Knots and links in 3–manifolds are studied by applying intersection invariants to
singular concordances. The resulting link invariants generalize the Arf invariant, the
mod 2 Sato–Levine invariants and Milnor’s triple linking numbers. Besides
fitting into a general theory of Whitney towers, these invariants provide
obstructions to the existence of a singular concordance which can be homotoped to
an embedding after stabilization by connected sums with S2× S2. Results
include classifications of stably slice links in orientable 3–manifolds, stable
knot concordance in products of an orientable surface with the circle and
stable link concordance for many links of null-homotopic knots in orientable
3–manifolds.