The isotope hydrology of quaternary climate change☆

Abstract

Understanding the links between climate change and human migration and culture is an important theme in Quaternary archaeology. While oxygen and hydrogen stable isotopes in high-latitude ice cores provide the ultimate detailed record of palaeoclimate extending back to the Middle Pleistocene, groundwater can act as a climate archive for areas at lower latitudes, permitting a degree of calibration for proxy records such as lake sediments, bones and organic matter. Not only can oxygen and hydrogen stable isotopes be measured on waters, but the temperature of recharge can be calculated from the amount of the noble gases neon, argon, krypton and xenon in solution, while residence time can be estimated from the decay of the radioisotopes carbon-14, chlorine-36 and krypton-81 over timescales comparable to the ice core record. The Pleistocene-Holocene transition is well characterised in aquifers worldwide, and it is apparent that isotope-temperature relationships of the present day are not necessarily transferable to past climatic regimes, with important implications for the interpretation of proxy isotope data. Groundwaters dating back to one million years, i.e. to beyond the Middle Pleistocene, are only found in major aquifer basins and information is relatively sparse and of low resolution. Speleothem fluid inclusions offer a way of considerably increasing this resolution, but both speleothem formation and large-scale groundwater recharge require humid conditions which may be relatively infrequent for areas currently experiencing arid climates. Both types of record therefore require caution in their interpretation when considering a particular archaeological context.

Temporal variation of stable isotopes in a precipitation–groundwater system: implications for determining the mechanism of groundwater recharge in high mountain–hills of the Loess Plateau, China

“…; Currell et al . ; Liu et al ., ; Darling ). In particular, the ancient groundwater recharged before Holocene generally shows much depleted oxygen isotopic signature (Li et al ., ).…”

Global Isotope Hydrogeology―Review

“…Fossil groundwater recharged during the late‐Pleistocene has been identified in over 100 aquifer systems around the globe (e.g., Münnich & Vogel, ; Edmunds & Wright, ; Fontes, ; Edmunds et al, , ; Darling, ; Haldorsen et al, ; Figure ; Table ). Measurements of fossil groundwater δ 18 O values can provide information about Pleistocene climate conditions (Andrews et al, ; Bertrand et al, ; Haggaz & Kheirallah, ; Joussaume & Jouzel, ) or the fate of paleo‐meltwaters derived from large Pleistocene ice sheets (e.g., the Laurentide ice sheet—Desaulniers et al, ; Siegel & Mandle, ; Bottomley et al, ; Siegel, ; Remenda et al, ; Grasby & Betcher, , ; Clark et al, ; Grasby & Chen, ; Ferguson et al, ; Person et al, ; Jasechko et al, ; McIntosh et al, ; Stotler et al, ; Ferguson & Jasechko, ; Vetter et al, ; Ellis & Jasechko, ; Birks et al, —and the Fennoscandian ice sheet—Boulton et al, ; Vaikmäe, Vallner, et al, ; Vaikmäe, Edmunds, et al, ; Raidla et al, ; Pärn et al, , ; Gerber et al, ).…”

“…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, ).…”

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

“…Changes to freeze-thaw conditions of the ground surface between the latter half of the last glacial time period and the modern climates may have impacted the seasonality of the fraction of precipitation recharging aquifers and thus 18 O late-glacial (Darling, 2004(Darling, , 2011Jasechko et al, 2014). Geomorphic evidence suggests permafrost covered portions of Hungary at the last glacial maximum, suggesting that land temperatures may have been up to 15 • C cooler than present day (Fábián et al, 2014), a larger late-glacial to late-Holocene temperature shift than earlier, noble gasbased reconstructions (5-7 • C; Deák et al, 1987).…”