scholarly journals Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

2017 ◽  
Author(s):  
Thomas J. Ryan-Keogh ◽  
Sandy J. Thomalla ◽  
Thato N. Mtshali ◽  
Hazel Little
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Production Model ◽  
Photosynthetic Parameters ◽  
Atlantic Sector ◽  
Mean Values ◽  
Chl A ◽  
Biogeochemical Models ◽  
The Absolute ◽  
Iron Addition

Abstract. The Atlantic sector of the Southern Ocean is characterized by markedly different frontal zones with specific seasonal and sub-seasonal dynamics. Demonstrated here is the effect of iron on the potential maximum productivity rates of the phytoplankton community. A series of iron addition productivity versus irradiance (PE) experiments utilising a unique experimental design that allowed for 24 hour incubations were performed within the austral summer of 2015/16. The addition of iron can result in the doubling of the photosynthetic parameters αB and PBmax, with subsequent changes in Ek. Mean values for each parameter under iron replete conditions were 1.46 ± 0.55 (μg (μg Chl a)−1 h−1 (μM photons m−2 s−1)−1), 72.55 ± 27.97 (μg (μg Chl a)−1 h−1) and 50.84 ± 11.89 (μM photons m−2 s−1); whereas mean values under the control conditions were 1.25 ± 0.92 (μg (μg Chl a)−1 h−1 (μM photons m−2 s−1)−1), 62.44 ± 36.96 (μg (μg Chl a)−1 h−1) and 55.81 ± 19.60 (μM photons m−2 s−1). There were no clear spatial patterns in either the absolute values or the absolute differences between the treatments at the experimental locations. When these parameters are integrated into a standard depth-integrated primary production model across a latitudinal transect, the effect of iron addition shows higher levels of primary production south of 50° S, with very little difference observed in the sub-Antarctic and Polar Frontal zone. These results emphasize the need for better parameterisation of photosynthetic parameters in biogeochemical models around sensitivities in their response to iron supply. Future biogeochemical models will need to consider the combined and individual effects of iron and light to better resolve the natural background in primary production and predict its response under a changing climate.

scholarly journals Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

2017 ◽  
Vol 14 (17) ◽  
pp. 3883-3897 ◽  
Author(s):  
Thomas J. Ryan-Keogh ◽  
Sandy J. Thomalla ◽  
Thato N. Mtshali ◽  
Hazel Little
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Austral Summer ◽  
Production Model ◽  
Photosynthetic Parameters ◽  
Atlantic Sector ◽  
Mean Values ◽  
Biogeochemical Models ◽  
The Absolute ◽  
Iron Addition

Abstract. The Atlantic sector of the Southern Ocean is characterized by markedly different frontal zones with specific seasonal and sub-seasonal dynamics. Demonstrated here is the effect of iron on the potential maximum productivity rates of the phytoplankton community. A series of iron addition productivity versus irradiance (PE) experiments utilizing a unique experimental design that allowed for 24 h incubations were performed within the austral summer of 2015/16 to determine the photosynthetic parameters αB, PBmax and Ek. Mean values for each photosynthetic parameter under iron-replete conditions were 1.46 ± 0.55 (µg (µg Chl a)−1 h−1 (µM photons m−2 s−1)−1) for αB, 72.55 ± 27.97 (µg (µg Chl a)−1 h−1) for PBmax and 50.84 ± 11.89 (µM photons m−2 s−1) for Ek, whereas mean values under the control conditions were 1.25 ± 0.92 (µg (µg Chl a)−1 h−1 (µM photons m−2 s−1)−1) for αB, 62.44 ± 36.96 (µg (µg Chl a)−1 h−1) for PBmax and 55.81 ± 19.60 (µM photons m−2 s−1) for Ek. There were no clear spatial patterns in either the absolute values or the absolute differences between the treatments at the experimental locations. When these parameters are integrated into a standard depth-integrated primary production model across a latitudinal transect, the effect of iron addition shows higher levels of primary production south of 50° S, with very little difference observed in the subantarctic and polar frontal zone. These results emphasize the need for better parameterization of photosynthetic parameters in biogeochemical models around sensitivities in their response to iron supply. Future biogeochemical models will need to consider the combined and individual effects of iron and light to better resolve the natural background in primary production and predict its response under a changing climate.

scholarly journals Antarctic slush-ice algal accumulation not quantified through conventional satellite imagery: Beware the ice of March

2015 ◽  
Vol 9 (6) ◽  
pp. 6187-6222 ◽  
Author(s):  
J. L. Lieser ◽  
M. A. J. Curran ◽  
A. R. Bowie ◽  
A. T. Davidson ◽  
S. J. Doust ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Satellite Imagery ◽  
Large Scale ◽  
Current Knowledge ◽  
Ocean Colour ◽  
Widespread Occurrence ◽  
Chl A ◽  
Terra Nova Bay ◽  
Direct Sampling

Abstract. Our current knowledge of broad-scale patterns of primary production in the Southern Ocean is derived from satellite ocean-colour estimates of chlorophyll a (Chl a) in the open ocean, typically in spring-summer. Here, we provide evidence that large-scale intra-ice phytoplankton surface aggregation occur off the coast of Antarctica during austral autumn, and that these "blooms" are largely undetected in satellite ocean-colour time series (which mask the ice-covered ocean). We present an analysis of (i) true-colour (visible) satellite imagery in combination with (ii) conventional ocean-colour data, and (iii) direct sampling from a research vessel, to identify and characterise a large-scale intra-ice algal occurrence off the coast of East Antarctica in early autumn (March) 2012. We also present evidence of these autumn "blooms" in other regions (for example, Princess Astrid Coast in 2012) and other years (for example, Terra Nova Bay in 2015) implying regular and widespread occurrence of these phenomena. The occurrence of such undetected algal accumulations implies that the magnitude of primary production in the Southern Ocean is currently underestimated.

scholarly journals Estimation of Size-Fractionated Primary Production from Satellite Ocean Colour in UK Shelf Seas

2018 ◽  
Vol 10 (9) ◽  
pp. 1389 ◽  
Author(s):  
Kieran Curran ◽  
Robert Brewin ◽  
Gavin Tilstone ◽  
Heather Bouman ◽  
Anna Hickman
Keyword(s):  
Primary Production ◽  
Ocean Model ◽  
Open Ocean ◽  
Photosynthetic Parameters ◽  
Ocean Colour ◽  
Chl A ◽  
In Situ Data ◽  
Shelf Seas ◽  
Shelf Sea

Satellite ocean-colour based models of size-fractionated primary production (PP) have been developed for the oceans on a global level. Uncertainties exist as to whether these models are accurate for temperate Shelf seas. In this paper, an existing ocean-colour based PP model is tuned using a large in situ database of size-fractionated measurements from the Celtic Sea and Western English Channel of chlorophyll-a (Chl a) and the photosynthetic parameters, the maximum photosynthetic rate ( P m B ) and light limited slope ( α B ). Estimates of size fractionated PP over an annual cycle in the UK shelf seas are compared with the original model that was parameterised using in situ data from the open ocean and a climatology of in situ PP from 2009 to 2015. The Shelf Sea model captured the seasonal patterns in size-fractionated PP for micro- and picophytoplankton, and generally performed better than the original open ocean model, except for nanophytoplankton PP which was over-estimated. The overestimation in PP is in part due to errors in the parameterisation of the biomass profile during summer, stratified conditions. Compared to the climatology of in situ data, the shelf sea model performed better when phytoplankton biomass was high, but overestimated PP at low Chl a.

scholarly journals A skill assessment of the biogeochemical model REcoM2 coupled to the finite element sea-ice ocean model (FESOM 1.3)

2014 ◽  
Vol 7 (4) ◽  
pp. 4153-4249
Author(s):  
V. Schourup-Kristensen ◽  
D. Sidorenko ◽  
D. A. Wolf-Gladrow ◽  
C. Völker
Keyword(s):  
Finite Element ◽  
Southern Ocean ◽  
Primary Production ◽  
Net Primary Production ◽  
Global Scale ◽  
Ocean Model ◽  
Biogeochemical Model ◽  
Biogeochemical Models ◽  
The Pacific ◽  
The Pacific Ocean

Abstract. In coupled ocean-biogeochemical models, the choice of numerical schemes in the ocean circulation component can have a large influence on the distribution of the biological tracers. Biogeochemical models are traditionally coupled to ocean general circulation models (OGCMs), which are based on dynamical cores employing quasi regular meshes, and therefore utilize limited spatial resolution in a global setting. An alternative approach is to use an unstructured-mesh ocean model, which allows variable mesh resolution. Here, we present initial results of a coupling between the Finite Element Sea-ice Ocean Model (FESOM) and the biogeochemical model REcoM2, with special focus on the Southern Ocean. Surface fields of nutrients, chlorophyll a and net primary production were compared to available data sets with focus on spatial distribution and seasonal cycle. The model produced realistic spatial distributions, especially regarding net primary production and chlorophyll a, whereas the iron concentration became too low in the Pacific Ocean. The modelled net primary production was 32.5 Pg C yr−1 and the export production 6.1 Pg C yr−1. This is lower than satellite-based estimates, mainly due to the excessive iron limitation in the Pacific along with too little coastal production. Overall, the model performed better in the Southern Ocean than on the global scale, though the assessment here is hindered by the lower availability of observations. The modelled net primary production was 3.1 Pg C yr−1 in the Southern Ocean and the export production 1.1 Pg C yr−1. All in all, the combination of a circulation model on an unstructured grid with an ocean biogeochemical model shows similar performance to other models at non-eddy-permitting resolution. It is well suited for studies of the Southern Ocean, but on the global scale deficiencies in the Pacific Ocean would have to be taken into account.

scholarly journals Validation of a Primary Production Algorithm of Vertically Generalized Production Model Derived from Multi-Satellite Data around the Waters of Taiwan

2020 ◽  
Vol 12 (10) ◽  
pp. 1627
Author(s):  
Kuo-Wei Lan ◽  
Li-Jhih Lian ◽  
Chun-Huei Li ◽  
Po-Yuan Hsiao ◽  
Sha-Yan Cheng
Keyword(s):  
Primary Production ◽  
Production Model ◽  
Dark Bottle ◽  
Kuroshio Water ◽  
Chl A ◽  
Basin Scale ◽  
Mean Square Difference ◽  
The Kuroshio ◽  
China Coast

Basin-scale sampling for high frequency oceanic primary production (PP) is available from satellites and must achieve a strong match-up with in situ observations. This study evaluated a regionally high-resolution satellite-derived PP using a vertically generalized production model (VGPM) with in situ PP. The aim was to compare the root mean square difference (RMSD) and relative percent bias (Bias) in different water masses around Taiwan. Determined using light–dark bottle methods, the spatial distribution of VGPM derived from different Chl-a data of MODIS Aqua (PPA), MODIS Terra (PPT), and averaged MODIS Aqua and Terra (PPA&T) exhibited similar seasonal patterns with in situ PP. The three types of satellite-derived PPs were linearly correlated with in situ PPs, the coefficients of which were higher throughout the year in PPA&T (r2 = 0.61) than in PPA (r2 = 0.42) and PPT (r2 = 0.38), respectively. The seasonal RMSR and bias for the satellite-derived PPs were in the range of 0.03 to 0.09 and −0.14 to −0.39, respectively, which suggests the PPA&T produces slightly more accurate PP measurements than PPA and PPT. On the basis of environmental conditions, the subareas were further divided into China Coast water, Taiwan Strait water, Northeastern upwelling water, and Kuroshio water. The VPGM PP in the four subareas displayed similar features to Chl-a variations, with the highest PP in the China Coast water and lowest PP in the Kuroshio water. The RMSD was higher in the Kuroshio water with an almost negative bias. The PPA exhibited significant correlations with in situ PP in the subareas; however, the sampling locations were insufficient to yield significant results in the China Coast water.

A phytoplankton class-specific primary production model applied to the Kerguelen Islands region (Southern Ocean)

2009 ◽  
Vol 56 (4) ◽  
pp. 541-560 ◽  
Author(s):  
Julia Uitz ◽  
Hervé Claustre ◽  
F. Brian Griffiths ◽  
Joséphine Ras ◽  
Nicole Garcia ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Production Model ◽  
Kerguelen Islands

ENERGY TRANSFER EFFICIENCIES ON LOWER TROPHIC LEVELS WITH INTENSIVE OYSTER FARMING IN HIROSHIMA BAY, JAPAN

2017 ◽  
Author(s):  
Akira Umehara ◽  
Akira Umehara ◽  
Satoshi Asaoka ◽  
Satoshi Asaoka ◽  
Naoki Fujii ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Primary Production ◽  
Skeletonema Costatum ◽  
Warm Season ◽  
Nutrient Supply ◽  
Trophic Levels ◽  
Phytoplankton Primary Production ◽  
Mean Values ◽  
Hiroshima Prefecture ◽  
Study Species

In enclosed water areas, organic matters are actively produced by phytoplankton due to abundant nutrient supply from the rivers. In our study area of the semi-enclosed Hiroshima Bay, oyster farming consuming high primary production has been developed since the 1950s, and the oyster production of Hiroshima prefecture have had the largest market share (ca. 60%) in Japan. In this study, species composition of phytoplankton, primary production, and secondary production of net zooplanktons and oysters were determined seasonally at seven stations in the bay between November 2014 and August 2015. In the bay, diatoms including Skeletonema costatum dominated during the period of the study. The primary productions markedly increased during summer (August), and its mean values in the northern part of the bay (NB) and the southern part (SB) were 530 and 313 mgC/m2/d, respectively. The productions of net zooplankton and oyster increased during the warm season, and its mean values in the NB were 14 and 1.2 mgC/m2/d, and in SB were 28 and 0.9 mgC/m2/d, respectively. The energy transfer efficiencies from the primary producers to the secondary producers in the NB and SB were 2.8% and 9.1%, respectively. However, the transfer efficiency to the oysters was approximately 0.3% in the bay. This study clearly showed the spatial difference of the productions and transfer efficiencies, and the low contribution of the production of oysters in secondary productions in Hiroshima Bay.

scholarly journals Ventilation of the abyss in the Atlantic sector of the Southern Ocean

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Camille Hayatte Akhoudas ◽  
Jean-Baptiste Sallée ◽  
F. Alexander Haumann ◽  
Michael P. Meredith ◽  
Alberto Naveira Garabato ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Bottom Water ◽  
Climate Models ◽  
Deep Ocean ◽  
Analytical Framework ◽  
Weddell Sea ◽  
Global Ocean ◽  
Shelf Water ◽  
Antarctic Bottom Water ◽  
Atlantic Sector

AbstractThe Atlantic sector of the Southern Ocean is the world’s main production site of Antarctic Bottom Water, a water-mass that is ventilated at the ocean surface before sinking and entraining older water-masses—ultimately replenishing the abyssal global ocean. In recent decades, numerous attempts at estimating the rates of ventilation and overturning of Antarctic Bottom Water in this region have led to a strikingly broad range of results, with water transport-based calculations (8.4–9.7 Sv) yielding larger rates than tracer-based estimates (3.7–4.9 Sv). Here, we reconcile these conflicting views by integrating transport- and tracer-based estimates within a common analytical framework, in which bottom water formation processes are explicitly quantified. We show that the layer of Antarctic Bottom Water denser than 28.36 kg m$$^{-3}$$ - 3 $$\gamma _{n}$$ γ n is exported northward at a rate of 8.4 ± 0.7 Sv, composed of 4.5 ± 0.3 Sv of well-ventilated Dense Shelf Water, and 3.9 ± 0.5 Sv of old Circumpolar Deep Water entrained into cascading plumes. The majority, but not all, of the Dense Shelf Water (3.4 ± 0.6 Sv) is generated on the continental shelves of the Weddell Sea. Only 55% of AABW exported from the region is well ventilated and thus draws down heat and carbon into the deep ocean. Our findings unify traditionally contrasting views of Antarctic Bottom Water production in the Atlantic sector, and define a baseline, process-discerning target for its realistic representation in climate models.

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