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  • 1
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    Theoretical considerations on factors confounding the interpretation of the oceanic carbon export ratio (2019)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Theoretical considerations on factors confounding the interpretation of the oceanic carbon export ratio. Global Biogeochemical Cycles, 32(11), (2018); 1644-1658, doi:10.1029/2018GB006003.
    Description: The fraction of primary production exported out of the surface ocean, known as the export ratio (ef ratio), is often used to assess how various factors, including temperature, primary production, phytoplankton size, and community structure, affect the export efficiency of an ecosystem. To investigate possible causes for reported discrepancies in the dominant factors influencing the export efficiency, we develop a metabolism‐based mechanistic model of the ef ratio. Consistent with earlier studies, we find based on theoretical considerations that the ef ratio is a negative function of temperature. We show that the ef ratio depends on the optical depth, defined as the physical depth times the light attenuation coefficient. As a result, varying light attenuation may confound the interpretation of ef ratio when measured at a fixed depth (e.g., 100 m) or at the base of the mixed layer. Finally, we decompose the contribution of individual factors on the seasonality of the ef ratio. Our results show that at high latitudes, the ef ratio at the base of mixed layer is strongly influenced by mixed layer depth and surface irradiation on seasonal time scales. Future studies should report the ef ratio at the base of the euphotic layer or account for the effect of varying light attenuation if measured at a different depth. Overall, our modeling study highlights the large number of factors confounding the interpretation of field observations of the ef ratio.
    Description: Z. L was supported by a NASA Earth and Space Science Fellowship (Grant NNX13AN85H) and the Postdoctoral Scholarship Program at Woods Hole Oceanographic Institution. N. C. was supported by NASA Grant 5109296. Satellite data, nutrient concentration, and monthly MLD climatology are downloaded from NASA ocean color (http://oceancolor.gsfc.nasa.gov/cms/), World Ocean Atlas (https://www.nodc.noaa.gov/OC5/woa13/), and http://www.ifremer.fr/cerweb/deboyer/mld/home.php, respectively.
    Description: 2019-04-13
    Keywords: Oceanic carbon export ratio ; Net community production ; Export production ; Net primary production
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Linking Southern Ocean mixed-layer dynamics to net community production on various timescales (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(10), (2021): e2021JC017537, https://doi.org/10.1029/2021JC017537.
    Description: Mixed-layer dynamics exert a first order control on nutrient and light availability for phytoplankton. In this study, we examine the influence of mixed-layer dynamics on net community production (NCP) in the Southern Ocean on intra-seasonal, seasonal, interannual, and decadal timescales, using biogeochemical Argo floats and satellite-derived NCP estimates during the period from 1997 to 2020. On intraseasonal timescales, the shoaling of the mixed layer is more likely to enhance NCP in austral spring and winter, suggesting an alleviation of light limitation. As expected, NCP generally increases with light availability on seasonal timescales. On interannual timescales, NCP is correlated with mixed layer depth (MLD) and mixed-layer-averaged photosynthetically active radiation (PAR) in austral spring and winter, especially in regions with deeper mixed layers. Though recent studies have argued that winter MLD controls the subsequent growing season's iron and light availability, the limited number of Argo float observations contemporaneous with our satellite observations do not show a significant correlation between NCP and the previous-winter's MLD on interannual timescales. Over the 1997–2020 period, we observe regional trends in NCP (e.g., increasing around S. America), but no trend for the entire Southern Ocean. Overall, our results show that the dependence of NCP on MLD is a complex function of timescales.
    Description: Work was supported by NSF OPP-1043339 to N.Cassar and NASA NNX13AC94G to M. S. Lozier. Z. Li was supported by a NASA Earth and Space Science Fellowship (Grant No. NNX13AN85H) and the Postdoctoral Scholarship Program at Woods Hole Oceanographic Institution.
    Description: 2022-03-21
    Keywords: Mixed layer depth ; Net community production ; Southern Ocean
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Decline in plankton diversity and carbon flux with reduced sea ice extent along the Western Antarctic Peninsula (2021)
    Nature Research
    Details
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, Y., Moreno, C., Marchetti, A., Ducklow, H., Schofield, O., Delage, E., Meredith, M., Li, Z., Eveillard, D., Chaffron, S., & Cassar, N. Decline in plankton diversity and carbon flux with reduced sea ice extent along the Western Antarctic Peninsula. Nature Communications, 12(1), (2021): 4948, https://doi.org/10.1038/s41467-021-25235-w.
    Description: Since the middle of the past century, the Western Antarctic Peninsula has warmed rapidly with a significant loss of sea ice but the impacts on plankton biodiversity and carbon cycling remain an open question. Here, using a 5-year dataset of eukaryotic plankton DNA metabarcoding, we assess changes in biodiversity and net community production in this region. Our results show that sea-ice extent is a dominant factor influencing eukaryotic plankton community composition, biodiversity, and net community production. Species richness and evenness decline with an increase in sea surface temperature (SST). In regions with low SST and shallow mixed layers, the community was dominated by a diverse assemblage of diatoms and dinoflagellates. Conversely, less diverse plankton assemblages were observed in waters with higher SST and/or deep mixed layers when sea ice extent was lower. A genetic programming machine-learning model explained up to 80% of the net community production variability at the Western Antarctic Peninsula. Among the biological explanatory variables, the sea-ice environment associated plankton assemblage is the best predictor of net community production. We conclude that eukaryotic plankton diversity and carbon cycling at the Western Antarctic Peninsula are strongly linked to sea-ice conditions.
    Description: This work is supported by NSF OPP-1643534 to N.C., NSF OPP-1341479 to A.M., and NSF PLR-1440435 to H.D. and O.S. (Palmer LTER).
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Satellite estimates of net community production based on O2/Ar observations and comparison to other estimates (2016)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 30 (5). pp. 735-752.
    Details
    Publication Date: 2020-05-13
    Description: We present two statistical algorithms for predicting global oceanic net community production (NCP) from satellite observations. To calibrate these two algorithms, we compiled a large data set of in situ O2/Ar‐NCP and remotely sensed observations, including sea surface temperature (SST), net primary production (NPP), phytoplankton size composition, and inherent optical properties. The first algorithm is based on genetic programming (GP) which simultaneously searches for the optimal form and coefficients of NCP equations. We find that several GP solutions are consistent with NPP and SST being strong predictors of NCP. The second algorithm uses support vector regression (SVR) to optimize a numerical relationship between O2/Ar‐NCP measurements and satellite observations. Both statistical algorithms can predict NCP relatively well, with a coefficient of determination (R2) of 0.68 for GP and 0.72 for SVR, which is comparable to other algorithms in the literature. However, our new algorithms predict more spatially uniform annual NCP distribution for the world's oceans and higher annual NCP values in the Southern Ocean and the five oligotrophic gyres
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015GB005314
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    An improved classification method for hyperspectral data based on spectral and morphological information (2011)
    Taylor & Francis
    Details
    Publication Date: 2011-05-25
    Print ISSN: 0143-1161
    Electronic ISSN: 1366-5901
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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  • 6
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    An improved classification method for hyperspectral data based on spectral and morphological information (2011)
    Taylor & Francis
    Details
    Publication Date: 2011-06-26
    Print ISSN: 0143-1161
    Electronic ISSN: 1366-5901
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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