Late-glacial to late-Holocene shifts in global precipitation δ<sup>18</sup>O

Abstract

Abstract. Reconstructions of Quaternary climate are often based on the isotopic content of paleo-precipitation preserved in proxy records. While many paleo-precipitation isotope records are available, few studies have synthesized these dispersed records to explore spatial patterns of late-glacial precipitation δ18O. Here we present a synthesis of 86 globally distributed groundwater (n = 59), cave calcite (n = 15) and ice core (n = 12) isotope records spanning the late-glacial (defined as ~ 50 000 to ~ 20 000 years ago) to the late-Holocene (within the past ~ 5000 years). We show that precipitation δ18O changes from the late-glacial to the late-Holocene range from −7.1 ‰ (δ18Olate-Holocene > δ18Olate-glacial) to +1.7 ‰ (δ18Olate-glacial > δ18Olate-Holocene), with the majority (77 %) of records having lower late-glacial δ18O than late-Holocene δ18O values. High-magnitude, negative precipitation δ18O shifts are common at high latitudes, high altitudes and continental interiors (δ18Olate-Holocene > δ18Olate-glacial by more than 3 ‰). Conversely, low-magnitude, positive precipitation δ18O shifts are concentrated along tropical and subtropical coasts (δ18Olate-glacial > δ18Olate-Holocene by less than 2 ‰). Broad, global patterns of late-glacial to late-Holocene precipitation δ18O shifts suggest that stronger-than-modern isotopic distillation of air masses prevailed during the late-glacial, likely impacted by larger global temperature differences between the tropics and the poles. Further, to test how well general circulation models reproduce global precipitation δ18O shifts, we compiled simulated precipitation δ18O shifts from five isotope-enabled general circulation models simulated under recent and last glacial maximum climate states. Climate simulations generally show better inter-model and model-measurement agreement in temperate regions than in the tropics, highlighting a need for further research to better understand how inter-model spread in convective rainout, seawater δ18O and glacial topography parameterizations impact simulated precipitation δ18O. Future research on paleo-precipitation δ18O records can use the global maps of measured and simulated late-glacial precipitation isotope compositions to target and prioritize field sites.

Global Isotope Hydrogeology―Review

“…Other studies have attempted to quantify the original isotope composition of the groundwater prior to evaporation by extrapolating groundwater δ 2 H‐δ 18 O trend lines to identify intersections with LMWLs (e.g., Harrington et al, ; Saka et al, ). Fossil groundwaters located in humid and semiarid tropical and subtropical areas may have different isotope compositions from modern recharge, because of the different climate conditions that prevailed when fossil groundwaters recharged the aquifer (e.g., Calf, ). Global fossil groundwater isotope compositions (section ) demonstrate that the offset between late‐Holocene versus late‐Pleistocene meteoric water δ 18 O varies widely across the tropics (Jasechko et al, ). To evaluate if the sampled groundwaters derive from precipitation occurring within the past few decades—rather than representing relict climate conditions—it is advisable to combine groundwater δ 18 O measurements with age tracer data (see sections and ). Precipitation isotope samples are commonly collected at monthly intervals.…”

“…Fossil groundwater stable oxygen and hydrogen isotope compositions have been reviewed for Europe (Andrews, ; Arppe & Karhu, ; Edmunds, ; Eichinger et al, ; Jiráková et al, ; Loosli et al, ; Négrel & Petelet‐Giraud, ; Rozanski, ; Vaikmäe, Edmunds, & Manzano, ), Africa (Edmunds, ; Edmunds et al, ; Sonntag et al, ; Zuppi & Sacchi, ), southeastern Asia (Aggarwal et al, ) and west Asia (Ferronsky et al, )), and North America (Jasechko et al, ).…”

“…Further intercomparison of fossil groundwater records with other paleoclimate records, such as vadose zone geochemistry (Edmunds & Tyler, ) and speleothems (comparison of the Uitenhage paleowater record and the Cango Cave stalagmite; Vogel, ), may improve interpretations of past climate conditions. Where different types of isotopic records in similar locations have been compared, resulting ∆δ 18 O late‐Pleistocene values are often similar (Jasechko et al, ). Further intercomparison of isotopic records derived from different kinds of archives may improve proxy record interpretations (Darling, ).…”

Isotopic evidence for widespread cold‐season‐biased groundwater recharge and young streamflow across central Canada

“…However, few studies have explicitly quantified seasonal groundwater recharge ratio biases, and fewer still have quantified large‐scale spatial distributions of recharge‐seasonality biases (e.g., Sánchez‐Murillo & Birkel, ). Understanding the spatial patterns and variability of recharge ratios is important in order to help predict how groundwater recharge may respond to climatic shifts or to decadal‐scale changes to seasonal water balances, and to interpret the many isotope‐based records of quaternary climate such as speleothems and fossil groundwater (e.g., Bertrand et al, ; Chen et al, ; Clark, Stute, Schlosser, Drenkard, & Bonani, ; Darling, Edmunds, & Smedley, ; Edmunds & Wright, ; Jasechko et al, ; Phillips, Peeters, Tansey, & Davis, ; Plummer, ; Wagner et al, ; Wang et al, ; Wang et al, ).…”

Water and carbon stable isotope records from natural archives: a new database and interactive online platform for data browsing, visualizing and downloading

“…Recently, Caley and Roche (2013) focused on the difference between the LGM and the late Holocene (last 1000 years) for the comparison of the simulation from the iLOVECLIM model and proxy data and selected 17 polar ice core records, 10 speleothems, and 116 deep-sea cores with a test on age control following the protocol previously applied for the synthesis of temperature reconstructions by the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) collaborative effort (Waelbroeck et al, 2009). Also, Jasechko et al (2015) compiled 88 isotope records from ground water, speleothems and ice cores spanning the period from the LGM to the Late Holocene and compared these data to five general circulation models. These model-data comparisons have only used limited information extracted from a fraction of available proxy records, while much broader information has been accumulated during decades of field and laboratory work worldwide.…”