Topology sheds new light on the emergence of unidirectional edge waves in a variety of physical
systems, from condensed matter to artificial lattices. Waves observed in geophysical flows are
also robust to perturbations, which suggests a role for topology. We show a topological origin for
two celebrated equatorially trapped waves known as Kelvin and Yanai modes, due to the Earth.s
rotation that breaks time-reversal symmetry. The non-trivial structure of the bulk Poincare .wave
modes encoded through the first Chern number of value 2 guarantees existence for these waves. The
invariant demonstrates that ocean and atmospheric waves share fundamental properties with
topological insulators, and that topology plays an unexpected role in the Earth climate system.
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