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  • 1
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    Multi-centennial scale SST and Indian summer monsoon precipitation variability since the mid-Holocene and its nonlinear response to solar activity (2015)
    Sage
    In: Holocene
    Details
    Publication Date: 2015-08-18
    Description: Indian Summer Monsoon (ISM) shows a weak correlation with solar variability in the 20th century. However, such climatological observations on solar activity–monsoon relationship are very short and hence uncertain. A few paleomonsoon records also exhibit prominent correspondence with solar activity during early Holocene and beyond. But despite the strong recent solar minima (e.g. Maunder, Spörer, Oort, Wolf), their correlation with monsoon precipitation is weak and inconclusive. Additionally, many of the earlier studies have been from the western Arabian Sea that provides records of the ISM wind intensity instead of the ISM precipitation. We present here mid-Holocene to recent sea surface temperature (SST) reconstructed from Mg/Ca measurements of planktic foraminifera ( Globigerinoides ruber ; white, sensu stricto) on a centennial-scale resolution from the southeastern Arabian. These measurements are used to correct the oxygen isotope ratios of G . ruber to reconstruct salinity related to monsoon runoff in this region more precisely than hitherto. The long-term trend indicates that the ISM precipitation has declined since the mid-Holocene similar to the solar activity. On shorter multi-centennial timescale, we show that the ISM precipitation declined concurrently with the recent periods of strong solar minima, but lagged by a couple of hundred years beyond 1300 yr BP toward the mid-Holocene – confirmed statistically using wavelet analysis. This nonstationary phase relationship between the ISM and the solar activity indicates the possible influence of the tropical coupled ocean–atmosphere phenomenon.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 2
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    Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-06-26
    Description: The modern Eastern Equatorial Pacific (EEP) Ocean is a large oceanic source of carbon to the atmosphere. Primary productivity over large areas of the EEP is limited by silicic acid and iron availability, and because of this constraint the organic carbon export to the deep ocean is unable to compensate for the outgassing of carbon dioxide that occurs through upwelling of deep waters. It has been suggested that the delivery of dust-borne iron to the glacial ocean could have increased primary productivity and enhanced deep-sea carbon export in this region, lowering atmospheric carbon dioxide concentrations during glacial periods. Such a role for the EEP is supported by higher organic carbon burial rates documented in underlying glacial sediments, but lower opal accumulation rates cast doubts on the importance of the EEP as an oceanic region for significant glacial carbon dioxide drawdown. Here we present a new silicon isotope record that suggests the paradoxical decline in opal accumulation rate in the glacial EEP results from a decrease in the silicon to carbon uptake ratio of diatoms under conditions of increased iron availability from enhanced dust input. Consequently, our study supports the idea of an invigorated biological pump in this region during the last glacial period that could have contributed to glacial carbon dioxide drawdown. Additionally, using evidence from silicon and nitrogen isotope changes, we infer that, in contrast to the modern situation, the biological productivity in this region is not constrained by the availability of iron, silicon and nitrogen during the glacial period. We hypothesize that an invigorated biological carbon dioxide pump constrained perhaps only by phosphorus limitation was a more common occurrence in low-latitude areas of the glacial ocean.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pichevin, L E -- Reynolds, B C -- Ganeshram, R S -- Cacho, I -- Pena, L -- Keefe, K -- Ellam, R M -- England -- Nature. 2009 Jun 25;459(7250):1114-7. doi: 10.1038/nature08101.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Geosciences, Grant Institute, University of Edinburgh, West Main Road, EH10 3JW, Edinburgh, UK. laetitia.pichevin@ed.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19553996" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon/chemistry/*metabolism ; Diatoms/metabolism ; Geologic Sediments/chemistry ; Pacific Ocean ; Silicon/analysis ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Impacts of atmospheric anthropogenic nitrogen on the open ocean (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-05-20
    Description: Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Duce, R A -- LaRoche, J -- Altieri, K -- Arrigo, K R -- Baker, A R -- Capone, D G -- Cornell, S -- Dentener, F -- Galloway, J -- Ganeshram, R S -- Geider, R J -- Jickells, T -- Kuypers, M M -- Langlois, R -- Liss, P S -- Liu, S M -- Middelburg, J J -- Moore, C M -- Nickovic, S -- Oschlies, A -- Pedersen, T -- Prospero, J -- Schlitzer, R -- Seitzinger, S -- Sorensen, L L -- Uematsu, M -- Ulloa, O -- Voss, M -- Ward, B -- Zamora, L -- New York, N.Y. -- Science. 2008 May 16;320(5878):893-7. doi: 10.1126/science.1150369.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departments of Oceanography and Atmospheric Sciences, Texas A&M University, College Station, TX 77843, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18487184" target="_blank"〉PubMed〈/a〉
    Keywords: *Atmosphere ; Carbon ; Carbon Dioxide/metabolism ; Ecosystem ; *Human Activities ; Humans ; *Nitrogen/metabolism ; Nitrogen Fixation ; Oceans and Seas ; *Reactive Nitrogen Species/metabolism ; *Seawater
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Silica burial enhanced by iron limitation in oceanic upwelling margins (2014)
    Springer Nature
    Details
    Publication Date: 2014-06-28
    Description: Nature Geoscience 7, 541 (2014). doi:10.1038/ngeo2181 Authors: L. E. Pichevin, R. S. Ganeshram, W. Geibert, R. Thunell & R. Hinton
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 5
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    Factors Controlling the Burial of Organic Carbon in Laminated and Bioturbated Sediments off NW Mexico (1998)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 1998-01-01
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
    Published by Mineralogical Society of Great Britain and Ireland
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  • 6
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    Silica burial enhanced by iron limitation in oceanic upwelling margins (2014)
    Springer Nature
    Details
    Publication Date: 2014-06-08
    Description: In large swaths of the ocean, primary production by diatoms may be limited by the availability of silica, which in turn limits the biological uptake of carbon dioxide. The burial of biogenic silica in the form of opal is the main sink of marine silicon. Opal burial occurs in equal parts in iron-limited open-ocean provinces and upwelling margins, especially the eastern Pacific upwelling zone. However, it is unclear why opal burial is so efficient in this margin. Here we measure fluxes of biogenic material, concentrations of diatom-bound iron and silicon isotope ratios using sediment traps and a sediment core from the Gulf of California upwelling margin. In the sediment trap material, we find that periods of intense upwelling are associated with transient iron limitation that results in a high export of silica relative to organic carbon. A similar correlation between enhanced silica burial and iron limitation is evident in the sediment core, which spans the past 26,000 years. A global compilation also indicates that hotspots of silicon burial in the ocean are all characterized by high silica to organic carbon export ratios, a diagnostic trait for diatoms growing under iron stress. We therefore propose that prevailing conditions of silica limitation in the ocean are largely caused by iron deficiency imposing an indirect constraint on oceanic carbon uptake. © 2014 Macmillan Publishers Limited.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 7
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    Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment (2011)
    Copernicus
    Details
    Publication Date: 2011-11-16
    Description: A high resolution time-series analysis of stable carbon isotopic signatures in particulate organic carbon (δ13CPOC) and associated biogeochemical parameters in sea ice and surface waters provides an insight into the factors affecting δ13CPOC in the coastal western Antarctic Peninsula (WAP) sea ice environment. The study covers two austral summer seasons in Ryder Bay, northern Marguerite Bay between 2004 and 2006. A shift in diatom species composition during the 2005/2006 summer bloom to near-complete biomass dominance of Proboscia inermis is strongly correlated with a large ~10‰ negative isotopic shift in δ13CPOC that cannot be explained by a concurrent change in concentration or isotopic signature of CO2. We hypothesise that the δ13CPOC shift may be driven by the contrasting biochemical mechanisms and utilisation of carbon-concentrating mechanisms in different diatom species. These short-lived yet pronounced negative δ13CPOC excursions drive a 4‰ decrease in the seasonal average δ13CPOC signal, which is transferred to sediment traps and core-top sediments and consequently has the potential for preservation in the sedimentary record. This 4‰ difference between seasons of contrasting sea ice conditions and upper water column stratification matches the full amplitude of glacial-interglacial Southern Ocean δ13CPOC variability and, as such, we invoke phytoplankton species changes as a potentially important factor influencing sedimentary δ13CPOC. We also find significantly higher δ13CPOC in sea ice than surface waters, consistent with autotrophic carbon fixation in a semi-closed environment and possible contributions from post-production degradation, biological utilisation of HCO3- and production of exopolymeric substances (EPS). This study demonstrates the importance of surface water diatom speciation effects and isotopically heavy sea ice-derived material for δ13CPOC in Antarctic coastal environments and underlying sediments, with consequences for the utility of diatom-based δ13CPOC in the sedimentary record.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean (2009)
    Springer Nature
    Details
    Publication Date: 2009-06-01
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 9
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    Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment (2012)
    Copernicus
    Details
    Publication Date: 2012-03-27
    Description: A high resolution time-series analysis of stable carbon isotopic signatures in particulate organic carbon (δ13CPOC) and associated biogeochemical parameters in sea ice and surface waters provides an insight into the factors affecting δ13CPOC in the coastal western Antarctic Peninsula sea ice environment. The study covers two austral summer seasons in Ryder Bay, northern Marguerite Bay between 2004 and 2006. A shift in diatom species composition during the 2005/06 summer bloom to near-complete biomass dominance of Proboscia inermis is strongly correlated with a large ~10 ‰ negative isotopic shift in δ13CPOC that cannot be explained by a concurrent change in concentration or isotopic signature of CO2. We hypothesise that the δ13CPOC shift may be driven by the contrasting biochemical mechanisms and utilisation of carbon-concentrating mechanisms (CCMs) in different diatom species. Specifically, very low δ13CPOC in P. inermis may be caused by the lack of a CCM, whilst some diatom species abundant at times of higher δ13CPOC may employ CCMs. These short-lived yet pronounced negative δ13CPOC excursions drive a 4 ‰ decrease in the seasonal average δ13CPOC signal, which is transferred to sediment traps and core-top sediments and consequently has the potential for preservation in the sedimentary record. This 4 ‰ difference between seasons of contrasting sea ice conditions and upper water column stratification matches the full amplitude of glacial-interglacial Southern Ocean δ13CPOC variability and, as such, we invoke phytoplankton species changes as a potentially important factor influencing sedimentary δ13CPOC. We also find significantly higher δ13CPOC in sea ice than surface waters, consistent with autotrophic carbon fixation in a semi-closed environment and possible contributions from post-production degradation, biological utilisation of HCO3− and production of exopolymeric substances. This study demonstrates the importance of surface water diatom speciation effects and isotopically heavy sea ice-derived material for δ13CPOC in Antarctic coastal environments and underlying sediments, with consequences for the utility of diatom-based δ13CPOC in the sedimentary record.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Nutrient cycling in the Atlantic basin: The evolution of nitrate isotope signatures in water masses (2015)
    American Geophysical Union
    Details
    Publication Date: 2015-10-01
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by American Geophysical Union
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