Seasonal variations of bio-optical properties and their interrelationships observed by Bio-Argo floats in the subpolar North Atlantic

Based on in situ data sets collected using two Bio-Argo floats deployed in the subpolar North Atlantic from June 2008 to May 2010, the present study focuses on the seasonal variability of three bio-optical properties, i.e., chlorophyll-a concentration ([Chla]), particle backscattering coefficient at 532 nm (b(bp)(532)), and particle beam attenuation coefficient at 660 nm (c(p)(660)). In addition, the interrelationships among these properties are examined. Our results show that: (1) [Chla], b(bp)(532) and c(p)(660) are largely well coupled with each other in the upper layer, all being minimum in mid-winter (January) and maximum in summer; (2) the backscattering coefficient presents an abrupt increase in late summer in the Icelandic Basin, likely due to a large contribution of coccolithophores following the diatom spring bloom; (3) the intercorrelations between the three bio-optical properties are basically consistent with previous studies; (4) seasonal variation in the of [Chla] to c(p)(660) ratio exhibits a clear light-dependence, most likely due to the phytoplankton photoacclimation.