| 1. |
- Dai, Yuhao, et al.
(författare)
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Deglacial Subantarctic CO2 outgassing driven by a weakened solubility pump
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- The Subantarctic Southern Ocean has long been thought to be an importantcontributor to increases in atmospheric carbon dioxide partial pressure(pCO2) during glacial-interglacial transitions. Extensive studies suggest that aweakened biological pump, a process associated with nutrient utilizationefficiency, drove up surface-water pCO2in this region during deglaciations. Bycontrast, regional influences of the solubility pump, a process mainly linked totemperature variations, have been largely overlooked. Here, we evaluaterelative roles of the biological and solubility pumps in determining surface-water pCO2variabilities in the Subantarctic Southern Ocean during the lastdeglaciation, based on paired reconstructions of surface-water pCO2,tem-perature, and nutrient utilization efficiency. We show that compared to thebiological pump, the solubility pumpimposed a strong impact on deglacialSubantarctic surface-water pCO2variabilities. Ourfindings therefore reveal apreviously underappreciated role of the solubility pump in modulatingdeglacial Subantarctic CO2release and possibly past atmospheric pCO2fluctuations.
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| 2. |
- Schiebel, Ralf, et al.
(författare)
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Advances in planktonic foraminifer research : New perspectives for paleoceanography
- 2018
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Ingår i: Revue de Micropaleontologie. - : Elsevier BV. - 0035-1598 .- 1873-4413. ; 61:3-4, s. 113-138
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Forskningsöversikt (refereegranskat)abstract
- Planktonic foraminifer tests are major archives of environmental change and provide a multitude of proxies in paleoceanography and paleoclimatology. The application of such proxies is contingent upon a collaborative effort to better understand how the living organisms record the properties of their environment and how the resulting signals are recorded in marine sediments. In this contribution, we provide a review of the rapidly developing sub-fields of research, where new advances have been made possibleby technological developments, and by cross-disciplinary work of the scientific community. Following brief historical overviews of the sub-fields, we discuss the latest advances in planktonic foraminifer research and highlight the resulting new perspectives in ocean and climate research. Natural classification based on consistent species concepts forms the basis for analysis of any foraminifer-derived proxy. New approaches in taxonomy and phylogeny of Cenozoic planktonic foraminifers (Section 2) are presented, highlighting new perspectives on sensitivity and response of planktonic foraminifers to the changing climate and environment (Section 4). Calibration of foraminifer-specific data and environmental parameters is improving along with the technical development of probes and the access to samples from the natural environment (Section 3), enhancing our understanding of the ever-changing climate and ocean system. Comprehension of sedimentation and flux dynamics facilitates maximum gain of information from fossil assemblages (Section 5). Subtle changes in the physical (e.g., temperature), chemical (e.g., pH), and biological (e.g., food) conditions of ambient seawater affect the abundance of species and composition of assemblages as well as the chemical composition of the foraminifer shell and provide increasingly-detailed proxy data on paleoenvironments (Section 6).
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| 3. |
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| 4. |
- Zhang, Yi Ge, et al.
(författare)
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A long history of equatorial deep-water upwelling in the Pacific Ocean
- 2017
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 467, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Cold, nutrient-and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air–sea CO2equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a “permanent El Niño-like” climate state. For this study, we test this supposition by reconstructing EEP “excess CO2” and upwelling history for the past 6.5million years using the alkenone-pCO2methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2disequilibrium and high nutrient delivery to surface waters — characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene – early Pliocene “biogenic bloom”.
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| 5. |
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