The seasonal cycle of ;delta;3CDIC in the North Atlantic subpolar gyre

Abstract

This study introduces for the first time the ;delta;3CDIC seasonality in the North Atlantic subpolar gyre (NASPG) using ;delta;3C 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 13CDIC 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 ;delta;3C DIC and DIC during all seasons. Winter data also showed a large decrease in ;delta;3CDIC associated with an increase in DIC between 2006 and 2011-2012, but the observed time rates (-0.04‰ yr-1 and +1.7 μ mol kg-1 yr-1) are much larger than the expected anthropogenic signal. © 2014 Auyhor(s).