Supplementary Information

Transcription

1 GSA Data Repository Solar forcing of Holocene summer sea-surface temperatures in the northern North Atlantic 8 Hui Jiang, Raimund Muscheler, Svante Björck, Marit-Solveig Seidenkrantz, Jesper Olsen, Longbin Sha, Jesper Sjolte, Jón Eiríksson, Lihua Ran, Karen-Luise Knudsen, and Mads F. Knudsen Supplementary Information

2 Supplementary Table DR1. Summer SST data from core MD99- on the North Icelandic Shelf Core depth (cm) Age (cal yr B.P.) Summer SSTs ( C)

3

4

5

6

7

8

9

10 Supplementary Table DR. Positions and the modern summer SSTs of the surface samples from around Iceland used for diatom-based summer SST reconstruction*. Sample name No. Water depth (m) Latitude Longitude Summer SST ( C) BS1191-K o 0.9 N o.00 W -0. BS1191-K1-1A o 11.9 N 9 o. W -0. JM9-11/GC o. N 0 o 8.00 W 8.1 JM9-119/1 x o 9.01 N 0 o.01 W 8. JM9-19/1GC o 01.0 N o W. JM9-1/1GC + 1 o.1 N o 8.80 W.0 BIOICE o 09.9 N 1 o.0 W 8.0 BIOICE08 08 o 1.1 N 1 o.91 W. BIOICE10 10 o.0 N 18 o.1 W. BIOICE o 1.18 N 18 o 8.8 W. BIOICE o 18.0 N o.90 W 9. BIOICE0 0 8 o 0.88 N o 9. W 9.9 BIOICE o 8.90 N o.0 W 9.9 BIOICE1 1 9 o 11.0 N o 1.10 W 9. BIOICE1 1 1 o.10 N o.0 W 10. BIOICE o.90 N o 9.90 W 9. BIOICE o 1.00 N o 1.00 W 9.9 BIOICE o 1.9 N o.80 W 9.8 BIOICE o 1.0 N o 9.80 W 9. BIOICE 800 o.0 N 0 o 0.9 W. BIOICE o 0.0 N 0 o 1.0 W 0. BIOICE 101 o.00 N 19 o 1.00 W.1 BIOICE o 0.00 N 1 o 0.00 W.1 BIOICE o. N 1 o.89 W.9 BIOICE 1 8 o.0 N 1 o 0.10 W. BIOICE9 9 8 o 1.0 N 19 o 0.0 W.0 BIOICE9 9 9 o.18 N 1 o. W.0 BIOICE98 98 o. N 1 o 1. W.1 BIOICE o.1 N 1 o.1 W 9. BIOICE o N 1 o. W 10. BIOICE o 0. N 1 o.8 W 11.1 BIOICE o N 18 o 0. W 11.8 BIOICE8 8 o.0 N o. W 10. BIOICE89 89 o.0 N o 1.90 W

11 BIOICE89 89 o 9.0 N o 1.9 W 9.8 BIOICE o. N 9 o 11.9 W 8. BIOICE o 0. N o 1.0 W. BIOICE o.18 N o 1.99 W 9. BIOICE90 90 o 1.8 N o 0.9 W 9.9 BIOICE9 9 1 o 08.1 N o.00 W 9. BIOICE o 0.9 N o 1.99 W 10. BIOICE9 9 1 o 0.10 N o.10 W 9.9 BIOICE o 1.9 N o 09.9 W. BIOICE1 1 8 o 1.89 N o.1 W 1. BIOICE10 10 o 9.91 N o. W.1 BIOICE1 1 o 0.1 N 8 o.19 W.8 K o.0 N 1 o 0.80 W.8 8K o.10 N 18 o.90 W 0. 9K o.0 N 0 o 11.0 W K o.80 N 19 o 0.80 W 0. 1K o 1.0 N 18 o 1.0 W 1.0 *Samples marked with + were provided by Anne Jennings, University of Colorado at Boulder, USA, samples marked with x are from Morten Hald, University of Tromsø, Norway, and samples marked with ++ are from Nalan Koç, Norwegian Polar Institute, Tromsø, Norway. All other samples were collected by the BIOICE project during the period of

12 Supplementary Table DR*. Test of numerical reconstruction methods. Six numerical reconstruction methods were tested, including weighted averaging (WA), weighted averaging with tolerance down-weighting (WA (tol) ), weighted averaging partial least squares (WA-PLS) and Modern analogue technique (MAT). Both inverse and classical deshrinking regression were used in the WA and WA (tol) reconstruction procedures. The results are presented as root-mean squared error of prediction based on the leave-one out jack-knifing (RMSEP (Jack) ) test, maximum bias (Max_Bias (Jack) ), and coefficient of determination between observed and predicted values r (Jack). WA-PLS using components results in low RMSEP (Jack) (0.9) and Max_Bias (Jack) (1.9), a high r (jack) (0.9) and a smaller number of useful components for reconstructing summer SSTs based on the modern data set of diatom and measured environmental variables from around Iceland and neighboring areas. Max_Bias (Jack) R (Jack) RMSEP (Jack) WA Inverse WA (tol) Inverse WA Classical WA (tol) Classical WA-PLS 1 component WA-PLS components WA-PLS components WA-PLS components WA-PLS components MAT 1 analogues MAT analogues MAT analogues MAT analogues MAT analogues * Telford and Birks (009) used the MAT and the WA-PLS methods to test the significance of transfer functions (diatom ph transfer function, benthic foraminifera salinity transfer function, planktonic foraminifera SST transfer function, dinoflagellate salinity transfer function, and pollen temperature and sunshine transfer functions) in autocorrelated environments. They found that in all cases except the diatom-ph training set, MAT outperforms WA-PLS. In our case, however, the MAT gave relatively high RMSEP (Jack) (1.) and Max_Bias (Jack) (1.8), and low 1

13 r (jack) (0.88). A reliable transfer function should have not only a low root mean squared error of prediction based on leave-one out jackknifing RMSEP(Jack), a low maximum bias, a high coefficient of determination between observed and predicted value (r), but also a small number of useful components (Birks 199, 1998). Hence, as the difference between the RMSEP(Jack) of the WA-PLS with components (0.9) and that of WA-PLS with components (0.89) is quite small, we used WA-PLS with components for our transfer function. 1

14 Supplementary Table DR. Information of 1 tephra layers and AMS 1 C dates from MD99-. The age of the core top is estimated to cal yr B.P. (AD 189) based on a comparison of overlapping proxy data between core MD99- and a multicore B0-00-MC0 retrieved at the same location and dated using 10 Pb and 1Cs via gamma spectrometry (cf. Knudsen et al., 009). The ages of the tephra markers are based on historical records from Iceland for the last 900 yr, correlation to the Greenland ice core chronology and age calculations based on soil accumulation rate (SAR) between dated tephra layers (Rasmussen et al., 00; Eiríksson et al., 011; Gudmundsdóttir et al., 011). The age model is constrained on the basis of the first appearance depth of each tephra marker and of the historical age or terrestrial radiocarbon date of the marker. MD99- AMS 1C dates and tephra markers Calibrations: Oxcal v.0 using Marine09 calibration curve Core depth Lab. no. Material dated 1 C age Cal 1 C yr B.P. Cal range (cm) (BP ±1 σ) (mean of range) (±1 σ) 0. Core Top. AAR-818 Thyasira equalis ± AAR-9808 Bathyarca glacialis 91± AAR-9809 Thyasira equalis ± AAR-0 Siphodentalium lobatum ± V 19, AD AAR-11 Thyasira equalis 9± AAR-11 Thyasira cf. equalis 8± V 11, AD AAR-089 Siphonodentalium lobatum 89± AAR-118 Thyasira cf. equalis 81± AAR-119 Nuculana sp. 9± V 1, AD V 110, AD (SAR) AAR-10 Thyasira equalis, Thyasira sp. 1± Hekla AAR-11 Thyasira equalis, Thyasira sp. 10± Hekla 110, AD AAR-91 Thyasira equalis 1± Settlement layer, AD 8 8 (IC)

15 . AAR-1 Siphonodentalium lobatum 110± AAR-9 Siphonodentalium lobatum 190± AAR-9 Bathyarca glacialis 00± AAR-0 Thyasira equalis ± Snæfellsjökull 1 18 ± AAR-9 Cf. Dentalium entalis ± AAR-98 Thyasira equalis 0± AAR-9 Cf. Siphonodentalium lobatum 0± AAR-1 Thyasira equalis 80± AAR-99 Siphonodentalium lobatum ± AAR-9 Thyasira sp. 110± AAR-90 Yoldiella fraterna 90± AAR-91 Thyasira equalis 90± AAR-9 Thyasira equalis 1± AAR-1 Thyasira cf. equalis ± AAR-9 Thyasira equalis, Yoldiella fraterna 0± Hekla 89 ± AAR-9 Thyasira equalis ± AAR-9 Siphonodentalium lobatum ± AAR-9 Thyasira equalis, Yoldiella fraterna 1± AAR-9 Thyasira equalis ± AAR-9 Tridonta elliptica, Yoldiella fraterna 9± AAR-98 Thyasira equalis 1± AAR-98 Bathyarca glacialis 9± Thyasira equalis, Thyasira sp., Yoldiella 81 AAR-99 fraterna 9± AAR-088 Siphonodentalium lobatum 980± AAR-90 Yoldiella fraterna 009± AAR-91 Thyasira equalis 0± Hekla 8 ± AAR-9 Siphonodentalium lobatum 1 ± AAR-9 Siphonodentalium lobatum 90 ±

16 9. AAR-1 Siphonodentalium lobatum 0 ± AAR-1 Siphonodentalium lobatum 0 ± AAR-9 Thyasira equalis 0 ± AAR-9 Yoldiella lenticula 80 ± AAR-8 Thyasira equalis 880 ± AAR-9 Thyasira equalis 10 ± AAR-91 Thyasira equalis 10 ± AAR-8 Yoldiella cf. lenticula 00 ± AAR-8 Cf. Dentalium entalis 0 ± AAR-91 Yoldiella fraterna, Thyasira sp. ± Hekla OE 01 ± AAR-90 Siphonodentalium lobatum 80 ± AAR-8 Yoldiella cf. lenticula ± Hekla DH, BC ±0 (SAR) AAR-8 Siphonodentalium lobatum ± AAR-81 Siphonodentalium lobatum 1 ± Hekla 108 ± AAR-9 Siphonodentalium lobatum 80 ± Siphonodentalium lobatum 90 ± AAR-91 Yoldiella fraterna, Lunatia pallida 1 ± Sudurøy 1 0 ± AAR-08 Bathyarca glacialis, Thyasira sp. 10 ± AAR-08 Bathyarca glacialis 0 ± AAR-80 Siphonodentalium lobatum 80 ± AAR-99 Siphonodentalium lobatum 809 ± AAR-980 Siphonodentalium lobatum, Yoldiella frigida 810 ± AAR-99 Cf. Siphonodentalium lobatum 910 ± AAR-981 Yoldiella fraterna, Yoldiella cf. lenticula, 90 ± Natica (Tectonatica) affinis 0. Saksunarvatn ash, BC 8 ±89 (IC)

17 Supplementary Figure DR1. Diatom-based jack-knife inferred summer SSTs against modern observed summer SSTs from the surface sample sites

18 Supplementary Figure DR. Comparison between diatom-based reconstructed summer SSTs from multicore B0-00-MC0 and instrumental summer SST data from HadISST1 and Siglunes. The multicore B0-00-MC0, with length of cm, covering about last 100 yr, was retrieved at the same location (.18 N; 1.0 W) as the studied core MD99- (Ran et al., 011). Diatom contents of samples were analyzed at every 1 cm and the same diatom-based transfer function was applied as for core MD99-. The instrumental SST data are from open ocean Hadley Centre Sea Ice and SST dataset version I (HadISST1) series for July (Rayner et al., 00) and the summer SSTs (mean of July to September SST) at the Siglunes profile (data from the Marine Research Institute, Reykjavik, Iceland). An alkenone-based summer SST record from the same core (Sicre et al., 008) shows a similar distribution pattern, but the difference between diatom-based and instrumental SSTs is smaller than that between the mean of the alkenone-derived SSTs and the instrumental SSTs (Ran et al., 011)

19 Supplementary Figure DR. Spectral analysis (Lomb-Scargle Fourier transform) of the reconstructed summer sea-surface temperature from piston core MD99-. The red line indicates the 9% red-noise false-alarm levels calculated using REDFIT

20 References Cited Birks, H.J.B., 199. Quantitative paleoenvironmental reconstructions, in: Maddy, D., Brew, J.S., eds., Statistical modelling of Quaternary Science Data Technical Guide : Quaternary Research Association, Cambridge, p Birks, H.J.B., Numerical tools in palaeolimnology - Progress, potentialities, and problems. Journal of Paleolimnology, v. 0, p. 0-, doi: 10.10/A: Eiríksson, J., Knudsen, K. L., Larsen, G., Olsen, J., Heinemeier, J., Bartels-Jónsdóttir, H. B., Jiang, H., Ran, L., and Símonarson, L. A., 011, Coupling of palaeoceanographic shifts and changes in marine reservoir ages off North Iceland through the last millennium: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 0, p , doi: /j.palaeo Gudmundsdóttir, E. R., Eiríksson, J., and Larsen, G., 011, Identification and definition of primary and reworked tephra in Late Glacial and Holocene marine shelf sediments off North Iceland: Journal of Quaternary Science, v., p. 89-0, doi: /jqs.1. Knudsen, K.L., Eiríksson, J., Jiang, H., Jónsdóttir, I., 009. Palaeoceanography and climate changes off North Iceland during the last millennium: comparison of foraminifera, diatoms and ice-rafted debris with instrumental and documentary data. Journal of Quaternary Science, v., p. 8, doi: /jqs.19. Ran, L., Jiang, H., Knudsen, K. L., and Eiríksson, J., 011, Diatom-based reconstruction of palaeoceanographic changes on the North Icelandic shelf during the last millennium: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 0, p , doi: /j.palaeo Rasmussen, S. O., Vinther, B. M., Clausen, H. B., and Andersen, K. K., 00, Early Holocene climate oscillations recorded in three Greenland ice cores: Quaternary Science Reviews, v., p , doi: /j.quascirev Rayner, N. A., Parker, D. E., Horton, E. B., Folland, C. K., Alexander, L. V., Rowell, D. P., Kent, E. C., and Kaplan, A., 00, Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century: Journal of Geophysical 0

21 8 Research, v. 108, p. 0, doi: /00jd000. Sicre, M.-A., Yiou, P., Eiríksson, J., Ezat, U., Guimbaut, E., Dahhaoui, I., Knudsen, K.L., Jansen, E., Turon, J.-L., 008, A 00-year reconstruction of sea surface temperature variability at decadal time-scales off North Iceland: Quaternary Science Reviews, v., p. 01 0, doi:10.101/j.quascirev Telford, R. J., and Birks, H. J. B., 009, Evaluation of transfer functions in spatially structured environments: Quaternary Science Reviews, v. 8, p , doi: /j.quascirev