The seasonal cycle of delta super(3)C sub(DIC) in the North Atlantic subpolar gyre

• Published in: Biogeosciences 2014-03, Vol.11 (6), p.1683-1692
• Main Authors: Racape, V, Metzl, N, Pierre, C, Reverdin, G, Quay, P D, Olafsdottir, SR
• Format: Article
• Language: English
• ISSN: 1726-4170; 1726-4189
• DOI: 10.5194/bg-11-1683-2014

This study introduces for the first time the delta super(13)C sub(DIC) seasonality in the North Atlantic subpolar gyre (NASPG) using delta super(13)C sub(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 delta super(13)C sub(DIC) values during summer than during winter, with a seasonal amplitude between 0.70 plus or minus 0.10ppt (August 2010-March 2011) and 0.77 plus or minus 0.07ppt (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 delta super(13)C sub(DIC) and DIC during all seasons. Winter data also showed a large decrease in delta super(13)C sub(DIC) associated with an increase in DIC between 2006 and 2011-2012, but the observed time rates (-0.04ppt yr super(-1)and +1.7 mu mol kg super(-1) yr super(-1)) are much larger than the expected anthropogenic signal.