FY 1993

Flow of deep and bottom waters in the Pacific at 10°N

Johnson, G.C., and J.M. Toole

Deep-Sea Res. Pt. I, 40(2), doi: 10.1016/0967-0637(93)90009-R, 371–394 (1993)

Flow of Lower Circumpolar Water and North Pacific Deep Water is described in the Pacific at 10°N primarily using a recent trans-Pacific CTD/O section. Water-mass properties are used to define boundaries at potential isotherms for these two water masses. In turn, zero-velocity surfaces are set at different potential isotherms in each ocean basin along 10°N, their selection guided by the water-mass properties and the thermal wind field. These surfaces are then applied to estimate transport for each of the water masses. Net transport of Lower Circumpolar Water is estimated at 5.8 × 10 m s (positive northward) in the East Mariana Basin and 8.1 × 10 m s in the Central Pacific Basin, while a small flow of 0.4 × 10 m s through the Yap Trench into the Philippines Basin is inferred. In the Northeast Pacific Basin a transport of -4.7 × 10 m s over the western flank of the East Pacific Rise is estimated. There is no Lower Circumpolar Water in the Guatemala Basin, thus the net transport of Lower Circumpolar Water across 10°N in the Pacific is estimated to be 9.6 × 10 m s. A net transport of -2.6 × 10 m s of North Pacific Deep Water is estimated across this latitude, with the most robust feature being a transport of -3.6 × 10 m s over the western flank of the East Pacific Rise in the Northeast Pacific Basin. Recent repeated hydrographic measurements in the Western Pacific are used to confirm the transport estimates for the two westernmost basins. Finally, small adjustments to the 10°N flow field (changes within the uncertainties of the present calculations) are shown to result in a transport scheme that is consistent with previous studies at 24°N.