Cryogenic cave minerals recorded the 1889 CE melt event in northeastern Greenland

• Published in: Climate of the Past
• Main Authors: A. Donner, P. Töchterle, C. Spötl, I. Hajdas, X. Li, R. L. Edwards, G. E. Moseley
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Greenland; greenlandic; Ice; Ice cap; Ice Sheet; permafrost
• Online Access: https://doi.org/10.5194/cp-19-1607-2023; https://doaj.org/article/0408f80ad1a44da795578c146221975c

The investigation of cryogenic cave minerals (CCMs) has developed in recent decades to be a particularly valuable proxy for palaeo-permafrost reconstruction. Due to difficulties, however, in obtaining reliable chronologies with the so-called “fine” form of these minerals, such studies have thus far utilised the “coarse” form. In this study, we successfully investigate the northernmost-known deposit of fine-grained CCMs, which are situated in Cove Cave (Greenlandic translation: Eqik Qaarusussuaq), a low-elevation permafrost cave in northeastern Greenland (80 ∘ N). The Cove Cave CCMs display a complex mineralogy that consists of fine-grained cryogenic cave carbonates and sulfate minerals (gypsum, eugsterite, mirabilite, and löweite). Until now, previous attempts to date fine-grained CCMs have been unsuccessful; however, here we demonstrate that precise dating is possible with both isochron-based 230 Th / <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e653eaf840568ee76bb20ba3bf368ae0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-19-1607-2023-ie00001.svg" width="8pt" height="14pt" src="cp-19-1607-2023-ie00001.png"/></svg:svg> U dating and 14 C dating if the dead carbon fraction is reliably known. The dating result ( 65±17 a BP; 1885±17 CE) shows that the Cove Cave CCMs formed during the late Little Ice Age, a time interval characterised by cold temperatures and abundant permafrost in northeastern Greenland, making water infiltration into Cove Cave dependent on the water amount and latent heat. We relate the CCM formation to a combination of black carbon deposition and anomalously high temperatures, which led to widespread melting over large areas of the Greenland ice sheet in the course of a few days. We propose that the anomalous weather conditions of 1889 CE also affected northeastern Greenland, where the enhanced melting of a local ice cap resulted in water entering the cave and rapidly freezing. ...