Variability of subduction rates of the subtropical North Pacific mode waters |
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| Authors: | Haibo Hu Qinyu Liu Yuan Zhang Wei Liu |
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| Institution: | HU Haibo 1,**,LIU Qinyu 2,ZHANG Yuan 3,LIU Wei 4 1 School of Atmospheric Sciences,Nanjing University,Nanjing 210093,China 2 Physical Oceanography Laboratory & Ocean-Atmosphere Interaction and Climate Laboratory,Ocean University of China,Qingdao 266100,China 3 School of Atmospheric Sciences,Nanjing University of Information Science and Technology,China 4 Center for Climatic Research and Department of Atmospheric and Oceanic Sciences University of Wisconsin-Madison,Madison,53705,... |
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| Abstract: | The climatology subduction rate for the entire Pacific is known, but the mechanism of interannual to decadal variation remains
unclear. In this study, we calculated the annual subduction rates of three types of North Pacific subtropical mode waters
using a general circulation model (LICOM1.0) for the period of 1958–2001. The model experiments focused on interannual variations
of ocean dynamical processes under daily wind forcings and seasonal heat fluxes. The mode water formation region was defined
by a potential vorticity minimum at outcrop locations. The model results show that two subduction rate maxima (>100 m/a) were
located in the Subtropical Mode Water (STMW) and the Central Mode Water (CMW) formation regions. These regions are consistent
with a climatologically calculated value. The subduction rate in the Eastern Subtropical Mode Water (ESTMW) formation region
was smaller at about 75 m/a. The subduction rate shows clear interannual and decadal variations associated with oceanic dynamic
variabilities. The average subduction rate of the STMW was much smaller during the period of 1981–1990 compared with other
periods, while that of the CMW had a negative anomaly before 1975 and a positive anomaly after 1978. The variability agreed
with Ekman and geostrophic advections and mixed layer depths. The interannual variability of the subduction rate for the ESTMW
was smallest during 1970–1990, as a result of a weak wind stress curl. This paper explores how interannual signals from the
atmosphere are stored in different parts of the ocean, and thus may contribute to a better understanding of feedback mechanisms
for the Pacific Decadal Oscillation (PDO) event. |
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| Keywords: | subduction rate North Pacific subtropical mode water ocean modeling |
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