How calculate maximum SST gradient over the 1000m isobath?

Dear all,

I need to find the maximum SST (sea surface temperature) gradient over a isobath of 1000 meters.

Basically, I have one matrix of bathymetry contour(lon,lat,h,[-1000 -1000]) and I need to find the indices of this contourline where my matrix of gradient of SST [where [FX,FY] = gradient(SST)]: contourf(lon,lat,FY) is maximum. I tried to use contourcs, contourc and contourdata, but they give me just xdata e ydata from level and I need the indices, I think.

Does anyone have any idea how I can do this?

Thank you.