Eddy-Driven Stratification Initiates North Atlantic Spring Phytoplankton Blooms

Mahadevan, Amala; D’Asaro, Eric A.; Lee, Craig; Perry, Mary Jane

doi:10.1126/science.1218740

Cited by 420 publications

(465 citation statements)

References 39 publications

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“…This variability likely reflects both enduring climatological differences within regions and transient, localized processes, such as storms, mesoscale eddies, horizontal advection of distinct water masses, tidal mixing and bathymetry (Greene et al, 2012;Mahadevan et al, 2012;McGillicuddy et al, 2007). Finally, our analysis compares well to the seasonal averages described for the Gulf of Maine by Thomas et al (2003) and differ from the descriptions of bloom initiation in Ji et al (2007) and Song et al (2010) because their study domains extended further north and eastward over the shallower areas of the Scotian Shelf.…”

Section: Discussionsupporting

confidence: 56%

Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

Friedland

Leaf

Kane

et al. 2015

Continental Shelf Research

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a b s t r a c tThe spring phytoplankton bloom on the US Northeast Continental Shelf is a feature of the ecosystem production cycle that varies annually in timing, spatial extent, and magnitude. To quantify this variability, we analyzed remotely-sensed ocean color data at two spatial scales, one based on ecologically defined sub-units of the ecosystem (production units) and the other on a regular grid (0.5°). Five units were defined: Gulf of Maine East and West, Georges Bank, and Middle Atlantic Bight North and South. The units averaged 47 Â 10 3 km 2 in size. The initiation and termination of the spring bloom were determined using change-point analysis with constraints on what was identified as a bloom based on climatological bloom patterns. A discrete spring bloom was detected in most years over much of the western Gulf of Maine production unit. However, bloom frequency declined in the eastern Gulf of Maine and transitioned to frequencies as low as 50% along the southern flank of the Georges Bank production unit. Detectable spring blooms were episodic in the Middle Atlantic Bight production units. In the western Gulf of Maine, bloom duration was inversely related to bloom start day; thus, early blooms tended to be longer lasting and larger magnitude blooms. We view this as a phenological mismatch between bloom timing and the "top-down" grazing pressure that terminates a bloom. Estimates of secondary production were available from plankton surveys that provided spring indices of zooplankton biovolume. Winter chlorophyll biomass had little effect on spring zooplankton biovolume, whereas spring chlorophyll biomass had mixed effects on biovolume. There was evidence of a "bottom up" response seen on Georges Bank where spring zooplankton biovolume was positively correlated with the concentration of chlorophyll. However, in the western Gulf of Maine, biovolume was uncorrelated with chlorophyll concentration, but was positively correlated with bloom start and negatively correlated with magnitude. This observation is consistent with both a "top-down" mechanism of control of the bloom and a "bottom-up" effect of bloom timing on zooplankton grazing. Our inability to form a consistent model of these relationships across adjacent systems underscores the need for further research.Published by Elsevier Ltd.

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Section: Discussionsupporting

confidence: 56%

Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

Friedland

Leaf

Kane

et al. 2015

Continental Shelf Research

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“…4). This broad trend supports the hypothesis that calcite wt% is a measure of water stratification and temperature Mahadevan et al, 2012;Thórdardóttir, 1984). There is a statistically significant relationship (n = 26, p = 0.0002) between 50 m water temperature and the weight% of carbonate for all sites, but excluding Djupall, which for its temperature, has anomalously high carbonate values.…”

Section: The Oceanographic Climatic and Physical Backgroundsupporting

confidence: 66%

Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

Andrews

Jennings

2014

Clim. Past

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Abstract. In the area of Denmark Strait (∼ 66 • N), the two modes of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are expressed in changes of the northward flux of Atlantic water and the southward advection of polar water in the East Iceland current. Proxies from marine cores along an environmental gradient from extensive to little or no drift ice, capture low frequency variations over the last 2000 cal yr BP. Key proxies are the weight% of calcite, a measure of surface water stratification and nutrient supply, the weight% of quartz, a measure of drift ice transport, and grain size. Records from Nansen and Kangerlussuaq fjords show variable ice-rafted debris (IRD) records but have distinct mineralogy associated with differences in the fjord catchment bedrock. A comparison between cores on either side of the Denmark Strait (MD99-2322 and MD99-2269) show a remarkable millennial-scale similarity in the trends of the weight% of calcite with a trough reached during the Little Ice Age. However, the quartz records from these two sites are quite different. The calcite records from the Denmark Strait parallel the 2000 yr Arctic summer-temperature reconstructions; analysis of the detrended calcite and quartz data reveal significant multi-decadal-century periodicities superimposed on a major environmental shift occurring ca. 1450 AD.

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“…In both cases, the length of the series poses a great limitation to ascribe observed trends to climate change (Henson et al, 2010), although it revealed a clear signature of climate forcing on interannual changes in bloom statistics. Other problems include the difficulties to interpret changes in remotely sensed chl a concentration (see Materials and Methods), the indirect treatment of mixed layer dynamics and the lack of some important drivers of phytoplankton and bloom dynamics, like advection and sub-mesoscale features (Lehahn et al, 2007;Mahadevan et al, 2012). Another interesting aspect revealed by this study was the importance of taking into account potential differences between satellite missions and between chl a algorithms (see the Supporting Text in the Supporting Information).…”

Section: Changes In Phytoplankton Seasonalitymentioning

confidence: 97%

Seasonality of North Atlantic phytoplankton from space: impact of environmental forcing on a changing phenology (1998–2012)

Taboada

Anadón

2014

Global Change Biology

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Seasonal pulses of phytoplankton drive seasonal cycles of carbon fixation and particle sedimentation, and might condition recruitment success in many exploited species. Taking advantage of long-term series of remotely sensed chlorophyll a (1998-2012), we analysed changes in phytoplankton seasonality in the North Atlantic Ocean. Phytoplankton phenology was analysed based on a probabilistic characterization of bloom incidence. This approach allowed us to detect changes in the prevalence of different seasonal cycles and, at the same time, to estimate bloom timing and magnitude taking into account uncertainty in bloom detection. Deviations between different sensors stressed the importance of a prolonged overlap between successive missions to ensure a correct assessment of phenological changes, as well as the advantage of semi-analytical chlorophyll algorithms over empirical ones to reduce biases. Earlier and more intense blooms were detected in the subpolar Atlantic, while advanced blooms of less magnitude were common in the Subtropical gyre. In the temperate North Atlantic, spring blooms advanced their timing and decreased in magnitude, whereas fall blooms delayed and increased their intensity. At the same time, the prevalence of locations with a single autumn/winter bloom or with a bimodal seasonal cycle increased, in consonance with a poleward expansion of subtropical conditions. Changes in bloom timing and magnitude presented a clear signature of environmental factors, especially wind forcing, although changes on incident photosynthetically active radiation and sea surface temperature were also important depending on latitude. Trends in bloom magnitude matched changes in mean chlorophyll a during the study period, suggesting that seasonal peaks drive long-term trends in chlorophyll a concentration. Our results link changes in North Atlantic climate with recent trends in the phenology of phytoplankton, suggesting an intensification of these impacts in the near future.

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Eddy-Driven Stratification Initiates North Atlantic Spring Phytoplankton Blooms

Cited by 420 publications

References 39 publications

Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

Seasonality of North Atlantic phytoplankton from space: impact of environmental forcing on a changing phenology (1998–2012)

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