Stable oxygen and carbon isotopes in planktonic foraminifera Neogloboquadrina pachyderma in the Arctic Ocean: An overview of published and new surface-sediment data

Abstract

A summary study on oxygen and carbon stable isotopes in planktonic foraminifera from Arctic Ocean floor appeared in Marine Geology 20 years ago (Spielhagen and Erlenkeuser, 1994). We revisit this topic with a wealth of new data focused on the western (Amerasian) Arctic, a spotlight in the current climatic and oceanic change. Neogloboquadrina pachyderma , the most abundant polar planktonic foraminiferal species, is an important tool for reconstructing surface/subsurface water changes in the Arctic. Our new data on N. pachyderma (150–250 μm) from the surface sediments show δ 18 O and δ 13 C values of < 1.5‰ and 0.8–1.5‰, respectively, in the ice covered Canada Basin, and 2–3.5‰ and 0.6–0.9‰, respectively, at the shelf break. Combined data from the western and eastern Arctic indicate that planktonic δ 18 O and δ 13 C are both influenced by complex water sources, water column structure, and foraminiferal depth habitat. The observed distribution of N. pachyderma stable isotopes confirms a shallow habitat of this species in the sea-ice covered central Arctic, especially in the Canada Basin, probably in relation to the shallow chlorophyll maximum. The associated light N. pachyderma δ 18 O reflects the long-term storage of fresh water. At the shelf break, a deeper dwelling of N. pachyderma with heavier δ 18 O is supported by a more extensive photic zone and nutrient availability. Air–sea exchange plays an important role in δ 13 C distribution and is consistent with heavy N. pachyderma δ 13 C in the perennially ice-covered central Arctic Ocean. Light δ 13 C composition at the shelf break is additionally influenced by shelf bottom waters enriched in isotopically light, remineralized terrestrial carbon. Distribution of foraminiferal δ 13 C on the Chukchi Shelf reflects primary production patterns in the area. • Shallow dwelling of N. pachyderma in the ice covered central Arctic Ocean. • Deeper N. pachyderma dwelling near shelf break follows deeper nutrient maximum. • N. pachyderma δ 18 O distribution in the Arctic mostly related to freshwater storage. • Accompanying δ 13 C values consistent with air–sea exchange patterns and DIC sources.