The modern depositional environment in Potter Cove, King George Island, Antarctica


Contact
gerhard.kuhn [ at ] awi.de

Abstract

King George Island belongs to the South Shetland Islands that are located north of the northern tip of the Antarctic Peninsula (AP). It is situated slightly north of the area where climatic warming in Antarctica is strongest. In places the annual mean temperatures increased by 0.5 K per decade through the past 60 years (Faraday/Vernadsky Station, AP). The air temperatures in the immediate working area increased by about 0.35 K per decade (Schloss et al. 2012) during the past 20 years which is still in the range of the recovery of temperatures from the Little Ice Age maximum to the end of the 19th century. IMCOAST, a multidisciplinary international project investigates the modern and the late Holocene environmental development of the fjordic environment of south King George Island. In this part of the project we aim at reconstructing the modern sediment distribution in the inner part of Potter Cove using an acoustic ground discrimination system (RoxAnn) and more than136 ground-truth samples. The impact of the warming trend is clearly visible in the form of retreating glaciers and melting ice sheets, loss of sea ice and strong meltwater discharge into the coastal zone. Potter Cove is a small fjord characterized by a series of moraine ridges produced by a tidewater glacier (Fourcade Glacier). Presumably, the farthest moraine is not much older than about 500 years (LIA maximum), hence the sediment cover is rather thin as evidenced by high resolution seismic data (see presentation by Wittenberg et al.). Since a few years at least the better part of the tidewater glacier has retreated onto the island’s mainland. It is suggested that such a fundamental change in the fjord’s physiography has also changed sedimentation patterns in the area. Potter Cove is characterized by silty-clayey sediments in the deeper inner parts of the cove. Sediments are coarser (fine sand to coarse sands and boulders) in the shallower areas; they also coarsen from the innermost basin to the mouth of the fjord. Textural structures follow the seabed morphology, i.e. small v-shaped passages through the moraine ridges. The glacier still produces large amounts of turbid melt waters that enter the cove at various places. We presume that very fine-grained sediments settle from the meltwater plumes and are eventually transported by mid-depth or even bottom currents towards the mouth of the fjord. Older sediments that are more distal to the glacier front and sediments in shallower places (e.g. on top of the moraine ridges) become increasingly overprinted by coarser sediments from the shallow areas of the fjord. These areas are prone to wave induced winnowing effects as well as disturbances by ploughing icebergs. It can be concluded that coarsening of the fjord sediments will continue while supply of fine-grained meltwater sediments might cease due to exhaustion of the reservoirs.



Item Type
Conference (Talk)
Authors
Programs
Peer revision
Peer-reviewed
Publication Status
Published
Event Details
25th International Polar Congress, 17 Mar 2013 - 22 Mar 2013, Hamburg.
Eprint ID
32138
Cite as
Hass, H. C. , Kuhn, G. , Wittenberg, N. , Wölfl, A. C. and Betzler, C. (2013): The modern depositional environment in Potter Cove, King George Island, Antarctica , 25th International Polar Congress, Hamburg, 17 March 2013 - 22 March 2013 .


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