Annual boom–bust cycles of polar phytoplankton biomass revealed by space-based lidar

Behrenfeld, Michael J.; Hu, Yongxiang; O’Malley, Robert T.; Boss, Emmanuel; Hostetler, C. A.; Siegel, David A.; Sarmiento, Jorge L.; Schulien, Jennifer A.; Hair, Johnathan W.; Lu, Xiaomei; Rodier, Sharon; Scarino, Amy Jo

doi:10.1038/ngeo2861

Cited by 184 publications

(176 citation statements)

References 35 publications

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“…While the comparison made here is not completely fair to satellite‐based studies, it does suggest that some caution is needed when interpreting them; regardless of the depth of the mixed layer, satellite observations may miss subsurface vertical structures in BGC variables (Carranza et al, ; Lacour et al, ). Some promising results have been shown by Behrenfeld et al () using Light Detection And Ranging sensors, which penetrate the water column deeper than satellite ocean color measurements, and may overcome this shortcoming of remotely sensed observations.…”

Section: Discussionmentioning

confidence: 99%

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

et al. 2019

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The spring bloom in the Southern Ocean is the rapid-growth phase of the seasonal cycle in phytoplankton. Many previous studies have characterized the spring bloom using chlorophyll estimates from satellite ocean color observations. Assumptions regarding the chlorophyll-to-carbon ratio within phytoplankton and vertical structure of biogeochemical variables lead to uncertainty in satellite-based estimates of phytoplankton carbon biomass. Here, we revisit the characterizations of the bloom using optical backscatter from biogeochemical floats deployed by the Southern Ocean Carbon and Climate Observations and Modeling and Southern Ocean and Climate Field Studies with Innovative Tools projects. In particular, by providing a three-dimensional view of the seasonal cycle, we are able to identify basin-wide bloom characteristics corresponding to physical features; biomass is low in Ekman downwelling regions north of the Antarctic Circumpolar Current region and high within and south of the Antarctic Circumpolar Current. Plain Language SummaryThe advent of satellites has allowed us to observe the ocean surface on unprecedented scale. One of the major biogeochemical findings from these observations was that phytoplankton in the Southern Ocean repeatedly went through a dramatic phase of growth every spring basin wide. Phytoplankton, however, exist not only at the ocean surface but also in the interior, generally in the top 100 m. In our study, we revisit the characterization of this spring growth using autonomous floats that vertically profile biogeochemical properties including phytoplankton concentration, providing three-dimensional estimates of phytoplankton. Our results support the conventional knowledge of there being a robust seasonal cycle in phytoplankton within and south of the Antarctic Circumpolar Current region, an energetic eastward current that wraps around Antarctica.

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Section: Discussionmentioning

confidence: 99%

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

et al. 2019

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“…The latter provides an opportunity to validate space‐derived biogeochemical products from another spatially and temporally extensive observation system, Ocean Color (OC). While much of the SO can be observed by OC year around, the regions south of 55°S are not observed for several months of the year due to either low sun angle or absence of sunlight [ Behrenfeld et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Revisiting Ocean Color algorithms for chlorophyll a and particulate organic carbon in the Southern Ocean using biogeochemical floats

2017

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The Southern Ocean (SO) ecosystem plays a key role in the carbon cycle by sinking a major part (43%) of the ocean uptake of anthropogenic CO2, and being an important source of nutrients for primary producers. However, undersampling of SO biogeochemical properties limits our understanding of the mechanisms taking place in this remote area. The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project has been deploying a large number of autonomous biogeochemical floats to study the SO (as of December 2016, 74 floats out of 200 have been deployed). SOCCOM floats measurements can be used to extend remote sensing chlorophyll a (chl a) and particulate organic carbon (POC) products under clouds or during the polar night as well as adding the depth dimension to the satellite‐based view of the SO. Chlorophyll a concentrations measured by a sensor embedded on the floats and POC concentrations derived from backscattering coefficients were calibrated with samples collected during the floats' deployment cruise. Float chl a and POC were compared with products derived from observations of MODIS and VIIRS sensors. We find the Ocean Color Index (OCI) global algorithm to agree well with the matchups (within 9%, on average, for the Visible Infrared Imaging Radiometer Suite (VIIRS) and 12%, on average, for the Moderate Resolution Imaging Spectroradiometer Aqua (MODIS)). SO‐specific algorithms estimating chl a are offset by ∼45% south of the Sea Ice Extent Front ( ∼60°S). In addition, POC estimates based on floats agree well with NASA's POC algorithm.

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“…Some in-situ and creative satellite-based estimates Behrenfeld et al, 2016;Lowry et al, 2014) have identified these events and sought to assess their importance to the annual cycling of carbon in the Arctic Ocean, but more study is needed to refine these broad estimates. It is also unclear, but vital to our Arctic climate models, whether recent increases in NPP and the occurrence of (more) under ice blooms will directly correlate to any increase in export.…”

Section: Export and Remineralization Of Poc In A Changing Arcticmentioning

confidence: 99%

An investigation of basin-scale controls on upper ocean export and remineralization

Black¹

2018

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The biological carbon pump (BCP) helps to moderate atmospheric carbon dioxide levels by bringing carbon to the deep ocean, where it can be sequestered on timescales of centuries to millennia. Climate change is predicted to decrease the efficiency of the global BCP, however, the magnitude and timescale of this shift is largely uncertain and will likely impact some areas of the global ocean more significantly than others. Therefore, it is imperative that we (1) accurately quantify surface export and remineralization of particulate organic carbon (POC) via the BCP over large regions of the global ocean, (2) examine the factors controlling these POC fluxes and their variability, which includes the cycling of biologically-relevant trace metals, and (3) establish if and how the BCP is changing over time.This thesis focuses on addressing various aspects of these objectives using the 234 Th-238 U method across basin-scale GEOTRACES transects. First, the export and remineralization of POC were examined across large gradients in productivity, upwelling, community structure, and dissolved oxygen in the southeastern tropical Pacific Ocean. Although low oxygen zones are traditionally thought to have decreased POC flux attenuation relative to other regions of the global ocean and the low oxygen Pacific locations followed this pattern, regions that were functionally anoxic had enhanced attenuation in the upper 400 m. Second, trace metal export and remineralization were quantified across the Pacific transect. Because many trace metals are necessary for the metabolic functions of marine organisms and can co-limit marine productivity, the controls on the cycling of trace metals in the upper ocean were examined. Lastly, POC export was determined across two transects in the Western Arctic Ocean, where light and nutrient availability drive the biological pump. Upper ocean export estimates in the central basin did not reflect a substantial change in the biological pump compared to studies from the last three decades, however, an extensive maximum in 234 Th relative to 238 U deeper in the water column indicated that rapid vertical transport had occurred, which could suggest a more efficient biological pump in the Arctic Ocean.

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Annual boom–bust cycles of polar phytoplankton biomass revealed by space-based lidar

Cited by 184 publications

References 35 publications

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

Revisiting Ocean Color algorithms for chlorophyll a and particulate organic carbon in the Southern Ocean using biogeochemical floats

An investigation of basin-scale controls on upper ocean export and remineralization

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