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 floatderived 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 depthintegrated 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.

Optical techniques for remote and in-situ characterization of particles pertinent to GEOTRACES

“…Using turbidity meters it is possible to obtain higher resolution than with backscattering sensors. For example, Boss et al (2008) obtained a minimal difference (7 counts) between the cleanest field water and the dark current. The higher resolution with turbidity meters is most likely due to the larger (though less well defined) sampling volume compared to backscattering sensors.…”

“…Sensors to measure marine particles have been routinely deployed on CTD rosettes (Bishop and Joyce, 1986;Bishop et al, 1992;Bishop et al, 2012;Bishop, 1999;Bishop and Wood, 2008;Dickey et al, 2006;Gardner et al, 1985;Gardner et al, 1993;Gardner et al, 2001;Hill et al, 2011;Karp-Boss et al, 2004;Stemmann et al, 2008a), during deployments of large volume insitu filtration systems (Bishop, 1999;Bishop et al, 1999;Bishop et al, 2012;Bishop and Wood, 2008;Moran et al, 1999), on slow-drop packages (packages that fall under their own weight, Barnard et al, 1998), towed pumping systems, (Holser et al, 2011), AUVs and profiling floats Bishop and Wood, 2009;Bishop et al, 2004;Boss et al, 2008;Checkley et al, 2008;Dickey et al, 2008), submarines, bottom tripods (Gardner et al, 1985;Slade et al, 2011) and moorings (Dickey et al, 2006;Gardner, 1989aGardner, , 1989bRichardson et al, 1993). Consideration of deployment platform should include potential of platform interference with particles (e.g.…”

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

“…Here, we propose a method to merge fluorescence profiles and satellite ocean colour observations, which is conceptually close to the Boss et al (2008) procedure. The main difference is that it is applicable on a single profile basis.…”

“…simultaneous irradiance profiles, Xing et al, 2011), on the shape of fluorescence profile or on satellite ocean colour Chl a C observations (Boss et al, 2008). The last method (Boss et al, 2008), although developed to correct a profiling float fluorometer, also points to a reliable way to merge fluorescence profiles and satellite observations.…”

“…simultaneous irradiance profiles, Xing et al, 2011), on the shape of fluorescence profile or on satellite ocean colour Chl a C observations (Boss et al, 2008). The last method (Boss et al, 2008), although developed to correct a profiling float fluorometer, also points to a reliable way to merge fluorescence profiles and satellite observations. However, the Boss et al (2008) approach, in its present form, was developed to be applied to a time series of profiles performed by a single fluorometer deployed on a profiling float and is likely not suitable for other data sets.…”