The seasonal cycle of δ 3 C DIC in the North Atlantic subpolar gyre

• Published in: Biogeosciences
• Main Authors: V. Racapé, N. Metzl, C. Pierre, G. Reverdin, P. D. Quay, S. R. Olafsdottir
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2014
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; North Atlantic
• Online Access: https://doi.org/10.5194/bg-11-1683-2014; https://doaj.org/article/60637616c15a4f7e9a5b3dad898e92d2

This study introduces for the first time the δ 13 C DIC seasonality in the North Atlantic subpolar gyre (NASPG) using δ 13 C DIC data obtained in 2005–2006 and 2010–2012 with dissolved inorganic carbon (DIC) and nutrient observations. On the seasonal scale, the NASPG is characterized by higher δ 13 C DIC values during summer than during winter, with a seasonal amplitude between 0.70 ± 0.10‰ (August 2010–March 2011) and 0.77 ± 0.07‰ (2005–2006). This is mainly attributed to photosynthetic activity in summer and to a deep remineralization process during winter convection, sometimes influenced by ocean dynamics and carbonate pumps. There is also a strong and negative linear relationship between δ 13 C DIC and DIC during all seasons. Winter data also showed a large decrease in δ 13 C DIC associated with an increase in DIC between 2006 and 2011–2012, but the observed time rates (−0.04‰ yr −1 and +1.7 μmol kg −1 yr −1 ) are much larger than the expected anthropogenic signal.