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 km², with an average areal retreat rate of 1.6 km²a⁻¹. The recession rate increased from ~1 km²a⁻¹ in first decades of the 20^th century up to ~3 km²a⁻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 hypspmetry, as well as fjord bathymetry and topography is analyzed. Large glacier systemswith 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 temperatures 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 calving depending on the relation between ice thickness and water depth. Despite the influence 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.