On bi-conservative surfaces in Minkowski 3-space

R. Caddeo et al. introduced the notion of bi-conservative submanifolds. By definition, such submanifolds have free divergence bi-tensor field, i.e. divS2=0, which is a generalization of biharmonic submanifolds. This work is done by proving that bi-conservative surfaces in the 3-dimensional Minkowski space are locally CMC surfaces, revolution of surfaces or null scrolls.