Information - GD01 Geodynamics of the Early Earth: The development of southern high-latitude seaways and their impact on global evolution
Plate tectonic reconstructions show that Drake Passage was most probably the final barrier to deep circumpolar ocean currents. The opening of the new gateway facilitated the formation of the Antarctic Circumpolar Current, which is proposed to have influenced the Cenozoic global cooling and the Antarctic glaciation. There is, however, a present debate about the relative importance of the Southern Ocean gateways on global cooling. In this respect, the abrupt EoceneľOligocene (ca. 33 Ma) cooling event may have started earlier than the full opening of Drake Passage. Alternative models propose that closure of low-latitude gateways may bear a greater relative importance for Cenozoic climate evolution than the opening of the southern gateways The analysis of coupled climate/ice-sheet simulations indicates that CO2 decline was the prime cause of the abrupt EoceneľOligocene cooling and that the opening of southern ocean gateways played only a minor role. It is suggested, however, using a coupled ocean-atmosphere model of intermediate complexity, that opening at shallow depths sufficed to bring about Southern Hemisphere cooling and a significant increase in Antarctic sea-ice, but North Atlantic thermohaline circulation and Northern Hemisphere warming occurred only when Drake Passage opened to full ocean depths. The timing of the opneign of the southern hemisphere gateways and their impact on global change will be analyzed during this session.
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