Trace gases in glaciated environments

Abstract

Trace gases play a variety of pivotal roles in atmospheric and earth surface processes despite being low in relative atmospheric abundance. Halogenated gases such as halocarbons contribute to the destruction of ozone; carbon dioxide (CO2), hydrogen (H2) and methane (CH4) can act as electron donors or acceptors to provide microbial energy; and CO2 links the chemical weathering of rocks to the global carbon cycle. However, there has been less research into the cycling of trace gases in glaciated environments. The subglacial environment can be isolated from the atmosphere and surface processes which would otherwise supply energy for microbial life and acidity for chemical weathering. It is unknown how such processes are driven when reactants become limited during long glaciations. The proglacial environment can be remote, particularly in regions such as the High Arctic, meaning fluxes of trace gases such as halocarbons can be particularly important due to distance from the major halocarbon source regions. Little research has been conducted on trace gas fluxes from the proglacial environment despite the ongoing expansion of these land surfaces as glaciers undergo widespread retreat in response to Arctic warming.

This thesis explores novel sources, sinks and the roles of trace gases in both sub- and pro- glacial environments using a combination of laboratory experiments, field experiments and analysis of long-term atmospheric datasets. Laboratory rock grinding experiments were used as an analogue to glacial bedrock erosion and demonstrated abiotic production of several trace gases at rates significant to subglacial microbial metabolism and chemical weathering. Field flux chamber measurements on the proglacial forefield of a High Arctic glacier demonstrated that halocarbon fluxes were significant despite the immaturity of the recently exposed soils. Analysis of long-term, frequent halocarbon measurements in the ambient Arctic atmosphere indicated the influence of local halocarbon production, with evidence of marine processes in particular. In conclusion, trace gases are important for a variety of processes related to the marginal and rapidly changing glaciated environment. Understanding the role of trace gases, and their sources and sinks in these environments can help further our understanding of extreme life, the influence of chemical weathering on the carbon cycle and the influence of marginal soils on the halogen budget of the atmosphere.

Date of Award	25 Jun 2019
Original language	English
Awarding Institution	University of Bristol
Supervisor	Jemma L Wadham (Supervisor) & Dan Lunt (Supervisor)