Annual layer counting using pollen grains of the Grigoriev ice core from the Tien Shan Mountains, central Asia

Abstract

Pollen grains are commonly found in ice cores, particularly those from mountain glaciers at low to middle latitudes. Because the release of pollen from flowers has a seasonality and varies among the plant species, pollen concentrations in ice cores are useful for distinguishing annual or seasonal layers and inferring past vegetation near glaciers. We analyzed major pollen grains in an 87-m-deep ice core drilled at the top of the Grigoriev Ice Cap (4563 m.a.s.l.) in the Tien Shan Mountains, Kyrgyz Republic. Microscopy showed that mainly five pollen taxa were contained in the ice core. Their abundance fluctuated with the depth of the core, indicating their seasonal deposition on the ice cap, while the seasonality of the stable isotopes was not particularly clear because of melting and refreezing signatures. Based on the pollen profiles, annual layers were determined back in time to 1780 AD at a depth of 63.6 m; at greater depth, they could not be distinguished due to ice layer thinning in the glacier. The pollen assemblages have gradually changed during the last 220 years and were particularly distinctive in the deeper part, suggesting the drastic change of vegetation in this region during the Holocene. ARTICLE HISTORY

Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core

“…This is slightly lower than the ∼ 20 % typically observed for cold and polythermal high-elevation glaciers (e.g. Jenk et al, 2009;Uglietti et al, 2016;Gabrielli et al, 2016;Licciulli et al, 2020) but likely more reasonable for a temperate glacier (e.g. Kaspari et al, 2020).…”

“…Pollen and rBC were selected because their concentrations were shown to be rather robust parameters in terms of signal preservation even under temperate ice conditions and the potential influence from meltwater percolation. With the signal of seasonal variability at least reasonably preserved, they proved to be particularly useful for the counting of annual layers in temperate ice (Kaspari et al, 2020;Takeuchi at al., 2019;Festi et al, 2017;Pavlova et al, 2015;Nakazawa, 2004). Also, both Pb and Cs were found to be reasonably well preserved, i.e.…”

Pollen as a potential indicator of the origin of massive ice in northwest Siberia

“…Pollen in the ice of mountain glaciers in temperate latitudes reflects regional vegetation patterns. Pollen assemblage changes have suggested the drastic changes to the regional vegetation during the Holocene in the Tien Shan Mountains 31 . The pollen spectra of Arctic ice caps are characterized by the presence of pollen from tree species and grasses exotic for these latitudes 23 .…”

“…Tree pollen was released in spring when higher heights and larger crowns produce maximum atmospheric turbulence such that abundant pollen is released during high wind speeds and with increased dispersal over long distances 34 . Pollen spectra in the ice and snow of mountain glaciers and Arctic ice caps were evidenced this way 31,35–39 . Long‐distance transport of pollen is one of the main contributors of pollen to the surface of Arctic glaciers 23,32,33 (Figure 18).…”

Glacio-environmental aspects recorded in two shallow ice cores drilled in 1980 at accumulation area of Khumbu Glacier of Mt. Everest in Nepal Himalayas

“…Pollen grains have also been used to determine annual layers in mountain ice cores because they are abundantly dispersed in the atmosphere during certain seasons (e.g., Nakazawa et al 2005;Takeuchi et al 2019). However, the concentration of pollen grains in the cores analyzed in this study was generally lower than those of the other ice cores drilled in Asian high mountains, and thus the fluctuation in pollen grain concentration cannot be used in these cores.…”