Modeling the distribution and seasonality of Neogloboquadrina pachyderma in the North Atlantic Ocean during Heinrich Stadial 1

• Published in: Paleoceanography
• Main Authors: Kretschmer, Kerstin, Kucera, Michal, Schulz, Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2016
• Subjects: Neogloboquadrina pachyderma; North Atlantic; Planktonic foraminifera; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/49671/; https://oceanrep.geomar.de/id/eprint/49671/1/2015PA002819.pdf; https://doi.org/10.1002/2015PA002819

Fossil shells of planktonic foraminifera serve as the prime source of information on past changes in surface ocean conditions. Because the population size of planktonic foraminifera species changes throughout the year, the signal preserved in fossil shells is biased toward the conditions when species production was at its maximum. The amplitude of the potential seasonal bias is a function of the magnitude of the seasonal cycle in production. Here we use a planktonic foraminifera model coupled to an ecosystem model to investigate to what degree seasonal variations in production of the species Neogloboquadrina pachyderma may affect paleoceanographic reconstructions during Heinrich Stadial 1 (∼ 18–15 cal ka B.P.) in the North Atlantic Ocean. The model implies that during Heinrich Stadial 1 the maximum seasonal production occurred later in the year compared to the Last Glacial Maximum (∼ 21–19 cal ka B.P.) and the preindustrial era north of 30°N. A diagnosis of the model output indicates that this change reflects the sensitivity of the species to the seasonal cycle of sea ice cover and food supply, which collectively lead to shifts in the modeled maximum production from the Last Glacial Maximum to Heinrich Stadial 1 by up to 6 months. Assuming equilibrium oxygen isotopic incorporation in the shells of N. pachyderma, the modeled changes in seasonality would result in an underestimation of the actual magnitude of the meltwater isotopic signal recorded by fossil assemblages of N. pachyderma wherever calcification is likely to take place.