Seasonal, spatial, and temporal variation of Biogenic silica (bSi) and Lithogenic silica (LSi) during MOSAiC and HAVOC expedition 2019/2020

Biogenic silica (bSi) and Lithogenic silica (LSi) concentrations from First Year (FYI) and Second Year (SYI) ice cores and water samples were collected with Ice Corer Kovacs Mark II (9-cm) and CTD AWI-OZE (respectively) aboard RV Polarstern during the MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) in 2019 to 2020 for projects MOSAiC and "Ridges – Safe HAVens for ice-associated flora and fauna in a seasonally ice-covered Arctic Ocean" (HAVOC). During MOSAiC and HAVOC, there were 95 events with a total of 750 samples for biogenic silica (bSi) and Lithogenic silica (LSi) concentration. Ice samples (once thawed) and water samples were filtered and kept for silica sequential extractions. First, filters went through a mild alkaline-leachable digestion with sodium carbonate (Na2CO3) to free reactive silica associated with the bSi pool. After filters were neutralized and dried, Hydroflouric Acid (HF) was added for a harsh digestion to release LSi.