PERMAFROST AND PERIGLACIAL PROCESSES Permafrost and Periglac. Process. 14: 291–293 (2003) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ppp.454 Short Communication The Rock Glaciers on Prins Karls Forland: Corrections of Surface Displacement Rates Ivar Berthling,* Bernd Etzelmu ¨ller, Trond Eiken and Johan Ludvig Sollid Department of Physical Geography, University of Oslo, Blindern, Oslo, Norway ABSTRACT The results from new global positioning system (GPS) surveys in 1998 and 2000 show, that errors exist in the results from terrestrial surveys in 1996. The published displacement values of Berthling et al. (1998) are too large. This note corrects these displacement values. Copyright # 2003 John Wiley & Sons, Ltd. KEY WORDS: rock glaciers; Svalbard; permafrost creep rates INTRODUCTION In an earlier paper (Berthling et al., 1998), we presented displacement data and interpretations from the rock glaciers on Prins Karls Forland, Svalbard. In short, these data showed that the rock glaciers were moving at rates of about 10 cm/year, and had a relatively simple surface flow field with extending flow along the talus cone and the talus cone—rock glacier transition. Towards the rock glaciers front, the flow was compressive. These data were used in combination with DC resistivity soundings to discuss the conceptual model of Haeberli and Vonder Mu ¨hll (1996) regarding the origin and development of ice content in rock glaciers, for the arctic case with a permafrost base well below that of the rock glaciers. The data were based on a combination of survey with theodolite and digital elevation model (DEM) from 1996 and carrier-phase differential GPS measure- ments from 1997. Prins Karls Forland is the westernmost island of the Svalbard archipelago. The study site is at the north- westernmost part of the island (78  50 0 N, 10  30 0 E), where rock glaciers form a continuous transition between the strandflat and steep, up to 500 m high, cliffs. Permafrost is continuous, but due to nearby mainly open waters, the mean annual air temperature is not very low, probably comparable to that of Isfjord radio (4.7  C), 120 km to the southeast. Geodetic measurements were initiated in 1996 on the two largest rock glaciers, numbers 12 and 15, and DC resistivity soundings (Berthling et al., 1998) and ground probing radar (GPR) soundings with a 50 MHz antenna (Berthling et al., 2000) have com- plemented the investigations. DISPLACEMENT MEASUREMENTS A geodetic network was established in 1996 from a benchmark at Fuglehuken, about 4 km north of rock glaciers 12 and 15. In 1997, the measurements were performed using carrier-phase differential GPS, fixing the reference points relative to the benchmark on Fuglehuken with static-, and the rock glacier target points with ‘Stop and Go’ kinematic GPS measure- ments. In 1998 and 2000, the rock glacier target points were again resurveyed using GPS. Based on the new GPS measurements, the 1996 data have been pro- cessed once more, and are incorporated in the mea- surement series we present here. The errors in the 1996 measurements were mainly owing to an unfortunate geometry of the geodetic network. Benchmarks were located on large stones on Received 28 February 2003 Copyright # 2003 John Wiley & Sons, Ltd. Accepted 20 April 2003 * Correspondence to: I. Berthling, Department of Physical Geography, University of Oslo, PO Box 1042, Blindern, N- 0316 Oslo, Norway. E-mail: ivar.berthling@geografi.uio.no