Unexpected Climate Dynamics in the Southern Tropical Pacific During Marine Isotope Stage 3. A high resolution glacial record of rainfall from a Niuean stalagmite
Unexpected Climate Dynamics in the Southern Tropical Pacific During Marine Isotope Stage 3. A high resolution glacial record of rainfall from a Niuean stalagmite
Date: 12 August 2016 Time: 4.00 pmSpeaker: Dr Dan Sinclair, Environmental Geochemist, Victoria University of Wellington
The climate of the glacial period (~12-110 ka) was fundamentally unstable. Rapid warming (Dansgaard-Oeschger Events) punctuated the cold conditions of the Northern Hemisphere, disrupting atmospheric circulation across much of the planet. In the tropics, these events manifested as wholesale northward shifts in the latitudinal position of the Intertropical Convergence Zone (ITCZ) – the band of storms and rainfall that girdles the equator. However, high-resolution paleoclimate records are completely lacking from the central tropical south Pacific, which hosts the largest yet most enigmatic component of tropical circulation: the South Pacific Convergence Zone (SPCZ). In this talk I present a new high-resolution record of SPCZ dynamics during Marine Isotope Stage 3 extracted from a stalagmite from the island of Niue.
The data suggest that the SPCZ experienced sudden shifts that lasted centuries. Between 45-37ka, rainfall changes at Niue were remarkably similar in timing and duration to several D-O Events recorded in Greenland ice cores, revealing for the first time that central tropical South Pacific climate could strongly couple with changes in the high northern latitudes. However, these results also present several puzzling contradictions: rainfall changes were in the opposite sense to predictions, and the coupling was not consistent through time. In this talk I reveal a new conceptual model for how climate in the southern tropical Pacific couples with high Northern latitudes, and why this might change in response to changing orbital parameters.