No abstract

The mechanism of glacier recession and its climatic controls are complex processes that differ across the Arctic region. Here, we investigate factors influencing front variations of Hansbreen, a glacier terminated in Hornsund fjord (SW Svalbard). We apply remote sensing data to observe glacier front fluctuations between 1992 and 2015 and compare them to atmospheric and oceanographic data, sea water depth at the terminus and surface velocity. Rate of subglacial meltwater discharge approximated by the seasonal positive degree‐day index (PDD) together with sea thermal conditions appear to be the main factors responsible for the fluctuations of the front of Hansbreen, while water depth at the front plays a secondary role. Taking into account ocean and air thermal conditions, the studied period has been divided into warm, cold and moderate years. The glacier retreated considerably throughout a bedrock overdeepening in the very warm period 2012–2014. This recession coincided with a slower ice flow due to intense subglacial runoff and increased submarine melting. The long‐term retreat was interrupted by glacier advances in colder years, regardless of water depth at the front. The slower recession rate was the combined effect of decreased subglacial melting and increased glacier movement associated with lower subglacial runoff. Although the seasonal PDD is a good indicator of the front fluctuations, the duration of the retreat and advance periods are strongly correlated with the sea surface temperature. Expected climate warming and an increase of water temperature in the West Spitsbergen Current will stimulate further recession of Hansbreen in future.

Pohjola, V.A., Kankaanpää, P., Moore, J.C. and Pastusiak, T., 2011. The International Polar Year Project ‘KINNVIKA’– Arctic warming and impact research at 80° N. Geografiska Annaler, Series A, Physical Geography, 93, 201–208. DOI: 10.1111/j.1468‐0459.2011.00436.x

No abstract

The data related to ice floe concentration and ice thickness were analysed. Sources of data have been verified by visual observation and by comparison in between information from different remote sensing sources. The results of this work exceeded initial expectations. The discrepancies of the information provided by various data sources result from the error of the measurement method, which can be as high as 15% of the concentration of ice floes. It should also be borne in mind that the more generalized information about the state of the ice cover, the lower probability of detection of ice floe patches of a high concentration and spatial extent. Each vessel that is planning voyage in ice should take into consideration inaccurate estimation of concentration and thickness of ice floes received by means of satellite remote sensing methods. The method of determining permissible speed of various ice class vessel in ice on basis of safe speed graph for the icebreaker was developed. A well-defined equation approximates relationship between speed of the icebreaker and the vessels of specified ice classes. Average distance of 24.1 Nm from sea ice extent line was related to all analysed lines representing 30-40% ice floe concentration (IUP product excluded) and 30.6 Nm for analysed lines representing 70-81-91% ice floe concentration. The maximal average distance of the furthest analysed line (IUP product excluded) was equal 37.2 Nm. The average standard deviation of that results was equal 8.3 Nm only. Average distances of analysed lines from sea ice extent line to maximal ice data values were found as follow: 8.4 Nm (23%) for NSIDC-CCAR ice age, 12.3 Nm (33%) for minimal distance of 30-40% ice concentration, 15.4 Nm (41%) for OSISAF ice type "ambiguous" zone from Open Water side, 25 Nm (67%) for minimal distance of 70-81-91% ice concentration, 26.6 Nm (72%) for OSISAF ice type "ambiguous" zone from 1st year ice age side, 35.9 Nm (97%) for maximal distance of 30-40% ice concentration and 36.3 Nm (98%) for maximal distance of 70-81-91% ice concentration data. In the parentheses placed relative distances from first ice data including IUP 40% concentration isolines. Sea ice extent of most of available data sources delineated the edge of "area to be avoided" for vessels of ice class lower than L1. Estimated average speed of L3 ice class vessel was from 3.3 knots till 5.2 knots at average speed 5.0 knots. For L1 ice class vessel estimated average speed was from 6.5 knots till 12.1 knots at average speed 9.7 knots. Relative standard deviation of averaged speed for both ice class vessels was equal 18%. The highest relative deviations were found up to 50% below the average speed value. The highest relative deviations upward were equal 22%. Above speeds for L3 and L1 ice class vessels corresponded well with average technical speed of "Norilsk SA-15" ULA class vessel equal 12,6 knots. The results of the work were not intended to be used for decision making on spot-"on-scene"-during direct guiding vessel in ice. They should be useful ...