Plate tectonics and polar ocean gateways: The keys to understanding long-term global change Water mass exchange between world oceans is of great significance for long-term global climatic change and is controlled by tectonic and sedimentary evolution of oceanic gateways and basins. Reconstructions of the geological history of polar oceanic basins and gateways feed into computer simulations of climate change. PLATES & GATES is an international program focussing on the tectonic and sedimentary formation of those areas of the Arctic and Antarctica which are in particular critical for global change.