Sediment <sup>231</sup>Pa/<sup>230</sup>Th as a recorder of the rate of the Atlantic meridional overturning circulation: insights from a 2-D model

Abstract

Abstract.A two dimensional scavenging model is used to investigate the patterns of sediment 231 Pa/ 230 Th generated by the Atlantic Meridional Overturning Circulation (AMOC) and further advance the application of this proxy for ocean paleocirculation studies. The scavenging parameters and the geometry of the overturning circulation cell have been chosen so that the model generates meridional sections of dissolved 230 Th and 231 Pa consistent with published water column profiles and an additional 12 previously unpublished profiles measured in the North and Equatorial Atlantic. The processes that generate the meridional sections of dissolved and particulate 230 Th, dissolved and particulate 231 Pa, dissolved and particulate 231 Pa/ 230 Th, and sediment 231 Pa/ 230 Th are discussed in detail. The results indicate that the relationship between sediment 231 Pa/ 230 Th at any given site and the overturning circulation is very complex. They clearly show that constraining past changes in the strength and geometry of the AMOC requires an extensive data set and they suggest strategies to maximize information from a limited number of samples.

<sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)

“…12c dash). Our results support that the depth dependence of particulate 231 Pa / 230 Th is mainly caused by lateral transport of 231 Pa by circulation (Gherardi et al, 2009;Lippold et al, 2011Lippold et al, , 2012aLuo et al, 2010;Rempfer et al, 2017). Overall, our model is able to simulate the correct magnitude of the sediment 231 Pa / 230 Th ratio response to the freshwater forcing.…”

“…However, the simulation of the particulate activity is not as good as the dissolved activity. Particulate activity is overall larger than observation in the surface ocean and smaller than observation in the deep ocean for both particulate 231 of 231 Pa from the North Atlantic to the Southern Ocean by AMOC (Gherardi et al, 2009;Lippold et al, 2011Lippold et al, , 2012aLuo et al, 2010;Rempfer et al, 2017). The sediment 231 Pa / 230 Th in CTRL is overall consistent with observations (references of observations are listed in Table 3).…”

“…The presence of 231 Pa and 230 Th has been simulated in previous modeling studies Luo et al, 2010;Marchal et al, 2000;Rempfer et al, 2017;Siddall et al, 2005). Marchal et al (2000) simulates 231 Pa and 230 Th in a zonally averaged circulation model, using the reversible scavenging model of Bacon and Anderson (1982).…”

State of the Climate in 2010

“…Trends in the MOC can also be determined through proxies of the MOC strength, such as paleo observations (e.g., Y. Luo et al 2010), tracers (e.g., Nelson et al 2010;LeBel et al 2008) and water mass characteristic (e.g. Kouketsu et al 2009;Zhang 2008).…”

A global scavenging and circulation ocean model of thorium-230 and protactinium-231 with realistic particle dynamics (NEMO–ProThorP 0.1)

“…The isotopes have been simulated in models of intermediate complexity, for instance by Henderson et al (1999) (LSG-OGCM), Marchal et al (2000) (EMIC 2.5D), Siddall et al (2007) (EMIC 3D), Heinze et al (2006) (HAMOCC) and Luo et al (2010). More complex ocean general circulation models models have also been used to simulate these tracers Dutay et al (2009) (NEMO-PISCES) and Rempfer et al (2017) (Bern3D).…”