/gdw] = A 210Pb [Bq/gdw] – A226Ra [Bq/gdw]

where A is the activity. For each slice, excess

210

(1)

Pb in Bq/gdw can be converted into Bq/cm2

through multiplication with (1-porosity), dry density [g/cm3] and slice interval [cm]. Subsequently, the total 210Pbxs in [Bq/cm2] per core can then be calculated from: 210

Pbxs [Bq/cm2] =Σall slices[210Pbxs[Bq/gdw] x (1-porosity) x dry density [g/cm3] x slice interval

[cm]]

(2)

Porosities were calculated and salinity-corrected for the YS-cores. The values decreased downcore, and were generally higher on the outer shelf regions (71-92% in 0-1 cm, 37-51% for deepest slice; YS-90, 98, 120) than close to the coast (44-62% in 0-1 cm, 26-37% for deepest slice; YS-35, 36, 37). Dry densities measured for the YS-cores gave an average value of 2.7 g/cm3 (n=6, stdev 0.36). The IK-cores were assumed to have porosities of 0.7 in the top slice and 0.6 deeper down, and dry densities of 2.7 g/cm3. The mean life of 210Pb (τ = 1/λ = 32.17 yr) can be used to derive 210Pbxs [Bq/cm2/yr]:

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210

Pbxs [Bq/cm2/yr] = 210Pbxs [Bq/cm2] / τ

The total inventories of

210

(3)

Pbxs are between 16±3.9 and 383±40 Bq/m2/yr (mean±stdev; Table S2,

S10), which is comparable to the suggested global range of unsupported

210

Pb of 50–150 Bq/m2/yr

(ref. 45), and comparable to fluxes in the northeast Atlantic (67-100 Bq/m2/yr (ref 44 and references therein)). Finally, the annual sediment OC accumulation can be derived as follows: Flux OC [mg OC/m2/yr] = 210Pbxs [Bq/m2/yr] x (OCz=0 [mgOC/gdw] / A210Pbxs at z=0 [Bq/gdw]) (4)

Note that for the cores YS-120, IK-114 and IK-118 there still was

210

Pbxs left in the deepest core

section, and their annual OC accumulation rates are therefore minimal numbers.

When sediment cores are not mixed or bioturbated, one can calculate the sedimentation rate through the slope of the regression of the natural logarithm of 210Pbxs against sediment depth. S=-λ /m

(5)

where S is sedimentation rate (cm/yr), λ is the decay constant of

210

Pb (0.031) and m is the slope.

We tested this approach on sediment cores YS-36, YS-37, and YS-90 where the degree of mixing seemed only minor (Fig. S3). This resulted in sedimentation rates of 0.11 to 0.16 cm/yr and OC accumulation fluxes of 28-52 gOC/m2/yr. The latter numbers are of similar magnitude as the fluxes in Table S2 (based on equation 4).

End-members for dual-carbon isotopic mixing model We have applied a dual-carbon (δ13C and Δ14C) isotopic mixing model, similar to refs 46 and 47, to distinguish between three sources (Fig. S4): (i) topsoil permafrost (topsoil-PF) OC, the topsoil of the terrestrial permafrost (ii) Ice Complex permafrost (ICD-PF) OC, consisting of Ice Complex deposits (coastal and inland, but predominantly exposed at the coast) and subsea permafrost and (iii) marine OC (Fig. S4). We define two different terrestrial end-members to be able to derive relative contributions of (a) contemporary terrestrial material (vegetation debris, topsoils, shallow active layer) that is delivered from inland by rivers and from the top of coastal bluffs through erosion and collapse, and (b) (late) Pleistocene Ice Complex material that is delivered through coastal, delta and riverbank erosion, and deep thermokarst. The following three equations are used: Ftopsoil-PF+ fICD-PF + fmarine = 1 13

13

(6) 13

13

δ Csample = ftopsoil-PF δ Ctopsoil-PF + fICD-PF δ C ICD-PF + fmarine δ Cmarine

(7)

Δ14Csample = ftopsoil-PF Δ14Ctopsoil-PF + fICD-PF Δ14C ICD-PF + fmarine Δ14Cmarine

(8)

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Where ftopsoil-PF, fICD-PF and fmarine are the fractions for topsoil permafrost OC, coastal Ice Complex permafrost OC and marine OC contribution to the samples, respectively.

Topsoil-PF end-member The topsoil-PF δ13C end-member (-28.2‰; stdev 1.96‰) is derived from a seasonal survey (AprilMay-June) of Kolyma and Lena River POC (n=17; -28.4‰, stdev 2.1‰) and DOC data (n=13; 28.0‰, stdev 1.8‰) from literature18,19 and unpublished data (http://arcticgreatrivers.org/data; ISSS-08; The Polaris Project; Table S3). We chose Spring/early Summer data only, to ensure water flow is restricted to shallow flow paths (i.e. topsoils) as active layer deepening is still absent or minimal. Similarly, the topsoil-PF Δ14C value (-126‰; stdev 54‰) is derived from the mean of POC (n=5, Vonk et al., unpublished results; -319‰, stdev 83‰) and DOC (n=13; -66.1‰, stdev 46‰) data18,19. The end-member values are calculated as the average of POC and DOC data (Table S3). Monte Carlo test simulations with stronger weighing of POC or DOC (2/3 POC and 1/3 DOC, or 1/3 POC and 2/3 DOC) for a range of stations with variable topsoil-PF contributions showed only small shifts in topsoil-PF contributions (-0.11 to +2.6% or -0.21 to -1.8%, respectively).

ICD-PF end-member The δ13C value of the ICD-PF end-member (-26.3‰, stdev 0.67‰, n=374) is taken from a recently published review20 that in detail describes the characteristics and origin of Ice Complex deposits in Siberia. We have calculated a mean value from the data in this paper (ref. 20, page 18/Table 5), using the mean values of 12 different sites and weighing them based on the number of samples. The 14C value of the ICD-PF end-member (-940‰, stdev 84‰, n=300) is based on a large amount of data from a range of circum-arctic studies (mostly Russia, but also Alaska and NW Canada) on Ice Complex deposits20-40 (Table S4). These papers typically report 14C ages as ky B.P., and we therefore have converted these ages into Fraction modern (Fm = e-age/8033) and subsequently into 14C (‰; 14C = [Fm x [elambda(1950-Yc) – 1] x 1000, where lambda is 1/(true mean-life of 14C) or 1/8267, and we have assumed Yc (year of collection) to be 1990). In total, these papers include 300 14C data points.

Marine end-member Literature reports on a wide range of marine 13C values for marine particulate organic matter in Arctic waters (Fig. S5, refs 1,7,9-13). Seasonally higher contributions of ice algae OC to the sedimentary OC are likely only minimal (4-26% of total primary production in seasonally ice-

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covered waters, ref. 48), but could also deliver a variety of 13C signatures. We measured a value of -24.0‰ (triplicate measurement, analytical error 0.016%) on plankton during ISSS-08, which we have decided to use as the central end-member value. Based on Arctic literature, we will apply a standard deviation of 3.0‰ (i.e. a range of -27‰ to -21‰) for the Monte Carlo simulations (Fig. S5). We have tested different marine end-member values for two stations (YS-90; outer shelf, YS-30, nearshore) that showed maximal and minimal marine inputs (54% and 7%, respectively, for the 24±3.0‰ end-member value). Monte Carlo simulations with two considerably different marine end-member values (-27±3‰, and -21±3‰) showed only a 40 m depth) Chaunskaya Bay

15

8.49

12

11.9

Long Strait

14

16.1

δ13C max (‰) min Laptev Sea -25.6 -24.3 -26.2 -25.9 -25.2 -27.5 -27.0 -25.8

3.88 -27.4 East Siberian Sea 20.4 -25.8 -23.8 4.06 -28.3 20.1 -25.5 -23.8 3.90 -27.3 10.4 -23.3 -21.2 7.60 -24.8 25.3 -25.9 -24.4 1.30 -27.0 21.9 -23.2 -21.9 11.0 -24.3

TOC/TN1

9.59 11.4 9.42

max min

n

15.3 3 3.00 14.9 11 9.40 12.5 1

14C (‰)

max min

-486

-557 -437 -622 -436 -

-516 -716

-

6.93 11.7 8.80 5.66 10.9 8.42

16.3 6.63 14.9 6.08 6.17 5.24 13.0 8.00 10.8 6.35

5

-675

4

-514

5

-422

-

-

-

-

-741 -600 -624 -425 -511 -332 -

For sediment OC and TOC/TN, outliers have been excluded (3 and 8 values respectively). Outliers

are defined as observations farther than 1.5 * interquartile range from the closest quartile.

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Table S2 | Fluxes of organic carbon to surface sediments in the East Siberian Arctic Shelf. Sediment core locations can be found in Fig. S2. Station

1

Core length

Depth

(cm)

(m)

Total stdev core 210 Pbxs (Bq/m2/yr)

3

IK-118-A

58

15

197

YS-223 YS-263 YS-35 IK-110-A IK-114-A3

15 14 11 13 40

20 16 31 17 16

313 178 38.7 16.2 26.2

YS-36 YS-37 YS-98 YS-1203 IK-105-A

14 15 12 11 25

32 42 48 33 37

51.1 123 87.1 249 383

YS-933 YS-90

14 17

51 63

140 51.2

OC bottom slice1 (mg/gdw)

Laptev Sea 15 18 East Siberian Sea West 14 12 11 8.7 6.4 13 3.9 4.7 3.2 6.2 Central 6.3 11 8.8 12 11 9.4 13 11 40 14 East/outer 10 8.0 8.5 7.2

Activity 210Pb

OC flux to sediment2

(Bq/gdw)

(gOC/m2/yr)

0.058

60

0.029 0.036 0.030 0.010 0.009

130 43 17 7.6 18

0.016 0.033 0.022 0.076 0.134

33 43 38 36 40

0.038 0.048 mean±95%CI4

29 7.7 36±17

For YS-22, YS-26 and YS-93, the OC content of the top slice was used. The other cores showed

no clear difference between OC content in the top versus bottom; the values were comparable and without any significant decrease downcore. 2

According to: Flux sediment OC [mg OC/m2/yr] = Σall

slices

210

Pbxs [Bq/m2/yr] x (OCz=0

[mgOC/gdw] / A210Pbxs at z=0 [Bq/gdw]). Further details can be found in the method section. 3

The deepest core slice still contained

210

Pbxs. The sediment OC accumulation fluxes for these

stations are therefore minimal estimates. 4

95% confidence interval for n=12 data points (East Siberian Sea only).

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Table S3 | Topsoil-PF end-member source data Combined literature and unpublished δ13C and 14C results on POC and DOC in the Kolyma and Lena Rivers during April, May and June (multiple years), used as source data for the topsoil-PF end-member. River Kolyma River

Lena River

Mean Average POC+DOC

Sampling date 11-Jun-04 15-Jun-04 25-Jun-04 22-Apr-05 30-Jun-05 05-Jun-09 12-Jun-09 21-Jun-09 11-Jun-03 30-Jun-03 28-May-03 30-Apr-11 01-Jun-11 31-May-11 14-Jun-11 13-Jun-11 09-Apr-04 05-Jun-04 07-Jun-04 27-May-05 04-Jun-05 06-Jun-06 31-May-09 05-Jun-09 11-Jun-09

δ13C (‰) DOC POC -26.5 -27.3 -28.1 -30.0 -29.7 -27.4 -34.6 -27.2 -30.5 -26.1 -27.4 -27.3 -28.0 -32.2 -27.9 -30

14C (‰) POC DOC 86.8 -3.9 44.8 20.4 -12.7

52.6 52.7 116 -203 -286 -310 -387 -410

-31.5 -27.7 -27.4 -27.8 -26.9 -27.8 -27.1 -27.2 -26.6 -29.0

-27.2 -27.3 -28.3 -25.2 -27.3

63.0 120 121 112 87.0

-28.5 -28.2

-319 44.6 -126.4

Source Ref. 19 Ref. 19 Ref. 19 Ref. 19 Ref. 19 http://arcticgreatrivers.org/data http://arcticgreatrivers.org/data http://arcticgreatrivers.org/data Ref. 18 Ref. 18 Ref. 18 Vonk et al., unpublished Vonk et al., unpublished Vonk et al., unpublished Vonk et al., unpublished Vonk et al., unpublished Ref. 19 Ref. 19 Ref. 19 Ref. 19 Ref. 19 Ref. 19 http://arcticgreatrivers.org/data http://arcticgreatrivers.org/data http://arcticgreatrivers.org/data

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Table S4 | ICD-PF end-member source data Collected ∆14C data from literature on Ice Complex deposits in Siberia, Alaska and Canada, used as source data for the ICD-PF end-member. Sample/ Lab ID #

Location

Lat (°N)

Long (°E)

Height1 (m)

Material

Kha-2-1 Kha-2-3 Kha-2-7 Kha-2-13 Kha-2-18 Kha-2-24 Kha-2-32 Muo-3-1 Muo-3-5 Muo-3-4 Muo-3-8 Muo-3-9 Muo-3-11 STO-1-6 STO-2-1 STO-2-2 STO-2-3 STO-3-1 STO-3-5 STO-3-8 BEL-2-1 BEL-3-1 BEL-3-3 BEL-7-1 Mya-1-1 Kys-2-4 KYS-2-5

Khardang Sise Island Khardang Sise Island Khardang Sise Island Khardang Sise Island Khardang Sise Island Khardang Sise Island Khardang Sise Island Muostakh Muostakh Muostakh Muostakh Muostakh Muostakh Stolbovoy Island Stolbovoy Island Stolbovoy Island Stolbovoy Island Stolbovoy Island Stolbovoy Island Stolbovoy Island Bel'kovsky Island Bel'kovsky Island Bel'kovsky Island Bel'kovsky Island N Kotel'ny Island, CapeKotel'ny Anisii Island, SW Khomurganakh River SW Kotel'ny Island (K. (K. R.) R.)

72.95 72.95 72.95 72.95 72.95 72.95 72.95 71.61 71.61 71.61 71.61 71.61 71.61 74.06 74.06 74.06 74.06 74.06 74.06 74.06 75.37 75.37 75.37 75.37 76.17 74.73 74.73

124.2 1 124.2 1 124.2 1 124.2 1 124.2 1 124.2 1 124.2 1 129.9 4 129.9 4 129.9 4 129.9 4 129.9 4 129.9 4 136.0 8 136.0 8 136.0 8 136.0 8 136.0 8 136.0 8 136.0 8 135.5 9 135.5 9 135.5 9 135.5 9 139.0 1 138.4 5 138.4 5

3.1 4.3 5 6.6 8.6 10.1 16.9 0.5 1 2 5 7.5 9.7 27 10 1 3 5 6 6.75 2.7 3.7 4.6 1 1.5 2.7 3

peat inclusion peat inclusion peat moss peat plant fragments wood fragments plant remains plant remains twigs twigs, moss plant remains carex, eriophorum twigs twigs, betula nana plant remains plant remains twigs moss moss twigs, moss twigs twigs moss twigs lemming excrement, seeds, insectremains remains plant plant remains

14

C2 (yrs BP) 43550 49030 52090 50200 29770 28050 20100 39110 46780 42800 38620 40340 19560 50890 40830 36440 52250 42430 54940 36580 54390 47660 39840 39980 27860 45960 52280

∆14C2,3 (‰)

Ref.4

Comments5

-996 -998 -998 -998 -976 -970 -918 -992 -997 -995 -992 -993 -913 -998 -994 -989 -999 -995 -999 -990 -999 -997 -993 -993 -969 -997 -999

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

min. age min. age min. age min. age

min. age min. age min. age min. age min. age min. age

min. age

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Kys-2-6 Kys-2-10 KLY-1-1 KLY-1-4 KLY-1-9 X-99-019 X-99-014 X-99-024 X-99-025 Oy7-08-32 Oy7-08-37 Oy7-08-38 Oy7-08-42 Oy7-08-47 Oy7-08-53 Oy7-08-57 Oy7-08-62 Oy7-08-63 MaK-1-9 MaK-1-12 MaK-2-1 MaK-2-6 MaK-2-9 MaK-3-7 MaK-3-14 MaK-3-17 MaK-5-3 MaK-6-4 MaK-9-5 MaK-10-5 MaK-10-8 MaK-11-2 MaK-12-1

SW Kotel'ny Island (K. R.) SW Kotel'ny Island (K. R.) Lyakhovsky Maly Island, Cape Vatgach Maly Lyakhovsky (C. V.) IslandLyakhovsky (C. V.) Maly Island (C. V.) Nos Cape Svyatoy Cape Svyatoy Nos Cape Svyatoy Nos Cape Svyatoy Nos Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Oyogos Yar coast Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk

74.73 74.73 74.25 74.25 74.25 72.84 72.84 72.84 72.84 72.68 72.68 72.68 72.68 72.68 72.68 72.68 72.68 72.68 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61 73.61

138.4 5 138.4 5 140.3 5 140.3 5 140.3 5 140.8 5 140.8 5 140.8 5 140.8 5 143.5 3 143.5 3 143.5 3 143.5 3 143.5 3 143.5 3 143.5 3 143.5 3 143.5 3 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8

4 8.4 5 3.3 1.5 14.6 9.6 17 24 9.5 12 15.5 17.1 19.2 22 24 26.5 27 4.3 5.3 6.2 8.3 9.8 7 10.3 13.2 14.3 16 21.9 24.3 25.2 2.5 0.5

moss plant remains moss plant remains twigs plant remains plant remains plant remains plant remains plant remains peat inclusion peat inclusion plant remains plant remains peat inclusion plant remains grass roots grass roots fine-sand silt, grass roots peaty palaeosol sand, organic free peaty palaeosol, cryoturbated, peat peaty palaeosol, cryoturbated, peat peaty palaeosol, fine-sand silt, small, discontinuous peaty palaeosol, peat peat inclusion inclusions peaty palaeosol, peat inclusions peat inclusion, palaeosol, wood sandy remains silt, vertical grass roots fine-sand silt, wood remains cryoturbated palaeosol, peat inclusionpalaeosol, cryoturbated peat inclusion sandy silt, plant remains peaty palaeosol, peat inclusions

52790 35370 38290 34680 27980 47640 45350 50290 36080 41420 43860 44840 48540 40850 44900 38600 34630 32220 44520 40410 37100 42260 44310 43510 43620 31250 24600 20640 16510 9480 9510 11060 27220

-999 -988 -992 -987 -969 -997 -996 -998 -989 -994 -996 -996 -998 -994 -996 -992 -987 -982 -996 -993 -990 -995 -996 -996 -996 -980 -953 -924 -873 -694 -695 -749 -966

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21

min. age

min. age min. age

min. age min. age

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RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

MaK-13-7 MaK-15-5 MaK-16-5 MaK-17-3 MaK-17-7 MaK-19-3 MaK-19-7 LD98 D6238 L 98 D6237 LD98 D6397 Nag 6+20-S-5 LD98 D7.502 BKh 3-S-25 BKh 3-S-23 BKh 3-S-19 BKh 3-S-14 BKh-O 65 BKh 3-S-14 DY II-2 DY II-2 DY II-2 Bkh2002 S20 Bkh2002 S16 Bkh2002 S22D Bkh2002 S48 Bkh2002 S25D Bkh2002 S46aD BKh2002 S45aD MKh99-5 Mkh99-8 Mkh99-9 Mkh99-23 Mkh99-10

Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Cape Mamontov Klyk Nagym, Island EbeBasyn-Sise Nagym, Island EbeBasyn-Sise Nagym, Island EbeBasyn-Sise Nagym, Island EbeBasyn-Sise Island Buor-Khaya, Kurungnakh-Sise (K. Buor-Khaya (K. S.) S.) Buor-Khaya (K. S.) Buor-Khaya (K. S.) Buor-Khaya (K. S.) Buor-Khaya (K. S.) Buor-Khaya (K. S.) Dzhangylakh/Khardan g Island Dzhangylakh/Khardan g Island Dzhangylakh/Khardan g Island Kurungnakh Kurungnakh Kurungnakh Kurungnakh Kurungnakh Kurungnakh Kurungnakh Bykovsky, Mamontovy Khataya (M. Bykovsky (M.K.) K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.)

73.61 73.61 73.61 73.61 73.61 73.61 73.61 72.88 72.88 72.88 72.88 72.33 72.33 72.33 72.33 72.33 72.33 72.33 72.95 72.95 72.95 72.33 72.33 72.33 72.33 72.33 72.33 72.33 71.81 71.81 71.81 71.81 71.81

117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 117.1 8 123.3 2 123.3 2 123.3 2 123.3 2 126.3 126.3 126.3 126.3 126.3 126.3 126.3 124.2 1 124.2 1 124.2 1 126.3 126.3 126.3 126.3 126.3 126.3 126.3 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2

4.3 6.6 9.3 11.5 13.6 15.3 17.1 14 11 5.1 22 14 31 28.5 24 21 20 15.9 18.8 19.6 29.2 29 26.3 24 23 19.8 17.9 35.5 33.5 32.6 31 30.2

fine-sand silt, few organic, wood remains fine-sand to silt, wood (twigs, roots) fine-sand to silt, wood (twigs, roots) peaty palaeosol, wood remains palaeosol sand, wood and plant remains sandy silt Wood plant remains root horizon Peat root horizon small twigs peat peat peat Equus sp. (radius) peat inclusion plant remains autochthonous peat autochthonous peat wood wood wood, leaves wood wood, moss, coarse leaves moss, leaf fragments plants plant plant grass roots, wood plant plant

24150 21890 20180 18920 17700 16350 14545 47480 42930 56790 45640 42910 16980 33490 38020 44470 34299 50090 52690 26420 25180 32920 31960 34830 40410 40020 41220 41330 13920 17160 17350 19340 20600

-951 -935 -919 -906 -890 -870 -837 -997 -995 -999 -997 -995 -880 -985 -991 -996 -986 -998 -999 -963 -957 -983 -981 -987 -993 -993 -994 -994 -824 -882 -885 -910 -923

21 21 21 21 21 21 21 22 22 22 22 22 22 22 22 22 22 22 22 22 22 23 23 23 23 23 23 23 24 24 24 24 24

min. age min. age min. age; conv. 14C

conv. 14C min. age; conv. 14C conv. 14C conv. 14C

WWW.NATURE.COM/NATURE | 24

RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

Mkh99 R1-30m Mkh 00-S-1 Mkh99-12 Mkh B18-28.5m Mkh99-14 Mkh99-16 Mkh99-18 Mkh-4.12-2a Mkh99-90 Mkh-KB7-5a Mkh-KB9-3 Mkh-KB7-3a Mkh-4-14C-8 Mkh-KB8-3 Mkh-KB6-3 Mkh-KB8-4 Mkh-KB4-6 Mkh-KB5-2 Mkh-KB5-2 Mkh-BR2 Mkh-KB4-4 Mkh-HB2-4 Mkh-HB2-8 Mkh-HB2-10 Mkh-HB2-2 Mkh-KB3-1 Mkh-KB2-2 Mkh-KB1-4 Mkh-KB1-2 Mkh-K1-14C-2 Mkh-3 Mkh-K1-5 Mkh-K1-14C-1

Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.)

71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81

128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2

30 30 28.8 28.5 27.5 26.2 24.7 24.1 23.3 22.3 22.2 20.7 20 18.5 18.4 17.5 17.2 17.2 17.2 16.8 16 15.2 15.6 15.8 15 15 14.8 13.8 13 11 10 10.5 8.8

insect remains plant remains grass roots, wood insect remains grass roots grass roots, wood grass roots, wood peat grass roots wood wood wood peat wood peat, moss, grass wood, plant wood peat, plant wood shrub, wood grass roots peat peat peat peat peat, wood moss wood wood wood peat inclusion moss grass

17160 18490 22060 23750 23800 24470 25570 24460 28110 33580 28470 33450 28502 35050 36020 34800 36800 37010 37760 34740 35860 44980 41390 41830 41740 39320 44280 44580 48140 47900 45090 45300 42630

-882 -900 -936 -948 -949 -953 -959 -953 -970 -985 -971 -985 -971 -987 -989 -987 -990 -990 -991 -987 -989 -996 -994 -995 -994 -993 -996 -996 -998 -997 -996 -996 -995

24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24

conv. 14C

min. age, conv. 14C conv. 14C min. age, conv. 14C

WWW.NATURE.COM/NATURE | 25

RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

Mkh-1.1-2 Mkh-1.2-14C-1 Mkh-6.1-2 Mkh-00-10-S-1 Mkh-00-10-S-1 Mkh-KB9-6 Mkh-KB-9-6 MB-6.3-1 Mkh-KB2-2 Mkh-HB2-4 Mkh-HB2-8 Mkh-HB2-8 Mkh-HB2-10 CM-1.2-1 Mkh99-4-KIA 10355 Khg-11/1-KIA 25714 Khg-11/2-KIA 20692 Khg-11/3-KIA20693 Neb-1/10-KIA25713 KIA Neb-1/620698 KIA Neb-1/220697 Neb-1/1-KIA 20696 Khg-17/12-KIA 20694 Khg-17/7-KIA 25712 Khg-17/1-KIA 20694 Mkh02-1/1- KIA 25715 Mkh02-1/3KIA 25716 Mkh02-1/5- KIA 25717 B-S-5-KIA 8166 B-S-7-KIA 8165 30/82-IM-767 19/82-IM-766 103/81-LU-1328

Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovksy (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (M. K.) Bykovsky (Cape Mammoth) Bykovsky (Mamontovy Khataya) Bykovsky (Khorogor Valley) Bykovsky (Khorogor Valley) (Khorogor Bykovsky Valley) (Khorogor Bykovsky Valley) (Khorogor Bykovsky Valley) (Khorogor Bykovsky Valley) Bykovsky (Khorogor Valley) (Khorogor Bykovsky Valley) Bykovsky (Khorogor Valley) (Khorogor Bykovsky Valley) Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula

71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81 71.81

128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2 128.4 2

3.4 2.7 1.3 0.2 1.7 23.8 23.9 1.5 14.8 15.25 15.55 15.55 15.75 24 36.4 36 35.4 35 4.2 3.45 2.6 2.1 7 6 4.8 36.35 35.25 34.75 20 10 20 11 7

grass roots peat, wood wood plant remains plant remains plant wood plant remains moss remains peat peat peat peat plant remains plant remains peat peat peat twigs peat peat plant remains peat twigs peat twigs twigs twigs wood peat peat peat peat

52870 58400 52900 54930 57180 10470 13230 47400 44280 43080 39500 36350 38610 35050 12790 11545 11710 12145 10440 10690 11260 11400 10120 10210 10190 10620 12890 14760 19330 53020 28180 23700 21630

-999 -999 -999 -999 -999 -730 -808 -997 -996 -995 -993 -989 -992 -987 -798 -764 -768 -781 -729 -737 -755 -759 -718 -721 -720 -735 -800 -842 -910 -999 -970 -948 -933

24 24 24 24 24 24 24 25 25 25 25 25 25 25 25 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 27 27 27

min. age

min. age min. age min. age

conv. 14C conv. 14C conv. 14C

WWW.NATURE.COM/NATURE | 26

RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

103/81-LU-1130 103/81-GIN-4597 103/81-GIN-4593 103/81-GIN-4391 BK-21-1 BK-21-2 BK-21-3 BK-21-4 Lena-64-5 Lena-64-7 Lena-64-8 Lena-64-9 M 2-5 M 2-3 M 5-3 M 5-5 M 6-3 M 6-6 M 7-5 OS-66783 OS-66784 Alpha-3292 OS-66785 OS-66786 USGS-1151 I-11,530 OS-66780 AA-2361 Alpha-3291 Alpha-3290 OS-66787 OS-66777 OS-66778

Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Bykovksy peninsula Buor-Khaya Cape Buor-Khaya Cape Buor-Khaya Cape Buor-Khaya Cape Olenek channel Olenek channel Olenek channel Olenek channel Muostakh Muostakh Muostakh Muostakh Muostakh Muostakh Muostakh Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik Alaska; Itkillik

71.81 71.81 71.81 71.81 71.92 71.92 71.92 71.92 72.32 72.32 72.32 72.32 71.61 71.61 71.61 71.61 71.61 71.61 71.61 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57 69.57

128.4 2 128.4 2 128.4 2 128.4 2 132.6 8 132.6 8 132.6 8 132.6 8 126.2 8 126.2 8 126.2 8 126.2 8 129.9 4 129.9 4 129.9 4 129.9 4 129.9 4 129.9 4 129.9 -4 -150.8 7 150.8 7 -150.8 7 150.8 7 -150.8 7 150.8 7 -150.8 7 150.8 7 150.8 7 150.8 7 -150.8 7 150.8 7 150.8 7 150.8 7

6 5 4 2.5 6 3 1 1 17 2 1 0.5 13 16 0.5 24 2 23 23 3 4 7.4 11 15 15 15 16 17.2 17.4 20 23 30.9 31.8

peat plant material plant material plant material bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil bulk soil twigs twigs loess twigs twigs fine-grained org. fine-grained org. twigs herbaceous plant loess loess fine-grained org. peat fine-grained org.

33040 40200 40400 40800 48000 7960 19450 14300 42500 16500 11450 15800 17300 15750 25500 15400 19950 9380 35200 14300 16550 12600 29300 26300 28610 32300 23900 21800 34700 34700 41700 48000 47500

-984 -993 -993 -994 -997 -631 -912 -832 -995 -872 -761 -861 -884 -860 -958 -854 -917 -690 -988 -832 -873 -793 -974 -962 -972 -982 -949 -934 -987 -987 -994 -997 -997

27 27 27 27 * * * * * * * * * * * * * * * 28 28 29 28 28 29 29 28 29 29 29 28 28 28

conv. 14C conv. 14C conv. 14C conv. 14C min. age

14C by thermoluminescence

min. age min. age

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RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

363/55-Hel-3942 363/77-Hel-4023 279/10-GIN-2473 279/13-GIN-2475 363/207-GIN8931 363/111-Hel-4046 279/16-GIN-2474 363/206-Hel-4043 363/62-Hel-4056 363/112-Hel-3943 279/23-GIN-2476 363/212-GIN8936 279/28-GIN-2477 363/211-Hel-201 363/208-Hel-3950 GIN-4983 GIN-4978 GIN-4977 GIN-4964 GIN-4979 GIN-4982 GIN-4987 GIN-4965 GIN-4981 GIN-3597 GIN-3591 GIN-3592 GIN-3595 GIN-3609 GIN-3603 GIN-3611

Kolyma; Medvezhka Kolyma; Zelenyi Mys Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Yamal: Seyaha Kular settlement Kular settlement Kular settlement Kular settlement Kular settlement Kular settlement Kular settlement Kular settlement Kular settlement Gudar settlement Gudar settlement Gudar settlement Gudar settlement Gudar settlement Gudar settlement Gudar settlement

69.65 68.8 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70.64 70.64 70.64 70.64 70.64 70.64 70.64 70.64 70.64 70.89 70.89 70.89 70.89 70.89 70.89 70.89

162.5 2 161.3 8 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 134.3 4 134.3 4 134.3 4 134.3 4 134.3 4 134.3 4 134.3 4 134.3 4 134.3 4 78.5 78.5 78.5 78.5 78.5 78.5 78.5

>10m d >10m d 0.8d 3.2d 8.6d 10d 11d 12d 12d 12d 12.2d 15.2d 16.2d 20.5d 20.9d 20.9d 20.9d 100 100 100.5 106 106.5 107 107 109 109 2 3 5 2 3 5 2

bulk soil bulk soil peat peat peat peat peat peat peat peat peat peat peat peat Peat Twig Peat Peat Wood Wood Bone Peat Rootlets Peat Bone Bone allochthonous OM allochthonous OM allochthonous OM allochthonous OM allochthonous OM allochthonous OM allochthonous OM

39860 26700 11620 17290 22700 22600 22510 22850 23500 24460 25300 27890 24300 29500 30100 31200 36800 40000 43700 41100 40500 35700 42400 33300 38700 37700 12300 13850 14400 13600 14590 14810 12090

-993 -964 -766 -884 -941 -940 -940 -942 -947 -953 -957 -969 -952 -975 -977 -980 -990 -993 -996 -994 -994 -988 -995 -984 -992 -991 -785 -823 -834 -817 -838 -843 -779

30 30 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32

min. age min. age

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RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

GIN-3608 GIN-3585 GIN-3862 GIN-3864 GIN-3865 GIN-4015 GIN-4018 GIN-3861 GIN-4016 GIN-4017 GIN-3868 EP-941555 MAG-592 GIN-3867 GIN-4588 GIN-3998 GIN-3996 GIN-8922 GIN-8925 GIN-8929 GIN-8930 TO-6968 Beta-161238 Beta-161239 TO-8304 TO-6967 BGS-1775 Beta-133410 BGS-1770 BGS-1768 BGS-1754 BGS-1758 BGS-1755

Gudar settlement Gudar settlement Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Duvanny Yar Utinoe Utinoe Utinoe Utinoe Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada

70.89 70.89 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 68.62 62.5 62.5 62.5 62.5 63.92 63.92 63.92 63.92 63.92 63.92 63.92 63.92 63.92 63.92 63.92 63.92

78.5 78.5 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 3 159.1 -3 -151.4 2 -151.4 2 151.4 2 151.4 2 -139.3 2 139.3 2 -139.3 2 139.3 2 -139.3 2 139.3 2 139.3 2 139.3 2 -139.3 2 139.3 2 139.3 2 139.3 2

3 5 20 21 22 25 30 38 38 40 45 46 42 15 10 9 7.5 334.8 334.9 334 332.8 -

allochthonous OM allochthonous OM Rootlets Rootlets Soil DAOPM DAOPM bone DAOPM DAOPM bone soil rootlets, stalks, branches bone black peat rootlets, stalks, branches rootlets, stalks, branches wood wood peat peat small twigs and grass grass draba sp. Seed capsule peat small twigs and grass grass bed peat salix sp. piece grasses grasses salix sp. Piece grasses

13100 15890 42600 38000 35100 37900 33400 33800 27600 22000 19480 13080 17850 28600 29900 30100 35400 32100 31390 42120 35500 23520 23990 24280 21880 22300 24025 25240 31000 28450 27150 26240 24025

-805 -862 -995 -991 -987 -991 -984 -985 -968 -936 -912 -805 -892 -972 -976 -977 -988 -982 -980 -995 -988 -947 -950 -952 -935 -938 -950 -957 -979 -971 -966 -962 -950

32 32 32 32 32 32 32 32 32 32 32 32 33 33 33 33 33 34 34 34 34 35 36 36 36 35 37 36 37 37 37 37 37

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RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

BGS-2015 BGS-2019 BGS-2018 TO-6968 TO-6967 Beta-111606 TO-6869 SI-1967 SI-1966 W-435 L-157A L-163J I-2116 Hv-1328 L-137X KIA 19138 KIA 19138 KIA 19139 Erl. 6152 Erl. 6154 Erl. 6157 Erl. 6153

Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Klondike, Canada Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Mamontova Gora Alaska, Eva Creek Alaska, Eva Creek Alaska, Eva Creek Alaska, Eva Creek Alaska, Eva Creek Alaska, Eva Creek Tumura River Tumura River Tumura River Tumura River Tumura River Tumura River Tumura River

63.92 63.92 63.92 63.92 63.92 63.92 63.92 62.48 62.48 62.48 62.48 62.48 62.48 62.48 62.48 62.48 62.48 62.48 62.48 62.48 64.83 64.83 64.83 64.83 64.83 64.83 63.6 63.6 63.6 63.6 63.6 63.6 63.6

139.3 2 -139.3 2 139.3 2 -139.3 2 139.3 2 -139.3 2 139.3 135.6 2 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 4 135.6 -4 148.0 5 -148.0 5 148.0 5 -148.0 5 148.0 5 148.0 129.9 5 7 129.9 7 129.9 7 129.9 7 129.9 7 129.9 7 129.9 7

5.5 3 8 4d 5d 8d 9d 10d 12d 14d 17d 23d 26d 2.5d Base Base Base 1.2d 1.2d 1.8d 2.6d 2.6d 2.6d 2.6d

wood rhizomes wood twigs twigs twigs/grass squirrel nest twigs from base silt? silt? silt? tree fragment unidentified mammal ribs

wood wood wood wood wood wood wood? roots humic acids humins roots humic acids humins humins Roots

49000 45500 40060 23520 22300 13910 11620 26800 40600 44000 34020 42150 46700 56000 56000 56000 46000 56000 43500 56000 23300 23000 30000 24400 56900 28000 13052 20285 9022 11801 17713 19301 9272

-998 -997 -993 -947 -938 -824 -766 -965 -994 -996 -986 -995 -997 -999 -999 -999 -997 -999 -996 -999 -945 -943 -976 -952 -999 -970 -804 -920 -676 -771 -890 -910 -686

38 38 38 38 38 38 38 39 39 39 39 39 39 39 39 39 39 39 39 39 39 39 39 39 39 39 40 40 40 40 40 40 40

beta-decay age determination beta-decay age determination beta-decay age determination beta-decay age determination

min. age min. age min. age min. age min. age min. age min. age min. age min. age min. age min. age

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RESEARCH SUPPLEMENTARY INFORMATION

doi:10.1038/nature11392

KIA 19140 Erl. 6155 Erl. 6155 Erl. 6156 Erl. 5203 KIA 18805 KIA 18805 Erl. 5203 Erl. 5204 1

Tumura River Tumura River Tumura River Tumura River Tumura River Tumura River Tumura River Tumura River Tumura River

63.6 63.6 63.6 63.6 63.6 63.6 63.6 63.6 63.6

129.9 7 129.9 7 129.9 7 129.9 7 129.9 7 129.9 7 129.9 7 129.9 7 129.9 7

3d 3d 3d 3d 4.4d 5d 5d 8.2d 10.9d

humins roots roots roots wood bone collagen bone collagen wood wood

29756 9275 9240 8945 46000 47110 49690 48000 51000

-975 -686 -685 -673 -997 -997 -998 -997 -998

40 40 40 40 40 40 40 40 40

min. age

min. age min. age

with “d” indicating depth instead of height. error and/or standard deviations can be found in the cited references. 3 the references mostly report 14C ages (in yrs BP), we have converted these ages to Fraction modern (Fm = e-age/8033) and subsequently into 14C (‰; 14C = [Fm x [elambda(1950-Yc) – 1] x 1000, where lambda is 1/(true mean-life of 14C) or 1/8267, and Yc year of collection (assumed 1990). 4 with * indicating Sánchez-García et al., unpublished results. 5 with “conv. 14C” meaning conventional 14C dating (not AMS), “min. age” meaning minimal age. 2

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Table S5 | Fractions of topsoil-PF, ICD-PF and marine OC in surface sediment OC in the East Siberian Arctic Shelf. Calculated with a Monte Carlo simulation strengthened dual-carbon isotopic mixing model. Depth (m)

Station

11 16 14 16 5 16 20 22 6 18 11 19 7 27

YS-4 YS-6 TB-19 TB-24 TB-28 TB-34 TB-38 TB-43 TB-46 TB-51 TB-59 YS-13 YS-14 YS-19

20 16 28 9 20 10 32 36 49 51 45 36 33 200 63 69

YS-22 YS-26 YS-28 YS-30 YS-31 YS-34B YS-36 YS-38 YS-40 YS-93 YS-95 YS-116 YS-120 YS-86 YS-90 YS-102

Fraction of sediment OC (mean) TopsoilPF ICD-PF Marine Laptev Sea 16% 46% 38% 25% 48% 27% 19% 64% 17% 20% 57% 23% 27% 52% 21% 22% 55% 24% 27% 49% 23% 22% 54% 24% 35% 43% 22% 25% 51% 24% 27% 50% 23% 23% 56% 21% 28% 51% 21% 21% 58% 21% East Siberian Sea 19% 73% 7.8% 17% 76% 7.1% 17% 70% 13% 22% 69% 8.5% 22% 64% 14% 32% 55% 13% 24% 56% 20% 23% 48% 29% 13% 46% 41% 14% 43% 43% 15% 54% 31% 12% 71% 16% 13% 63% 24% 4.8% 42% 53% 10% 36% 54% 5.3% 51% 44%

(stdev) TopsoilPF

ICD-PF

Marine

11% 14% 10% 12% 13% 13% 14% 13% 15% 14% 14% 12% 14% 12%

4.7% 5.4% 4.8% 5.1% 5.4% 5.2% 5.5% 5.2% 5.7% 5.4% 5.4% 5.2% 5.4% 5.2%

10% 12% 8.4% 10% 11% 10% 11% 10% 12% 11% 11% 10% 11% 10%

7.9% 7.3% 9.1% 8.7% 10% 12% 12% 14% 10% 11% 11% 8.2% 9.3% 4.2% 7.8% 4.5%

4.2% 4.0% 4.5% 4.4% 4.9% 5.1% 5.3% 5.2% 4.4% 4.5% 4.6% 4.2% 4.3% 3.8% 4.4% 3.5%

6.0% 5.5% 7.3% 6.6% 8.3% 9.3% 10% 11% 8.5% 8.9% 9.0% 7.0% 7.9% 4.7% 7.1% 4.7%

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Table S6 | Summary of coastal and shelf carbon fluxes in the East Siberian Arctic Shelf. All values are in Tg OC, and reported as mean± 95% confidence intervals. Fraction of ICD-PF to OC input onto shelf 50%-50% 25%-75% 75%-25% 1 Burial on shelf 20±8 20±8 20±8 Released onto shelf From coastal erosion 11±4 5.6±2 17±6 From seafloor erosion 11±4 17±6 5.6±2 Total 22±8 22±8 22±8 Degradation Released as CO2 in shelf waters2 2.5±2 2.5±2 2.5±2 Released as CO2 on coastal slopes3 22±8 11±4 32±12 Total 24±8 13±4 35±12 Annual thaw/erosion of Pleistocene carbon From coastal erosion 33±9 16±5 49±14 From seafloor erosion 11±4 17±6 5.6±2 Total 44±10 33±8 55±14 1

Calculated according to: annual OC flux (36±17 gOC/m2/yr; (mean±95% confidence interval)) x

fraction accumulation bottoms (0.6; depth>30m where no resuspension occurs and pelite dominates) x average fraction ICD-OC (57±1.6%; (mean±95% confidence interval)). The total was multiplied by 1.6 to extrapolate to the entire ESAS, i.e. including the Laptev Sea. 2

Annual POC degradation (mean±stdev) in the ESAS41.

3

Assuming 66±16% (mean±stdev) loss of ICD-OC onland as CO2 (i.e. 34±16% is released as OC

onto shelf)

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Table S7 | Elemental, isotopic and molecular composition of the Muostakh Island soil samples. The concentration of terrestrial lipid biomarkers is expressed as mg/g OC. The δ13C and 14C age are measured relative to VPDB and Oxalic Acid I standards, respectively. Slope 2

Slope 5

Slope 7

Slope 6

2-5

2-3

2-2

5-3

5-5

6-3

6-6

7-5

Profile height

13

16

18

1

24

2

23

23

Soil TOC (%)

0.69

1.0

3.5

0.74

1.5

1.1

3.3

2.5

TOC/TN

7.5

9.2

18

7.7

10

9.1

16

13

δ C (‰)

-23.9

-24.2

-28.8

-23.5

-24.3

-24.0

-27.0

-27.2

C age (kyrs)

17

16

5.1

26

15

20

9.4

35

 C-OC (‰)

-885

-860

-474

-959

-854

-917

-691

-988

0.86

0.77

3.3

0.69

0.91

0.64

2.7

14

7.0

6.7

3.9

3.2

3.0

11

7.1

4.0

0.71

0.70

0.12

0.51

0.39

0.27

0.025

0.51

1.6

3.0

23

0.76

2.8

11

7.0

6.3

4.1

6.7

5.9

4.0

4.7

7.2

4.4

3.0

1.8

3.9

7.2

1.1

3.0

18

2.6

0.45

1.1

3.2

31

0.31

0.31

1.4

6.6

11

14

15

6.6

9.3

6.3

18

27.

62

0

2.2

2.0

0

0

1.4

2.8

4.1

Bulk properties

13

14

14

n-alkanes HMW n-alkanesa b

CPI 21-31

even≤C20/odd≥C27

c

n-alkanoic acids HMWn-alkanoic acidsa b

CPI 20-30 HMWn-alkanoic acids/HMWn-alkanes alkalkanes n-alkanols

HMWn-alkanolsa b

CPI 20-30

β-sitosterol /HMWn-alkanes f

a

HMW is high-molecular weight, sum of C20-C34 for n-alkanes, sum of C20-C30 for n-alkanoic

acids and sum of C20-C30 for n-alkanols. b

Calculated CPIi-n, carbon preference index, = ½ Σ(Xi+Xi+2+...+Xn)/ Σ (Xi-1+Xi+1+...+Xn-1) + ½

Σ(Xi+Xi+2+...+Xn)/ Σ(Xi+1+Xi+3+...+Xn+1), where X is concentration. c

Even and low-molecular weight n-alkanes (C16-C20) to odd and high-molecular weight n-alkanes

(C27-C31). f

24-Ethylcholest-5-en-3β-ol.

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Table S8 | CO2 fluxes on Muostakh Island. CO2 fluxes (mmol/m2/day) recorded along five slope transects (n=28) on Muostakh Island.

CO2 transects

n

Transect 1

3 3 3 3 3 3 3 3 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 1 3 3 3 3 3 3 3 3 3 3

Transect 2

Transect 3

Transect 4 Transect 5

Lat (°N) 71.6125 71.6126 71.6129 71.6130 71.6130 71.6124 71.6125 71.6126 71.6093 71.6094 71.6096 71.6096 71.6096 71.6099 71.6104 71.6106 71.6108 71.6108 71.6104 71.6106 71.6108 71.6108 71.6106 71.6108 71.6108 71.6101 71.6101 71.6029 71.6029 71.6028 71.6027 71.6027 71.6025 71.6019 71.6014 71.6013 71.6014

Long (°E) 129.9376 129.9378 129.9379 129.9379 129.9382 129.9442 129.9442 129.9442 129.9466 129.9469 129.9470 129.9473 129.9473 129.9509 129.9525 129.9533 129.9533 129.9533 129.9525 129.9533 129.9533 129.9533 129.9533 129.9533 129.9533 129.9569 129.9568 129.9799 129.9797 129.9796 129.9794 129.9792 129.9792 129.9753 129.9658 129.9653 129.9650

CO2 flux (mmol/m2/day) mean stdev 17 36 3.2 0.5 12 2.0 4.0 2.6 14 5.3 6.0 3.5 4.9 1.0 10 3.8 13 62 12 4.3 8.2 0.6 15 11 23 12 18 0.6 12 1.2 28 8.6 26 14 5.2 0 6.3 2.5 18 3.6 13 1.8 17 2.2 27 3.0 4.0 1.3 440 25 24 13 48 0 110 30 8.9 4.4 17 9.7 96 18 9.2 4.9 15 6.7 27 8.7 21 10 220 71 17 2.2

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Table S9 | Individual data for bulk geochemical data for surface sediments in the East Siberian Arctic Shelf. For sediment OC and TOC/TN, outliers have been excluded (3 and 8 values respectively). Outliers (marked with *) are defined as observations farther than 1.5 x interquartile range from the closest quartile. Year 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2004 2004 2004 2004 2004

Station 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 43 25 27 29 30 31

δ13C

Lat

Long

Depth

Sed.OC

TOC/TN

(°N)

(°E)

m

mg/gdw

stdev

‰

stdev

73.04 73.61 74.27 74.84 73.86 73.57 72.92 72.00 71.63 71.24 71.62 71.99 71.66 71.43 71.00 70.43 70.00 70.33 70.72 70.43 70.15 70.01 69.92 70.24 70.48 70.67 70.48 70.85 70.63 71.12 72.49 72.59 72.97 73.02 73.14 73.85 74.76 74.49 74.33

146.82 146.83 146.83 146.84 148.92 151.00 151.00 150.99 152.49 153.99 154.99 155.99 157.34 158.90 159.89 161.20 161.20 162.49 163.99 166.99 172.15 176.31 176.07 177.16 178.00 178.47 171.99 167.99 164.99 161.99 154.00 151.00 148.34 143.14 134.64 137.16 140.00 140.23 140.38

11 12 16.4 11 16 16 15 9 14 14 15 17.5 12 14 10 10 11 9 11.2 25 31 38 11.8 50 50 42 35 41.6 18 20 29 15.5 10 12 18 22 9 27 10

13.0 8.2 6.1 5.1 6.0 13.0 6.7 17.9 20.4 18.9 11.3 11.2 12.7 10.6 13.0 6.9 12.4 11.1 3.9 10.1 14.5 15.3 11.0 17.2 14.9 11.2 9.3 16.0 8.7 8.7 13.6 10.2 14.8 8.9 5.5 16.2 7.0 20.8 10.0

-

-25.1 -24.6 -24.4 -23.8 -24.0 -24.5 -25.2 -25.6 -25.7 -25.6 -25.5 -25.2 -26.0 -25.3 -25.6 -25.3 -25.4 -25.0 -24.2 -24.6 -24.0 -23.0 -24.3 -22.4 -21.9 -22.4 -23.8 -24.2 -24.9 -24.9 -25.2 -25.1 -25.6 -24.6 -25.8 -26.0 -25.8 -26.4 -27.1

-

15.1 14.4 13.1 16.3 14.8 21.4* 13.1 16.1 13.9 12.1 11.6 12.0 12.7 11.7 11.6 10.9 11.7 11.1 10.6 10.2 10.2 9.21 10.8 10.5 9.36 9.90 8.57 9.46 11.9 10.1 12.9 12.0 14.0 13.5 11.0 10.1 10.0 11.0 12.5

Δ14C ‰

error

-

-

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2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004

36 37 38 39 40 42 43 44 46 47 49 51 53 55 56 58 60 62 64 65 66 67 68 69 72 74 75 78 79 80 81 82 83 84 85 86 87 88 89 91 95 96 97 99 100 101 102 103 104

74.80 74.16 73.52 72.86 72.80 72.45 72.10 71.75 71.03 71.70 72.37 73.00 72.30 71.50 71.59 72.02 72.50 71.70 71.02 70.73 70.45 70.17 69.83 69.73 70.00 70.09 70.18 69.63 69.38 69.13 68.99 68.86 69.02 69.18 69.18 69.35 69.52 69.55 69.88 70.21 69.96 70.10 70.27 70.42 70.58 70.74 70.51 70.50 70.50

146.50 146.67 146.84 147.00 148.50 150.00 150.76 151.51 153.00 153.00 153.00 153.00 156.26 156.26 157.84 159.42 161.50 161.16 161.07 161.14 161.20 161.27 161.35 162.37 165.14 167.53 168.49 169.55 169.42 169.29 169.65 170.02 170.30 170.58 169.88 170.16 170.43 169.92 169.77 170.39 176.11 176.63 177.20 177.78 178.29 178.66 177.57 176.10 174.63

14 15 12 9 11 9 7 10 9 15 19 21 19 12.5 15 21 23 20 12 9 9.4 9 9 12 24 35 39 15 14 10 12 10.4 13 11 15 15.4 11 15.8 16 31 22 46 50 47.8 47.2 30 44 45 41.6

11.0 10.2 6.4 15.0 13.0 8.5 9.0 19.0 12.8 19.0 6.0 7.0 10.7 12.0 4.8 16.0 9.5 7.3 12.1 5.7 9.0 37.3* 18.0 16.4 13.0 8.6 13.9 11.4 4.8 1.8 6.4 1.3 9.9 18.0 13.1 23.4 17.0 25.3 10.0 20.1 20.5 12.6 18.6 21.9 17.4 13.8 19.7 18.7 12.6

-

-25.2 -26.0 -26.3 -27.3 -27.0 -27.1 -27.0 -27.4 -26.8 -26.9 -26.0 -25.6 -26.3 -26.6 -26.1 -28.3 -25.9 -25.9 -26.1 -26.0 -26.3 -25.6 -27.0 -27.3 -26.0 -25.2 -26.0 -25.3 -24.4 -24.4 -26.9 -25.0 -26.7 -26.9 -26.1 -26.4 -27.0 -26.5 -25.8 -25.8 -24.2 -23.6 -23.1 -22.9 -22.8 -24.2 -22.9 -23.4 -23.9

-

12.2 20.4* 10.7 13.6 11.8 12.1 12.9 12.7 11.6 11.2 10.0 10.0 10.7 10.0 9.60 13.3 8.64 8.11 9.31 9.50 1.00* 124* 1.00* 14.9 9.29 8.60 10.7 10.4 8.00 9.00 12.8 13.0 12.4 12.9 10.1 10.2 12.1 9.73 10.0 9.14 0.86* 0.88* 7.75 7.55 7.57 7.67 6.35 6.45 7.88

-

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-

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2004 2004 2004 2004 2004 2004 2004 2004 2004 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008

105 106 107 108 110 111 112 113 114 TB-01 TB-02 TB-03 TB-04 TB-05 TB-06 TB-07 TB-08 TB-09 TB-10 TB-11 TB-12 TB-13 TB-14 TB-15 TB-16 TB-17 TB-18 TB-19 TB-20 4 6 13 14 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 35

70.48 70.48 70.48 70.46 70.83 73.43 74.14 74.56 75.00 74.84 74.83 74.84 74.59 74.59 74.59 74.33 74.33 74.34 74.08 74.08 74.08 73.83 73.83 73.83 73.58 73.58 73.58 73.33 73.32 75.99 74.72 71.97 71.63 73.11 73.31 73.09 72.88 72.79 73.05 73.14 72.46 72.57 72.65 72.20 71.36 71.59 70.57 70.17 69.82

173.13 171.60 170.12 168.62 162.88 155.08 153.31 153.43 153.53 129.04 130.01 131.00 130.99 130.02 129.03 128.99 130.03 131.00 130.99 130.01 129.00 129.00 130.00 131.00 130.99 130.00 129.00 130.14 131.00 129.98 130.02 131.70 130.05 137.30 139.89 140.35 140.63 142.67 142.67 142.67 150.60 152.37 154.19 153.17 152.15 161.69 161.22 161.22 164.06

37.2 30.8 26 28 17.6 34.2 18.4 14.4 16 41 37 28 27 32 26 19 22 26 24 15.5 16 16 19 20 20 14 21 25 25 50 32 19 7 27 8 15 20 10 15 10 16 18 28 18 9 20 9 8 31

14.6 16.3 16.1 19.6 4.9 10.3 8.2 9.4 6.6 13.1 16.8 14.8 6.1 15.2 11.3 0.5 1.0 3.9 2.1 1.7 0.5 0.3 3.0 1.9 16.5 0.9 19.2 13.6 18.5 13.4 18.6 18.9 19.1 18.2 3.9 8.1 11.8 9.1 7.7 10.2 8.7 4.1 8.7 6.3 13.5 5.6 4.2 4.0 12.2

0.3 0.2 0.4 0.3 0.1 0.5 0.1 0.1 0.2 1.3 0.3 0.1 0.2 0.2 0.1 0.3 0.2 0.4 0.3 0.1 0.1 0.2 0.3 1.5 0.3 0.3 0.2 0.1 0.1 0.3 0.2 0.1 0.2 0.5 3.4

-24.3 -24.9 -25.4 -25.4 -25.5 -25.1 -25.1 -25.0 -25.2 -25.4 -25.7 -25.7 -25.6 -25.7 -25.6 -26.1 -24.9 -25.7 -26 -25.9 -25.1 -25.1 -25.7 -25.5 -25.4 -25.7 -26.2 -25.9 -25.8 -24.3 -25.6 -25.9 -26.2 -25.8 -26.9 -27.0 -27.4 -27.2 -27.4 -27.3 -27.4 -26.2 -26.2 -26.6 -27.4 -26.5 -26.4 -26.2 -26.8

0.1 0.1 0.2 0.1 0.1 0.1 1.3 0.5 0.1 0.8 0.7 0.3 1.1 0.2 0.4 0.1 0.7 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.5

7.68 7.41 7.67 7.26 8.17 7.92 8.20 9.40 9.43 8.73 8.40 9.87 15.3 10.9 10.3 5.00 10.0 13.0 10.5 8.50 5.00 3.00 15.0 9.50 9.17 9.00 12.0 11.3 9.74 8.03 9.46 10.7 13.9 10.0 6.93 8.20 9.28 8.86 9.02 8.91 8.42 6.88 6.94 7.83 8.85 6.60 6.60 6.48 8.93

-437 -465 -543 -504 -557 -716 -741 -672 -682 -624 -

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2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008

36 37 38 39 40 41 86 88 90 91 93 95 97 98 99 100 102 104 106 111 112 116 118 120 131 22B 34B TB-17 TB-18 TB-19 TB-22 TB-23 TB-24 TB-25 TB-26 TB-27 TB-28 TB-30 TB-31 TB-32 TB-33 TB-34 TB-35 TB-36 TB-37 TB-38 TB-39 TB-40 TB-43

69.82 70.13 70.70 71.22 71.48 71.97 75.30 75.10 74.67 74.43 74.42 74.42 75.27 75.55 75.17 75.72 76.56 76.93 76.97 75.00 74.83 74.58 74.33 73.29 76.40 72.89 69.71 72.29 72.17 72.09 71.88 71.83 71.76 71.72 71.69 71.66 71.62 71.87 71.86 71.86 72.09 72.29 72.46 72.59 72.71 72.93 72.93 72.93 72.89

166.00 168.01 169.13 169.37 170.55 171.79 174.40 172.19 172.39 170.85 166.00 161.34 160.89 160.75 163.59 164.08 160.07 155.17 150.29 160.01 159.33 157.00 156.01 155.17 125.47 140.62 162.69 132.92 133.00 132.78 132.11 131.67 131.17 130.83 130.58 130.33 130.04 129.83 130.32 131.09 131.09 131.09 131.09 131.10 131.09 130.84 130.66 130.03 131.93

32 42 36 44 49 43 200 142 63 56 51 45 49 48 50 58 69 57 43 46 42 36 28 33 50 15 10 21 16 14 15 20 16 13 12.5 10.6 5.3 5 12 12 14.5 16 16.5 17 18.5 20 20 6 21.8

8.0 9.4 10.0 12.3 13.6 13.2 8.9 10.4 8.5 8.2 8.0 9.7 8.5 7.7 7.7 7.6 7.7 9.1 8.7 8.0 8.8 6.0 7.1 9.9 4.0 10.7 11.2 15.1 8.0 4.7 3.2 15.9 18.7 18.8 20.9 18.6 21.5 20.4 22.5 18.4 21.9 18.5 22.2 21.2 23.9 23.5 23.0 15.0 15.6

0.1 0.4 0.1 0.1 0.3 0.3 0.2 0.1 0.1 0.2 0.1 0.4 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 1.1 0.3 0.08 0.04 0.02 0.01 0.02 0.02 0.01 -

-26.0 -25.7 -25.3 -24.3 -23.9 -23.9 -21.2 -21.5 -22.4 -23.3 -23.8 -24.8 -24.1 -23.9 -23.4 -22.4 -22.3 -23.1 -23.8 -24.2 -24.6 -25.5 -25.2 -25.0 -24.3 -27.4 -27.3 -25.6 -25.7 -26.0 -25.2 -25.8 -25.6 -25.8 -25.8 -25.9 -26.2 -26.0 -25.9 -25.6 -25.8 -25.7 -25.9 -25.9 -26.0 -26.0 -25.9 -26.0 -25.6

0.1 0.1 0.2 0.2 0.1 0.2 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.2 0.1 0.2 0.1 0.2 0.2 0.1 0.2 0.23 0.28 0.08 0.02 0.13 0.05 0.07 -

6.80 6.67 6.47 6.12 6.17 6.08 5.24 5.48 5.62 5.64 5.45 5.72 5.53 5.43 5.45 5.76 5.51 5.85 6.06 5.94 6.17 6.63 6.79 6.70 6.62 9.51 9.96 9.94 10.5 11.2 9.44 10.0 10.3 10.6 12.2 13.1 14.6 14.9 12.1 10.5 11.0 11.8 11.9 12.1 12.4 12.3 13.3 13.1 10.3

-547 -462 -425 -391 -332 -398 -511 -476 -682 -600 -554 -622 -549 -513 -526 -482 -517

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2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008

TB-44 TB-45 TB-46 TB-48 TB-49 TB-50 TB-51 TB-52 TB-53 TB-54 TB-55 TB-56 TB-57 TB-59

72.71 72.70 72.70 72.59 72.59 72.59 72.46 72.45 72.28 72.28 72.29 72.10 72.00 72.09

131.66 130.66 130.18 130.12 130.68 131.66 131.66 130.67 130.07 130.59 131.72 131.72 131.77 130.06

18.8 15 6 6.5 14 18 18 12.5 8.5 10 17 15 10 11

20.9 22.4 25.8 38.1* 20.2 18.2 21.4 13.4 95.1* 8.8 19.7 18.0 18.3 18.7

1.42 -

-25.9 -25.9 -26.5 -26.6 -25.8 -25.7 -25.8 -25.8 -27.5 -25.7 -25.8 -25.7 -25.7 -26.0

0.09 -

11.4 12.4 14.3 16.2* 12.5 11.4 11.3 11.6 23.2* 11.7 11.1 10.4 10.5 12.7

-436 -495 -493

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Table S10 | Raw radiochronological data for East Siberian Arctic Shelf sediment cores. slice interval cm

210

226

Pb

210

Ra

Bq/gdw

stdev

Bq/gdw

stdev

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15

0.051 0.056 0.054 0.060 0.074 0.052 0.051 0.066 0.065 0.054 0.054 0.054 0.068 0.072 0.078

0.003 0.004 0.004 0.003 0.005 0.005 0.003 0.004 0.003 0.004 0.004 0.003 0.004 0.004 0.004

0.022 0.030 0.025 0.021 0.022 0.026 0.023 0.028 0.027 0.025 0.002 0.026 0.012 0.023 0.028

0.002 0.002 0.002 0.002 0.003 0.003 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14

0.071 0.062 0.039 0.063 0.058 0.067 0.054 0.039 0.053 0.062 0.046 0.043 0.053 0.053

0.005 0.004 0.003 0.005 0.004 0.005 0.003 0.003 0.004 0.003 0.003 0.003 0.003 0.003

0.035 0.036 0.037 0.015 0.018 0.036 0.021 0.018 0.023 0.023 0.026 0.033 0.046 0.041

0.003 0.003 0.002 0.003 0.003 0.003 0.002 0.002 0.003 0.002 0.002 0.002 0.002 0.002

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11

0.052 0.033 0.035 0.037 0.028 0.027 0.028 0.032 0.030 0.032 0.030

0.004 0.004 0.002 0.003 0.004 0.004 0.002 0.004 0.004 0.004 0.002

0.023 0.020 0.022 0.026 0.027 0.024 0.027 0.027 0.036 0.036 0.035

0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001

Pbxs

porosity

Bq/gdw stdev YS-22 0.029 0.004 0.026 0.004 0.029 0.005 0.039 0.003 0.052 0.005 0.026 0.005 0.028 0.003 0.038 0.004 0.039 0.004 0.029 0.004 0.052 0.004 0.029 0.004 0.057 0.004 0.049 0.005 0.049 0.004 YS-26 0.036 0.006 0.026 0.005 0.003 0.003 0.048 0.003 0.040 0.005 0.030 0.006 0.033 0.004 0.021 0.004 0.030 0.005 0.039 0.003 0.020 0.004 0.011 0.004 0.008 0.004 0.012 0.003 YS-35 0.030 0.013 0.012 0.011 0.001 0.003 0.001 0.004 0 0 0

0.004 0.004 0.002 0.004 0.004 0.005 0.002 0.004 0.004 0.005 0.002

210

Dry density

Pbxs

g/cm3

stdev

Bq/m2

stdev

0.39 0.36 0.34 0.32 0.34 0.36 0.35 0.34 0.37 0.34 0.33 0.28 0.29 0.37 0.42

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

484 451 520 721 931 453 485 680 654 515 929 553 1090 832 776

87 97 110 110 160 110 85 120 110 110 150 100 170 140 120

0.56 0.45 0.33 0.38 0.43 0.45 0.40 0.31 0.36 0.37 0.34 0.33 0.34 0.32

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

432 386 46.6 804 614 453 531 399 518 653 350 191 137 217

90 86 62 140 120 110 93 92 110 100 83 75 77 65

0.44 0.36 0.35 0.35 0.34 0.29 0.29 0.32 0.35 0.32 0.26

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

443 218 214 189 23.7 61.7 12.3 81.4 0 0 0

88 80 49 69 79 91 37 75 0 0 0

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YS-36 0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14

0.044 0.054 0.044 0.039 0.041 0.036 0.041 0.034 0.030 0.022 0.030 0.027 0.026 0.024

0.004 0.004 0.004 0.003 0.004 0.004 0.003 0.003 0.004 0.003 0.002 0.004 0.002 0.004

0.028 0.026 0.023 0.026 0.032 0.031 0.033 0.032 0.026 0.027 0.028 0.029 0.027 0.027

0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001

0.016 0.004 0.028 0.004 0.021 0.004 0.013 0.003 0.010 0.004 0.006 0.004 0.009 0.003 0.002 0.003 0.004 0.004 0 0.003 0.001 0.002 0 0.004 0 0.002 0 0.004 YS-37

0.54 0.47 0.43 0.41 0.39 0.36 0.34 0.33 0.32 0.32 0.31 0.31 0.31 0.29

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

200 403 317 208 158 98.9 153 35.7 70.0 0 0 0 0 0

57 79 79 63 69 74 53 58 68 0 0 0 0 0

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15

0.060 0.064 0.063 0.056 0.049 0.053 0.045 0.037 0.040 0.036 0.037 0.027 0.036 0.033 0.028

0.004 0.003 0.003 0.005 0.005 0.004 0.002 0.004 0.004 0.002 0.003 0.005 0.005 0.003 0.004

0.027 0.023 0.023 0.031 0.024 0.020 0.024 0.027 0.024 0.025 0.027 0.024 0.022 0.026 0.028

0.002 0.001 0.001 0.002 0.001 0.001 0.001 0.002 0.001 0.001 0.001 0.001 0.002 0.001 0.002

0.033 0.005 0.041 0.003 0.040 0.004 0.025 0.005 0.026 0.005 0.032 0.005 0.021 0.003 0.011 0.004 0.016 0.004 0.011 0.002 0.010 0.003 0.003 0.005 0.014 0.005 0.007 0.003 0.001 0.004 YS-90

0.62 0.57 0.54 0.53 0.51 0.46 0.43 0.43 0.39 0.36 0.36 0.35 0.36 0.36 0.37

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

336 479 491 312 339 478 331 162 261 189 179 44.3 239 116 10.6

64 73 78 74 80 93 60 72 77 48 62 82 93 50 68

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16

0.074 0.053 0.052 0.048 0.039 0.035 0.040 0.032 0.028 0.020 0.024 0.024 0.021 0.019 0.020 0.021

0.01 0.01 0.01 0.01 0.01 0.004 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.004 0.01

0.027 0.029 0.031 0.030 0.027 0.024 0.025 0.025 0.023 0.025 0.024 0.023 0.024 0.022 0.022 0.022

0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001

0.048 0.024 0.021 0.018 0.012 0.011 0.015 0.007 0.006 0 0.000 0.001 0 0 0 0

0.76 0.66 0.61 0.58 0.55 0.53 0.50 0.44 0.39 0.37 0.36 0.37 0.34 0.35 0.34 0.35

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

315 222 225 206 141 135 204 108 92.7 0 0 0 0 0 0 0

82 77 90 96 91 58 100 100 110 0 0 0 0 0 0 0

0.011 0.008 0.008 0.008 0.007 0.004 0.007 0.007 0.006 0.007 0.006 0.007 0.006 0.007 0.004 0.006

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16-17

0.025

0.01

0.023

0.001

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14

0.109 0.113 0.101 0.092 0.076 0.082 0.055 0.061 0.065 0.061 0.053 0.046 0.057 0.057

0.004 0.005 0.003 0.004 0.006 0.005 0.003 0.005 0.003 0.005 0.005 0.004 0.004 0.003

0.070 0.056 0.056 0.049 0.038 0.048 0.055 0.039 0.045 0.035 0.037 0.039 0.050 0.043

0.003 0.003 0.002 0.003 0.004 0.003 0.002 0.004 0.002 0.004 0.003 0.002 0.003 0.002

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12

0.046 0.086 0.083 0.073 0.061 0.080 0.037 0.043 0.043 0.032 0.039 0.032

0.02 0.01 0.00 0.01 0.01 0.01 0.01 0.00 0.01 0.01 0.00 0.01

0.024 0.039 0.046 0.040 0.038 0.039 0.033 0.032 0.028 0.030 0.032 0.032

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11

0.117 0.133 0.120 0.109 0.112 0.121 0.121 0.124 0.127 0.126 0.102

0.007 0.005 0.005 0.003 0.007 0.008 0.008 0.005 0.007 0.007 0.008

0.194 0.061 0.068 0.096 0.071 0.053

0.014 0.011 0.013 0.006 0.013 0.015

0-1 2-3 4-5 5-6 6-7 9-10

0.001 0.007 YS-93 0.038 0.005 0.057 0.006 0.045 0.004 0.043 0.005 0.038 0.007 0.034 0.006 0 0.004 0.022 0.006 0.020 0.004 0.026 0.007 0.016 0.006 0.007 0.004 0.008 0.005 0.014 0.004 YS-98

0.36

2.7

0.36

0

0

0.71 0.63 0.59 0.58 0.53 0.49 0.46 0.46 0.45 0.44 0.43 0.42 0.41 0.42

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

297 574 502 486 479 468 2.66 316 295 393 252 104 125 218

55 96 78 83 110 100 55 100 74 120 92 68 74 63

0.006 0.002 0.002 0.002 0.003 0.002 0.002 0.001 0.002 0.002 0.001 0.003

0.022 0.016 0.046 0.008 0.037 0.005 0.034 0.007 0.024 0.007 0.041 0.007 0.004 0.007 0.011 0.004 0.015 0.007 0.003 0.008 0.007 0.004 0.000 0.007 YS-120

0.92 0.67 0.58 0.54 0.52 0.47 0.44 0.43 0.41 0.42 0.41 0.40

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

44.6 408 415 423 307 588 55.2 169 235 41.2 114 0

34 87 77 110 100 130 110 72 120 120 72 110

0.040 0.044 0.043 0.051 0.054 0.051 0.049 0.054 0.060 0.060 0.057

0.003 0.001 0.001 0.001 0.002 0.003 0.002 0.002 0.003 0.002 0.002

0.076 0.007 0.089 0.005 0.076 0.005 0.058 0.003 0.059 0.008 0.070 0.008 0.072 0.008 0.069 0.005 0.067 0.008 0.067 0.008 0.044 0.008 IK-1051

0.71 0.64 0.61 0.60 0.59 0.60 0.60 0.59 0.58 0.55 0.51

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

608 860 807 632 645 764 783 761 766 811 583

99 130 120 91 120 130 140 120 140 140 130

0.060 0.035 0.041 0.005 0.025 0.034

0.010 0.007 0.012 0.004 0.008 0.009

0.134 0.026 0.027 0.091 0.046 0.019

0.7 0.6 0.6 0.6 0.6 0.6

2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36

1090 285 289 981 496 202

200 140 200 150 170 190

0.017 0.013 0.018 0.007 0.015 0.017

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1

14-15 16-17 24-25

0.060 0.038 0.067

0.007 0.011 0.008

0.006 0.053 0.020

0.005 0.008 0.006

0.054 0.009 0 0.013 0.047 0.009 IK-110

0.6 0.6 0.6

2.7 2.7 2.7

0.36 0.36 0.36

588 0 504

120 0 120

0-1 1-2 2-3 3-4 4-5 6-7 7-8 12-13

0.013 0.010 0.027 0.017 0.038 0.023 0.000 0.002

0.005 0.004 0.004 0.003 0.006 0.004 0.004 0.004

0.003 0.017 0.033 0.035 0.009 0.011 0.013 0.022

0.004 0.004 0.004 0.002 0.005 0.004 0.004 0.004

0.010 0.006 0 0.006 0 0.006 0 0.004 0.029 0.008 0.012 0.005 0 0.005 0 0.006 IK-114

0.7 0.6 0.6 0.6 0.6 0.6 0.6 0.6

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

80.8 0 0 0 312 128 0 0

49 0 0 0 97 60 0 0

0-5 9-15 10-15 15-22 20-25 27-30 30-35 35-40

0.028 0.031 0.031 0.032 0.027 0.030 0.031 0.032

0.003 0.003 0.003 0.002 0.001 0.002 0.002 0.002

0.019 0.018 0.022 0.018 0.024 0.019 0.025 0.016

0.003 0.003 0.004 0.002 0.001 0.001 0.001 0.001

0.009 0.004 0.013 0.004 0.009 0.005 0.015 0.003 0.002 0.002 0.011 0.002 0.006 0.002 0.016 0.003 IK-118

0.7 0.6 0.6 0.6 0.6 0.6 0.6 0.6

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

72.8 140 100 157 23.2 114 67.2 170

31 47 53 36 21 28 25 36

0-5.5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-58

0.125 0.131 0.052 0.044 0.066 0.070 0.099 0.061 0.074 0.073 0.113 0.069

0.009 0.010 0.007 0.007 0.008 0.012 0.012 0.004 0.009 0.005 0.005 0.008

0.067 0.030 0.062 0.000 0.013 0.046 0.047 0.000 0.020 0.028 0.051 0.025

0.009 0.008 0.007 0.000 0.009 0.013 0.011 0.000 0.009 0.005 0.006 0.006

0.058 0.101 0 0.044 0.054 0.023 0.052 0.061 0.055 0.045 0.063 0.044

0.7 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7

0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

473 1090 0 480 578 250 558 662 589 488 679 476

120 200 0 98 160 190 190 99 160 100 120 130

0.013 0.013 0.010 0.007 0.012 0.018 0.017 0.004 0.012 0.007 0.008 0.010

Only 9cm of the 25cm core has been counted, so a correction factor of 2.8 has been used when

calculating the total 210Pbxs (Bq/m2/yr).

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