MAL5

The Antarctic Ice sheet is a key component of the Earth system, impacting on global sea level, ocean circulation and atmospheric processes. Meltwater is generated at the ice sheet base primarily by geothermal heating and friction associated with ice flow, and this feeds a vast network of lakes and rivers creating a unique hydrological environment. Subglacial lakes play a fundamental role in the Antarctic ice sheet hydrological system because outbursts from ‘active’ lakes can trigger, (i) change in ice speed, (ii) a burst of freshwater input into the ocean which generates buoyant meltwater plumes, and (iii) evolution of glacial landforms and sub-glacial habitats. Despite the key role that sub-glacial hydrology plays on the ice sheet environment, there are limited observations of repeat sub-glacial lake activity resulting in poor knowledge of the timing and frequency of these events. Even rarer are examples of interconnected lake activity, where the draining of one lake triggers filling of another. Observations of this nature help us better characterise these events and the impact they may have on Antarctica’s hydrological budget, and will advance our knowledge of the physical mechanism responsible for triggering this activity. In this study we analyse 9-years of CryoSat-2 radar altimetry data, to investigate a newly identified sub-glacial network in the Amery basin, East Antarctica. CryoSat-2 data was processed in ‘swath mode’, increasing the density of elevation measurements across the study area. The plane fit method was employed in 500 m by 500 m grid cells, to measure surface elevation change at relatively high spatial resolution. We identified a network of 10 active subglacial lakes in the Amery basin. 7 of these lakes, located below Lambert Glacier, show interconnected hydrological behaviour, with filling and drainage events throughout the study period. We observed ice surface height change of up to 6 meters on multiple lakes, and these observations were validated by independently acquired TanDEM-X DEM differencing. This case study is an important decade long record of hydrological activity beneath the Antarctic Ice Sheet which demonstrates the importance of high resolution swath mode measurements. In the future the Lambert lake network will be used to better understand the filling and draining life cycle of sub-glacial hydrological activity under the Antarctic Ice Sheet.

How to cite: Hogg, A., Gourmelen, N., Rigby, R., and Slater, T.: Draining and Filling of an Interconnected Sub-glacial Lake Network in East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16570, https://doi.org/10.5194/egusphere-egu21-16570, 2021.

An understanding of the former configuration and dynamics of ice sheets is essential to constrain numerical models of past environmental conditions and predict the likely future responses of ice sheets to climate change. Evidence of past ice-sheet activity is often well-preserved on and beneath the seafloor of glaciated continental margins, where it can be analysed using a variety of marine geophysical techniques. In this presentation, I will describe how marine geophysical data can be used to investigate former ice-sheet behaviour at different temporal scales, drawing on recent examples from my research. First, 2D and 3D seismic data show how mid- and high-latitude continental margins have been shaped by the repeated advance and retreat of ice sheets during the last three million years. Secondly, bathymetric data enable the interpretation of glacial landforms preserved on the seafloor, revealing the dynamic behaviour of ice masses since the Last Glacial Maximum. Finally, the recent application of autonomous underwater vehicles to acquire high-resolution geophysical data provides a step-change in our ability to image submarine landforms and facilitates new interpretations about ice dynamics at fine temporal and spatial scales.

How to cite: Batchelor, C.: The Marine Geophysical Record of Past Ice Sheets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2776, https://doi.org/10.5194/egusphere-egu21-2776, 2021.

Glacier biogeochemistry grew out of hydrochemical studies of water movement through small valley glaciers in the 1970’s into modern studies of ice sheet runoff and ice berg fertilisation of the oceans. This talk will briefly review how this happened, and then look at the current research agenda with a view to identifying research needs and future research directions. Research on subglacial lakes, nutrient export to the oceans, biological ice sheet darkening and the production of bioavialable, yet ancient, dissolved organic carbon on glaciers will be covered. Finally, when you think you know it all, a new process fundamental process turns up. Recent work on the release and production of bioavailable chemicals by glacier erosion will be highlighted, including the significance of the this work in the search for life beyound Earth.  

How to cite: Tranter, M.: Glacier biogeochemistry: from Haut Glacier d’Arolla to the Antarctic and Greenland Ice Sheets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16360, https://doi.org/10.5194/egusphere-egu21-16360, 2021.