Surface Water Radiocarbon (Δ¹⁴C) Reconstructed from Reef-Building Zooxanthellate Corals

T. P. Guilderson^1,2, D. P. Schrag³, S. J. Fallon^1,4, R. B. Dunbar⁵, K. H. Kilbourne⁶, and N. Grumet Prouty⁷

¹Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore CA 94551
²Department of Ocean Sciences, and Institute of Marine Science, University of California-Santa Cruz, Santa Cruz CA 95064
³Department of Earth and Planetary Sciences, Harvard University, Cambridge MA 02138
⁴Research School of the Earth Sciences, Australian National University, Canberra ACT, Australia
⁵Department of Earth and Environmental Sciences, Stanford University, Stanford CA
⁶Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons MD 20688
⁷USGS Pacific Coastal & Marine Science Center, 400 Natural Bridges Drive Santa Cruz, CA 95060

Data Files        Documentation (PDF file)

Introduction

The surface water radiocarbon (as Δ‰) data presented in this archive are derived from surface dwelling, reef-building hermatypic corals which have been shown to be reliable archives of ocean Σ¹⁴CO₂ [eg., Guilderson et al., 1998; Kilbourne et al., 2007; and references therein]. All of the data presented in this archive have been published and the users of the data are encouraged to take advantage of the primary references to place the results in a more detailed dynamic context.

All samples were prepared and analyzed at the Center for Accelerator Mass Spectrometry (CAMS), Lawrence Livermore National Laboratory. Data are reported according to the internationally standardized nomenclature put forth in Stuiver and Polach [1977]. Results are presented as "age-corrected" Δ¹⁴C (‰) and contain corrections for both background subtraction (using ¹⁴C-free calcite) and δ¹³C on splits of the same material used for ¹⁴C analyses, or a representative estimate when such data do not exist for a specific sample. Thus, the data are exactly Δ but due to muddling in the literature, we refer to them as “age-corrected” Δ¹⁴C to make sure that there are no misinterpretations of the data presentation. Uncertainty (reproducibility as monitored by an in-house homogenized coral standard) in the data is variable, with earlier produced data (eg., Nauru, Guadalcanal, Galapagos) ±4.5‰ versus more recent results of ±3.5‰ (eg., Lankai, Padang Bai, Puerto Rico). The precision of the data is completely consistent with WOCE data. The time-series focus on the latter half of the 20th century, nominally post-1950.

The age-correction uses an independent stable isotope (δ¹⁸O, δ¹³C) and minor element ([Sr/Ca]), or density-band count age model. Because we were most interested in an accurate surface water ¹⁴C reconstruction, the sub-annual age models were ‘tuned’ using instrumental sea surface temperature and or precipitation data [eg., IGOSS, "Kaplan" products or local precipitation data available through the GCHN network]. Linear growth rate estimates and the sampling (in distance and thus time) allowed for bimonthly or better resolution, except for Puerto Rico dataset which by design is annual. Alignment of stable isotope or minor element peaks/troughs in conjunction with classical sclerochronology [eg. Dodge and Vainys, 1980] was straightforward and the error on the age assignment is estimated to be no more than 2 months; i.e., approximately the resolution of the sampling. In the case of the Indonesian seaway records, we fixed the seasonal minimum and maximum of coral δ¹⁸O (a proxy for sea surface temperature and δ¹⁸Ow) to March/April and September, consistent with instrumental data [cf., Fallon and Guilderson 2008; Guilderson et al., 2009]. Similar to the Indonesian seaway time-series, Watamu’s chronology was derived by anchoring the coral δ¹⁸O to a fixed seasonal cycle. The Puerto Rico record is an annually resolved record with an age model based on annual density bands. Each sample is approximately centered on January and the final record has an estimated age model error of ±1 year at 1750 [cf. Kilbourne et al., 2007].

Location Name	Lat (°N)	Lon (°E)	Start	End	Resolution	Reference
Guadalcanal (Solomon Sea)	-9° 00'	160° 00'	1943	1995	~bimonthly	Guilderson 2004
Isla Isabella (Galapagos)	-0° 24’	-91° 15’	1957	1982	~bimonthly	Guilderson 1998
Lankai (Makassar St)	-5° 02'	119° 04'	1870	1990	~bimonthly	Fallon 2008
Nauru (W. Eq. Pacific)	-0° 30'	166° 00'	1947	1997	~bimonthly	Guilderson 1998
Padang Bai (Lombok St)	-8° 15'	115° 30'	1937	1990	~bimonthly	Guilderson 2009
Puerto Rico (Carib-Atl)	17° 56'	67° 1'	1751	2004	annual	Kilbourne 2007
Rarotonga (Cook Islands)	-21° 14'	-149° 49'	1950	1997	~bimonthly	Guilderson 2000
Watamu (W. Africa)	-3° 23'	39° 52'	1947	1987	~bimonthly	Grumet 2004

Acknowledgements

The samples and or data presented herein were acquired with funding from the National Science Foundation, the National Oceanic and Atmospheric Administration, and the Lawrence Livermore National Laboratory’s Directed Research and Development Program. Technical support at the Laboratory of Geological Oceanography, Harvard University; the Stable Isotope Laboratory, Stanford University; the Paleo-Laboratory at the University of South Florida; and the Natural Carbon Research Group’s graphite preparation laboratory (CAMS) are all gratefully acknowledged. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405- Eng-48 and in part under Contract DE-AC52-07NA27344.

References including primary data source

• Fallon, S. J., and Guilderson, T. P., 2008. Surface water processes in the Indonesian Throughflow as documented by a high-resolution coral Δ¹⁴C record. J. Geophys. Res. doi:10.1029/2008JC004722.
• Dodge, R. E., and J. R. Vaisnys, 1980. Skeletal growth chronologies of recent and fossil corals, Skeletal Growth of Aquatic Organisms. Top. Geobiology, Vol. 1. D. C. Rhoads and R. A. Lutz, Eds., Plenum, pp. 493-517.
• Grumet, N. S., Guilderson, T. P., and Dunbar, R. B., 2002. Coral Radiocarbon as a Tracer for Meridional Transport in the Indian Ocean. J. of Marine Research 60:725-742.
• Guilderson, T. P., Fallon, S. J., Moore, M., Schrag, D. P., and Charles, C. D., 2009. Seasonally Resolved Surface Water Δ¹⁴C Variability in the Lombok Strait: a Coralline Perspective. J. Geophys. Res., doi:10.1029/2008JC004876
• Guilderson, T. P., Schrag, D. P., and Cane, M. A., 2004. Surface water mixing in the Solomon Sea as documented by a high-resolution coral Δ¹⁴C record. J. of Climate 17:1147-1156.
• Guilderson, T. P., Schrag, D. P., Goddard, E., Kashgarian, M., Wellington, G. M., and Linsley. B. K., 2000. Southwest subtropical Pacific surface water radiocarbon in a high-resolution coral record. Radiocarbon, 42(2):249-256.
• Guilderson, T. P., and Schrag, D. P., 1998. Abrupt shift in subsurface temperatures in the eastern tropical Pacific associated with recent changes in El Niño. Science 281:240-243.
• Guilderson, T. P., D. P. Schrag, M. Kashgarian, and J. Southon 1998. Radiocarbon Variability in the Western Equatorial Pacific Inferred from a High-Resolution Coral Record from Nauru Island. J. Geophys. Res., 103:24641-24650.
• Kilbourne, K. H., Quinn, T. M., Guilderson, T. P., Webb, R.S., and Taylor, F. W., 2007. Decadal to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon. Climate Dynamics, 29, 51-62, doi:10.1007/s00382-007-0224-2.
• Stuiver, M., and H. A. Polach, 1977. Discussion and reporting of ¹⁴C data, Radiocarbon, 19:355-363.