Deep ocean circulation and transport where the East Pacific Rise at 9–10°N meets the Lamont seamount chain
Animation 1: Model potential temperature (color) and horizontal currents sampled every 2 h at a depth of 2525 m, just above the ridge crest depth. Seamounts display in white. (13.15Mb)
Animation 2: Model potential temperature (color) and flow vectors sampled every 2 h on a zonal transect across the EPR at 9.5°N. The aspect ratio for the vectors is identical to that shown for the topography. (19.21Mb)
Animation 3: Model vertical velocities sampled every 2 h at a depth of 2500 m. Outward radiating internal waves are seen to be generated primarily at the Lamont Seamounts. Internal wave reflections at domain boundaries are successfully suppressed by the model sponge in these 74 day model integrations. (18.33Mb)
Animation 4: The 7 day averaged flow vectors sampled daily at a depth of 2500 m. To highlight north and south directional flow, vectors east of 104.5°W were colored red (blue) when flow had a north (south) component. (3.402Mb)
Animation 5: Contours in color of vertically integrated model SF6 tracer concentrations on a log scale. Mimicking the field experiment, 3 kg of tracer were discharged at the ridge crest at 9.5°N on 12 November 2006. Subsequent SF6 field sampling locations and times are indicated by fleeting cyan triangles. (8.945Mb)
Lavelle, J. William
Thurnherr, Andreas M.
Ledwell, James R.
McGillicuddy, Dennis J.
Mullineaux, Lauren S.
MetadataShow full item record
KeywordMid-ocean ridge; Abyssal ocean currents; Numerical model; SF6 tracer; Inverse calculation; Eastern tropical Pacific
We report the first 3-D numerical model study of abyssal ocean circulation and transport over the steep topography of the East Pacific Rise (EPR) and adjoining Lamont seamount chain in the eastern tropical Pacific. We begin by comparing results of hydrodynamical model calculations with observations of currents, hydrography, and SF6 tracer dispersion taken during Larval Dispersal on the Deep East Pacific Rise (LADDER) field expeditions in 2006–2007. Model results are then used to extend observations in time and space. Regional patterns are pronounced in their temporal variability at M2 tidal and subinertial periods. Mean velocities show ridge-trapped current jets flowing poleward west and equatorward east of the ridge, with time-varying magnitudes (weekly average maximum of ∼10 cm s−1) that make the jets important features with regard to ridge-originating particle/larval transport. Isotherms bow upward over the ridge and plunge downward into seamount flanks below ridge crest depth. The passage (P1) between the EPR and the first Lamont seamount to the west is a choke point for northward flux at ridge crest depths and below. Weekly averaged velocities show times of anticyclonic flow around the Lamont seamount chain as a whole and anticyclonic flow around individual seamounts. Results show that during the LADDER tracer experiment SF6 reached P1 from the south in the western flank jet. A short-lived change in regional flow direction, just at the time of SF6 arrival at P1, started the transport of SF6 to the west on a course south of the seamounts, as field observations suggest. Approximately 20 days later, a longer-lasting shift in regional flow from west to SSE returned a small fraction of the tracer to the EPR ridge crest.
Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C12073, doi:10.1029/2010JC006426.
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