Permafrost occurrence of Seymour Island and James Ross Island. Antarctic Peninsula Region

M FUKUDA; J. STRELIN; K. SHIMOKAWA; N. TAKAHASHI; T. SONE; D. TROMBOTTO

Recent Progress in Antarctic Earth Science

Terra Scientific Publishing Company

Lugar: Tokyo; Año: 1992; p. 745 - 750

A field survey on Seymour Island and James Ross Island, Antarctic Peninsula region was conducted in 1989/1990 specifically related to the genesis and occurrence of permafrost. On Seymour Island, marine terraces occur at three different levels. The thickness of permafrost on each terrace was investigated by means of measurements of geo-electrical resistivity in the ground. The depths of permafrost base on Seymour Island were estimated to be 200 m, 105 m and 35 m, respectively. Annual mean ground temperatrures at various depths in the ground on lower terraces were calculated from the obtained data of temperature fluctuations for two years. Temperature gradient indicate the depth of permafrost on the lowest terraces as to be 34 m, which coincides with the value derived from geo-electrical resistivity profile in the ground. Tundra polygons with ice-wedge development on both upper and lower terraces indicate that active cracking occurs under present climatic condition. On James Ross Island, coastal terraces have been formed near Santa Marta Cove in Croft Bay. Results of geo-electrical resistivity measurements indicate that depths of permafrost on the upper and lower terraces are to be 45-40 m and 6 m, respectively, 14C dating measurements using fossil shells from the sedimentary revealed the upheaval of the lower terrace above the sea level at 2500 y BP. Thus the rate of permafrost formation is estimated at about 0.002 m/y.