Fluctuations of tidewater glaciers in Hornsund Fjord (Southern Svalbard) since the beginning of the 20th century

Significant retreat of glaciers terminating in Hornsund Fjord (Southern Spits− bergen, Svalbard) has been observed during the 20 th century and in the first decade of the 21 st century. The objective of this paper is to present, as complete as possible, a record of front positions changes of 14 tidewater glaciers during this period and to distinguish the main factors influencing their fluctuations. Results are based on a GIS analysis of archival maps, field measurements, and aerial and satellite images. Accuracy was based on an as− sessment of seasonal fluctuations of a glacier's ice cliff position with respect to its mini− mum length in winter (November-December) and its maximum advance position in June or July. Morphometric features and the environmental setting of each glacier are also pre− sented. The total area of the glacier cover in Hornsund Fjord in the period of 1899-2010 diminished approximately 172 km 2 , with an average areal retreat rate of 1.6 km 2 a −1 .T he recession rate increased from ~1 km 2 a −1 in first decades of the 20 th century up to ~3 km 2 a −1 in years 2001-2010. The latest period was more thoroughly studied using optical satellite images acquired almost every year. The importance of glacier morphology and hypso− metry, as well as fjord bathymetry and topography is analyzed. Large glacier systems with low slopes terminating in deeper waters are retreating faster than small steep glaciers ter− minating in shallower water. A relation between mean annual air temperature and aerial retreat rate of tidewater glaciers was found for long time scales. A sudden temperature in− crease, known as the early 20 th century warming in Svalbard, and an increase in tempera− tures during recent decades are well reflected in deglaciation rate. Influence of sea water temperatures on calving and retreat of glaciers was considered and is significant in short−time intervals of the last decade. Surge events are non−climatic factors which com− plicate the record. They are reflected in front advance or fast retreat due to a massive calv− ing depending on the relation between ice thickness and water depth. Despite the influ− ence of many factors, the response of tidewater glaciers to climate change is evident. The average linear retreat rate of all the tidewater glaciers in Hornsund amounted to ~70 ma −1 in 2001-2010 and was higher than the average retreat of other Svalbard tidewater glaciers (~45 ma −1 ). Thus, glaciers of this basin can be considered as more sensitive to climate than glaciers of other regions of the archipelago.