80 research outputs found
Assessing the uncertainties of model estimates of primary productivity in the tropical Pacific Ocean
Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 76 (2009): 113-133, doi:10.1016/j.jmarsys.2008.05.010.Depth-integrated primary productivity (PP) estimates obtained from satellite
ocean color based models (SatPPMs) and those generated from biogeochemical ocean
general circulation models (BOGCMs) represent a key resource for biogeochemical and
ecological studies at global as well as regional scales. Calibration and validation of these
PP models are not straightforward, however, and comparative studies show large
differences between model estimates. The goal of this paper is to compare PP estimates
obtained from 30 different models (21 SatPPMs and 9 BOGCMs) to a tropical Pacific PP
database consisting of ~1000 14C measurements spanning more than a decade (1983-
1996). Primary findings include: skill varied significantly between models, but
performance was not a function of model complexity or type (i.e. SatPPM vs. BOGCM);
nearly all models underestimated the observed variance of PP, specifically yielding too
few low PP (< 0.2 gC m-2d-2) values; more than half of the total root-mean-squared
model-data differences associated with the satellite-based PP models might be accounted
for by uncertainties in the input variables and/or the PP data; and the tropical Pacific
database captures a broad scale shift from low biomass-normalized productivity in the
1980s to higher biomass-normalized productivity in the 1990s, which was not
successfully captured by any of the models. This latter result suggests that interdecadal
and global changes will be a significant challenge for both SatPPMs and BOGCMs.
Finally, average root-mean-squared differences between in situ PP data on the equator at
140°W and PP estimates from the satellite-based productivity models were 58% lower
than analogous values computed in a previous PP model comparison six years ago. The
success of these types of comparison exercises is illustrated by the continual modification
and improvement of the participating models and the resulting increase in model skill.This research was supported by a grant from the National Aeronautics and Space Agency
Ocean Biology and Biogeochemistry program (NNG06GA03G), as well as by numerous
other grants to the various participating investigator
Inter-Annual Variability of the Seawater Light Absorption in Surface Layer of the Northeastern Black Sea in Connection with Hydrometeorological Factors
Model of the in vivo spectral absorption of algal pigments. Part 1. Mathematical apparatus
Existing statistical models of in vivo light absorption by phytoplankton (Woźniak
& Ostrowska 1990, Bricaud et al. 1995, 1998) describe the dependence of the
phytoplankton specific spectral absorption coefficient a∗
pl(λ) on the chlorophyll a concentration Ca in seawater. However, the models do not take into account the
variability in this relationship due to phytoplankton acclimation. The observed
variability in the light absorption coefficient and its components due to various
pigments with depth and geographical position at sea, requires further accurate
modelling in order to improve satellite remote sensing algorithms and interpretation
of ocean colour maps.
The aim of this paper is to formulate an improved model of the phytoplankton
spectral absorption capacity which takes account of the pigment composition and
absorption changes resulting from photo- and chromatic acclimation processes,
and the pigment package effect. It is a synthesis of earlier models and the
following statistical generalisations: (1) statistical relationships between various
pigment group concentrations and light field properties in the sea (described by
Majchrowski & Ostrowska 2000, this volume); (2) a model of light absorption by
phytoplankton capable of determining the mathematical relationships between the
spectral absorption coefficients of the various photosynthetic and photoprotecting
pigment groups, and their concentrations in seawater (Woźniak et al. 1999); (3)
bio-optical models of light propagation in oceanic Case 1 Waters and Baltic Case 2
Waters (Woźniak et al. 1992a, b, 1995a,b). The generalised model described in this
paper permits the total phytoplankton light absorption coefficient in vivo as well as
its components related to the various photosynthetic and photoprotecting pigments
to be determined using only the surface irradiance PAR(0+) surface chlorophyll
concentration Ca(0) and depth z in the sea as input data
Model of the in vivo spectral absorption of algal pigments. Part 2. Practical applications of the model
The article describes applications and accuracy analyses of a statistical model of
light absorption by phytoplankton that accounts for the influence of photo- and
chromatic acclimation on its absorption properties. Part 1 of this work (seeWoźniak
et al. 2000, this volume) describes the mathematical apparatus of the model. Earlier
models by Woźniak & Ostrowska (1990) and by Bricaud et al. (1995, 1998) are analysed for comparison. Empirical verification of these three models shows that
the new model provides a much better approximation of phytoplankton absorption
properties than do the earlier models. The statistical errors in estimating the mean
absorption coefficient apl, for example, are σ+ = 36% for the new model, whereas
for the earlier models the figures are σ+ = 43% (Bricaud et al. 1995, 1998) and
σ+ = 59% (Woźniak & Ostrowska 1990). Example applications are given of the
new model illustrating the variability in phytoplankton absorption properties with
depth and trophicity of the sea
Distinct distribution pattern of abundance and diversity of aerobic anoxygenic phototrophic bacteria in the global ocean
Book reviews: Lieth, H. and Whittaker, R. H., editors, I975: Primary productivity of the biosphere. Eco logical Studies No. I4. New York, Berlin and Heidelberg: Springer-Verlag. UK distribu tors: Chapman and Hall. viii+339 pp. $28.50 (DM 69,40)
Planktonic ecosystems. The effects of dystrophic conditions on structure and function in the gulf of fos
A depth controlled tow system for hydrographic and current measurements with applications
A simple and rapid device for measuring planktonic primary production by in situ sampling, and 14C injection and incubation
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