Pa.Th.Final - 231 Pa/ 230 Th A Paleocirculation Proxy...

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Unformatted text preview: 231 Pa/ 230 Th A Paleocirculation Proxy Andrea, Carly, Mitra, and Amanda 10/4/2010 231 Pa/ 230 Th • Ratios of 231 Pa/ 230 Th are used to study the rate of the Atlantic Meridional Overturning Circulation (AMOC) and the response of AMOC to external forcings • Pa and Th are produced from dissolved Uranium ( 235 U and 234 U) in the water column. 231 Pa/ 230 Th • 231 Pa – Half-life = 32.5 kyr – Residence time in water column = 200 years • 230 Th – Half-life = 75.7 kyr – Residence time in water column = 30 years Pa/Th Ratio • The residence time of 231 Pa is similar to the present residence time of North Atlantic Deep Water (NADW) • Nearly half 231 Pa is exported out of the Atlantic Ocean by deep-water circulation, while 230 Th does not significantly vary laterally. Pa/Th Ratio • Therefore, ratios of Pa/Th allow us to make inferences about water circulation rates in the past (Pa/Th correlates with Abrupt Climate Change) • Decreased AMOC rates occur during colder periods • Increased AMOC rates occur during warm periods Pa/Th: Analysis of samples...
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Pa.Th.Final - 231 Pa/ 230 Th A Paleocirculation Proxy...

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