OPTICAL OCEANOGRAPHY AND UV RADIATION (CO
SPONSORED BY IOP AND EOS)
Location: Arts Building, 125 LR1
Location of Posters: Arts Building, 126 LR2
Wednesday 28 July AM
OPTICAL AND BIO-OPTICAL MEASUREMENTS
Presiding Chair: Jim Aiken (Plymouth Marine Laboratory, Prospect Place, Plymouth)
Introduction 0900
Jim Aiken, Ray Smith and Andre Morel
P15/E/02-B3 Invited 0915
NEW BIO-OPTICAL MEASUREMENTS FROM AUTONOMOUS PLATFORMS
T. DICKEY (University of California at Santa Barbara, 6487 Calle Real, Suite A, Goleta, CA 93117, (805) 893-7354; email: tommy@icess.ucsb.edu)
During the past few years, our group and collaborators have made bio-optical and physical observations using autonomous platforms including moorings and autonomous underwater vehicles (AUVs). The variety of optical (and chemical) measurements is expanding rapidly. Our work has focused on the development of new systems capitalizing on emerging multi-spectral sensors, novel platforms, and specialized telemetry technologies. In this review, examples of these new interdisciplinary sampling systems, data acquired with the systems, and interpretation of these data will be discussed. Sites for the studies include the North Atlantic near Bermuda (Bermuda Testbed Mooring) and coastal waters off the east coast of the United States. Phenomena including eddies, fronts, internal waves, sediment resuspension, and ocean response to hurricanes have been captured during these studies. The relations among physical, biological, and optical properties and processes are being explored and modeled using these data sets.
P15/W/01-B3 1000
MEASUREMENTS AND MODELS OF THE BACKWARD SCATTERING COEFFICIENT
Robert A. MAFFIONE (Hydro-Optics, Biology, and Instrumentation Laboratories, 55 Penny Lane, Watsonville, CA 95076, email: maffione@hobilabs.com)
The backward-scattering coefficient, bb, has historically been one of the most undersampled ocean-optical properties. Yet it is a key optical parameter for ocean-color remote sensing and underwater visibility. Due to the difficulty in measuring bb, most investigators have resorted to modeling it based on other optical parameters which can be measured and on chlorophyll concentration. Now, with the availability of new instrumentation, namely the HydroScat backscattering sensors, bb can be easily and accurately measured at selected wavelengths across the visibile spectrum. How bb is measured with the HydroScat will be presented, along with results from a number of cruises in coastal waters around the east and west coasts of the United States. Results include not only spectral measurements of bb, but also concomitant measurements of the spectral absorption and beam attenuation coefficients, remote-sensing reflectance, chlorophyll concentration, and particle size distributions. These results were used to both test published models involving bb, and to derive new models based on more complete data set than has historically been available.
P15/W/03-B3 1025
BIO-OPTICAL INVESTIGATION OF THE AMAZON OUTFLOW REGION IN DIFFERENT SEASONS
Eugeny Afonin, Alexey MISHONOV, (Marine Hydrophysical Institute, 2 Kapitanskaya St., 335000, Sevastopol, Ukraine, e-mail: mishonov@alpha.mhi.iuf.net); Oleg Yunev (Institute of Biology of the Southern Seas, 2 Nakhimov Ave., 335011, Sevastopol, Ukraine, e-mail: yunev@ibss.iuf.net); Bob Williams (Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH, United Kingdom, e-mail: bw@ccms.ac.uk).
A large data set of bio-optical parameters: upwelling radiation spectra, Secchi disk depth, colour of the seawater and concentration of phytoplankton pigments was obtained in the western tropical Atlantic during three expeditions of the RV Akademik Vernadsky (36th, 37th & 41st cruises). Research was carried out during different seasons (spring, summer & autumn) and against a background of different hydrographic situations. The region where the Amazon water mixes with oceanic water produces a wide variety of conditions in optical, biological and hydrographic properties. Remotely sensed seawater colour data for this region, obtained from CZCS and SeaWIFS sensors, were analysed to build up pictures of seasonal patterns. These patterns were correlated against ship collected spectrophotometer data and parameters measured in-situ in the three seasons. Measurements were taken of water transparency, chlorophyll concentration, number & biomass of the phytoplankton cells. These data were obtained from surface samples simultaneously together with hydrographic data. Changes in water colour in frontal zones were investigated and described.
P15/L/26-B3 1110
PARTICULATE ABSORPTION VARIABILITY IN THE ARABIAN SEA DURING BRITISH AND US JGOFS CRUISES
C.C. TREES (Center for Hydro-Optics & Remote Sensing, San Diego State University, 6505 Alvarado Rd., Suite 206, San Diego, CA 92120, ctrees@chors.sdsu.edu); J. Aiken (Plymouth Marine Laboratory, Prospect Place, Plymouth, United Kingdom); R. Bidigare (Department of Oceanography, University of Hawaii, Honolulu, HI 96822); J. Marra (Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964)
Bio-optical properties were measured in the Arabian Sea and the Gulf of Oman during two British and five US JGOFS cruises (August 1994 to December 1995). Remote sensing algorithms have been developed relating water-leaving radiance ratios to diffuse attenuation coefficients, HPLC measured pigments and particulate absorption coefficients. Pigment specific total particulate and phytoplankton absorptions, when normalized to HPLC measured chlorophyll a, showed no spatial or temporal trends, indicating that the 'pigment packaging effect' is minimal. The variability in the pigment specific absorption coefficient is so large that for primary productivity modelling efforts, the use of a constant coefficient is probably not appropriate
for this region.
P15/L/22-B3 1135
ACTIVE IMAGING THROUGH TURBID WATER USING POLARIZED LIGHT
J G WALKER, P C Y Chang, E Jakeman K I Hopcraft, B Ablitt, (University of Nottingham, University Park, Nottingham, NG7 2RD, UK) D L Jordan and G D Lewis (Defence Research Agency, Malvern, Worcestershire WR14 3PS, UK)
Results are presented of a Monte Carlo study of the influence of using polarising optics in underwater imaging. The study considers a number of single-ended illumination and imaging geometries. The study is concerned with active illumination systems and considers both linear and circular polarisation illuminations. The simulation tracks the propagation of the light through the multiply scattering medium and rigorously calculates the Stokes vectors describing the polarisation state of each ray as it propagates. Results are presented for three types of scattering particles; spherical Rayleigh particles, non-spherical Rayleigh particles and spherical Mie particles. The object is treated as a planar diffuse reflector with various polarisation properties; namely, a target which preserves the incident polarisation state and a target which randomises the polarisation state of the light it scatters. The results clearly indicate that the effectiveness of polarisation discrimination in active-illumination imaging systems in overcoming the effects of light scattering are critically dependent on the polarisation properties of the surface to be imaged as well as those of the scattering medium.
Presiding Chair: Andre Morel
RADIATIVE TRANSFER AND BIO-OPTICAL MODELLING
P15/L/28-B3 Invited 1200
APPARENT OPTICAL PROPERTIES AND LAMBERT-BEER’S LAW, A NEW THE ORETICAL APPROACH
Robert MAFFIONE (Hydro-Optics, Biology, and Instrumentation Laboratories, 55 Penny Lane, Watsonville, CA 95076, email: maffione@hobilabs.com)
In the development of simplified radiative transfer or bio-optical models, a common approach is to apply the so-called Lambert-Beer's law to diffuse attenuation coefficients, usually referred to as apparent optical properties (AOP's). The diffuse attenuation coefficients are therefore treated as a linear sum of the individual attenuation coefficients of the various constituents of sea water. It is straightforward to show that this is theoretically incorrect, although this approach is thought to be a fairly good approximation. However, there is also a problem with the interpretation of the constituent attenuation coefficients that seems to have been overlooked. By a proper redefinition of the constituent attenuation coefficients, given here, a more useful interpretation arises and, moreover, the Lambert-Beer's law is shown to apply in a completely consistent mathematical fashion. Other useful mathematical results from this redefinition are described.
Wednesday 28 July PM
Presiding Chair: Andre Morel
RADIATIVE TRANSFER AND BIO-OPTICAL MODELLING
P15/W/02-B3 1400
USING ANALYTICAL OPTIC CHANGES PREDICTIONS OF PLANKTON DEMOGRAPHY
Liu Cheng-Cheng (Huxley School, Imperial College, London SW7 2BP email: c.c.liu@ic.ac.uk); John Woods (Huxley School, Imperial College, London SW7 2BP email: j.woods@ic.ac.uk)
We report the first successful use of the Radiative Transfer Equation (RTE) to compute the irradiance profile interactively in a plankton ecosystem model. We have done so by incorporating a modified version of the analytical Hydrolight code (Mobley 1994) into the WB plankton ecosystem model (Woods and Barkmann 1994), which previously followed normal practice in using an empirical code (Morel 1988) to compute the vertical distribution of solar irradiance. When integrated by the Lagrangian Ensemble method (Woods and Barkmann 1994) the model simulates the demographies of explicit populations of diatoms and copepods treated as individuals. We have compared the annual cycle of those demographies in simulations based on the two optical methods: analytical and empirical. The former simulates BOFS (Lowry and Cramer 1994) data much better than the latter. However, the empirical code provides a good first order simulation of the annual cycle in plankton demography. Compared with the empirical method, the analytical method predicts that the peak of the spring bloom in phytoplankton occurs 10 days later, and that copepod reproduction is 15% lower. Analytical optics provides a better prediction of satellite observations of the spring bloom.
P15/W/06-B3 1420
MODELLING THE SPECTRAL ALBEDO OF THE SEA JUST ABOVE THE WATER SURFACE FOR DIFFERENT TROPHIC TYPES OF CASE I WATERS.
Slawomir B. WOZNIAK (Institute of Oceanology, Polish Academy of Sciences (PAS), ul.Powstancow Warszawy 55, Sopot, PL 81-712, Poland, email: woznjr@iopan.gda.pl)
A theoretical spectral model for calculating albedo of the sea just above the surface is developed. Model takes into account a part of irradiance reflected from the sea surface, as well as a part of irradiance scattered backward in the water body. As a 'surface part' of the model the previously developed model of downwelling and upwelling irradiance reflectance from and transmittance through a wind-ruffled sea surface was used. As an 'underwater part' of the model the theoretical formulae for distribution of radiance just below the sea surface (quasi single scattering model) and semi-empirical spectral model of absorption and backscattering were used. Based on the mathematical apparatus of the model the numerical calculations for different meteorological and hydrodynamic conditions and different trophic types of water were performed. Selected parts of calculations containing complex spherical integration were approximated with the polynomial functions. That procedure enabled to develop the simplified polynomial method for estimating the values of the albedo of the sea.
P15/E/03-B3 1440
DETERMINATION OF INHERENT OPTICAL PROPERTIES FROM SEAWIFS IMAGES
Gerald MOORE (CCMS, Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK,
email: G.Moore@CCMS.AC.UK); Jim Aiken (Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK, email: J.Aiken@CCMS.AC.UK)
Models that invert inherent optical properties (IOPs) from satellite observations of reflectance provide an important intermediate stage in deriving remote sensed products that can be tuned for regional optical properties. The spectral reflectance derived from satellite observations in dependant on the absorption (a) and backscatter (bb) of the water itself, the a and bb of the biogeochemical constituents of the water column, the solar illumination and viewing geometry. Results from the Atlantic Meridional Transect (AMT) cruises and other published studies indicate that a and bb are highly constrained by the biogeochemistry. These biogeochemical constraints on the IOPs have been used to develop a model that can be solved by an interative procedure to determine the IOPs of both Case I and Case II waters, from measurements of above and below surface radiance reflectance, and irradiance reflectance. The effects of the viewing geometry are resolved by using discrete optical models for each viewing geometry. The procedure thus accounts for the BDRF effects on reflectance and enables the determination of the true normalised water reflectance and the diffuse attenuation coefficient.
Results are shown for SeaWiFS imagery concurrent with the AMT-6 and AMT-6B cruises. Results from the model are validated against in-situ absorption, bio-optical measures and HPLC pigment analysis.
P15/L/19-B3 1500
BIO-OPTICAL MODELLING IN THE GULF OF AQABA (EILAT)
L. SOKOLETSKY, Z. Dubinsky, N. Stambler, D. Iluz and M. Shoshany (Bar-Ilan University, 52900 Ramat-Gan, Israel tel.: 972-3-5340856, 972-3-5358283; e-mail: sokolel@mail.biu.ac.i)
According to recently carried out Monte-Carlo simulations of H. R. Gordon and co-workers, four factors influence the upwelling radiance beneath the sea surface (Lu): the downwelling irradiance (Ed), the attenuation coefficient of Ed(Kd), the backscattering coefficient (bb) and the solar zenith angle beneath the sea surface (tetaw). We examine these factors on the basis of statistical processing of measured marine and atmospheric optical characteristics and of chlorophyll a (Chl a) and pheophytin concentrations, during the period 1990-1998 in the Gulf of Aqaba (Eilat) at different layers. We show that Lu is: (1) proportional to Ed; (2) decreases slowly with increase in Kd; (3) does not have a significant connection with bb and tetaw. Simple relationships between Kd, Ed and Luat the wavelength of 443 nm were obtained. Analogous, highly significant relationships between Chl a and these optical characteristics were also established. Our regional results, validated by us from ground-truth data for the northern Red Sea, will be compared with the global multichannel relationships used today by satellite sensors, such as SeaWiFS. Our aim will be to develop an optimal algorithm in term of precision and simplicity to suit the seasonally variable meso-oligotrophic waters under investigation.
DISCUSSION 1520
Presiding Chair: Ray Smith (Institute for Computational Earth System Science (ICESS) University of California, USA)
REMOTE SENSING, CALIBRATION, VALIDATION,
INTERPRETATION AND METHODOLOGY
P15/L/29-B3 Invited 1550
CAN REMOTELY SENSED MEASUREMENTS PROVIDE ALL THE VARIABLES REQUIRED FOR OCEANIC CARBON CYCLE MODELS?
Jim AIKEN (Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK,
email: J.Aiken@CCMS.AC.UK)
Biological production drives all the processes in the ocean which relate to natural resources, fisheries and the sustainability of ecosystems and the air-sea exchange of biogenic gases, which are implicated in or responsive to the role of the oceans in the natural and anthropogenically forced green house effect and global climate change. A holistic approach, coupling large-area satellite remotely sensed observations of the marine environment, with oceanographic measurements of process rates and parameter values for models is a widely accepted approach for biological oceanography. Models can be used with remote sensing data, to extrapolate the in situ measurements horizontally to ocean basin scales and vertically to sub-surface layers, not measured by most remote sensors in space. Ultimately models will be used to predict the effects of pelagic primary production on the global biosphere and the responses of oceanic ecosystems to climate change.
Recent innovations of new measurements of phytoplankton photosynthetic parameter values (by Fast Repetition Rate Fluorometry, FRRF), new ocean colour sensors (SeaWiFS) and novel analytical bio-optical models have advanced the prospects for improved accuracy of basin scale productivity and carbon-cycle models. The models will be discussed, the availability of remotely sensed data assessed and the extrapolation to sub-surface layers considered.
P15/W/05-B3 1630
SATELLITE SENSING AND IN-SITU VALIDATION OF OCEANIC WATERS OF WESTERN AUSTRALIA
Peter RCS FEARNS, James E Davies, Mervyn J LYNCH (Remote Sensing and Satellite Research Group, School of Physical Sciences, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia); Wilma J Vincent (School of Environmental Biology, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia); Alan F Pearce (CSIRO Marine Laboratories, PO Box 20 North Beach WA 6020, Australia)
Curtin University researchers, in association with scientists from the CSIRO Marine Research and Fisheries Western Australia, have been conducting in situ validation of remotely sensed ocean colour products off Perth, Western Australia. On a monthly basis over a 27-month period, numerous biological and physical measurements have been made along a 40 km transect west of Hillarys Marina (20 km north of Perth). The 1997 launch of the ocean color sensor SeaWiFS (Sea-viewing Wide Field-of-view Sensor) provided remotely sensed ocean products coincident with in situ measurements along the Hillarys transect between November 1997 and December 1998.This paper presents a review of the in situ validation measurements of chlorophyll concentration, phytoplankton species counts, sea surface temperature (SST), temperature profiles, salinity profiles, and comparisons with satellite derived chlorophyll and SST measurements.
P15/W/07-B3 1650
HANDLING, PROCESSING AND FIRST INTERPRETATION OF SeaWIFS DATA IN THE GEOSONAR PROJECT.
T. KNUDSEN, N. F. Carlsen, O. B. Andersen, and P. Knudsen (all at National Survey and Cadastre, Copenhagen NV, Denmark, email: thk@kms.dk); A. A. Nielsen, K. B. Hilger (both at IMM, Technical Uiversity of Denmark, Lyngby, Denmark)
The interdisciplinary project GEOSONAR (funded by the Danish Earth observation programme) analyses multi-disciplinary contributions to sea level and its variations on different time scales. This includes geodetic, oceanographic and meteorological effects on sea level, focussed in the North Atlantic and particularly the North Sea. In addition to traditional geodetic remote sensing techniques, such as altimetry, this project also involves the use of multi-channel scanning radiometers data, in the visible and infrared wavelengths. Data have been obtained from the Sea-viewing Wide Field-of-view Sensor (SeaWIFS), as well as from the NOAA advanced very high resolution radiometer (AVHRR), and the ERS along track scanning radiometer (ATSR). The results of a new handling and enhanced cloud removal scheme for SeaWIFS data is presented and the results are compared with data processed using the existing cloud removal scheme. This new cloud removal technique is based on maximum auto-correlation factors analysis (MAF). Extracting geodetic and oceanographic signal from these merged multi-channel data sources is non-trivial, however, the MAF analysis tool has also proven to valuable in the processing and initial interpretation of the data.
P15/W/08-B3 1710
SEASONAL BLENDED IN-SITU AND REMOTELY-SENSED OCEAN CHLOROPHYLL CLIMATOLOGIES
M.E. CONKRIGHT (NOAA/NODC, Ocean Climate Laboratory E/OC5, 1315 East-West Highway, Silver Spring, MD, 20910, USA, Email: mconkright@nodc.noaa.gov.W.W. Gregg (NASA/GSFC, Laboratory for Hydrospheric processes, Greenbelt, MD, USA, Email: gregg@cabin.gsfc.nasa.gov)
We have developed global seasonal climatologies of ocean chlorophyll, through the blending of in situ data (NOAA/NODC archives) and remotely-sensed data (NASA/GSFC archives) using the Conditional Relaxation Analysis Method. Blending of in situ chlorophyll and satellite remotely-sensed provides us with an enhanced data set by maximizing the strengths of each observational platform. Satellite chlorophyll data provide large horizontal coverage and improved temporal resolution but poor accuracy whereas in-situ data provide high quality (accuracy) but poor spatial and temporal coverage.
We focus on historical data from the Coastal Zone Color Scanner (CZCS) era (1978-1986), since sufficient in situ data are available for this time period. Differences between the blended and CZCS seasonal chlorophyll climatologies are observed primarily in coastal regions for all seasons. The blended climatologies are higher in these areas than the satellite data. These differences may have several sources, including time mismatches, sampling bias, and interannual variability. As data become available from satellites (e.g., from the Ocean Color and Temperature Scanner and Sea-Viewing Wide Field-of-View Sensor), and corresponding in-situ data are obtained, these methods will be expanded to produce a long-term blended data set encompassing the years 1978-1986 (years when CZCS was operational) and 1997-2002 (the period for which ocean color mission data are expected to be available.
P15/L/24-B3 1730
DERIVING BATHYMETRY FROM HYPERSPECTRAL DATA
W. D. PHILPOT (email: wdp2@cornell.edu, Cornell University, 220 Hollister Hall, Ithaca, NY 14853); and D.D. Kohler (email: ddk6@cornell.edu, Cornell University, 220 Hollister Hall, Ithaca, NY 14853)
Deriving bathymetric maps from passive remotely sensed imagery is an appealing prospect, but one that is prone to large errors and uncertainties. The advent of hyperspectral imagery raises the possibility of deriving more accurate bathymetric maps. Greater accuracy may be possible using standard analysis procedures but optimizing solutions using the greater number of spectral bands. It is more likely that new analysis procedures based on the spectral content of the data will yield greater accuracy in depth estimates as well as providing some information as to water quality and bottom reflectance. A new procedure that does take this extra information into account has been developed. The technique which is based on the use of spectral derivatives, significantly improves the accuracy of the depth estimates in test data. The technique is being adapted for use with hyperspectral image data.
DISCUSSION 1750
Thursday 29 July AM
Presiding Chair: Ray Smith (Institute for Computational Earth System Science (ICESS) University of California, USA)
REMOTE SENSING, CALIBRATION, VALIDATION,
INTERPRETATION AND METHODOLOGY (Continued)
P15/E/01-B4 0900
ATMOSPHERIC CORRECTION OF SEAWIFS IMAGERY OVER HIGHLY TURBID CASE II WATERS.
Samantha LAVENDER (CCMS, Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK, email S.Lavender@CCMS.AC.UK); Gerald Moore (CCMS, Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK, email G.Moore@CCMS.AC.UK)
The successful exploitation of remotely sensed observations of water colour requires the development of atmospheric correction methods in coastal waters, and the determination of the concentration of suspended particulate matter (SPM) concentrations in gravimetric units for use in mass flux studies and hydrodynamic models. The remote sensing of turbid waters (Case II) using SeaWiFS requires new approaches for the atmospheric correction of the data. Unlike open ocean waters (Case I) there is significant water leaving radiance at infrared wavelengths, so conventional ‘dark pixel’ atmospheric correction procedures are invalid. A coupled hydrological atmosphere model is described that solves the water leaving radiance and atmospheric path radiance in the near infra-red (NIR) over Case II turbid waters. The theoretical basis of this model is described, together with its implementation in the current CCMS/PML processing architecture called the SeaWiFS Automated data processing system (SeaAPS). SeaAPS and the resulting products are being validated using both in-situ measurements of water-leaving radiance and suspended particulate matter, in collaboration with European research projects. This research is an important step in deriving biogeochemical parameters for turbid Case II waters.
P15/L/21-B4 0925
ESTIMATION OF AEROSOL PROPERTIES FROM OCTS AND POLDER DATA FOR OCEAN COLOR REMOTE SENSING
Yasushi MITOMI (1), Riko HIGUTCH (1), Hajime FUKUSHIMA (2), and Tamio TAKAMURA (3).
(1) Remote Sensing Technology Center of Japan , Roppongi First Bldg. 8F, 1-9-9, Roppongi, Minato-ku, Tokyo 106-0032, Japan, Email: mitomi@restec.or.jp, hriko@restec.or.jp
(2) School of High-Technology for Human Welfare, Tokai University, 317 Nishino, Numazu 410-0395, Japan, Email: hajime@fksh.fc.u-tokai.ac.jp
(3) Center for Environmental Remote Sensing, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
The atmospheric correction in ocean color remote sensing seeks to retrieve the water leaving radiances from the total radiances observed at satellite altitude. Its accuracy depends on the estimation error of the radiance scattered and absorbed by aerosol which is highly variable in both space and time. ADEOS/OCTS has three observation bands (670, 765, and 865nm) in the near-infrared region to measure aerosol properties (eg., aerosol type and optical thickness) and the radiances at 670 and 865nm are used to generate NASDA's OCTS ocean color productrs. POLDER onboard ADEOS together with OCTS has the aerosol observation bands similar to the OCTS and also has multi-angle polarization data, but its spacial resolution (7km * 6km) is inferior to the OCTS (700m at nadir). In this research, the aerosol informations derived by OCTS and POLDER were compared. Furthermore, an estimation method of the aerosol properties by the composite data from the two different sensors was discussed in order to improve an accuracy of the atmospheric correction. These results are reported in this presentation.
Presiding Chair: John Cullen (Center for Environmental Observation Technology and Research, Department of Oceanography, Nova Scotia Canada,)
PRIMARY PRODUCTION AND BIOGEOCHEMICAL FLUXES
P15/L/30-B4 Invited 0950
PRIMARY PRODUCTION FROM NEW SATELLITE OCEAN COLOUR SENSORS
André Morel and David Antoine
Based on a spectral light-photosynthesis model, previously operated in conjunction with the CZCS imagery, the primary production at global (and basin) scales has been derived from SeaWIFS data, namely from the monthly composites of the chlorophyll distribution, and over a period of one year. Climatological fields of temperature and mixed layer depth have been utilised for the derivation. The actual cloudiness fields, contemporaneous of the SeaWIFS data capture are not yet available, so that the climatological cloudiness fields (ISCCP data base, for the 1983-1990 period , previously used with the CZCS data) were again used to estimate the incident irradiation at the ocean surface, which is an input for the model.
Therefore the difference between the primary production estimates based on the data delivered by the two sensors (CZCS and SeaWIFS) can only originate from differences in the chlorophyll fields and in their temporal evolutions. The excellent consistency between the chlorophyll determinations made by the two sensors leads to an excellent agreement between the derived annual primary production at global and basin scales, despite slightly differing temporal evolution (in Pacific, in particular). Chlorophyll data from the OCTS instrument are also transformed in the same way into primary production maps, for a 8 months period, prior to the launch of the SeaWIFS instrument. A more realistic and accurate comparison between these results will be possible as soon as the actual cloudiness distribution for the involved periods are available. Sensitivity analyses effected with the model allow to predict that replacing an « academic » cloud field by an actual one will not entail large differences in terms of production.
P15/W/04-B4 1055
STATISTICAL RELATIONSHIPS BETWEEN LIGHT CONDITIONS IN THE SEA AND PHOTO-PHYSIOLOGICAL CHARACTERISTICS OF MARINE ALGAE.
Bogdan WOZNIAK (1,2), Jerzy Dera (1), Dariusz Ficek (2), Roman Majchrowski (2), Slawomir Kaczmarek (1), Miroslawa Ostrowska (1), Olga J. Koblentz-Mishke (3).1) Institute of Oceanology, Polish Academy of Sciences (PAS),ul. Powstancow Warszawy 55, Sopot, Poland, PL 81 -712,
e-mail: wozniak@iopan.gda.pl 2) Institute of Physics, Pedagogical University in Slupsk,ul Arciszewskiego 22, Slupsk, Poland, PL 76 – 200 3) Shirshov Institute of Oceanology, Russian Academy of Sciences (RAS),ul. Krasikova 23, Moscow, Russia 117218.
Due to photo- and chromatic - acclimation processes of phytoplankton cells the light conditions in the sea affect the particular photosyntetic and photoprotecting pigments contents in marine phytoplankton cells. It is manifested in diversity of spectral absorption properties of phytoplankton and has also indirect influence on quantum yield of photosynthesis. The aim of this work is to find relationships between spectral composition and absolute level of the PAR irradiance in the sea and photophysiological characteristic of algae. This aim was achieved with statistical analysis of appropriate data sets from a few hundred stations from the world oceans. As a result the model which allows to estimate as follow: the phytoplankton pigments composition, the light absorption coefficient for all pigments and its components from photosynthetic and photoprotecting pigments for the given light conditions in the sea, was worked out. This model also allows to determine variability of quantum yield of photosynthesis due to changes in proportions between photosynthetic and photoprotecting phytoplankton pigments.
P15/W/09-B4 1115
MODELLED AND MEASURED PRIMARY PRODUCTION DISTRIBUTION IN THE BALTIC
Slawomir Kaczmarek (1), Miroslawa Ostrowska (1), Olga J. Koblentz-Mishke (2), Bogdan Wozniak (1). 1) Institute of Oceanology, Polish Academy of Sciences (PAS), ul. Powstancow Warszawy 55, Sopot, Poland, PL 81 -712, e-mail: kaczmar@iopan.gda.pl. 2) Shirshov Institute of Oceanology, Russian Academy of Sciences (RAS), ul. Krasikova 23, Moscow, Russia 117218.
The results of primary production modelling for the Baltic Sea, which is typical case 2 waters basin, are presented. Earlier established, the bio-optical relationships for oceanic case 1 water were a base of a primary production model. Using the empirical data gathered from the Baltic Sea the model's parameters were adopted to obtain a model appropriate for the Baltic. This model was used to estimate primary production in the Southern Baltic region, divided into 20 sub-regions. The mean monthly primary production have been calculated for each month of the year. As the model input data, the long-term (over 20 years) monthly means of hydro-meteorological parameters and surface chlorophyll a concentration have been used. The model results were compared with the map of yearly primary production obtained after analyses of long-term "in situ" measured data. Both data sets relate to the same period. Such comparison allows discuss the advantages and limitations of the primary production bio-optical modelling especially in the context of remote sensing data assimilation.
P15/E/04-B4 1135
DETERMINATION OF PHYTOPLANKTON PHOTOSYNTHETIC CHARACTERISTICS AND PRODUCTION FROM REMOTE SENSED REFLECTANCE.
Gerald MOORE (CCMS, Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK,
email: G.Moore@CCMS.AC.UK); Jim Aiken (Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK, email: J.Aiken@CCMS.AC.UK)
Currently available remote sensed algorithms supply information in terms of biomass normalised to chlorophyll concentration. In addition, these algorithms implicitly fix the spectral shape of the absorption characteristics of phytoplankton, by using simple band ratios, and assume that optically active dissolved organic material (ODOM) is a fixed proportion of phytoplankton absorption. The use of an algorithm that inverts remote sensed reflectance to the IOPs of spectral absorption (a) and backscatter (bb) enables the determination of the major pigment classes chlorophyll, photosynthetic carotenoids, photoprotectant carotenoids, and co-varying ODOM concentration.
The results from the optical model have been used to differentiate the rate of phytoplankton photosynthetic pigment absorption from non-photosynthetic absorption, and thus derive production estimates based on fixed quantum yield.
The absorption model measurements are compared with data from the Atlantic Meridional Transect (AMT) cruise using in-situ absorption and simulated absorption derived HPLC pigment concentrations. The production estimates are compared with 14C measurements taken on the AMT-6 cruise. Production maps of the AMT cruise region are computed from data from the SeaWiFS sensor.
DISCUSSION 1155
P15/L/01-B4 Invited 1205
PRIMARY PRODUCTIVITY OF THE WESTERN ANTARCTIC PENINSULA REGION AND THE SOUTHERN OCEAN
Raymond SMITH & Heidi Dierssen (Institute for Computational Earth System Science (ICESS); University of California, Santa Barbara, CA, 93106, USA, email: ray@icess.ucsb.edu, dierssen@icess.ucsb.edu); Karen Baker & Maria Vernet (Scripps Institution of Oceanography(SIO/MRD); University of California, San Diego, La Jolla, CA 92093-0218, USA,
email: kbaker@ucsd.edu, mvernet@ucsd.edu)
Phytoplankton production in the Southern Ocean is poorly known compared to temperate ecosystems. The relative inaccessibility, paucity of data, large area, extreme environmental conditions, and the potential role of the Southern Ocean carbon cycle in response to rising atmospheric CO2 are compelling reasons for optimizing models for the estimation of phytoplankton production remotely. Further, there is now strong evidence that the bio-optical roperties of these Antarctic waters are significantly different than temperate waters. Consequently, both the retrieval of chlorophyll concentrations and the subsequent estimation of phytoplankton production from satellite sensed reflectance measurements require regional specific algorithms for optimum accuracy. Based upon data from the Palmer Long Term Ecological Research (PAL/LTER) program we have optimized retrieval algorithms and utilized a depth-integrated primary productivity model to estimate biomass and productivity in Antarctic waters. Poductivity results are compared with previous published estimates and sensitivity studies evaluated. The space-time distribution and the seasonal and interannual variability are discussed within the context of contribution to the overall Southern Ocean marine ecology.
Thursday 29 July PM
Presiding Chair: Tom Dickey (University of California at Santa Barbara, Goleta, CA, USA)
UV RADIATION MEASUREMNENTS AND ECOLOGICAL
CONSEQUENCES
P15/L/18-B4 1400
ESTIMATING UV ATTENUATION AND PHOTOCHEMICAL REACTION RATES FROM REMOTE SENSING OF OCEAN COLOR
John J. CULLEN, Richard F. Davis, Barbara Nieke (all at Center for Environmental Observation Technology and Research, Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada, Email: John.Cullen@Dal.ca, Richard.Davis@Dal.ca, bnieke@raptor.ocean.dal.ca), Sophia Johannessen and William L. Miller (both at Department of Oceanography, Dalhousie University, Email: schjohan@is2.dal.ca, William.Miller@Dal.ca).
Previously, we outlined a method for using measurements of upwelling radiance in the visible to quantify UV-dependent processes in aquatic systems: 1) attenuation coefficients for UV and visible irradiance are estimated from spectra of upwelling radiance at the surface, based on empirical relationships between ratios of upwelling radiance and near-surface diffuse attenuation coefficients; 2) total absorption is related to attenuation by accounting for geometry of the radiance field; 3) total absorption is partitioned among colored dissolved organic matter (CDOM; essential to photochemistry), water, and particulate matter using published coefficients for water, estimates of chlorophyll from blue:green reflectance ratios, and assumed chlorophyll-specific particulate absorption spectra; 4) solar irradiance at the surface is calculated from a model, tuned with observations from a filter-based radiometer; and 5) laboratory-derived action spectra, modeled irradiance, and estimated CDOM vs total absorption are used to quantify rates of photochemical transformation. In principle, this approach can yield synoptic estimates of photochemistry from airborne sensors. Here, we parameterize the model with recently obtained data from several marine environments, along with an action spectrum for photochemical production of carbon monoxide from CDOM, to estimate the photochemical production of CO using aircraft remote sensing of ocean color. The precision of key empirical relationships (e.g., between diffuse attenuation coefficients in the UV and ratios of upwelling radiance in the visible) is assessed, and the uncertainty of estimates is partially described.
P15/E/05-B4 1445
PENETRATION OF UVB IRRADIANCE INTO THE NORDIC SEAS AND ADJACENT COASTAL WATERS
Eyvind AAS (Department of Geophysics, University of Oslo, N-0315 Oslo, Norway,
Email: eyvind.aas@geofysikk.uio.no); Niels K. Hoejerslev (Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen, DK-2100 Copenhagen O, Denmark, Email:nkh@gfy.ku.dk)
Data for downward UVB irradiance at about 200 stations in the Nordic Seas and the adjacent coastal waters have been analysed. The depth where the irradiance is reduced to 10% of its surface value, Z(10%), ranges from 0.1 to 16 m. For comparison very clear ocean water (Gulf of Mexico) has a Z(10%) value around 35 m. In the German Bight the mean value of Z(10%) is 0.8 m, in the Kattegat 0.9 m, and in the Skagerrak 2.5 m. In the Norwegian Coastal Current the observed mean value is 4.6 m, while the mean values of Z(10%) in Svalbard waters have been observed to be either 5 or 10 m, depending on season. The Norwegian Atlantic Current has the mean value 15 m during non-bloom conditions, but phytoplankton blooms seem to be able to reduce Z(10%) by a factor of up to 3. Yellow substance, suspended organic and inorganic matter all contribute to the variation of Z(10%) in highly different proportions depending on both location and season. Solar elevations have a minor effect on Z(10%) according to the measurements performed in the region considered. Finally, penetration of UVB irradiance in waters dominated by yellow substance is not straightforward to model based on spectral irradiance measurements in the visible part of the spectrum. This is due to the fact that the spectral absorbance of yellow substance is much more complex than previously and traditionally anticipated.
P15/L/16-B4 1505
SEASONAL VARIABILITY IN THE RELATIVE PENETRATION OF UVR AND PAR IN TEMPERATE COASTAL WATERS
KUWAHARA, V. S.1, H. Ogawa2, T. Toda1, T. Kikuchi3, S. Taguchi1; (Faculty of Engineering, Soka University1; Faculty of Ocean Research, Tokyo University2; Faculty of Education and Human Sciences, Yokohama National University3)
Seasonal UVR penetration variability was surveyed for three consecutive years in the temperate coastal waters of Sagami Bay, Japan. Integrated mixed layer samples of sea- water were concurrently collected for chlorophyll a analysis. Dissolved organic carbon (DOC), particulate organic carbon (POC), and the absorption coefficient of the dissolved (acDM) and particulate material (acPM) were also measured during one year. The 1% attenuation depth of 305, 320, 340 and 380nm calculated from the diffuse attenuation coefficient (Kd) averaged 11.4Å}6.34, 14.06Å}8.30, 18.68±10.90, and 29.81Å}15.79m, respectively for the three years with minimum penetration occurring near summer solstice. Breaks in the slopes of Kd (multiple Kd patterns) were also observed during particular summer months for 340nm, 380nm, and PAR. The relative penetration of UVR into the euphotic zone (1% penetration depth of PAR) averaged 19Å}9% for 305nm, 24Å}11% for 320nm, 32Å}14% for 340nm, and 49Å}20% for 380nm accordingly. Seasonal variability in UVR transparency was attributable to changes in concentrations of DOC, Chl a, and POC. This was further supported by results from the acDM and acPM analysis. The percent contribution of acDM and acPM varied with season.
DISCUSSION 1525
P15/L/17-B4 1550
FLUX OF CARBONYL SULFIDE FROM THE OCEANS USING SEAWIFS CHLOROPHYLL CONCENTRATION ESTIMATESA.
J. KETTLE, T. S. Rhee, M. V. Hobe, and M. O. Andreae (Biogeochemistry Department,
Max Planck Institute for Chemistry, P. O. Box 3060, D-55020 Mainz, Germany,
email: ajkettle@mpch-mainz.mpg.de)
Carbonyl sulfide (COS) is a long lived atmospheric molecule which is oxidized in the stratosphere to sulfate particles which may alter the radiation budget of the earth’s surface. One of the more important sources of COS is the upper ocean where it is produced photochemically as the result of the interaction of solar ultraviolet light with colored dissolved organic matter. The principal sinks of the molecule from the oceanic mixed layer are hydrolysis and surface outgassing to the atmosphere. The interaction between the production and loss terms controls the flux of the molecule to the atmosphere. The recent meridional transect of the James Clark Ross from England to the Falkland Islands in September-October, 1998 provided an opportunity to investigate the flux of COS to the atmosphere. During the cruise, atmospheric and sea surface concentrations of COS were measured, in addition to the ultraviolet absorbance and fluorescence of seawater, chlorophyll concentration, insolation, wind speed, and other meteorological parameters. Earlier measurements have suggested a relationship between the ultraviolet absorbance of seawater and the chlorophyll concentration. Using this relationship, it is proposed that the SEAWIFS data can be used to estimate the global CDOM absorbance. The global photochemical production of COS can then be estimated using climatological information for insolation. Using climatological temperature fields to constrain the physical hydrolysis process and climatological mixed layer depths to constrain the amount of dilution of the tracer, it is possible to develop a simple model of global COS near surface concentration and outgassing to the atmosphere.
The results of the ship expedition are used to verify the predictions of this simple model.
P15/L/05-B4 1610
RESPONSE OF BACTERIOPLANKTON TO DIFFERENT INTENSITIES OF ULTRAVIOLET-B RADIATION: A MESOCOSM STUDY
Khaled CHATILA, Serge Demers, Behzad Mostajir, Jean-Pierre Chanut (all at Groupe de Recherche en Environnement Côtier, Institut des Sciences de la Mer de Rimouski (ISMER), Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski (Québec), Canada, G5L 3A1,
email: khaled_chatila@uqar.uquebec.ca) Patrick Monfort (Laboratoire d’Hydrobiologie Marine et Continentale, Unité Mixte de Recherche "Écosystèmes lagunaires", Université Montpellier II - CNRS (UMR 5556) Case 093, F-34095 Montpellier Cedex 05, France, email: pmonfort@crit.univ-montp2.fr)
The recent decreasing trends of stratospheric ozone concentration and the subsequent increases of ultraviolet-B radiation (UVBR) reaching the Earth’s surface have raised concern about the possible impact of this radiation on aquatic ecosystems. In July 1996, the effects of excluded, natural and artificially enhanced UVBR on the summer planktonic community (<240mm) of the lower St. Lawrence Estuary (Québec, Canada) were studied during a week-long mesocosm experiment. Experimental water was continuously mixed by a pumping system. The present work was a part of this experiment and addressed the response of bacteria to the tested light regimes. Our data suggest that UVBR may have both inhibiting (by directly acting on cellular processes) and stimulating effects on bacterioplankton (by increasing the release of labile substrates from UVBR stressed phytoplankton or by decreasing cells removal by UVBR sensitive bacterivores). On an ecosystem level, overall bacterial response to UVBR will be the net result of these competing processes.
P15/L/27-B4 1630
GLOBAL MAPPING OF UNDERWATER UV FLUXES AND DNA-WEIGHTED EXPOSURES USING TOMS AND SEAWIFS DATA PRODUCTS
Alexander VASILKOV, Nickolay Krotkov (both at Raytheon ITSS Co., 4400 Forbes Blvd., Lanham, 20706 USA), Jay Herman (NASA/Goddard Space Flight Center, Greenbelt, 20771 USA)
The global stratospheric ozone layer depletion results in an increase in biologically harmful ultraviolet (UV) radiation reaching the surface and penetrating to ecologically significant depths in the natural waters. Such an increase could be estimated on a global scale by combining satellite estimates of the UV irradiance at the ocean surface from the Total Ozone Mapping Spectrometer (TOMS) satellite instrument with the satellite ocean color measurements in the visible spectral region from the SeaWiFS instrument. In this paper we propose a model of seawater optical properties in the UV spectral region based on the Case 1 water model in the visible range. The inputs of the model are standard products of ocean color sensors: chlorophyll concentration and the diffuse attenuation coefficient at 490 nm. Penetration of solar UV radiation at different depths into open ocean waters is calculated using the quasi-single scattering approximation of the radiative transfer (RT) in the water. The separation of the ocean and atmospheric RT problems in the UV spectral region is discussed. The accuracy of the RT approximation in the water is tested using accurate Monte Carlo modeling. The sensitivity study of the underwater UV irradiance to atmospheric and oceanic optical properties is performed based on the model proposed. The simulations have shown that the main environmental parameters controlling the levels of the most harmful UVB (280-320nm) radiation underwater for clear sky conditions are: solar zenith angle, water optical properties and total ozone.Weekly maps of underwater UV irradiance and DNA weighted exposure are calculated using monthly mean SeaWiFS chlorophyll a and diffuse attenuation coefficient products and the TOMS-derived surface UV irradiance weekly maps. The final products include global maps of depths, at which UVB flux and DNA weighted dose rate are equal to 10% of their surface values.
CONCLUDING DISCUSSIONS 1650