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  • 1
    Publication Date: 2020-02-06
    Description: The Last Glacial Maximum (LGM, 21 000 years ago) is one of the suite of paleoclimate simulations included in the current phase of the Coupled Model Intercomparison Project (CMIP6). It is an interval when insolation was similar to the present, but global ice volume was at a maximum, eustatic sea level was at or close to a minimum, greenhouse gas concentrations were lower, atmospheric aerosol loadings were higher than today, and vegetation and land-surface characteristics were different from today. The LGM has been a focus for the Paleoclimate Modelling Intercomparison Project (PMIP) since its inception, and thus many of the problems that might be associated with simulating such a radically different climate are well documented. The LGM state provides an ideal case study for evaluating climate model performance because the changes in forcing and temperature between the LGM and pre-industrial are of the same order of magnitude as those projected for the end of the 21st century. Thus, the CMIP6 LGM experiment could provide additional information that can be used to constrain estimates of climate sensitivity. The design of the Tier 1 LGM experiment (lgm) includes an assessment of uncertainties in boundary conditions, in particular through the use of different reconstructions of the ice sheets and of the change in dust forcing. Additional (Tier 2) sensitivity experiments have been designed to quantify feedbacks associated with land-surface changes and aerosol loadings, and to isolate the role of individual forcings. Model analysis and evaluation will capitalize on the relative abundance of paleoenvironmental observations and quantitative climate reconstructions already available for the LGM.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
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  • 2
    Publication Date: 2023-02-08
    Description: Rapid monsoon changes since the last deglaciation remain poorly constrained due to the scarcity of geological archives. Here we present a high-resolution scanning X-ray fluorescence (XRF) analysis of a 13.5 m terrace succession on the western Chinese Loess Plateau (CLP) to infer rapid monsoon changes since the last deglaciation. Our results indicate that Rb∕Sr and Zr∕Rb are sensitive indicators of chemical weathering and wind sorting, respectively, which are further linked to the strength of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM). During the last deglaciation, two cold intervals of the Heinrich event 1 and Younger Dryas were characterized by intensified winter monsoon and weakened summer monsoon. The EAWM gradually weakened at the beginning of the Holocene, while the EASM remained steady till 9.9 ka and then grew stronger. Both the EASM and EAWM intensities were relatively weak during the Middle Holocene, indicating a mid-Holocene climatic optimum. Rb∕Sr and Zr∕Rb exhibit an antiphase relationship between the summer and winter monsoon changes on a centennial timescale during 16–1 ka. Comparison of these monsoon changes with solar activity and North Atlantic cooling events reveals that both factors can lead to abrupt changes on a centennial timescale in the Early Holocene. During the Late Holocene, North Atlantic cooling became the major forcing of centennial monsoon events.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2022-03-10
    Description: Geological records show that vast proglacial lakes existed along the land terminating margins of palaeo ice sheets in Europe and North America. Proglacial lakes impact ice sheet dynamics by imposing marine-like boundary conditions at the ice margin. These lacustrine boundary conditions include changes in the ice sheet’s geometry, stress balance and frontal ablation and therefore affect the entire ice sheet’s mass balance. This interaction, however, has not been rigorously implemented in ice sheet models. In this study, the implementation of an adaptive lake boundary into the Parallel Ice Sheet Model (PISM) is described and applied to the glacial retreat of the Laurentide Ice Sheet (LIS). The results show that the presence of proglacial lakes locally enhances the ice flow. Along the continental ice margin, ice streams and ice lobes can be observed. Lacustrine terminating ice streams cause immense thinning of the ice sheet’s interior and thus play a significant role in the demise of the LIS. Due to the presence of lakes, a process similar to the marine ice sheet instability causes the collapse of the ice saddle over Hudson Bay, which blocked drainage via the Hudson Strait. In control experiments without a lake model, Hudson Bay is still glaciated at the end of the simulation. Future studies should target the development of parametrizations that better describe the glacial-lacustrine interactions.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2016-10-18
    Description: Author(s): Chengxian Zhang, Xu-Chen Yang, and Xin Wang We study theoretically the responses of the dynamically corrected gates to time-dependent noises in the exchange-only spin-qubit system. We consider 1 / f noises having spectra proportional to 1 / ω α , where the exponent α indicates the strength of correlation within the noise. The quantum gate errors du… [Phys. Rev. A 94, 042323] Published Mon Oct 17, 2016
    Keywords: Quantum information
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
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  • 5
    Publication Date: 2023-08-01
    Description: During the Late Pleistocene and Holocene retreat of paleo-ice sheets in North America and Europe, vast proglacial lakes existed along the land terminating margins. These proglacial lakes impacted ice sheet dynamics by imposing boundary conditions analogous to a marine terminating margin. Such lacustrine boundary conditions cause changes in the ice sheet geometry, stress balance and frontal ablation and therefore affect the mass balance of the entire ice sheet. Despite this, dynamically evolving proglacial lakes have rarely been considered in detail in ice sheet modeling endeavors. In this study, we describe the implementation of an adaptive lake boundary in the Parallel Ice Sheet Model (PISM), which we call PISM-LakeCC. We test our model with a simplified glacial retreat setup of the Laurentide Ice Sheet (LIS). By comparing the experiments with lakes to control runs with no lakes, we show that the presence of proglacial lakes locally enhances the ice flow, which leads to a lowering of the ice sheet surface. In some cases, this also results in an advance of the ice margin and the emergence of ice lobes. In the warming climate, increased melting on the lowered ice surface drives the glacial retreat. For the LIS, the presence of lakes triggers a process similar to marine ice sheet instability, which caused the collapse of the ice saddle over Hudson Bay. In the control experiments without lakes, Hudson Bay is still glaciated when the climate reaches present-day (PD) conditions. The results of our study demonstrate that glacio-lacustrine interactions play a significant role in the retreat of land terminating ice sheet margins.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2018-04-17
    Description: Author(s): Chengxian Zhang, Xu-Chen Yang, and Xin Wang A triple-quantum-dot system can be operated as either an exchange-only qubit or a resonant-exchange qubit. While it is generally believed that the decisive advantage of the resonant-exchange qubit is the suppression of charge noise because it is operated at a sweet spot, we show that the leakage is ... [Phys. Rev. A 97, 042326] Published Mon Apr 16, 2018
    Keywords: Quantum information
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
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  • 7
    Publication Date: 2014-02-19
    Description: Author(s): Yunhui Wang, Chao Yu, Qi Shi, Yadong Zhang, Xu Cao, Shicheng Jiang, and Ruifeng Lu We theoretically investigate harmonic generation driven by intense midinfrared lasers. A valleylike structure is observed at very low-order harmonics because of a low-energy photoelectron suppression effect. Further, at the beginning of a broad supercontinuum, a convex structure appears that is dist... [Phys. Rev. A 89, 023825] Published Tue Feb 18, 2014
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
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  • 8
    Publication Date: 2014-01-15
    Description: Author(s): Zhe Zhang, Xu Shan, Tian Wang, Enliang Wang, and Xiangjun Chen We report the first measurement on vibrationally resolved electron momentum spectroscopy of H2 by using a high-resolution (e, 2e) spectrometer. The vibrational-specific experimental momentum profiles have been obtained and shown to be in agreement with calculations of (e, 2e) ionization cross sectio... [Phys. Rev. Lett. 112, 023204] Published Tue Jan 14, 2014
    Keywords: Atomic, Molecular, and Optical Physics
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 9
    Publication Date: 2017-11-08
    Description: Author(s): Mingliang Zhang, Xu Zhang, Ling-Yi Huang, Hai-Qing Lin, and Gang Lu Charge transport is crucial to the performance of hybrid halide perovskite solar cells. A theoretical model based on large polarons is proposed to elucidate charge transport properties in the perovskites. Critical new physical insights are incorporated into the model, including the recognitions that... [Phys. Rev. B 96, 195203] Published Tue Nov 07, 2017
    Keywords: Semiconductors I: bulk
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 10
    Publication Date: 2017-11-18
    Description: Author(s): Robert E. Throckmorton, Chengxian Zhang, Xu-Chen Yang, Xin Wang, Edwin Barnes, and S. Das Sarma We present a set of experimentally feasible pulse sequences that implement any single-qubit gate on a singlet-triplet spin qubit and demonstrate that these new sequences are up to three times faster than existing sequences in the literature. We show that these sequences can be extended to incorporat... [Phys. Rev. B 96, 195424] Published Fri Nov 17, 2017
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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