Late-glacial to late-Holocene shifts in global precipitation δsup18/supO

摘要

Reconstructions of Quaternary climate are often based on the isotopiccontent of paleo-precipitation preserved in proxy records. While manypaleo-precipitation isotope records are available, few studies havesynthesized these dispersed records to explore spatial patterns oflate-glacial precipitation δ18O. Here we present a synthesisof 86 globally distributed groundwater (n = 59), cave calcite (n = 15) andice core (n = 12) isotope records spanning the late-glacial (defined as~ 50 000 to ~ 20 000 years ago) to thelate-Holocene (within the past ~ 5000 years). We show thatprecipitation δ18O changes from the late-glacial to thelate-Holocene range from ?7.1 ‰ (δ18O_{late-Holocene} > δ18O_late-glacial) to +1.7 ‰ (δ18O_late-glacial > δ18O_{late-Holocene}), with the majority (77 %) of recordshaving lower late-glacial δ18O than late-Holocene δ18O values. High-magnitude, negative precipitation δ18Oshifts are common at high latitudes, high altitudes and continentalinteriors (δ18O_{late-Holocene} > δ18O_late-glacial by more than 3 ‰).Conversely, low-magnitude, positive precipitation δ18O shiftsare concentrated along tropical and subtropical coasts (δ18O_late-glacial > δ18O_{late-Holocene} by less than 2 ‰).Broad, global patterns of late-glacial to late-Holocene precipitationδ18O shifts suggest that stronger-than-modern isotopicdistillation of air masses prevailed during the late-glacial, likelyimpacted by larger global temperature differences between the tropics andthe poles. Further, to test how well general circulation models reproduceglobal precipitation δ18O shifts, we compiled simulatedprecipitation δ18O shifts from five isotope-enabled generalcirculation models simulated under recent and last glacial maximum climatestates. Climate simulations generally show better inter-model andmodel-measurement agreement in temperate regions than in the tropics,highlighting a need for further research to better understand howinter-model spread in convective rainout, seawater δ18O andglacial topography parameterizations impact simulated precipitation δ18O. Future research on paleo-precipitation δ18O recordscan use the global maps of measured and simulated late-glacialprecipitation isotope compositions to target and prioritize field sites.