Polychlorinated Biphenyls in a Temperate Alpine Glacier: 1. Effect of Percolating Meltwater on their Distribution in Glacier Ice

Abstract

In Alpine regions, glaciers act as environmental archives and can accumulate significant amounts of atmospherically derived pollutants. Due to the current climate-warming-induced accelerated melting, these pollutants are being released at correspondingly higher rates. To examine the effect of melting on the redistribution of legacy pollutants in Alpine glaciers, we analyzed polychlorinated biphenyls in an ice core from the temperate Silvretta glacier, located in eastern Switzerland. This glacier is affected by surface melting in summer. As a result, liquid water percolates down and particles are enriched in the current annual surface layer. Dating the ice core was a challenge because meltwater percolation also affects the traditionally used parameters. Instead, we counted annual layers of particulate black carbon in the ice core, adding the years with negative glacier mass balance, that is, years with melting and subsequent loss of the entire annual snow accumulation. The analyzed samples cover the time period 1930-2011. The concentration of indicator PCBs (iPCBs) in the Silvretta ice core follows the emission history, peaking in the 1970s (2.5 ng/L). High PCB values in the 1990s and 1930s are attributed to meltwater-induced relocation within the glacier. The total iPCB load at the Silvretta ice core site is 5 ng/cm(2). A significant amount of the total PCB burden in the Silvretta glacier has been released to the environment.

The abandoned ice sheet base at Camp Century, Greenland, in a warming climate

“…Liquid meltwater can also persist year‐round within GrIS firn, forming an active englacial aquifer that saturates pore space below 20 m depth [ Forster et al , ]. PCBs could therefore be remobilized from Camp Century by englacial water flow decades before surface runoff is observed at the site [ Pavlova et al , ]. Such hydrologic remobilization, primarily via dispersion, and subsequent englacial flow would transport these toxins down hydraulic gradient from Camp Century, deeper into the ice, before eventually reaching proglacial regions [ Sharma et al , ].…”

Melt‐Induced Fractionation of Major Ions and Trace Elements in an Alpine Snowpack

“…Concentration records of Ca, Mg, or the rare‐earth elements can be used to reconstruct historic variations of mineral dust emissions to the atmosphere (Gabrieli et al, ; Gabrielli et al, ). However, postdepositional melting induced by climate warming can significantly alter concentration records of atmospheric trace species from high‐altitude glaciers and snowpack as shown for MIs, organic pollutants, or water stable isotopes (WSIs; Eichler et al, ; Herreros et al, ; Kang et al, ; Müller‐Tautges et al, ; Pavlova et al, ; Sinclair & MacDonell, ; You et al, ). As glaciers, which have served as environmental archives to assess the natural and anthropogenic impact on the atmosphere, are progressively in danger of being affected by melting (Zhang et al, ), there is an increasing need to understand the impact of melting on the preservation of various environmental proxies in these archives.…”

Twentieth Century Black Carbon and Dust Deposition on South Cascade Glacier, Washington State, USA, as Reconstructed From a 158‐m‐Long Ice Core

“…It has a half‐life of 22.3 years resulting in an accessible dating range of about 100–150 years, and allows the depth age scale of ice cores to be constrained (Eichler et al, ; Gabrielli et al, ; Gäggeler et al, ; Olivier et al, ; C. Wang et al, ). More recently, this method was also applied successfully to constrain the dating of an ice core from a temperate glacier (Pavlova et al, ). The SCG ice core was sampled for 210 Pb at ~5‐m discontinuous intervals and processed for final measurement by α‐spectroscopy at the Paul Scherrer Institute following the standard method established by Gäggeler et al ().…”