Relating changes in seabed properties and retreating glacier fronts in West-Antarctic fjords.

Retreating marine terminating glaciers influence the rate at which larger ice mass is lost, and thus the rate at which global sea levels rise. About 90% of the circa 240 glaciers terminating in fjords along the West-Antarctic Peninsula coastline are retreating. This happens at variable rates as these fjords have internal feedback mechanisms with e.g. the oceanographic make-up of the bay and the geology / geomorphology of the local hinterland. The NERC-CONICYT funded “ICEBERGS” project is a UK-Chile research collaboration to assess the effects of ice loss and deglaciation on benthic marine ecosystems in Antarctica. Three West-Antarctic fjords where glaciers have been consistently retreating in the last few decades were investigated: Marian Cove (King George Island), Börgen Bay (Anvers Island) and Ryder Bay (Adelaide Island). As part of this project, we monitored the changes in seabed bathymetry and backscatter intensity as a signature of past and on-going ice flow and ice retreat. Together with sediment analyses, the data provide insights in glacial landscape development and on sediment accumulation / seabed erosion rates. We also managed to insonify parts of the changing glacier ice fronts, detailing the grounding zones at the seabed. At the time of abstract submission, the third of three surveys was just underway. In this presentation we will explore the preliminary search for spatial and temporal relationships between grounded ice advance and retreat, undercutting of the grounded glacier terminus, sediment discharge, ice berg scouring, glacial landscape development and mass waste deposits. Our direct time-lapse observations of the seabed and glacier fronts of different fjord systems will help us understand how the local fjord environments define the dynamics of the retreating glaciers they host, whilst the results help elucidate the impact of that deglaciation on the newly emerged seabed and the fast-growing ecosystem it supports. Understanding the ice-filled fjord dynamics in the present-day and in the recent past will also help interpretations made from data representing these environments in the distant past.