The Role of Southern High Latitude Wind Stress in Global Climate |
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Authors: | MA Hao WU Lixin and LI Chun |
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Institution: | Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100,Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100,Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100 |
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Abstract: | In this paper, the role of westerly winds at southern high
latitudes in global climate is investigated in a fully coupled
ocean-atmosphere general circulation model. In the model, the wind
stress south of 40oS is turned off with ocean and
atmosphere fully coupled both locally and elsewhere. The coupled
model explicitly demonstrates that a shutdown of southern high
latitude wind stress induces a general cooling over the Antarctic
Circumpolar Current (ACC) region, with surface Ekman flow and
vertical mixing playing competitive roles. This cooling leads to an
equatorward expansion of sea ice and triggers an equivalent
barotropic response in the atmosphere to accelerate westerly
anomalies.
The shutdown of southern high latitude wind stress also
significantly reduces global meridional overturning circulation
(MOC). The Antarctic MOC (AnMOC) nearly disappears while the
Atlantic MOC (AMOC) is weakened by 50%, suggesting a strong
control of the southern high latitude winds over the thermohaline
circulation (THC). In spite of a substantial weakening of the AMOC,
the interhemispheric SST seesaw appears to be not significant due to
an equatorward extension of the southern extratropical cooling
through coupled wind-evaporation-SST (WES) feedback. In addition, it
is found that the weakening of Atlantic MOC by as much as 50% is
capable of cooling the time mean subpolar Atlantic temperature by
only about 1oC. |
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Keywords: | Antarctic Circumpolar Current wind stress SST thermohaline circulation |
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