Seki et al.( 2010) published new pCO 2 estimates from the boron isotope and alkenone proxies from a site not included in the Pagani et al.( 2010) study, but the same time range. The top panel shows previous pCO 2 estimates for the period( colour bands are selected sites from Pagani et al. 2010; black diamonds are bulk organic � 13 C estimates from Raymo et al., 1996; red circles are stomatal estimates from Kurschner et al., 1996; and blue diamonds are the old boron isotope data from Pearson and Palmer, 2000; the green line at the left is the ice core air bubble data from Luthi et al., 2008). Panel b is new boron isotope estimates from the species G. ruber with different assumptions about alkalinity( the different symbols) and panel c is the alkenone data both uncorrected( red band) and corrected( between the red squares) for changing cell size effect. It can be seen from this that the Pliocene boron estimates are mostly in the 300-350 ppm range but just exceed 400 ppm around 3 Ma given certain assumptions. The alkenone estimates exceed 400 ppm for a few values around 5 Ma but only if the size correction is taken into account.
vii. Bartoli et al.( 2011)
Fig. 7. Boron isotope, δ 18 O and pCO 2 reconstruction by Bartoli et al.( 2011). Red line added.
This record is from boron isotopes in the planktonic foraminifer G. sacculifer. The estimates are shown on the bottom panel together with some previous( mostly alkenone) records for comparison as