Observations of pigment and particle distributions in the western North Atlantic from an autonomous float and ocean color satellite

Abstract

Profiling floats with optical sensors can provide important complementary data to satellite ocean color determinations by providing information about the vertical structure of ocean waters, as well as surface waters obscured by clouds. Here we demonstrate this ability by pairing satellite ocean color data with records from a profiling float that obtained continuous, high-quality optical data for 3 yr in the North Atlantic Ocean. Good agreement was found between satellite and float data, and the relationship between satellite chlorophyll and float-derived particulate backscattering was consistent with previously published data. Upper ocean biogeochemical dynamics were evidenced in float measurements, which displayed strong seasonal patterns associated with phytoplankton blooms, and depth and seasonal patterns associated with an increase in pigmentation per particle at low light. Surface optical variables had shorter decorrelation timescales than did physical variables (unlike at low latitudes), suggesting that biogeochemical rather than physical processes controlled much of the observed variability. After 2.25 yr in the subpolar North Atlantic between Newfoundland and Greenland, the float crossed the North Atlantic Current to warmer waters, where it sampled an unusual eddy for 3 months. This anticyclonic feature contained elevated particulate material from surface to 1000-m depth and was the only such event in the float's record. This eddy was associated with weakly elevated surface pigment and backscattering, but depth-integrated backscattering was similar to that previously observed during spring blooms. Such seldom-observed eddies, if frequent, are likely to make an important contribution to the delivery of particles to depth. © 2008 by the American Society of Limnology and Oceanography, Inc.