Coralline algal Barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability

Hetzinger, S.; Halfar, J.; Zack, T.; Mecking, J. V.; Kunz, B. E; Jacob, D. E. and Adey, W. H. (2013). Coralline algal Barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability. Scientific reports, 3, article no. 1761.

DOI: https://doi.org/10.1038/srep01761

Abstract

During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes.