Large deglacial shifts of the Pacific Intertropical Convergence Zone

Abstract

The position of the Intertropical Convergence Zone (ITCZ) is sensitive to changes in the balance of heat between the hemispheres which has fundamental implications for tropical hydrology and atmospheric circulation. Although the ITCZ is thought to experience the largest shifts in position during deglacial stadial events, the magnitude of shifts has proven difficult to reconstruct, in part because of a paucity of high-resolution records, particularly those including spatial components. Here we track the position of the ITCZ from 150 to 110 ka at three sites in the central equatorial Pacific at sub-millennial time resolution. Our results provide evidence of large, abrupt changes in tropical climate during the penultimate deglaciation, coincident with North Atlantic Heinrich Stadial 11 (∼136–129 ka). We identify this event both as a Northern Hemisphere increase in aeolian dust and as a shift in the mean position of the ITCZ a minimum of 4° southwards at 160° W.

The Penultimate Glacial Termination and Variability of the Pacific Intertropical Convergence Zone

“…We calculated dust fluxes for cores 20BB and 28BB based on the 230 Th‐derived 232 Th flux (Figure c). At these sites, MIS 6 dust fluxes are more than twice as large as MIS 5 dust fluxes, generally matching the glacial/interglacial pattern previously found in this transect (Jacobel et al, ). The largest dust flux is found at 20BB during the onset of HS11, where dust flux peaks at 135 kyr.…”

“…Paleo‐proxy records during the penultimate deglaciation. The oxygen isotope data for cores 17PC, 31BB, and 37 are from Lynch‐Stieglitz et al (), while the dust flux for those same cores are from Jacobel et al (). (a) Sanbao cave δ18O time series (SB11—cyan; SB23—light blue; SB25—blue; SB25‐2—dark blue); see references for errors (Cheng et al, ; Y. Wang et al, ).…”

“…The 230 Th‐normalized dust flux, using 232 Th as the proxy for dust and assuming an average crustal 232 Th concentration of 10.7 ppm (Taylor & McLennan, ). The 20BB and 28BB errors are standard error for 17PC, 31BB, and 37BB errors Jacobel et al (). Symbols as in panel (b).…”

“…There have been several studies which have determined changes in dust fluxes to the equatorial Pacific through the last climate cycles (e.g., Anderson et al, ; Costa et al, ; Kienast et al, ; Loveley et al, ; McGee et al, ; Pichat et al, ; Winckler et al, ). Some have used this information to reconstruct movements of the ITCZ on millennial (Jacobel et al, ; Loveley et al, ) and glacial‐interglacial timescales (Jacobel, McManus, et al, ), but few studies combine equatorial Pacific flux estimates with radiogenic isotope data, which can highlight possible dust sources (Pichat et al, ; Xie & Marcantonio, ). Here, that approach allows us to evaluate changes in the provenance of dust delivered to the CEP at 158°W along a transect from 0.48°N to 7.04°N.…”

Investigating the use of 232Th/230Th as a dust proxy using co-located seawater and sediment samples from the low-latitude North Atlantic

“…This depth dependence is likely caused by either a deficit of 230 Th burial at depth compared to the production in the overlying water column, through addition of constrained parameters such as the surface properties of the dust source regions, giving rise 9 to uncertainties in simulated fluxes . Given the relative scarcity of 10 direct observations ), geochemical proxy methods provide a 11 means of testing and improving these models as well as our knowledge of dust fluxes 12 (Anderson et al, 2016). 13 14 A widely used method has been the measurement of Al concentrations in the dissolved 15 phase in seawater e.g.…”