A Tibetan ice core covering the past 1,300 years radiometrically dated with ³⁹ Ar

Abstract

Ice cores from alpine glaciers are unique archives of past global and regional climate conditions. However, recovering climate records from these ice cores is often hindered by the lack of a reliable chronology, especially in the age range of 100 to 500 anni (a) for which radiometric dating has not been available so far. We report on radiometric 39 Ar dating of an ice core from the Tibetan Plateau and the construction of a chronology covering the past 1,300 a using the obtained 39 Ar ages. This is made possible by advances in the analysis of 39 Ar using the laser-based detection method atom trap trace analysis, resulting in a twofold increase in the upper age limit of 39 Ar dating. By measuring the anthropogenic 85 Kr along with 39 Ar we quantify and correct modern air contamination, thus removing a major systematic uncertainty of 39 Ar dating. Moreover, the 85 Kr data for the top part of the ice core provide information on firn processes, including the age difference between the ice and its enclosed gas. This first application of 39 Ar and 85 Kr to an ice core facilitates further ice cores from nonpolar glaciers to be used for recovering climate records of the Common Era, a period including pronounced anomalies such as the Little Ice Age and the Medieval Warm Period.

First insights into the age of the giant ice deposits in the Eisriesenwelt cave (Austria)

“…Finally, there is a novel radiometric technique emerging which utilizes the very rare noble gas 39 Ar radioisotope, trapped in ice during its formation. The half-life of 39 Ar is 269 years, permitting the direct dating of ice as old as about two millennia 46 . In a test study, 4.2–6.7 kg samples of ice from the base of two glaciers in the Tyrolian and the Swiss Alps were analyzed.…”

A constructed PDO history for the past three centuries derived from an ice core isotope record on the central Tibetan Plateau

“…Interannual variations in precipitation δ 18 O driven by ENSO can also be preserved in ice core records. Simulation studies have demonstrated a close relationship between the interannual variation of δ 18 O in the Dasuopu ice core from the Himalayas and monsoon index, highlighting the strong influence of large-scale monsoon circulation 13 . Variations in δ 18 O and dust in ice core records are significantly correlated with large-scale atmospheric circulation patterns in the central TP 14 .…”

“…Oxygen isotopes (δ 18 O) in ice cores serve as natural proxies for past climate change and atmospheric circulation variations 1,2 . Ice core analyses in polar regions have yielded valuable insights into Earth's paleoclimate history during the Glacial-Interglacial timescale 3,4 .…”

“…Additionally, δ 18 O records in ice cores drilled on the Tibetan Plateau (TP) have been interpreted as temperature proxies 5,6 , however, this interpretation has been subject to debate 7 . Recent studies on isotopic composition of tropical and monsoon precipitation have demonstrated that regional convective intensity, rather than the local temperature, is the dominant factor controlling precipitation δ 18 O influenced by both the local precipitation process and the δ 18 O of upstream water vapor that feeds subsequent precipitation 8,9 . The Asian monsoon (AM) is significantly influenced by El Niño-Southern Oscillation (ENSO) activities 10 , which subsequently affect the precipitation δ 18 O 11,12 .…”

“…Recent studies on isotopic composition of tropical and monsoon precipitation have demonstrated that regional convective intensity, rather than the local temperature, is the dominant factor controlling precipitation δ 18 O influenced by both the local precipitation process and the δ 18 O of upstream water vapor that feeds subsequent precipitation 8,9 . The Asian monsoon (AM) is significantly influenced by El Niño-Southern Oscillation (ENSO) activities 10 , which subsequently affect the precipitation δ 18 O 11,12 .…”