Evidence of radionuclide fractionation due to meltwater percolation in a temperate glacier

• Main Authors: Stefano, Elena, Baccolo, Giovanni, Clemenza, Massimiliano, Delmonte, Barbara, Fiorini, Deborah, Garzonio, Roberto, Schwikowski, Margit, Maggi, Valter
• Format: Text
• Language: English
• Published: 2023
• Subjects: ice core
• Online Access: https://doi.org/10.5194/tc-2023-108; https://tc.copernicus.org/preprints/tc-2023-108/

The article discusses the use of 3 H and 137 Cs as temporal markers in ice cores extracted from temperate glaciers. We present a complete tritium ( 3 H) profile for a 46 m ice core drilled from Adamello glacier, a temperate glacier in the Italian Alps, and compare it to 137 Cs profile from the same ice core. Our analysis reveals contamination of tritium between 19 and 32 m of depth, which can be attributed to the worldwide radioactive contamination caused by atmospheric nuclear bomb testing in the 1950s and 1960s. Results show that the radioactive peak associated with 1963 is not coincident for 3 H and 137 Cs, but the 3 H peak occurs 1.5 m above the 137 Cs one. This misalignment is caused by meltwater-induced postdepositional processes that affect 137 Cs, which is more sensitive to percolation than 3 H. The total inventory of 137 Cs in this ice core is also among the lowest ever reported, providing additional evidence that meltwater disturbed its distribution into the ice. On the contrary, the total tritium inventory is comparable to what is reported in literature, making it a more reliable temporal marker for temperate glaciers.