Seasonal variability of bio‐optical and physical properties in the Sargasso Sea

Abstract

The seasonal variability of bio‐optical and physical properties within the upper ocean at a site in the Sargasso Sea (34°N, 70°W) has been observed using multivariable moored systems (MVMS) during a 9‐month period (March through November 1987). In addition, complementary meteorological data, sea surface height (Geosat) and sea surface temperature maps, and expendable bathythermograph (XBT) and shipboard profile data (physical and bio‐optical) have been utilized for interpretation. The observations during March are characteristic of late wintertime conditions of a deep isothermal layer (∼18–19°C), but with intervening periods of warming due to the advection of warm outbreak waters associated with Gulf Stream meanders. The mixed layer depth shoals from greater than 160 m to about 25 m in late March (spring transition). Phytoplankton blooms follow the mixed layer shoaling. A succession of phytoplankton populations occurs during this transitional interval. Mesoscale variability associated with cold core rings and warm outbreak waters associated with the Gulf Stream are evident at various times. The mixed layer remains near 25 m for the summer and deepens in mid‐September. A relatively intense subsurface maximum in chlorophyll develops at ∼75 m following the spring transition. The maximum persists, but weakens in mid‐summer. The present study clearly indicates that important processes associated with and contributing to the seasonal cycle occur on short time and space scales and that integrated data sets obtained from moorings, ships, and satellites can be used to effectively study bio‐optical and physical phenomena on time scales from minutes to seasons.

Nearshore physical processes and bio‐optical properties in the New York Bight

“…The current study builds on previous experiments that investigated temporal and spatial variability of bio‐optical properties as related to physical processes in the coastal ocean (e.g., CMO [ Chang , 1999; Chang and Dickey , 2001] and open ocean sites [ Dickey et al , 1991, 1993, 1994, 1998a, 1998b, 2001]) using moorings and tripods, drifters (e.g., Coastal Transition Zone (CTZ) program in the California Current [ Abbott et al , 1995; Abbott and Letelier , 1998]), and shipboard transects (e.g., Marine Light‐Mixed Layers (MLML) program using profile and tow‐yo data [ Washburn et al , 1998] and SeaSoar data in the Arabian Sea [ Lee et al , 2000]). Physical processes found important to bio‐optical variability in the Middle Atlantic Bight (MAB) during the CMO program include, but are not limited to: storms and hurricanes, shelf slope frontal movement, Gulf Stream eddies, meanders, filaments, jets, tides, and internal solitary waves (ISWs) [ Chang , 1999; Chang and Dickey , 2001].…”

Modeling of wave-induced irradiance variability in the upper ocean mixed layer

“…But one should keep in mind that bio-optical and physical properties of the sea strongly vary with season and region (e.g. Dickey et al, 1993;de Boyer Montegut et al, 2004).…”

Surface solar irradiance from the International Satellite Cloud Climatology Project 1983–1991

“…We will revisit the FIRE/SRB comparison (section 3.1). We have also compared our daily all-sky (including the effects of clouds) and clear sky data, to daily averages derived from contemporaneous high-frequency (<20 min) data sets obtained from sensors deployed on ocean moorings during the 1987 Bio-WATT [Dickey et al, 1993] and the 1989 and 1991 Marine Light Mixed Layer (MLML) (Dickey et al [1994], Pluddeman et al [1995]) experiments (section 3.2). A further validation effort employs hourly resolved data sets obtained from island locations of Samoa, Kwajalein, Cape Grim, and Bermuda.…”