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Crump SE, Fréchette B, Power M, Cutler S, de Wet G, Raynolds MK, Raberg JH, Briner JP, Thomas EK, Sepúlveda J, Shapiro B, Bunce M, Miller GH. Ancient plant DNA reveals High Arctic greening during the Last Interglacial. Proc Natl Acad Sci U S A 2021; 118:e2019069118. [PMID: 33723011 PMCID: PMC8020792 DOI: 10.1073/pnas.2019069118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Summer warming is driving a greening trend across the Arctic, with the potential for large-scale amplification of climate change due to vegetation-related feedbacks [Pearson et al., Nat. Clim. Chang. (3), 673-677 (2013)]. Because observational records are sparse and temporally limited, past episodes of Arctic warming can help elucidate the magnitude of vegetation response to temperature change. The Last Interglacial ([LIG], 129,000 to 116,000 y ago) was the most recent episode of Arctic warming on par with predicted 21st century temperature change [Otto-Bliesner et al., Philos. Trans. A Math. Phys. Eng. Sci. (371), 20130097 (2013) and Post et al., SciAdv (5), eaaw9883 (2019)]. However, high-latitude terrestrial records from this period are rare, so LIG vegetation distributions are incompletely known. Pollen-based vegetation reconstructions can be biased by long-distance pollen transport, further obscuring the paleoenvironmental record. Here, we present a LIG vegetation record based on ancient DNA in lake sediment and compare it with fossil pollen. Comprehensive plant community reconstructions through the last and current interglacial (the Holocene) on Baffin Island, Arctic Canada, reveal coherent climate-driven community shifts across both interglacials. Peak LIG warmth featured a ∼400-km northward range shift of dwarf birch, a key woody shrub that is again expanding northward. Greening of the High Arctic-documented here by multiple proxies-likely represented a strong positive feedback on high-latitude LIG warming. Authenticated ancient DNA from this lake sediment also extends the useful preservation window for the technique and highlights the utility of combining traditional and molecular approaches for gleaning paleoenvironmental insights to better anticipate a warmer future.
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Affiliation(s)
- Sarah E Crump
- Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, CO 80303;
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95064
| | - Bianca Fréchette
- Geotop, Université du Québec à Montréal, Montréal, H2L 2C4, Canada
| | - Matthew Power
- Trace and Environmental DNA Laboratory, School of Molecular and Life Sciences, Curtin University, 6845 Bentley, Australia
| | - Sam Cutler
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95064
| | - Gregory de Wet
- Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, CO 80303
- Department of Geosciences, Smith College, Northampton, MA 01063
| | - Martha K Raynolds
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775
| | - Jonathan H Raberg
- Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, CO 80303
| | - Jason P Briner
- Department of Geology, University at Buffalo, Buffalo, NY 14260
| | | | - Julio Sepúlveda
- Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, CO 80303
| | - Beth Shapiro
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95064
- HHMI, University of California, Santa Cruz, CA 95064
| | - Michael Bunce
- Trace and Environmental DNA Laboratory, School of Molecular and Life Sciences, Curtin University, 6845 Bentley, Australia
- New Zealand Environment Protection Authority, 6011 Wellington, New Zealand
| | - Gifford H Miller
- Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, CO 80303
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Affiliation(s)
- Yusuke Yokoyama
- Atmosphere and Ocean Research Institute and Department of Earth and Planetary Sciences, School of Science, The University of Tokyo, Chiba, Japan.
| | - Tezer M Esat
- Research School of Earth Sciences, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia.
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Robinson LF, Siddall M. Palaeoceanography: motivations and challenges for the future. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:5540-5566. [PMID: 23129712 DOI: 10.1098/rsta.2012.0396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The ocean interacts with the atmosphere, biosphere and cryosphere in a complex way, modulating climate through the storage and transport of heat, nutrients and carbon. As such, it is important that we understand the ways in which the ocean behaves and the factors that can lead to change. In order to gain this understanding, we need to look back into the past, on time scales from recent decadal-scale change, through the abrupt changes of the Pleistocene and back to times when the Earth's climate was significantly different than the Holocene. A key challenge facing the field of palaeoceanography is to combine data and modelling in a common framework. Coupling palaeo-data and models should improve our knowledge of how the Earth works, and perhaps of more direct societal relevance, might enable us to provide better predictive capabilities in climate modelling. In this discussion paper, we examine the motivations, past successes and challenges facing palaeoceanographic studies. We then suggest a number of areas and approaches that we believe will allow palaeoceanography to continue to provide new insights into processes that affect future climate change.
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Abstract
During the last interglacial period, ~125,000 years ago, sea level was at least several meters higher than at present, with substantial variability observed for peak sea level at geographically diverse sites. Speculation that the West Antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice-sheet dynamics during this time interval. We provide an internally consistent database of coral U-Th ages to assess last interglacial sea-level observations in the context of isostatic modeling and stratigraphic evidence. These data indicate that global (eustatic) sea level peaked 5.5 to 9 meters above present sea level, requiring smaller ice sheets in both Greenland and Antarctica relative to today and indicating strong sea-level sensitivity to small changes in radiative forcing.
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Affiliation(s)
- A Dutton
- Research School of Earth Sciences, The Australian National University, 1 Mills Road, Canberra, ACT 0200, Australia.
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Huybers P, Wunsch C. Paleophysical oceanography with an emphasis on transport rates. ANNUAL REVIEW OF MARINE SCIENCE 2010; 2:1-34. [PMID: 21141656 DOI: 10.1146/annurev-marine-120308-081056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Paleophysical oceanography is the study of the behavior of the fluid ocean of the past, with a specific emphasis on its climate implications, leading to a focus on the general circulation. Even if the circulation is not of primary concern, heavy reliance on deep-sea cores for past climate information means that knowledge of the oceanic state when the sediments were laid down is a necessity. Like the modern problem, paleoceanography depends heavily on observations, and central difficulties lie with the very limited data types and coverage that are, and perhaps ever will be, available. An approximate separation can be made into static descriptors of the circulation (e.g., its water-mass properties and volumes) and the more difficult problem of determining transport rates of mass and other properties. Determination of the circulation of the Last Glacial Maximum is used to outline some of the main challenges to progress. Apart from sampling issues, major difficulties lie with physical interpretation of the proxies, transferring core depths to an accurate timescale (the "age-model problem"), and understanding the accuracy of time-stepping oceanic or coupled-climate models when run unconstrained by observations. Despite the existence of many plausible explanatory scenarios, few features of the paleocirculation in any period are yet known with certainty.
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Affiliation(s)
- Peter Huybers
- Department of Earth and Planetary Sciences, Harvard University; Cambridge, Massachusetts 02138, USA.
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Drysdale RN, Hellstrom JC, Zanchetta G, Fallick AE, Sánchez Goñi MF, Couchoud I, McDonald J, Maas R, Lohmann G, Isola I. Evidence for Obliquity Forcing of Glacial Termination II. Science 2009; 325:1527-31. [DOI: 10.1126/science.1170371] [Citation(s) in RCA: 170] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- R. N. Drysdale
- Environmental and Climate Change Group, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - J. C. Hellstrom
- School of Earth Sciences, University of Melbourne, Parkville, Victoria 2010, Australia
| | - G. Zanchetta
- Department of Earth Sciences, University of Pisa, Pisa 56100, Italy
- Istituto Nazionale di Geofisica e Vulcanologia, via della Fagiola, Pisa 56126, Italy
- IGG-CNR, Via Moruzzi, 1 56100 Pisa, Italy
| | - A. E. Fallick
- Scottish Universities Environmental Research Centre, East Kilbride G75 0GF, UK
| | | | - I. Couchoud
- Environmental and Climate Change Group, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - J. McDonald
- Environmental and Climate Change Group, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - R. Maas
- School of Earth Sciences, University of Melbourne, Parkville, Victoria 2010, Australia
| | - G. Lohmann
- Alfred Wegener Institute for Polar and Marine Research, Bussestrasse 24, D-27570 Bremerhaven, Germany
| | - I. Isola
- Istituto Nazionale di Geofisica e Vulcanologia, via della Fagiola, Pisa 56126, Italy
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Phillips FM, Zreda M, Plummer MA, Elmore D, Clark DH. Glacial geology and chronology of Bishop Creek and vicinity, eastern Sierra Nevada, California. ACTA ACUST UNITED AC 2009. [DOI: 10.1130/b26271.1] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fred M. Phillips
- Earth & Environmental Science Department, New Mexico Tech, Socorro, New Mexico 87801, USA
| | - Marek Zreda
- Department of Hydrology & Water Resources, University of Arizona, Tucson, Arizona 85712, USA
| | - Mitchell A. Plummer
- Earth & Environmental Science Department, New Mexico Tech, Socorro, New Mexico 87801, USA
| | - David Elmore
- Purdue Rare Isotope Measurement Laboratory, Physics Department, Purdue University, West Lafayette, Indiana 47907-1396, USA
| | - Douglas H. Clark
- Department of Geology, Western Washington University, Bellingham, Washington 98225-9080, USA
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Thomas AL, Henderson GM, Deschamps P, Yokoyama Y, Mason AJ, Bard E, Hamelin B, Durand N, Camoin G. Penultimate deglacial sea-level timing from uranium/thorium dating of Tahitian corals. Science 2009; 324:1186-9. [PMID: 19390000 DOI: 10.1126/science.1168754] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The timing of sea-level change provides important constraints on the mechanisms driving Earth's climate between glacial and interglacial states. Fossil corals constrain the timing of past sea level by their suitability for dating and their growth position close to sea level. The coral-derived age for the last deglaciation is consistent with climate change forced by Northern Hemisphere summer insolation (NHI), but the timing of the penultimate deglaciation is more controversial. We found, by means of uranium/thorium dating of fossil corals, that sea level during the penultimate deglaciation had risen to ~85 meters below the present sea level by 137,000 years ago, and that it fluctuated on a millennial time scale during deglaciation. This indicates that the penultimate deglaciation occurred earlier with respect to NHI than the last deglacial, beginning when NHI was at a minimum.
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Affiliation(s)
- Alex L Thomas
- Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, UK.
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31. The last and the penultimate interglacial as recorded by speleothems from a climatically sensitive high-elevation cave site in the alps. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s1571-0866(07)80056-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Shimada S, Li YH, Rao MLN, Tanaka M. A PtIII2Si2 Four-Membered Cycle and a Dinuclear Platinum Complex Bridged by a Cyclodisiloxane Ring. Organometallics 2006. [DOI: 10.1021/om0604019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shigeru Shimada
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Yong-Hua Li
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Maddali L. N. Rao
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Masato Tanaka
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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Ingleson M, Fan H, Pink M, Tomaszewski J, Caulton KG. Three-Coordinate Co(I) Provides Access to Unsaturated Dihydrido-Co(III) and Seven-Coordinate Co(V). J Am Chem Soc 2006; 128:1804-5. [PMID: 16464075 DOI: 10.1021/ja0572452] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The three-coordinate, T-shaped Co(I) complex, PNPCo (PNP = [(tBu2PCH2SiMe2)2N-], is readily synthesized by magnesium reduction of divalent PNPCoCl. Triplet (S = 1) PNPCo is coordinatively and electronically unsaturated and undergoes a thermally reversible oxidative addition reaction with H2, producing trivalent PNPCo(H)2. In contrast, the reaction with excess primary silane PhSiH3 quantitatively generates the base-stabilized silylene Co(V) compound {kappa2-tBu2PCH2Me2SiNSiMe2CH2tBu2P(H)Si=}Co(H)3(SiH2Ph)2.
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Affiliation(s)
- Michael Ingleson
- Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405, USA
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Abstract
Quantum chemical calculations at DFT (BP86, B3LYP, BHLYP), MP2, CCSD, and CCSD(T) levels have been carried out on various fluoro complexes of gold in oxidation states +V through +VII to evaluate the previously claimed existence of AuF7. The calculations indicate clearly that elimination of F2 from AuF7 is a strongly exothermic reaction with a low activation barrier. This is inconsistent with the reported stability of AuF7 up to room temperature. A reported experimental vibrational frequency at 734 cm(-1) for AuF7 could not be verified computationally. It is concluded that the reported observation of AuF7 was probably erroneous. As the calculations indicate also an extremely large electron affinity and little stability for AuF6, Au(V) remains the highest well-established gold oxidation state.
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Affiliation(s)
- Sebastian Riedel
- Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
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Abrupt climate change of East Asian Monsoon at 130 kaBP inferred from a high resolution stalagmite δ18O record. CHINESE SCIENCE BULLETIN-CHINESE 2005. [DOI: 10.1007/bf02899648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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16
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Shimada S, Rao MLN, Li YH, Tanaka M. Reaction of 1-(Dimethylsilyl)-2-silylbenzene with Platinum(0) Phosphine Complexes. Organometallics 2005. [DOI: 10.1021/om050498j] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shigeru Shimada
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Maddali L. N. Rao
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Yong-Hua Li
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Masato Tanaka
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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Abstract
Sea level is a sensitive index of global climate that has been linked to Earth's orbital variations, with a minimum periodicity of about 21,000 years. Although there is ample evidence for climate oscillations that are too frequent to be explained by orbital forcing, suborbital-frequency sea-level change has been difficult to resolve, primarily because of problems with uranium/thorium coral dating. Here we use a new approach that corrects coral ages for the frequently observed open-system behavior of uranium-series nuclides, substantially improving the resolution of sea-level reconstruction. This curve reveals persistent sea-level oscillations that are too frequent to be explained exclusively by orbital forcing.
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Affiliation(s)
- William G Thompson
- Lamont-Doherty Earth Observatory (LDEO) and Department of Earth and Environmental Sciences, Columbia University, Palisades, NY 10964, USA.
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Chen W, Shimada S, Tanaka M, Kobayashi Y, Saigo K. Reaction of [2-(SiH3)C6H4]2SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)2: characterization of eta2-(Si-H)Ni and NiIV-H complexes. J Am Chem Soc 2004; 126:8072-3. [PMID: 15225021 DOI: 10.1021/ja039244k] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction of (2-SiH3C6H4)2SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)2 afforded a new silylnickel complex, which, in the solid state, was determined to be a bis(silyl)eta2-(Si-H)nickel complex, the first example of eta2-(Si-H)nickel complex by single-crystal X-ray analysis. Variable-temperature NMR spectroscopy revealed fluxional behavior of the complex in solution; at room temperature, exchange of five hydrogens (two SiH2 and one hydrogen bound to nickel) was observed, while at -80 degrees C the exchange of hydrogens appeared frozen to adopt a tris(silyl)(hydrido)nickel(IV) structure, which was confirmed by theoretical calculation. The latter complex is the first example of hydridonickel(IV) complex.
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Affiliation(s)
- Wanzhi Chen
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
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Yuan D, Cheng H, Edwards RL, Dykoski CA, Kelly MJ, Zhang M, Qing J, Lin Y, Wang Y, Wu J, Dorale JA, An Z, Cai Y. Timing, Duration, and Transitions of the Last Interglacial Asian Monsoon. Science 2004; 304:575-8. [PMID: 15105497 DOI: 10.1126/science.1091220] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Thorium-230 ages and oxygen isotope ratios of stalagmites from Dongge Cave, China, characterize the Asian Monsoon and low-latitude precipitation over the past 160,000 years. Numerous abrupt changes in 18O/16O values result from changes in tropical and subtropical precipitation driven by insolation and millennial-scale circulation shifts. The Last Interglacial Monsoon lasted 9.7 +/- 1.1 thousand years, beginning with an abrupt (less than 200 years) drop in 18O/16O values 129.3 +/- 0.9 thousand years ago and ending with an abrupt (less than 300 years) rise in 18O/16O values 119.6 +/- 0.6 thousand years ago. The start coincides with insolation rise and measures of full interglacial conditions, indicating that insolation triggered the final rise to full interglacial conditions.
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Affiliation(s)
- Daoxian Yuan
- Karst Dynamics Laboratory, Ministry of Land and Resources, 40 Qixing Road, Guilin 541004, China
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Lambeck K, Esat TM, Potter EK. Links between climate and sea levels for the past three million years. Nature 2002; 419:199-206. [PMID: 12226674 DOI: 10.1038/nature01089] [Citation(s) in RCA: 196] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on Earth -- the ice sheets and the oceans. Since the latest of these oscillations, the Last Glacial Maximum (between about 30,000 and 19,000 years ago), approximately 50 million cubic kilometres of ice has melted from the land-based ice sheets, raising global sea level by approximately 130 metres. Such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere, oceans, ice sheets and solid earth, all of which have different response timescales. The trigger for the sea-level fluctuations most probably lies with changes in insolation, caused by astronomical forcing, but internal feedback cycles complicate the simple model of causes and effects.
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Affiliation(s)
- Kurt Lambeck
- Research School of Earth Sciences, Australian National University, Canberra 0200, Australia
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Abstract
Is the Sun the controller of climate changes, only the instigator of changes that are mostly forced by the system feedbacks, or simply a convenient scapegoat for climate variations lacking any other obvious cause? This question is addressed for suggested solar forcing mechanisms operating on time scales from billions of years to decades. Each mechanism fails to generate the expected climate response in important respects, although some relations are found. The magnitude of the system feedbacks or variability appears as large or larger than that of the solar forcing, making the Sun's true role ambiguous. As the Sun provides an explicit external forcing, a better understanding of its cause and effect in climate change could help us evaluate the importance of other climate forcings (such as past and future greenhouse gas changes).
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Affiliation(s)
- D Rind
- NASA Goddard Institute for Space Studies (GISS) at Columbia University, 2880 Broadway, New York, NY 10025, USA.
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Affiliation(s)
- Thomas J Crowley
- Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA.
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