The Influence Of Deep Water Circulation On The Distribution Of Pa-231 And Th-230 In The Pacific Ocean

Sedimentary Pa-231/Th-230 ratios have been used in the Atlantic Ocean as a proxy to reconstruct past changes in the strength and geometry of the Atlantic Meridional Overturning Circulation (AMOC), stemming from the southward export of Pa-231 by the North Atlantic Deep Water (NADW). However, deep waters in the Pacific Ocean have a longer residence time, so that Pacific sedimentary Pa-231/Th-230 ratios are more strongly affected by particle/boundary scavenging, which obscures the influence of deep water circulation. The goal of this study is to examine how the Pacific Meridional Overturning Circulation (PMOC) affects the distribution of Pa-231 and Th-230 in the water column and sediment of the Pacific Ocean, and to explore whether sedimentary 231 Pa/ 23 degrees Th ratios could provide useful constraints on past changes of the deep Pacific circulation. We examine the existing Pacific sedimentary Pa-231/Th-230 database and demonstrate that the Pacific Meridional Overturning Circulation (PMOC) has a distinctive influence on the distribution of sedimentary Pa-231/Th-230. Using a 2D scavenging model with a simplified representation of the Pacific deep water circulation, we show that Pacific sedimentary Pa-231/Th-230 could potentially provide information on past variability in PMOC. (C) 2020 Elsevier B.V. All rights reserved.