Richey Julie N.

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Julie N.

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Now showing 1 - 4 of 4
  • Dataset
    Record of d2H of dinosterol variability in down core lake sediments from Clear Lake, Palau
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact:, 2019-08-02) Sachs, Julian P. ; Richey, Julie N.
    Record of d2H of dinosterol variability in down core lake sediments from Clear Lake, Palau. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at:
  • Article
    Remote and local drivers of Pleistocene South Asian summer monsoon precipitation: a test for future predictions
    (American Association for the Advancement of Science, 2021-06-04) Clemens, Steven C. ; Yamamoto, Masanobu ; Thirumalai, Kaustubh ; Giosan, Liviu ; Richey, Julie N. ; Nilsson-Kerr, Katrina ; Rosenthal, Yair ; Anand, Pallavi ; McGrath, Sarah M.
    South Asian precipitation amount and extreme variability are predicted to increase due to thermodynamic effects of increased 21st-century greenhouse gases, accompanied by an increased supply of moisture from the southern hemisphere Indian Ocean. We reconstructed South Asian summer monsoon precipitation and runoff into the Bay of Bengal to assess the extent to which these factors also operated in the Pleistocene, a time of large-scale natural changes in carbon dioxide and ice volume. South Asian precipitation and runoff are strongly coherent with, and lag, atmospheric carbon dioxide changes at Earth’s orbital eccentricity, obliquity, and precession bands and are closely tied to cross-equatorial wind strength at the precession band. We find that the projected monsoon response to ongoing, rapid high-latitude ice melt and rising carbon dioxide levels is fully consistent with dynamics of the past 0.9 million years.
  • Article
    GDGT and alkenone flux in the northern Gulf of Mexico : implications for the TEX86 and UK'37 paleothermometers
    (John Wiley & Sons, 2016-12-19) Richey, Julie N. ; Tierney, Jessica E.
    The TEX86 and UKˈ37 molecular biomarker proxies have been broadly applied in downcore marine sediments to reconstruct past sea surface temperature (SST). Although both TEX86 and UKˈ37 have been interpreted as proxies for mean annual SST throughout the global ocean, regional studies of glycerol dibiphytanyl glycerol tetraethers (GDGTs) and alkenones in sinking particles are required to understand the influence of seasonality, depth distribution, and diagenesis on downcore variability. We measure GDGT and alkenone flux, as well as the TEX86 and UKˈ 37 indices in a 4 year sediment trap time series (2010–2014) in the northern Gulf of Mexico (nGoM), and compare these data with core-top sediments at the same location. GDGT and alkenone fluxes do not show a consistent seasonal cycle; however, the largest flux peaks for both occurs in winter. UKˈ 37 covaries with SST over the 4 year sampling interval, but the UKˈ 37-SST relationship in this data set implies a smaller slope or nonlinearity at high temperatures when compared with existing calibrations. Furthermore, the flux-weightedUKˈ 37 value from sinking particles is significantly lower than that of underlying core-top sediments, suggesting preferential diagenetic loss of the tri-unsaturated alkenone in sediments. TEX86 does not covary with SST, suggesting production in the subsurface upper water column. The flux-weighted mean TEX86 matches that of core-top sediments, confirming that TEX86 in the nGoM reflects local planktonic production rather than allochthonous or in situ sedimentary production. We explore potential sources of uncertainty in both proxies in the nGoM but demonstrate that they show nearly identical trends in twentieth century SST, despite these factors.
  • Article
    Merging late Holocene molecular organic and foraminiferal-based geochemical records of sea surface temperature in the Gulf of Mexico
    (American Geophysical Union, 2011-03-09) Richey, Julie N. ; Hollander, David J. ; Flower, Benjamin P. ; Eglinton, Timothy I.
    A molecular organic geochemical proxy (TEX86) for sea surface temperature (SST) is compared with a foraminifera-based SST proxy (Mg/Ca) in a decadal-resolution marine sedimentary record spanning the last 1000 years from the Gulf of Mexico. We assess the relative strengths of the organic and inorganic paleoceanographic techniques for reconstructing high-resolution SST variability during recent climate events, including the Little Ice Age (LIA) and the Medieval Warm Period (MWP). SST estimates based on the molecular organic proxy TEX86 show a similar magnitude and pattern of SST variability to foraminiferal Mg/Ca-SST estimates but with some important differences. For instance, both proxies show a cooling (1°C–2°C) of Gulf of Mexico SSTs during the LIA. During the MWP, however, Mg/Ca-SSTs are similar to near-modern SSTs, while TEX86 indicates SSTs that were cooler than modern. Using the respective SST calibrations for each proxy results in TEX86-SST estimates that are 2°C–4°C warmer than Mg/Ca-SST throughout the 1000 year record. We interpret the TEX86-SST as a summer-weighted SST signal from the upper mixed layer, whereas the Mg/Ca-SST better reflects the mean annual SST. Downcore differences in the SST estimates between the two proxies (ΔT = TEX86 − Mg/Ca) are interpreted in the context of varying seasonality and/or changing water column temperature gradients.