Estimates and Implications of Surface Eddy Diffusivity in the Southern Ocean Derived from Tracer Transport

نویسندگان

  • JOHN MARSHALL
  • EMILY SHUCKBURGH
  • HELEN JONES
  • CHRIS HILL
چکیده

Near-surface “effective diffusivities” associated with geostrophic eddies in the Southern Ocean are estimated by numerically monitoring the lengthening of idealized tracer contours as they are strained by surface geostrophic flow observed by satellite altimetry. The resulting surface diffusivities show considerable spatial variability and are large (2000 m s ) on the equatorward flank of the Antarctic Circumpolar Current and are small (500 m s ) at the jet axis. Regions of high and low effective diffusivity are shown to be collocated with regions of, respectively, weak and strong isentropic potential vorticity gradients. The maps of diffusivity are used, along with climatological estimates of surface wind stress and air–sea buoyancy flux, to estimate surface meridional residual flows and the relative importance of Eulerian and eddy-induced circulation in the streamwise-averaged dynamics of the Antarctic Circumpolar Current.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Understanding the Regional Variability of Eddy Diffusivity in the Pacific Sector of the Southern Ocean

A diagnostic framework is presented, based on the Nakamura effective diffusivity, to investigate the regional variation in eddy diffusivity. Comparison of three different diffusivity calculations enables the effects of locally enhanced tracer diffusion to be distinguished from the streamwise average. It also enables the distinction to be made between locally generated complexity in the tracer s...

متن کامل

Quantifying the eddy diffusivity of the Southern Ocean II: spatial variability and the role of the mean flow

A diagnostic framework is presented, based on the Nakamura effective diffusivity, to investigate the regional variation in eddy diffusivity. Comparison of three different diffusivity calculations enables the effects of locally enhanced tracer diffusion to be distinguished from the streamwise average and the distinction between locally generated complexity in the tracer structure and between tha...

متن کامل

Evidence for deep eddy mixing in the Southern Ocean

Satellite altimetric observations of the ocean reveal surface pressure patterns in the core of the Antarctic Circumpolar Current (ACC) that propagate downstream (eastward) but slower than the mean surface current by about 25%. We argue that these observations are suggestive of baroclinically unstable waves that have a steering level at a depth of about 1 km. Detailed linear stability calculatio...

متن کامل

Mixed layer lateral eddy fluxes mediated by air-sea interaction

The modulation of air-sea heat fluxes by geostrophic eddies due to the stirring of temperature at the sea surface is discussed and quantified. It is argued that the damping of eddy temperature variance by such air-sea fluxes enhances the dissipation of surface temperature fields. Depending on the timescale of damping relative to that of the eddying motions, surface eddy diffusivities can be sig...

متن کامل

The Southern Ocean Overturning: Parameterized versus Permitted Eddies

Four versions of the same global climate model, with horizontal resolution ranging from 1.88 3 3.68 to 0.28 3 0.48, are employed to evaluate the resolution dependence of the Southern Ocean meridional overturning circulation. At coarse resolutions North Atlantic Deep Water tends to upwell diabatically at low latitudes, so that the Southern Ocean is weakly coupled with the rest of the ocean. As r...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2005