Testing the²³¹Pa/²³⁰Th paleocirculation proxy: A data versus 2D model comparison

231Pa/230Th evidence for a weakened but persistent Atlantic meridional overturning circulation during Heinrich Stadial 1

“…Data north of 45°S were used for the LGM and HS1 to account for the northward shift of the Southern Ocean opal belt during the LGM, in keeping with Yu et al 1 The average 231 Pa/ 230 Th ratio in LGM sediments (0.065±0.005; n ¼ 79) is similar to the value obtained by Yu et al 1 (0.059±0.007; n ¼ 26; Fig. 2); this study 15,16,[20][21][22][23]25,27,28,30,39,40,[54][55][56] . The average ratio for HS1 (0.074 ± 0.009; n ¼ 26) is somewhat greater than the LGM value, but not significantly different at the 95% confidence level; this study 15,16,21,22,25,27,30,39,40,54 .…”

“…The average ratio for HS1 (0.074 ± 0.009; n ¼ 26) is somewhat greater than the LGM value, but not significantly different at the 95% confidence level; this study 15,16,21,22,25,27,30,39,40,54 . The average 231 Pa/ 230 Th ratio in Holocene sediment north of 50°S (0.070 ± 0.004; n ¼ 165) is greater than Yu et al, a result that is significant at the 95% confidence level (Yu et al Holocene 231 Pa/ 230 Th: 0.060 ± 0.004; n ¼ 68); this study 1,15,16,[20][21][22]25,27,28,30,39,40,[54][55][56][57][58][59][60][61][62][63][64][65][66] . Because many of the older data were generated using alpha counting, the relative errors are somewhat larger.…”

“…2b). The highest ratio, measured at 1.2 km in the NE Atlantic, is in an area characterized by high scavenging today 27 , while deeper cores show lower ratios 21,28,29 (Fig. 2b).…”

‘Study the past, if you would divine the future’: a retrospective on measuring and understanding Quaternary climate change

“…Both isotopes are produced in seawater by the decay of uranium but protactinium is less easily adsorbed onto settling particles, and so is more likely to be carried away by currents. As the strength of the AMOC declines, therefore, the ratio of 231 Pa to 230 Th approaches the mean value of seawater (Siddall et al ., ; Gherardi et al ., ; Lippold et al ., ).…”

Relative timing of precipitation and ocean circulation changes in the western equatorial Atlantic over the last 45 ky

“…Recent studies have shown that the caveats that may apply to this proxy in some areas do not apply to the western tropical Atlantic region. More specifically, a study including core top material from the western tropical Atlantic margin and using a 2-D model (Luo et al, 2010) showed that the measured Pa/Th vertical profile is consistent with a dominant role of the overturning circulation, rather than particle scavenging, thereby demonstrating that Pa/Th can be used to record changes in water mass overturning rates in that 15 region (Lippold et al, 2011). However, because there are large increases in terrigenous material deposition on the north-east scavenging by boundary scavenging can be intensified in times of reduced overturning circulation due to boundary scavenging becoming the main control on sedimentary Pa/Th.…”