Review status: this preprint has been withdrawn by the authors.
First continuous phosphate record from Greenland ice cores
H. A. Kjær1,A. Svensson1,P. Vallelonga1,E. Kettner1,S. Schüpbach2,M. Bigler2,J. P. Steffensen1,and M. E. Hansson3H. A. Kjær et al.H. A. Kjær1,A. Svensson1,P. Vallelonga1,E. Kettner1,S. Schüpbach2,M. Bigler2,J. P. Steffensen1,and M. E. Hansson3
Received: 26 Oct 2011 – Accepted for review: 05 Nov 2011 – Discussion started: 18 Nov 2011
Abstract. A continuous and highly sensitive absorption method for detection of soluble phosphate in ice cores has been developed using a molybdate reagent and a 2 m liquid waveguide (LWCC). The method is optimized to meet the low concentrations of phosphate in Greenland ice, it has a detection limit of around 0.1 ppb and a depth resolution of approximately 2 cm. The new method has been applied to obtain phosphate concentrations from segments of two Northern Greenland ice cores: from a shallow firn core covering the most recent 120 yr and from the recently obtained deep NEEM ice core in which sections from the late glacial period have been analysed. Phosphate concentrations in 20th century ice are around 0.32 ppb with no indication of anthropogenic influence in the most recent ice. In the glacial part of the NEEM ice core concentrations in the cold stadial periods are significantly higher, in the range of 6–24 ppb, while interstadial ice concentrations are around 2 ppb. In the shallow firn core, a strong correlation between concentrations of phosphate and insoluble dust suggests a similar deposition pattern for phosphate and dust. In the glacial ice, phosphate and dust also correlate quite strongly, however it is most likely that this correlation originates from the phosphate binding to dust during transport, with only a fraction coming directly from dust. Additionally a constant ratio between phosphate and potassium concentrations shows evidence of a possible biogenic land source.
Please note: The technique for continuous phosphate determination reported here has been subsequently improved and published in Environmental Science & Technology. The technique reported here determines an unquantifiable mixture of soluble and insoluble phosphate, and hence may lead to variable phosphate recoveries from in ice core samples from different climatic periods. This deficiency has been avoided in the Environ. Sci. Technol. publication, by filtering insoluble particles from the sample before the addition of a reagent.
This preprint has been withdrawn.
How to cite. Kjær, H. A., Svensson, A., Vallelonga, P., Kettner, E., Schüpbach, S., Bigler, M., Steffensen, J. P., and Hansson, M. E.: First continuous phosphate record from Greenland ice cores, Clim. Past Discuss., 7, 3959–3989, https://doi.org/10.5194/cpd-7-3959-2011, 2011.