The extent, thickness and age of Arctic sea ice has dramatically declined since the late 1990s, and these trends are predicted to continue. Polar bears rely on sea ice for hunting, resting, travelling and in some parts of the Arctic also reproduction. Hence, exploring the habitat use of this sea-ice-dependent species can help us understand which resources they use and how their distribution responds to a changing environment.
This map service displays the number of days with polar bear habitat in the Barents Sea. It is based on a habitat model using polar bear telemetry data collected during the last three decades (Lone et al. 2017). Optimal habitat found in the Barents Sea during different seasons is shown for three time periods: mid-90’s (1992 - 96, used as reference period), mid-00’s (2002 - 06) and the mid-10’s (2012 - 16). The different seasons are based on annual sea ice fluctuations and the biology of polar bears: winter (1 November – 31 March; 151/152 days), sea ice break-up (1 April – 31 July; 122 days), and sea ice freeze-up (1 August – 31 October; 92 days). Additionally, changes in sea ice habitat are available between the mid90’s reference period and the mid-00’s as well as the mid-10’s.
Change in average number of days with optimal habitat, relative to a mid-90’s reference period. Stippled lines illustrate maximum seasonal extent of polar bear habitat during the reference period.Change in average number of days with optimal habitat, relative to a mid-90’s reference period. Stippled lines illustrate maximum seasonal extent of polar bear habitat during the reference period.
In addition to decadal changes in available polar bear habitat, annual changes in seasonal habitat throughout the last 28 years (1992 - 2018) are visualized as animations below.
RSF Fall:
RSF Winter:
RSF Spring:
The marginal sea ice zone was identified to be primary polar bear habitat in the Barents Sea. It has moved north- and eastwards during the last decades as is also apparent in a north and eastward shift of optimal polar bear habitat in all seasons during the last three decades. In general, this resulted in less available habitat and a reduced overall area suitable as polar bear habitat in the Barents Sea. Please note, each seasonal polar bear habitat model is based on sea ice concentration data retrieved from the University of Hamburg (Kaleschke et al. 2001, Spreen et al. 2008). The original data resolution of 12.5 x 12.5 km was interpolated to 3 x 3 km for these images. Further, data points close to land have been interpolated into the land to avoid a pixelated view of the coastlines. Therefore, the maps published here should only be used for visualization and not for scientific studies.
REFERENCES
Kaleschke, L., et al. (2001). "SSM/I sea ice remote sensing for mesoscale ocean-atmosphere interaction analysis." Canadian Journal of Remote Sensing 27(5): 526-537. Lone, K., et al. (2017). “Sea ice resource selection models for polar bears in the Barents Sea subpopulation” Ecography 41(4): 567-578. Spreen, G., et al. (2008). "Sea ice remote sensing using AMSR-E 89-GHz channels." Journal of Geophysical Research-Oceans 113(C2).