A Mesoscale Iron Enrichment in the Western Subarctic Pacific Induces a Large Centric Diatom Bloom

Tsuda, Atsushi; Takeda, Shigenobu; Saito, Hiroaki; Nishioka, Jun; Nojiri, Yukihiro; Kudo, Isao; Kiyosawa, Hiroshi; Shiomoto, Akihiro; Imai, Keiri; Ono, Tsuneo; Shimamoto, Akifumi; Tsumune, Daisuke; Yoshimura, Takeshi; Aono, Tatsuo; Hinuma, Akira; Kinugasa, Masatoshi; Suzuki, Koji; Sohrin, Yoshiki; Noiri, Yoshifumi; Tani, Heihachiro; Deguchi, Yuji; Tsurushima, Nobuo; Ogawa, Hiroshi; Fukami, Kimio; Kuma, Kenshi; Saino, Toshiro

doi:10.1126/science.1082000

Cited by 477 publications

(283 citation statements)

References 17 publications

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“…This current may be less important for diatom growth in the far northwestern Pacific, even though a western branch of the Aleutian Current today reaches all the way up to Site MD01-2416 (traced by plastic toys; Ebbesmeyer et al [2007]). In addition, wind-borne iron forms a limiting trace nutrient [Tsuda et al, 2003] that may have strongly increased during glacial and early deglacial times.…”

Section: Discussionmentioning

confidence: 99%

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Gebhardt¹,

Sarnthein²,

et al. 2008

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[1] Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale changes in the meridional overturning circulation (MOC) of the subarctic North Pacific. Particular concerns are the vertical mixing, the present and past abundance of nutrients in surface waters despite strong stratification, and the North Pacific-North Atlantic seesaw of oscillations in sea surface temperature (SST). We do this by generating and interpreting multiple records for glacial terminations I-V down two long piston cores, one each from the western and eastern subarctic Pacific. Chlorins and biogenic opal are proxies for surface water productivity; d 13 C of epibenthic foraminifera is a record of deepwater ventilation; and the d 13 C of N. pachyderma sin. is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing. The degree of mixing is traced by pairing SST and d 18 O records of planktic surface and subsurface (pycnocline) dwellers. Tight age control is deduced from a suite of age-calibrated 14 C plateau boundaries for Termination I and benthic d 18 O and geomagnetic events for the last 800 ka. Carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short-term changes in MOC over Termination I. We have defined a standard sequence of short-term productivity events for Termination I, also evident during terminations II to V and subsequent interglacials over the last 450 ka. The peak glacial regime of stable stratification and low productivity terminated, together with the end of ice rafting and melting, near 17 ka, $2000 years after the onset of Termination I. Pulses of vertical mixing and incursion of warm surface waters from the subtropics followed. Convected young water masses finally penetrated down to 3600-m water depth at 17.0 to less than 14.5 ka, significantly improving bottom water ventilation through the late deglacial and earliest interglacial. Mixing with upwelled nutrients from the pycnocline induced short-term maxima in algal production of chlorins and biogenic opal near 17-15 and 15-12 ka, respectively. Deglacial meltwater incursions in the Aleutian Current and silica input from North American rivers also promoted East Pacific productivity after 15.5 ka. Productivity decreased during the late deglacial and early interglacial, coeval with an exceptional peak in CaCO 3 preservation caused by both low organic flux and well-ventilated deepwater. Subsequently, low salinity and cool surface waters and in turn, stratification were gradually restored. A second, opaldominated productivity maximum marked the ends of interglacials. The deglacial pulses of vertical mixing around 17-11 ka imply an important contribution of the North Pacific to the coeval release of oceanic CO 2 into the atmosphere and support the east-west seesaw model of climate change.Citation: Gebhardt, H., M. Sarnthein, P. M. Grootes, T. Kiefer, H. Kuehn, F. Schmieder, and U. Röhl (2008), Paleonutrient and productivity records from the subarctic North ...

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Section: Discussionmentioning

confidence: 99%

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Gebhardt¹,

Sarnthein²,

et al. 2008

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“…Today large sections of the North Pacific Ocean are Fe limited with respect to diatom growth (Harrison et al, 1999;Tsuda et al, 2003;Yuan and Zhang, 2006). The impact of increased Fe availability on diatoms is well documented with Fe limitation leading to increases in cell Si:N and Si:C ratios and decreases in diatom growth rates (see Hutchins and Bruland, (1998);Takeda, (1998) and reviews in de Baar et al, (2005) and Ragueneau et al, (2006)).…”

Section: Uncorrected Copymentioning

confidence: 99%

Isotope offsets in marine diatom δ¹⁸O over the last 200 ka

Swann

Leng

Sloane

et al. 2008

J Quaternary Science

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Previous work has suggested that a species effect may be present in diatom oxygen isotope ratios ( δ 18 Odiatom).While predominantly attributed to be a size related species effect, currently the precise mechanism remains unknown. Here, two size fractions of diatoms (38-75 μm and >100 μm) covering the last 200 ka are analysed for δ 18 O from ODP Site 882 in the North West Pacific Ocean. Synchronous variations of up to 13‰ occur in both size fractions. However, large isotope offsets (mean = 2.02‰) exist between the two fractions with no relationship between their magnitude and the overlying palaeoenvironmental conditions. In contrast to earlier work from the same site, no one size fraction is constantly higher or lower in δ 18 O relative to the other. As such, the dominant mechanism is most likely separate to the size effect previously detected. In addition, no relationship exists between the magnitude of the offsets and the species composition of the two size fractions. The presence of these isotope offsets imposes significant constraints upon the future use of δ 18 Odiatom in palaeoceanographic reconstructions and reiterates the need to extract and analyse only species and size specific diatom samples.

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“…This paper describes results from EisenEx (Smetacek, 2001), a mesoscale iron enrichment experiment in the Atlantic sector of the Southern Ocean performed in October/November 2000. Further mesoscale experiments have taken place since EisenEx in the Southern Ocean, SOFeX, and in the North Pacific, SEEDS (Tsuda et al, 2003) and SERIES.…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. concentrations increased at the depth of the chlorophyll maximum when iron concentrations returned to pre-infusion concentrations (b80 pM) possibly due to biological production related to iron reductase activity.In this work, Fe(II) and dissolved iron were used as tracers themselves for subsequent iron infusions when no further SF 6 was added. EisenEx was subject to periods of weak and strong mixing. Slow mixing after the second infusion allowed significant concentrations of Fe(II) and Fe to exist for several days. During this time, dissolved and total iron in the infusion plume behaved almost conservatively as it was trapped between a relict mixed layer and a new rain-induced mixed layer. Using dissolved iron, a value for the vertical diffusion coefficient K z =6.7F0.7 cm 2 s À1 was obtained for this 2-day period. During a subsequent surface survey of the iron-enriched patch, elevated levels of Fe(II) were found in surface waters presumably from Fe(II) dissolved in the rainwater that was falling at this time.Model results suggest that the reaction between uncomplexed Fe(III) and O 2 À was a significant source of Fe(II) during EisenEx and helped to maintain high levels of Fe(II) in the water column. This phenomenon may occur in iron enrichment experiments when two conditions are met: (i) When Fe is added to a system already saturated with regard to organic complexation and (ii) when mixing processes are slow, thereby reducing the dispersion of iron into under-saturated waters. D

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A Mesoscale Iron Enrichment in the Western Subarctic Pacific Induces a Large Centric Diatom Bloom

Cited by 477 publications

References 17 publications

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Isotope offsets in marine diatom δ¹⁸O over the last 200 ka

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

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A Mesoscale Iron Enrichment in the Western Subarctic Pacific Induces a Large Centric Diatom Bloom

Cited by 477 publications

References 17 publications

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Isotope offsets in marine diatom δ18O over the last 200 ka

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

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Isotope offsets in marine diatom δ¹⁸O over the last 200 ka