Glacimarine sedimentary processes and products at fjord-terminating tidewater glacier margins

Abstract

Tidewater glaciers terminate in the ocean and provide an important link between the terrestrial and marine realm, which makes them particularly vulnerable to both atmospheric and oceanographic changes. Tidewater glacier dynamics are affected by sea-level rise, which, in combination with ocean warming, can amplify glacier retreat. Most glaciers that drain the large contemporary ice sheets of Greenland and Antarctica are marine-terminating, fast-flowing outlets, and the dynamics of these glaciers have a large impact on ice sheet stability and sea level. Understanding how such glaciers have responded to climate change in the past therefore provides an important analogue for assessing current and future changes of the large ice sheets in Greenland and Antarctica. Fjords have proven to be very useful in this context, as their protected environment allows for the accumulation of thick, undisturbed sedimentary sequences, which enable the investigation of past ice sheet change at a high temporal resolution.
This study uses multibeam swath-bathymetry, sub-bottom profiler data, and sediment cores from fjords in Spitsbergen and West Greenland to investigate the glacial landforms and sedimentary facies in front of fjord-terminating tidewater glaciers. The identified landform-sediment assemblages are compared to other High-Arctic fjords and are summarised in a new conceptual model. They are used to infer common sedimentary processes in glacimarine environments, to identify the factors controlling them, and to reconstruct Holocene regional ice dynamics. The results demonstrate that while the sedimentary processes are largely similar between the different regions, differences arise in the landform-sediment assemblages, even between adjacent fjords. This implies that glacier dynamics are not simply controlled by changes in the air or ocean temperatures, but can be highly variable in space and time.