Depth-integrated steric height as a tool for detecting non-Sverdrup behavior in the global ocean
Authors: Godfrey, J. Stuart; Dunn, Jeff R.
Source: Journal of Marine Research, Volume 68, Numbers 3-4, May-July 2010 , pp. 387-412(26)
Publisher: Sears Foundation for Marine Research
Abstract:Godfrey's (1989) (referred to below as G89) calculation of the global field of annual mean Depth-Integrated Steric Height, or Sverdrup et al.'s (1942) "Transport Function," (Q) is revisited, using newer products for wind stresses, temperature and salinity. Observed Q and its wind-estimated equivalent QW are compared more extensively along eastern oceanic boundaries than in G89. Q and QW are also compared along the inner edge of the Pacific western boundary, at locations where G89 theory suggests that such a comparison is possible. A similar comparison along the western Atlantic improves after a 16 Sv correction for the supply of North Atlantic Deep Water. The observed circumpolar zero contour of Q is used to define an "ACC boundary." South of it, G89 fails grossly as expected. North of the boundary in each ocean basin, a "tongue" of high Q, about 1000 km wide, extends much farther eastward from its western boundary source than in comparable features in the northern hemisphere. The uninterrupted existence of this tongue across the full width of the Indian Ocean occurs because there is no analog in Q to the strong "meridional tip jet" west of southern Tasmania, found in QW—i.e. the East Australian Current is weaker in observed Q than predicted by G89. Elsewhere, each MTJ in QW does have an analog in observed Q; but the latter jets tend to follow local Sverdrup flow rather than being zonal. A final section provides qualitative discussion of the possible dynamics of these observed departures of Q from Sverdrup balance, north of the ACC.
Document Type: Research article
Publication date: 2010-05-01