Englacial Architecture of Lambert Glacier, East Antarctica

The analysis of englacial layers using radio-echo sounding data enables the characterisation and reconstruction of current and past ice-sheet flow. Despite the Lambert Glacier catchment being one of the largest in Antarctica, discharging ~16 % of East Antarctica&rsquo;s ice, its englacial architecture has been little analysed. Here, we present a comprehensive analysis of Lambert Glacier&rsquo;s englacial architecture using radio-echo sounding data collected by the Antarctica's Gamburtsev Province Project (AGAP) North survey. We used an &ldquo;internal-layering continuity index&rdquo; (ILCI) to characterise the internal architecture of the ice and identify four macro-scale ILCI zones with distinct glaciological contexts. Whilst the catchment is dominated by continuous englacial layering, disrupted or discontinuous layering is highlighted by the ILCI at both the onset of enhanced ice flow (defined here as &gt;15 ma&minus;1) and along the shear margin, revealing the transition from internal-deformation-controlled to basal-sliding-dominated ice flow. These zones are characterised by buckled and folded englacial layers which align with the current ice-flow regime, and which we interpret as evidence that the flow direction of the Lambert Glacier trunk has changed little, if at all, during the Holocene. However, disturbed englacial layers along a deep subglacial channel that does not correspond to modern ice-flow routing suggest that ice-flow change has occurred in a former tributary which fed Lambert Glacier from grid north. As large outlet systems such as Lambert Glacier are likely to play a vital role in the future drainage of the East Antarctic Ice Sheet, constraining their englacial architecture to reconstruct their past ice flow and assess basal conditions is important.</p

Subglacial lakes and hydrology across the Ellsworth Subglacial Highlands, West Antarctica

Subglacial water plays an important role in ice sheet dynamics and stability. Subglacial lakes are often located at the onset of ice streams and have been hypothesised to enhance ice flow downstream by lubricating the ice–bed interface. The most recent subglacial-lake inventory of Antarctica mapped nearly 400 lakes, of which ∼ 14 % are found in West Antarctica. Despite the potential importance of subglacial water for ice dynamics, there is a lack of detailed subglacial-water characterisation in West Antarctica. Using radio-echo sounding data, we analyse the ice–bed interface to detect subglacial lakes. We report 33 previously uncharted subglacial lakes and present a systematic analysis of their physical properties. This represents a ∼ 40 % increase in subglacial lakes in West Antarctica. Additionally, a new digital elevation model of basal topography of the Ellsworth Subglacial Highlands was built and used to create a hydropotential model to simulate the subglacial hydrological network. This allows us to characterise basal hydrology, determine subglacial water catchments and assess their connectivity. We show that the simulated subglacial hydrological catchments of the Rutford Ice Stream, Pine Island Glacier and Thwaites Glacier do not correspond to their ice surface catchments

Characterising the ice-water-bedrock interface of Ellsworth Subglacial Highlands, West Antarctica

Antarctica is the largest mass of ice on Earth and is losing ice at increasing rates. This has direct consequences for society in many ways, such as sea level rise or changes in ocean circulation. The international scientific community is focusing on understanding the present and past ice flow dynamics in order to reduce the uncertainties on the sea level rise projections. Subglacial conditions are a fundamental part to understand the ice flow dynamics. In particular, the role of subglacial hydrology is critical to the behaviour of the ice because it can enhance ice flow downstream by lubricating the ice-bed interface. Despite the importance of the subglacial hydrological system ice dynamics, there is a lack of detailed subglacial-water characterisation in West Antarctica. In addition, subglacial topography also plays a key role in ice dynamics, and therefore a thorough understanding of it is of great interest to the scientific community. In this thesis, I present new findings of subglacial hydrology in the Ellsworth Subglacial Highlands, located in the interior of West Antarctica, and characterise the evolution of the hydrological system over the last 150 kyr. Additionally, I update the subglacial topography using unpublished RES data and describe new topographical features that affect both the subglacial hydrological system and the ice flow dynamics. Moreover, an exhaustive description and analysis of internal reflection horizons are also provided in order to elucidate past ice flow dynamics and to better understand the influence of subglacial hydrology on the ice flow dynamics. Lastly, I present the potential implication of the results of this thesis on the current Subglacial Lake CECs exploration program. Integration of these new findings in ice sheet models will improve our understanding of the evolution of the West Antarctic Ice Sheet, and its sensitivity to the subglacial hydrological system

Probing the exchange of CO2 and O2 in the shallow critical zone during weathering of marl and black shale

No abstract available