Cryoconite holes are small, quasi-cylindrical meltwater features that form on the surface of glaciers. In Antarctica, due to the harsh surface conditions, they form lids of refrozen ice, which separate the meltwaters from the atmosphere. The freezing process is not well-documented in Antarctic cryoconite holes because of the challenges associated with direct sampling techniques. This study presents geochemical modelling as a suitable alternative, using data from Bagshaw et al, (2007) and Fortner et al., (2005) to examine important changes in meltwater chemistry as the seasonal cryoconite hole freeze-up takes place. In the high melt season, lidded cryoconite holes are more alkaline than their open counterparts. However, when calcite begins to precipitate at approximately 90% Freezing, pH collapses in lidded cryoconite holes. By contrast, atmospheric equilibrium in terms of pCO2 in open cryoconite holes buffers the reduction in pH, decreasing the magnitude of change. pH in closed cryoconite holes therefore undergoes a transition from moderately-alkaline to moderately-acidic. pCO2 is forced to remain at equilibrium in open cryoconite holes, but in lidded cryoconite holes, pCO2 increases to values above atmospheric levels, as CO2 is squeezed into the headspace from the meltwater as the volume of meltwater decreases at a slower rate than the volume of the headspace. This leads to the build up of gas pressure in the headspace. The large range of conditions that an Antarctic cryoconite hole experiences throughout the freezing process are likely to provide further stress to psychrotolerant species inhabiting the microenvironment.
|Date of Award||6 Nov 2018|
- The University of Bristol
|Supervisor||Martyn Tranter (Supervisor)|