Dissolved and particulate stable silicon isotope measurements from CTD niskin depth profiles from cruise JR17005 in the Fram Strait during May-June 2018.

Dissolved and particulate stable silicon isotopes were determined in seawater samples collected onboard R.R.S James Clark Ross in the Fram Strait from 08-May-2018 to 08-Jun-2018 as part of the Changing Arctic Ocean programme. Seawater samples were filtered inline from Niskin bottles, acidified to 0.1% v/v and kept at 4°C until analysis on land. Samples were measured for δ29Si(OH)4 with reference to international reference material NBS28 on a Nu Plasma II MC-ICP-MS using the MAGIC co-precipitation method and purified through column chemistry. International standards BigBatch, ALOHA300 and ALOHA1000 were run alongside seawater samples for inter-comparability. Final values were converted to δ30Si(OH)4 using the conversion factor of 1.96 for comparability. Reproducibility is 0.05 and 0.1‰ for δ29Si(OH)4 and δ30Si(OH)4 respectively.