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  • 1
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    Explaining the global distribution of peak-spectrum variability of sea surface height (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 35 (2008): L14602, doi:10.1029/2008GL034312.
    Description: A 14-year satellite observation of sea surface height (SSH) reveals an interesting pattern. Along any latitude, there is a frequency at which the SSH power spectrum peaks, regardless of which hemisphere or oceanic basin. This peak-spectrum frequency is nearly identical to the critical frequency at which the zonal energy propagation of Rossby waves becomes stagnant. The interior ocean adjusts to atmospheric forcing by radiating energy away through Rossby waves. There are two distinct groups of Rossby waves, long ones carry the energy to the west while short ones send the energy to the east. At the critical frequency, these two waves merge and their zonal energy propagation becomes stagnant. Consequently, the energy from atmospheric forcing may accumulate in the ocean interior, and thus result in a spectrum peak.
    Description: This study is supported by China’s National Basic Research Priorities Programmer (2005CB422303 and 2007CB411804), the key project of the International Science and Technology Cooperation program of China (2006DFB21250), the Ministry of Education’s 111 Project (B07036), the Program for New Century Excellent Talents in University (NECT-07-0781), and the US National Science Foundation (OCE-0351055).
    Keywords: Sea surface height ; Peak spectrum ; Stagnant Rossby wave
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    The Kuroshio Extension : a leading mechanism for the seasonal sea-level variability along the west coast of Japan (2010)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Ocean Dynamics 60 (2010): 667-672, doi:10.1007/s10236-009-0239-9.
    Description: Sea level changes coherently along the two coasts of Japan on the seasonal time scale. AVISO satellite altimetry data and OFES (OGCM for the Earth Simulator) results indicate that the variation propagates clockwise from Japan's east coast through the Tsushima Strait into the Japan/East Sea (JES) and then northward along the west coast. In this study, we hypothesize and test numerically that the sea level variability along the west coast of Japan is remotely forced by the Kuroshio Extension (KE) off the east coast. Topographic Rossby waves and boundary Kelvin waves facilitate the connection. Our 3-d POM model when forced by observed wind stress reproduces well the seasonal changes in the vicinity of JES. Two additional experiments were conducted to examine the relative roles of remote forcing and local forcing. The sea level variability inside the JES was dramatically reduced when the Tsushima Strait is blocked in one experiment. The removal of the local forcing, in another experiment, has little effect on the JES variability. Both experiments support our hypothesis that the open-ocean forcing, possibly through the KE variability, is the leading forcing mechanism for sea level change along the west coast of Japan.
    Description: This work was conducted when Chao Ma was a visiting graduate student at WHOI. His visit has been supported by China Scholarship Council and WHOI Academics Office. This study has been supported by WHOI’s Coastal Ocean Institute, the National Basic Research Program of China 2005CB422303 and 2007CB481804), the International Science and Technology Cooperation Program of China (2006DFB21250), the Natural Science Foundation of China (40706006) , and the Ministry of Education’s 111 Project (B07036). Lin was supported by the Program for New Century Excellent Talents in University (NECT-07-0781).
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 3
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    Wind-driven exchanges between two basins : some topographic and latitudinal effects (2013)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 4585–4599, doi:10.1002/jgrc.20333.
    Description: This study examines some topographic effects on the island rule. We use an idealized and barotropic model to investigate the throughflow between a semienclosed marginal sea and a larger oceanic basin that are connected to each other by two channels. Two sets of experiments are conducted in parallel, one with a flat bottom and the other with a ridge between two basins. The model results show that the ridge affects the island rule considerably in several ways. First, the ridge blocks geostrophic contours and restricts a free exchange between two basins. The bottom pressure torque (or the form drag) is a dominant term in the balance of the depth-integrated vorticity budget and always results in a significant reduction of the throughflow transport. Second, horizontal friction promotes cross-isobathic flows and enhances the throughflow transport over the ridge. This is the opposite of what friction does in the original island rule in which a friction tends to reduce the throughflow transport. Third, the forcing region in the open ocean for the marginal-sea throughflow is shifted meridionally. Last, the topographic effect becomes small near the equator due to its dependence on f. This may explain why the PV barrier effect is smaller in the South China Sea than in the Japan/East Sea. The limitation of the barotropic model and some baroclinic effects will be discussed.
    Description: This study has been supported by the National Science Foundation grants OCE 1028739, OCE 0927017, ARC 1107412, and ARC 0902090 (J.Y.), the WHOI Coastal Institute, and by the Ministry of Education’s 111 Project (B07036), National Basic Research Priorities Programmer (2013CB956202), Natural Science Foundation (41222037, 41221063), Natural Science Foundation of Shandong (JQ201111), and Public Welfare Scientific Research Project (201205018) of China (X.L. and D.W.).
    Description: 2014-03-18
    Keywords: Topography
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    On the mechanism of the cyclonic circulation in the Gulf of Tonkin in the summer (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C09029, doi:10.1029/2007JC004208.
    Description: The circulation in the Gulf of Tonkin had been traditionally considered to be anticyclonic in the summer. This view was challenged recently by results from reanalyzing observational data, which clearly revealed that the circulation is cyclonic in all seasons. The surface wind stress is monsoonal, southwesterly in the summer and reversed in the winter. It remains unexplained why the circulation is always cyclonic, while the surface forcing reverses seasonally. In this study, we hypothesize that the inflow through Qiongzhou Strait, a shallow and narrow channel between Hainan Island and the Chinese mainland, is responsible for maintaining the cyclonic circulation in the summer. Besides the requirements of mass conservation and bathymetry constraint, this flow, even with a rather small transport, carries a considerable amount of potential vorticity (PV) into the gulf, and the integral constraint of PV requires the presence of a frictional torque to be associated with a cyclonic circulation. Several numerical experiments with a three-dimensional model have been conducted to test this hypothesis. When the westward flow through Qiongzhou Strait is blocked, the model simulates an anticyclonic circulation in the summer. When the westward flow through Qiongzhou Strait is allowed, the circulation changes to a cyclonic one, consistent with our hypothesis.
    Description: This study is supported by the National Basic Research Program of China under contract 2005CB422302 and 2007CB411804, the key project of the International Science and Technology Cooperation program of China under contract 2006DFB21250, and the 111 project under contract B07036.
    Keywords: Gulf of Tonkin ; Cyclonic circulation ; Potential vorticity
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 5
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    An open-ocean forcing in the East China and Yellow seas (2011)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C12056, doi:10.1029/2010JC006179.
    Description: Recent studies have demonstrated that the annual mean barotropic currents over the East China and Yellow seas (ECYS) are forced primarily by the oceanic circulation in the open-ocean basin through the Kuroshio Current (KC), the western boundary current of the subtropical gyre in the North Pacific Ocean. The local wind stress forcing plays an important but secondary role. Those previous results were mainly qualitative and from a simple barotropic model forced by a steady wind stress field. They remain to be tested in a more complete 3-D model with both wind stress and buoyancy fluxes. In addition, the seasonal variability of major ECYS currents may involve different forcing mechanisms than their annually averaged fields do, and this can only be addressed when a seasonally varying forcing is used in the model. In this paper, we will address these issues by using a 3-D baroclinic model. Our results confirm the finding from the previous studies that the KC is the primary forcing mechanism for major annually mean currents in the ECYS, which include the Taiwan Strait Current, the Tsushima Warm Current, and the Yellow Sea Warm Current (YSWC), etc. However, the local monsoonal forcing plays a prominent role in modulating the seasonal variability of all major currents in the region. A deep northwestward intrusion of the YSWC in winter, for instance, is mainly due to a robustly developed China Coastal Current and Korea Coastal Current, which draw water along the Yellow Sea Trough to feed the southward flows along the west and east coasts of the Yellow Sea.
    Description: This work was supported by the National Basic Research Program of China (2005CB422302), the International Science and Technology Cooperation Program of China (2006DFB21250), the Program of Introducing Talents of Discipline to Universities (B07036), the National Natural Science Foundation of China (41006003), and the U.S. National Science Foundation.
    Keywords: East China and Yellow seas ; Kuroshio Current ; POM
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    On the dynamics of the seasonal variation in the South China Sea throughflow transport (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 6854–6866, doi:10.1002/2013JC009367.
    Description: The Luzon Strait transport (LST) of water mass from the Pacific Ocean to the South China Sea (SCS) varies significantly with seasons. The mechanisms for this large variability are still not well understood. The steady-state island rule, which is derived from a steady-state model, is not applicable to seasonal time scale variations in a large basin like the Pacific Ocean. In this paper, we will use a theoretical model that is based on the circulation integral around the Philippines. The model relates the LST variability to changes in the boundary currents along the east coast of the Philippines, including the North Equatorial Current (NEC) Bifurcation Latitude (NECBL), the transports of Kuroshio and Mindanao Currents (KC and MC), and to the local wind-stress forcing. Our result shows that a northward shift of the NECBL, a weakening of the KC or a strengthening of the MC would enhance the LST into the SCS. This relationship between the LST and the NEC-KC-MC is consistent with observations. The analytical result is tested by a set of idealized numerical simulations.
    Description: This study has been supported by the National Science Foundation Grants (OCE 1028739, 0927017) (JY), and by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA11010103), the project of Global Change and Air-Sea interaction (GASI-03-01-01-02), the Natural Science Foundation of China (40930844, 41222037), the National Basic Research Program of China (2013CB956202), Ministry of Education’s 111 Project (B07036) of China, Yong Science Foundation of Shandong (JQ201111) and Public science and technology research funds projects of ocean (201205018) (XL and DW).
    Description: 2014-06-16
    Keywords: South China Sea ; Throughflow ; Transport ; Seasonal variations ; Island rule
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    On the dynamics of the South China Sea Warm Current (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C08003, doi:10.1029/2007JC004427.
    Description: The South China Sea Warm Current (SCSWC) flows northeastward over the shelf and continental slope in the northern South China Sea (SCS). This current persists in its northeastward direction in all seasons despite the fact that the annually averaged wind stress is decisively southwestward against it. Two major mechanisms have been proposed in previous studies, one attributing it directly to the wind stress forcing within the SCS and the other to the Kuroshio intrusion through the Luzon Strait. In this study we use a simple model to demonstrate that neither of them is the leading forcing mechanism. Instead, the SCSWC is a source- and sink-driven flow induced by the Taiwan Strait Current (TSC), a year-round northward flow through the Taiwan Strait. The two previously suggested mechanisms are important but secondary. The model simulations show that the local wind stress alone would force a current in the opposite direction to the SCSWC. Blocking the Kuroshio intrusion through the Luzon Strait, on the other hand, only weakens the SCSWC. The SCSWC vanishes when the Taiwan Strait is closed in the model.
    Description: This study has been supported by the U.S. National Science Foundation (OCE-0351055), China’s International Science and Technology Cooperation Program (2006DFB21250), and China’s National Basic Research Priorities Program (2005CB422302).
    Keywords: South China Sea ; Warm current ; Dynamics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Western boundary currents regulated by interaction between ocean eddies and the atmosphere (2016)
    Nature Research
    In:  Nature, 535 (7613). pp. 533-537.
    Details
    Publication Date: 2019-09-23
    Description: Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean’s western boundaries1. Even with an enhanced grid resolution to resolve ocean mesoscale eddies—energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents—the bias problem can still persist2; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air–sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20–40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models’ representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events3, 4, 5, 6, as well as in the projection of the effect on these events of climate change.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/nature18640
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  • 9
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    Model-based estimate of the heat budget in the East China Sea (2010)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 115 (C8). C08026.
    Details
    Publication Date: 2018-01-18
    Description: Using a global ocean model with regionally focused high resolution (1/10°) in the East China Sea (ECS), we studied the oceanic heat budget in the ECS. The modeled sea surface height variability and eddy kinetic energy are consistent with those derived from satellite altimetry. Significant levels of eddy kinetic energy are found east of the Ryukyu Islands and east of Taiwan, where the short-term variability is spawned by active mesoscale eddies coalescing with the circulation. Furthermore, the simulated vertical cross-stream structure of the Kuroshio (along the Pollution Nagasaki line) and the volume transport through each channel in the ECS are in good agreement with the observational estimates. The time-averaged temperature fluxes across the Taiwan Strait (TWS), Tsushima Strait (TSS), and the 200 m isobath between Taiwan and Japan are 0.20 PW, 0.21 PW, and 0.05 PW, respectively. The residual heat flux of 0.04 PW into the ECS is balanced by the surface heat loss. The eddy temperature flux across the 200 m isobath is 0.005 PW, which accounts for 11.2% of the total temperature flux. The Kuroshio onshore temperature flux has two major sources: the Kuroshio intrusion northeast of Taiwan and southwest of Kyushu. The Ekman temperature flux induced by the wind stress in the ECS shows the same seasonal cycle and amplitude as the onshore temperature flux, with a maximum in autumn and a minimum in summer. We conclude that the Ekman temperature flux dominates the seasonal cycle of Kuroshio onshore flux.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2009JC005869
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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