Many luminaries of oceanography have articulated the problem of adequately sampling a multiplicity of
interdisciplinary ocean processes. Progress has accelerated within the past two decades as societal and
naval interests in monitoring and predicting the state of the ocean environment has heightened.
Oceanographers are capitalizing on a host of new platform and sensing technologies. Some recent
programs contributing to improved 4-dimensional open and coastal ocean multi-disciplinary observations
are used to highlight the development of new integrated optical, chemical, and physical measurement
systems that can be deployed from stationary and mobile platforms to telemeter data in near real-time or
real-time. For example, the NOPP O-SCOPE and MOSEAN projects have developed and tested several
optical and chemical sensors in deep waters off Bermuda and Hawaii, at OWS 'P' in the North Pacific
Ocean, and in coastal waters off Santa Barbara and Monterey, California. Most of the testing for these
projects has been conducted using moorings; however, NOPP instrumentation is also being used on mobile
platforms including AUVs, profiling floats, and gliders. Progress in adequately sampling the temporal and
spatial variability of selected ocean 'sampling volumes' using multi-platform, multi-disciplinary sampling
is described using examples from selected recent programs.
During the past decade, interdisciplinary process studies have been conducted in may regions of the world oceans. The focus of this review is on studies which have been deployed from multiple sampling platforms. These studies have led to increased understanding of ocean processes which are of interest for problems concerning 1) fundamental ocean optics, 2) remote sensing of the ocean, 3) the ocean's ecology and renewable resources, 4) the ocean's role in global climate change, and 5) pollution and its effects. Here we describe some of the methodologies which have enabled advances and provide brief summaries of a few studies in diverse geographical regions.
Light scattering induced by turbulent flow in seawater has been studied and the effect of seawater turbulence on the propagation of a collimated light beam has been characterized. Our approach is to describe the interaction of light with inhomogeneities in the refractive index (IRI) by solving Maxwell's equations. This set of equations is converted into the parabolized Helmholtz equation in the case of light propagating through water with IRI. We characterize the light scattering within a water parcel by the volume scattering function (VSF). Field measurements of small-angle VSF exhibit a sharp peak which is orders of magnitude greater than that obtained from either laboratory measurements or Mie calculations for suspended particles. Our computer simulations show that the volume scattering function obtained is indeed characterized by an exponential decrease with scattering angle and is in quantitative agreement with in situ observations in the case of high temperature variance dissipation, (chi) . It appears that 0(1 degree(s)) is the upper limit of turbulent induced light scattering in the ocean.
Measurements were taken from a mooring in order to address questions concerning variability of bio-optical and physical properties in the upper ocean. The measurements are relevant to questions involving: 1) the identification of bio-optical processes and their time scales; 2) relationships between bio-optical variability and physical forcing; and 3) the development and testing of coupled bio-optical and physical models. The concurrent measurements provide time series of beam attenuation coefficient, chlorophyll fluorescence, photosynthetically available radiation, and dissolved oxygen along with horizontal cutrents and temperature. Data were obtained during three consecutive mooring periods in the upper 160m from 7 to 8 depths in the Sargasso Sea (34N 70W). Sampling was done at 4 minute intervals during a nine month period in 1987. Here, data obtained from the first deployment (March 1 through May 10) are described. Some of the primary observations include: 1) the abrupt onset of springtime stratification and episodic changes in the beam attenuation coefficient and chlorophyll fluorescence; 2) advective water mass variations associated with a cold core ring and warm Gulf Stream outbreak waters in the vicinity of the mooring; and 3) diurnal variations in the near surface beam attenuation coefficient and chlorophyll fluorescence
which are associated with daily cycles of biological primary productivity. The present in situ, high frequency, long-term observations provide an impetus for similar future observations relevant to studies of optical property variability, primary productivity, and particulate fluxes.
Concurrent time series measurements including: percent transmission of a collimated beam of 660 nm light (converted to beam attenuation coefficient, C), photosynthetically available radiation (PAR), and chlorophyll (chl) fluorescence were obtained at 7-8 depths within the upper 160m of the Sargasso Sea (34N 70W) from Mar-Oct 1987 using a moored array of instruments (see Dickey et al., this volume). A subset of these data, the spring deployment (the first of three) from March to mid May, has been analyzed with respect to the diel phase variations in the bio-optical properties. Among the features noted, the relationship between PAR and chl-fl changed from cM-fl lagging the PAR signal by ca 90 degrees, through 180 degrees of shift to leading by -90 degrees. The transition period corresponding to this change was marked by inconsistent behavior in thephase relationships between other bio-optical variables, but the changes were short-lived and returned to their previous offsets from the daily PAR. These changes are thought to be the result of a succession of species caused by a combination of warm outbreaks of Gulf Stream waters importing a foreign particle assemblage into the Sargasso Sea, contemporaneous with wind events causing deep mixing. This hypothesis is consistent with recent observations at sea and in laboratory studies.