Yang Xiao-Yi

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Yang
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Xiao-Yi
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  • Article
    Time dependent flow of Atlantic water on the continental slope of the Beaufort Sea based on moorings
    (American Geophysical Union, 2021-05-26) Li, Jianqiang ; Lin, Peigen ; Pickart, Robert S. ; Yang, Xiao-Yi
    The flow and transformation of warm, salty Atlantic-origin water (AW) in the Arctic Ocean plays an important role in the global overturning circulation that helps regulate Earth's climate. The heat that it transports also impacts ice melt in different parts of the Arctic. This study uses data from a mooring array deployed across the shelf/slope of the Alaskan Beaufort Sea from 2002–2004 to investigate the flow of AW. A short-lived “rebound jet” of AW on the upper continental slope regularly follows wind-driven upwelling events. A total of 57 such events, lasting on average 3 days each, occurred over the 2 year period. As the easterly wind subsides, the rebound jet quickly spins up while the isopycnals continue to slump from their upwelled state. The strength of the jet is related to the cross-slope isopycnal displacement, which in turn is dependent on the magnitude of the wind, in line with previous modeling. Seaward of the rebound jet, the offshore-most mooring of the array measured the onshore branch of the AW boundary flowing eastward in the Canada Basin. However, the signature of the boundary current was only evident in the second year of the mooring timeseries. We suspect that this is due to the varying influence of the Beaufort Gyre in the two years, associated with a change in pattern of the wind stress curl that helps drive the gyre.
  • Article
    Decadal changes of wind stress over the Southern Ocean associated with Antarctic ozone depletion
    (American Meteorological Society, 2007-07-15) Yang, Xiao-Yi ; Huang, Rui Xin ; Wang, Dong Xiao
    Using 40-yr ECMWF Re-Analysis (ERA-40) data and in situ observations, the positive trend of Southern Ocean surface wind stress during two recent decades is detected, and its close linkage with spring Antarctic ozone depletion is established. The spring Antarctic ozone depletion affects the Southern Hemisphere lower-stratospheric circulation in late spring/early summer. The positive feedback involves the strengthening and cooling of the polar vortex, the enhancement of meridional temperature gradients and the meridional and vertical potential vorticity gradients, the acceleration of the circumpolar westerlies, and the reduction of the upward wave flux. This feedback loop, together with the ozone-related photochemical interaction, leads to the upward tendency of lower-stratospheric zonal wind in austral summer. In addition, the stratosphere–troposphere coupling, facilitated by ozone-related dynamics and the Southern Annular Mode, cooperates to relay the zonal wind anomalies to the upper troposphere. The wave–mean flow interaction and the meridional circulation work together in the form of the Southern Annular Mode, which transfers anomalous wind signals downward to the surface, triggering a striking strengthening of surface wind stress over the Southern Ocean.
  • Article
    Connection between the decadal variability in the Southern Ocean circulation and the Southern Annular Mode
    (American Geophysical Union, 2007-08-22) Yang, Xiao-Yi ; Wang, Dong Xiao ; Wang, Jia ; Huang, Rui Xin
    Previous studies demonstrated the remarkable upward trend of the Southern Annular Mode (SAM) and Southern Ocean wind stress in association with anthropogenic forcing. An oceanic reanalysis data set is used to investigate the response of the circulation in the Southern Ocean to the decadal variability of SAM. Our results indicate the strengthening and the poleward shift of the northward Ekman velocity as well as the Ekman pumping rate, which led to a corresponding strengthening trend in the Deacon Cell. This strengthening, in turn, intensified the meridional density gradient and the tilting of the isopycnal surfaces. On the interannual time scale, the Antarctic Circumpolar Currents (ACC) transport exhibits a positive correlation with SAM index as seen separately in observations. However, there is no significant trend in the total transport of ACC. Possible reasons are discussed.
  • Preprint
    Delayed baroclinic response of the Antarctic circumpolar current to surface wind stress
    ( 2008-01-11) Yang, Xiao-Yi ; Huang, Rui Xin ; Wang, Jia ; Wang, Dong Xiao
    Antarctic Circumpolar Current (ACC) responds to the surface windstress via two processes, i.e., instant barotropic process and delayed baroclinic process. This study focuses on the baroclinic instability mechanism in ACC. That is, the strengthening of surface zonal windstress causes the enhanced tilting of the isopycnal surface, which leads to the intense baroclinic instability. Simultaneously, the mesoscale eddies resulting from the baroclinic instability facilitate the transformation of mean potential energy to eddy energy, which causes the remarkable decrease of the ACC volume transport with the 2-year lag time. This delayed negative correlation between the ACC transport and the zonal windstress may account for the steadiness of the ACC transport in these two decades.