HR: 0800h
AN: OS31A-0565    [Abstracts]
TI: Deacadal variations in hydrographic properties of Circumpolar Deep Water: revisit of WHP P6, A10, I3 and I4.
AU: * Kaneko, I
EM: ikuo-kaneko@jamstec.go.jp
AF: JAMSTEC, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Kawano, T
AF: JAMSTEC, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Yamamoto, H
AF: JAMSTEC, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Uchida, H
AF: JAMSTEC, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Fukasawa, M
AF: JAMSTEC, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Schneider, W
AF: Universidad de Concepcion, Departamento de Oceanografia, Barrio Universitario S/N, Concepcion, Cabina 5 Chile
AB: We compare potential temperature, salinity and dissolved oxygen (DO) along WHP-P6, A10, I3 and I4 sections observed in 2003 (BEAGLE2003) with those in the early 1990s (WOCE), focusing on inflows of the Circumpolar Deep Water (CDW) to the Pacific, Atlantic and Indian Oceans. Potential temperatures in the bottom and/or deep layers became higher by $0.01\deg$C or more in 2003 in the Brazil, Wharton and Southwest Basins, where the CDW enters each ocean without major modification. The near bottom salinities did not show common changes among the basins. Intensive analyses in the Southwest Pacific Basin revealed that potential temperatures in CDW increased by 0.01-$0.02\deg$C, while salinity and DO decreased by 0.004 and 3 $\mu$mol/kg, respectively, at maximum. The NADW salinity maximum core of S $>$ 34.72, which was lying at 3000 - 4000 m from the deep western boundary to the east of the Louisville Seamount Chain previously (1991-1992), shrank by half to the west of the chain. To clarify the cause of these changes, we compared the $\theta$-S and $\theta$-DO plots of P6-rivisit with those of P15S (in 1996). The P15S is a meridional section crossing P6 at $32.5\deg$S, $170\deg$W and covers a northward flow of the CDW toward the central Pacific Ocean. It was found that around $32.5\deg$S, $170\deg$W in 2003, the $\theta$-S and $\theta$-DO plots have shifted to the low-salinity and low-oxygen sides in $\theta$ $<$ $1.2\deg$C, but they were almost identical to the plots at $29\deg$S of P15S in 1996. This suggests that the meridional property distributions characterizing the northward intrusion and dissipation of CDW receded southward by 400 km in 2003. Meridional geostrophic transport integrated over the Southwest Pacific Basin beneath the reference level of 3500 dbar is 10.8 Sv (northward), which is 30% smaller than that in 1992. The similar result is obtained with an alternative reference level at $\theta$=$1.2\deg$C or $\gamma$$^{n}$=28.1, which corresponds to the upper boundary of the CDW. Thus, it is reasonable to suppose that the CDW inflow actually decreased during this decade. The time scale of the variations in properties and geostrophic flow should be clarified in further study. At the time of presentation, we will also show the results in other oceans.
DE: 4215 Climate and interannual variability (3309)
DE: 4271 Physical and chemical properties of seawater
DE: 4532 General circulation
DE: 4536 Hydrography
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting