Back in time in the Sør Rondane Mountains, Antarctica
Today, Sør Rondane Mountains in the Queen Maud Land acts as a barrier to the Eastern Antarctic Ice Sheet in Antarctica. This is displayed by the difference in altitude of the ice surface to the south and north of the mountain chain. To the south, ice surface reaches altitudes above 2500 meters above sea level and forms an ice plateau. Lowlands of ice are found at altitudes of around 1500 meters to the north of the mountain chain. Huge glacier tongues, such as Hansen, Gunnestad and Byrd glaciers among others, are actively draining the ice from the plateau to the lowlands.
This season, we identified abandoned valleys during our fieldwork in the Sør Rondane Mountains in the Queen Maud Land. These abandoned valleys are located few hundred meters above today’s active glaciers and free of ice. Based on the presence of such valleys and the geomorphology of the nunataks in this region, we conclude that the Eastern Antarctic Ice Sheet was in the past thicker than today and had a different pattern of drainage, i.e. most of the Sør Rondane Mountains were overridden by the ice and nunataks were much smaller in size. The dramatic surface lowering of East Antarctic Ice Sheet during the last million years resulted in the change in the drainage and thus the abandonment of some valleys in the mountain chain.
In the field, we studied two of such valleys in detail. We took stereoscopic pictures with a drone for building of the digital elevation models of the valleys. We used these as a base for our detailed mapping of glacial geomorphological features. In order to go back in time with the drainage pattern of the Eastern Antarctic Ice Sheet, we collected surface samples from the erratic boulders left in these valleys by the ice at the time of surface lowering. We will analyze the accumulation of cosmogenic nuclides in these samples and then determine the timing of the thinning of the ice sheet.
Our study will provide insight into the surface lowering history and change in drainage pattern of the Eastern Antarctic Ice Sheet that has occurred in this region. On a global scale, we will have a better understanding of how the world will be affected by changes in the largest ice sheet in the planet.