Southward displacement of the glacial westerly jet over Asia driven by enhanced Arctic amplification after the Mid-Brunhes Event

Evaluating the Drivers of Quaternary Dust Fluxes to the Western North Pacific: East Asian Dustiness and Northern Hemisphere Gustiness

“…Wang et al, 2018). We note that the hypothesis of Jonas et al (2023) could explain the relatively similar glacial dust fluxes at ODP 1208 during the late Pleistocene, as the westerlies would be located south of major dust sources during each one of these glacial intervals. However, this leaves the question of why, if the westerlies are no longer located over major Asian dust source regions, dust is still higher during glacials compared to interglacials in the mid-latitude and subarctic North Pacific, which has been widely observed (Hovan et al, 1991;Kawahata et al, 2000;Maeda et al, 2002;Rea & Leinen, 1988;Serno et al, 2017;Xu et al, 2015).…”

“…(2021), who state that the westerlies move equatorward and intensify during glacials after the intensification of Northern Hemisphere Glaciation due to the development of ice sheets and strengthened meridional temperature gradients, then it may be suggested that during progressively more intense glacials such as those found during the late Quaternary, the westerlies could hypothetically shift so far south that ODP 1208 would have received less Asian dust during glacials at some point in the Quaternary. In fact, recent work has put forth this exact mechanism to explain decreased n‐alkane fluxes to the mid‐latitude North Pacific after the Mid‐Bruhnes Event (Jonas et al., 2023). We can evaluate this hypothesis considering our three proposed scenarios described above along with the major assumption that, outside of climatic thresholds, the position and intensity of the westerlies scale with meridional temperature gradients and ice volume.…”

“…Jonas et al. (2023) suggest that this major positional change in the westerlies could occur if the westerly jet stream was permanently located south of the Tibetan Plateau during peak glacial conditions. At present, the results from other proxy and modeling work could be used to both confirm or reject this notion (e.g., Gray et al., 2020; Lei et al., 2021; N. Wang et al., 2018).…”

“…Considering modeling output of dust deposition to the Pacific Ocean (e.g., Albani et al, 2014), it would likely require an extreme shift of the westerlies between late Pliocene-early Pleistocene glacials and those of the late Pleistocene in order to produce the approximately two-fold reduction in glacial dust deposition observed at ODP 1208. Jonas et al (2023) suggest that this major positional change in the westerlies could occur if the westerly jet stream was permanently located south of the Tibetan Plateau during peak glacial conditions. At present, the results from other proxy and modeling work could be used to both confirm or reject this notion (e.g., Gray et al, 2020;Lei et al, 2021;N.…”