Mechanisms of
northern 
North
Atlantic biomass 
variability

McKinley, Galen A.; Ritzer, Alexis L.; Lovenduski, Nicole S.

doi:10.5194/bg-2018-89

Cited by 3 publications

(6 citation statements)

References 40 publications

(66 reference statements)

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“…Significant physical changes in the subpolar gyre influence the simulated nutrient and light fields. The model barotropic streamfunction experiences a positive change from a minimum value of −41 Sv for 1998-2000 to −28 Sv for 2005-2007. With this anomaly, the zero line of the streamfunction shifts several degrees north at 45-40 • W and more modestly to the north in the east (bold black contours in Fig.…”

Section: Physical Changes and Their Impacts On Light And Nutrient Limmentioning

confidence: 95%

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Mechanisms of northern North Atlantic biomass variability

McKinley¹,

Ritzer²,

Lovenduski

2018

Biogeosciences

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Abstract. In the North Atlantic Ocean north of 40∘ N, intense biological productivity occurs to form the base of a highly productive marine food web. SeaWiFS satellite observations indicate trends of biomass in this region over 1998–2007. Significant biomass increases occur in the northwest subpolar gyre and there are simultaneous significant declines to the east of 30–35∘ W. These short-term changes, attributable to internal variability, offer an opportunity to explore the mechanisms of the coupled physical–biogeochemical system. We use a regional biogeochemical model that captures the observed changes for this exploration. Biomass increases in the northwest are due to a weakening of the subpolar gyre and associated shoaling of mixed layers that relieves light limitation. Biomass declines to the east of 30–35∘ W are due to reduced horizontal convergence of phosphate. This reduced convergence is attributable to declines in vertical phosphate supply in the regions of deepest winter mixing that lie to the west of 30–35∘ W. Over the full time frame of the model experiment, 1949–2009, variability of both horizontal and vertical phosphate supply drive variability in biomass on the northeastern flank of the subtropical gyre. In the northeast subpolar gyre horizontal fluxes drive biomass variability for both time frames. Though physically driven changes in nutrient supply or light availability are the ultimate drivers of biomass changes, clear mechanistic links between biomass and standard physical variables or climate indices remain largely elusive.

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Section: Physical Changes and Their Impacts On Light And Nutrient Limmentioning

confidence: 95%

“…Annual anomalies of surface ocean biomass forSeaW- iFS (1998-2007, red), MODIS (2003 and our model(1998-2009, 0-100 m, black): (a) SE region, (b) NE region and (c) NW region. The corresponding monthly time series is shown in Fig.…”

mentioning

confidence: 99%

Mechanisms of northern North Atlantic biomass variability

McKinley¹,

Ritzer²,

Lovenduski

2018

Biogeosciences

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“…To correct for uncertainties in air-sea fluxes, SST and SSS (sea surface salinity) are relaxed to monthly historical SST (Had1SSTv1.0, Rayner et al, 2003) and climatological SSS (Antonov et al, 2006) observations, on the timescale of 2 and 4 weeks, respectively . To characterize subgrid-scale processes, the Gent-McWilliams (Gent and McWilliams, 1990) eddy parameterization, the K-profile parameterization boundary layer mixing schemes (Large et al, 1994), and Fox-Kemper et al (2008) submesoscale physical parameterization are used. The phosphorus-based ecosystem is parameterized following Dutkiewicz et al (2005), and with modest revisions by Bennington et al (2009).…”

Section: Regional Hindcast Modelmentioning

confidence: 99%

“…We will use these regions for discussion and for averaging of biogeochemical and physical terms. In the northeastern subtropical gyre, or intergyre (Follows and Dutkiewicz, 2002), lies our southeast (SE) region, just south of the physical separation between the subpolar and subtropical gyre based on In these three regions, annual anomalies of simulated biomass are compared to estimates from the SeaWiFS (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) and MODIS (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) satellites (Fig. 2).…”

Section: Model Comparison To Observationsmentioning

confidence: 99%

Response to reviewer 2

McKinley¹

2018

Preprint

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In the North Atlantic Ocean north of 40 • N, intense biological productivity occurs to form the base of a highly productive marine food web. SeaWiFS satellite observations indicate trends of biomass in this region over 1998-2007. Significant biomass increases occur in the northwest subpolar gyre and there are simultaneous significant declines to the east of 30-35 • W. These short-term changes, attributable to internal variability, offer an opportunity to explore the mechanisms of the coupled physicalbiogeochemical system. We use a regional biogeochemical model that captures the observed changes for this exploration. Biomass increases in the northwest are due to a weakening of the subpolar gyre and associated shoaling of mixed layers that relieves light limitation. Biomass declines to the east of 30-35 • W are due to reduced horizontal convergence of phosphate. This reduced convergence is attributable to declines in vertical phosphate supply in the regions of deepest winter mixing that lie to the west of 30-35 • W. Over the full time frame of the model experiment, 1949-2009, variability of both horizontal and vertical phosphate supply drive variability in biomass on the northeastern flank of the subtropical gyre. In the northeast subpolar gyre horizontal fluxes drive biomass variability for both time frames. Though physically driven changes in nutrient supply or light availability are the ultimate drivers of biomass changes, clear mechanistic links between biomass and standard physical variables or climate indices remain largely elusive.

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“…Multiple studies have used coupled Earth system models (ESMs) or stand‐alone ocean biogeochemical models to illustrate the influence of internal climate variability on biological processes, often through the lens of air‐sea carbon flux (Bopp et al., 2013; Hauck et al., 2013; Le Quéré et al., 2000; Lenton & Matear, 2007; McKinley et al., 2018; Wang & Moore, 2012). For example, several modeling studies suggest that SAM has a marked influence on phytoplankton productivity in the Southern Ocean (Hauck et al., 2013; Lenton & Matear, 2007; Wang & Moore, 2012) while ENSO has been demonstrated to impact net primary production (NPP) in tropical regions (Kwiatkowski et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

Alternate History: A Synthetic Ensemble of Ocean Chlorophyll Concentrations

Elsworth

Lovenduski

McKinnon

2021

Global Biogeochemical Cycles

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The ocean biosphere strongly influences biogeochemical cycling, carbon export, and air-sea carbon flux. Although phytoplankton constitute a relatively small reservoir of carbon, their ability to photosynthetically fix carbon from the atmosphere enhances the ocean's role as a carbon sink, allowing the ocean to store 45 times more carbon than the atmosphere (Friedlingstein et al., 2019). The efficiency and strength of the ocean biological pump can influence atmospheric carbon dioxide concentrations; in the absence of the ocean biosphere, atmospheric carbon dioxide concentrations would increase by approximately 50% of preindustrial values (McKinley et al., 2017).Internal climate variability plays an important role in the abundance and distribution of phytoplankton in the global ocean. Modes of internal climate variability, such as the El Niño Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the North Atlantic Oscillation (NAO), alter the physical and chemical environment for, and thus the abundance of, phytoplankton on timescales ranging from interannual to multi-decadal (

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Mechanisms of northern North Atlantic biomass variability

Abstract: Biogeosciences Discuss., https://doi

Cited by 3 publications

References 40 publications

Mechanisms of northern North Atlantic biomass variability

Mechanisms of northern North Atlantic biomass variability

Response to reviewer 2

Alternate History: A Synthetic Ensemble of Ocean Chlorophyll Concentrations

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