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Abstract Terrestrial‐marine dust fluxes, pedogenic carbonate δ13C values, and various paleovegetation proxies suggest that Africa experienced gradual cooling and drying across the Pliocene‐Pleistocene (Plio‐Pleistocene) boundary (2.58 million years ago [Ma]). However, the timing, magnitude, resolution, and relative influences of orbitally‐driven changes in high latitude glaciations and low latitude insolation differ by region and proxy. To disentangle these forcings and investigate equatorial eastern African climate across the Plio‐Pleistocene boundary, we generated a high‐resolution (∼3,000‐year) data set of compound‐specificn‐alkane leaf wax δ2H values—a robust proxy for atmospheric circulation and precipitation amount—from the HSPDP‐BTB13‐1A core, which spans a ∼3.3–2.6 Ma sequence in the Baringo‐Tugen Hills‐Barsemoi Basin of central Kenya. In combination with the physical sedimentology, our data indicate that precipitation varied strongly with orbital obliquity, not precession, during the late Pliocene, perhaps imparted by variations in the cross‐equatorial insolation gradient. We also observe a marked shift toward wetter conditions beginning ∼3 Ma that corresponds with global cooling, drying in western Australia, and a steepening of the west‐east zonal Indian Ocean (IO) sea surface temperature (SST) gradient. We propose that northward migration of the Subtropical Front reduced Agulhas current leakage, warming the western IO and causing changes in the IO zonal SST gradient at 3 Ma, a process that has been observed in the latest Pleistocene‐Holocene but not over longer timescales. Thus, the late Cenozoic moisture history of eastern Africa is driven by a complex mixture of low‐latitude insolation, the IO SST gradient, and teleconnections to distal high‐latitude cooling.
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Jovian Sodium Nebula and Io Plasma Torus S + and Brightnesses 2017–2023: Insights Into Volcanic Versus Sublimation Supply
Abstract We present first results derived from the largest collection of contemporaneously recorded Jovian sodium nebula and Io plasma torus in [S II] 6731 Å images assembled to date. The data were recorded by the Planetary Science Institute's Io Input/Output observatory and provide important context to Io geologic and atmospheric studies as well as theJunomission and supporting observations. Enhancements in the observed emission are common, typically lasting 1–3 months, such that the average flux of material from Io is determined by the enhancements, not any quiescent state. The enhancements are not seen at periodicities associated with modulation in solar insolation of Io's surface, thus physical process(es) other than insolation‐driven sublimation must ultimately drive the bulk of Io's atmospheric escape. We suggest that geologic activity, likely involving volcanic plumes, drives escape.
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- Award ID(s):
- 2109219
- PAR ID:
- 10531505
- Publisher / Repository:
- AGU Publications/Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 129
- Issue:
- 3
- ISSN:
- 2169-9380
- Subject(s) / Keyword(s):
- Io, Jovian sodium nebula, Io plasma torus, Jupiter magnetosphere, Io volcanism
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1029/2023JA032081
