ITCZ MOVEMENT
NASA GOES Satellite image of the ITCZ
I have been working on tracking past changes in the position of the Intertropical Convergence Zone (ITCZ) since I was a graduate student. Our work began using dust (232Th) to track ITCZ-related aerosol rainout and has continued as our work on the central equatorial Pacific’s Line Islands region has expanded.
New Controls on Sedimentation and Climate in the Central Equatorial Pacific Ocean
(In Review with GChron)
Abstract:
The equatorial Pacific is a nexus of oceanic and atmospheric phenomena, and its regional climate has critical implications for the partitioning of CO2, hydroclimate, and temperature on a global scale. The spatial complexity of climate signals across the basin has long posed a challenge for interpreting the interplay of different climate phenomena including changes in the Intertropical Convergence Zone and El Niño Southern Oscillation. Here, we present new, millennially resolved sediment core records from three sites, and updated chronologies for four previously studied cores from the central equatorial Pacific’s Line Islands region. We use planktonic δ18O data to draw inferences about surface water salinity and to infer a southward-shifted position for the ITCZ at the Last Glacial Maximum (18-24 ka) and Marine Isotope Stage 6 (138-144 ka). We also present new records of coarse fraction abundance and individual foraminifera density to investigate changes in deep sea carbonate saturation and alkalinity. These new sites improve our understanding of equatorial Pacific climate and show strong promise for surface and deep ocean paleoclimate reconstructions over the last several glacial cycles.
Note the changes in the spread of d18O with (colors indicate core latitude) through time. Our new work interprets changes in the d18O gradient (in tandem with Mg/Ca) as indicative of ITCZ shifts impacting the Line Islands.
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.
Read the LDEO press release here