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

Abstract

Temporal and spatial variability of physical, biological, and optical properties on scales of minutes to months and meters to ∼50 km are examined using an extensive data set collected on the New York Bight continental shelf during the Hyperspectral Coastal Ocean Dynamics Experiment. Measurements from a midshelf mooring and bottom tripod (∼25 km offshore, 24 m water depth) and two nearshore profiling nodes (∼5 km offshore, 15 m water depth) are utilized to quantify and correlate midshelf and nearshore variability. Towed shipboard undulating profilers and a high‐frequency radar (CODAR) array provide complementary spatial data. We show that phytoplankton and dissolved matter each accounted for roughly 50% of total absorption (440 nm) at midshelf. In contrast, particulate compared to gelbstoff absorption dominated total absorption at the nearshore location. A relatively high‐salinity, low‐temperature, low particulate coastal jet decreased turbidity nearshore and advected lower‐salinity, higher‐chlorophyll waters to the midshelf region, resulting in increased biomass at midshelf. Small‐scale (order of a few kilometers) convergence and divergence zones formed from the interaction of semidiurnal tides with mean currents and a water mass/turbidity front. The front resulted in increased decorrelation scales from nearshore (∼1 day) toward midshelf (2–3 days) for optical and biological parameters. We conclude that optical and biological variability and distributions at midshelf and nearshore locations were influenced mainly by semidiurnal tides and the coastal jet. We present insights into nearshore coastal processes and their effects on biology and optics as well as for the design of future nearshore interdisciplinary coastal programs.