The Bølling-Allerød deglacial event is marked by high diatom productivity and opal deposition throughout the subarctic Pacific. To investigate the cause of this event, we quantified several productivity-related sedimentary parameters that reflect the near-surface biogeochemistry from the Integrated Ocean Drilling Program (IODP) Site 323-U1340 in the Bering Sea. Silicon isotopes (δ29Si and δ30Si) from single-genus Coscinodiscus diatom frustules. Diatom silicon isotope values were generated in the Keck Laboratory at the University of California, Santa Cruz using the following methods. Freeze-dried samples were washed on a 63μm sieve to remove clays and dried in a 55°C oven. Samples were then cleaned with the M2 method, without the Calgon step, in non-glass containers and again oven-dried. To isolate a single diatom genus, samples were dry-sieved and ice rafted debris, radiolarians, spicules, and other genera were removed from the 63-125 μm portion by picking under a microscope and visually confirmed to be >99% Coscinodiscus specimens. Coscinodiscus species present were >95% Coscinodiscus marginatus with occasional Coscinodiscus oculus-iridis and Coscinodiscus radiatus. To dissolve samples, ≤0.002 g was transferred to 100 μL of 10 M NaOH in screw-top Teflon vials and reacted in Parr vessels at 200°C for three days. Samples were transferred to BioRad 50W X8 cation exchange columns previously cleaned with HCl and Milli-Q water (after Georg et al., 2006; doi:10.1016/j.chemgeo.2006.06.006), and eluted in Milli-Q water. Intensities of 28Si, 29Si and 30Si were measured using standard-sample bracketing on a Neptune MC ICP-MS at high resolution equipped with an Apex Omega desolvating nebulizer. All values are reported vs. NBS 28.