Snow on Antarctic Sea Ice
Investigation of spring transition of Antartic sea ice and its snow cover
The high-latitude Southern Ocean is covered by sea ice, which undergoes a large seasonal cycle, reaching maximum annual extent in September. Once the surface ocean has frozen over, this sea-ice cover provides a surface for (solid) precipitation to accumulate. This precipitation may build up on the sea ice and take a range of shapes, including so-called dunes unless transported away by advection. As this snow on sea ice ages it undergoes metamorphism, which changes its physical structure including grain size, density, albedo and others.
Close to the Antarctic coast fast ice is a dominating feature. It provides a substrate that supports ecosystems ranging from primary production to higher predators including penguins and seals. Fast ice is also underpinning a range of operational activities. Hence, understanding the processes that modify the characteristics of the fast ice is critical.
Here we will research the changes in the fast ice and its snow cover with focus on the spring transition. At this time increased shortwave radiation is available at the snow- and sea-ice surface. While the relatively high albedo of both snow and sea ice reflects much of the incoming radiation, a significant amount contributes to the melt of snow or sea ice near the surface and some of the radiation also being absorbed by the snow and the sea ice. This study will assess (a) the ratio of reflected versus absorbed shortwave radiation and its dependency on the surface characteristics; (b) the radiative processes associated with these and if they can be observed by remote-sensing methods; and (c) the internal erosion near the sub-surface of the sea ice including how this changes the physical and biological environment within the sea-ice column. The results from this project will be invaluable to understanding how small-scale processes in the ice-snow system impact the regional characteristics of Antarctic sea ice.”
Radiative signature of Antarctic icebergs
As the glacial ice slides off the Antarctic continent it grows floating ice shelves, which at their base are exposed to ocean water. At this interface, given correct conditions, marine ice may attach itself to the base ice the ice shelf. This marine ice has a different appearance than the glacial ice. Once an iceberg has calved from the ice shelf, it undergoes melt and consequently may roll over, hence exposing marine ice above the sea surface. The exposed marine ice may be of green, blue or intermediate colour, leading to the naming of green or jade bergs. The variation in colour is most likely due to different ratios of iron or trace elements within the ice matrix of the berg. As icebergs traverse huge distances before they finally melt and disperse meltwater and with it any enclosed substances, it is important to understand the particle- and hence nutrient transport in the Soutehrn Ocean due to iceberg motion.
Here we will study the radiative signatures of icebergs across a range of satellite-borne sensors to check if different coloured icebergs can be identified, and if the sensors can detect differences in the particle load of the icebergs.
Satellite-based detection of snow wetness and wave-induced surface wetting of Antarctic sea ice
Wave-ice interaction is a dominant process in characterizing the Antarctic sea ice including the seasonal evolution of the sea-ice extent. Wave interaction is a process that defines the Marginal Ice Zone, which separates the blue water from the established pack ice. Wave action also gives rise to the overwash of the sea ice, wetting the sea-ice surface and with it of any snow that may be present on top of the sea ice. This overwash does affect the morphology of the snow cover and the upper ice surface and may support the formation of meltponds on the sea ice. All these will change the radiative transfer at the sea-ice surface and will modify the remotely sensed signature of the snow and the sea ice.
This project will research if the modification of the snow (and sea-ice surface) induces radiative signatures that can be detected by satellite-based sensors, and will be using data from satellite-borne altimeters (i.e., ICESat-2) to correlate these marginal-ice zone processes, such as wave invasion into the sea-ice zone.”
Glaciology, Ocean-Sea Ice-Atmosphere, Radiative Transfer