Seafloor geomorphology of western Antarctic Peninsula bays: a signature of ice flow behaviour

Abstract

Glacial geomorphology is used in Antarctica to reconstruct ice advance during the Last Glacial Maximum and subsequent retreat across the continental shelf. Analogous geomorphic assemblages are found in glaciated fjords and are used to interpret the glacial history and glacial dynamics in those areas. In addition, understanding the distribution of submarine landforms in bays and the local controls exerted on ice flow can help improve numerical models by providing constraints through these drainage areas. We present multibeam swath bathymetry from several bays in the South Shetland Islands and the western Antarctic Peninsula. The submarine landforms are described and interpreted in detail. A schematic model was developed showing the features found in the bays: from glacial lineations and moraines in the inner bay to grounding zone wedges and drumlinoid features in the middle bay and streamlined features and meltwater channels in the outer bay areas. In addition, we analysed local variables in the bays and observed the following: (1) the number of landforms found in the bays scales to the size of the bay, but the geometry of the bays dictates the types of features that form; specifically, we observe a correlation between the bay width and the number of transverse features present in the bays. (2) The smaller seafloor features are present only in the smaller glacial systems, indicating that short-lived atmospheric and oceanographic fluctuations, responsible for the formation of these landforms, are only recorded in these smaller systems. (3) Meltwater channels are abundant on the seafloor, but some are subglacial, carved in bedrock, and some are modern erosional features, carved on soft sediment. Lastly, based on geomorphological evidence, we propose the features found in some of the proximal bay areas were formed during a recent glacial advance, likely the Little Ice Age.