Polar Research https://polarresearch.net/index.php/polar <p><em>Polar Research</em>&nbsp;is the international, peer-reviewed journal of the&nbsp;<strong><a href="http://www.npolar.no/en/">Norwegian Polar Institute</a></strong>, Norway's central institution for research, environmental monitoring and mapping of the polar regions.&nbsp;</p> Norwegian Polar Institute en-US Polar Research 1751-8369 <p><span style="color: #4b7d92;">This work is licensed under a <a href="https://creativecommons.org/licenses/by-nc/4.0/" target="_blank" rel="noopener">Creative Commons Attribution-Noncommercial 4.0 Unported License</a>.<br>Authors retain copyright of their work, with first publication rights granted to the Norwegian Polar Institute.</span></p> <p><img src="/public/site/images/ecsemiczky/88x31_CC_BY1.png"></p> <p>&nbsp;</p> Modelling polar bear maternity den habitat in east Svalbard https://polarresearch.net/index.php/polar/article/view/3447 <p>We evaluated a novel tool that predicts possible maternity den habitat of the polar bear (<em>Ursus maritimus</em>) based on a physical snow transport model, a digital terrain model and weather data. We observed and compared den locations in three important denning areas in east Svalbard (Kongsøya,&nbsp;<em>n</em>&nbsp;= 288; Svenskøya,&nbsp;<em>n</em>&nbsp;= 86; Hopen,&nbsp;<em>n</em>&nbsp;= 115) with modelled snowdrift distributions for 24 years. Accounting for a likely position uncertainty of 100 m, 69% of all dens were located within year-specific modelled snowdrifts. These covered on average 1.8%, 2.1% and 24.7% of the three study islands, respectively. Our snowdrift model accurately predicted maternity den positions (<em>R</em><sup>2</sup>&nbsp;= 0.42, area under the receiving operating characteristic curve [AUC] = 0.85). A model based on slope and altitude, also predicted den positions reasonably well (<em>R</em><sup>2</sup>&nbsp;= 0.35, AUC = 0.88). Habitat maps identifying both current and future areas for maternity denning will become important in managing the Barents Sea population as well as other Arctic populations where changes in sea-ice conditions alter the accessibility to traditional denning areas.</p> Benjamin Merkel Jon Aars Glen E Liston Copyright (c) 2020-03-24 2020-03-24 10.33265/polar.v39.3447 Eurasian winter temperature change in recent decades and its association with Arctic sea ice loss https://polarresearch.net/index.php/polar/article/view/3363 <p>The surface air temperature in the northern mid-latitudes during winter showed a significant cooling trend from the late 1990s to the early 2010s, in spite of increasing greenhouse gas concentrations. This unexpected cooling, which was particularly strong across Eurasia, has been partly attributed to Arctic sea-ice loss. Here, the statistical relationship between Arctic sea-ice loss and surface air-temperature change during winter in Eurasia, which is often referred to as the warm Arctic–cold Eurasia pattern, is re-evaluated by using a break-point trend analysis and maximum covariance analysis. A significant time-lagged covariability is observed between the Arctic sea-ice concentration over the Barents–Kara seas and the Eurasian surface air temperature during winter, with the former leading the latter by approximately two months. More importantly, the timing of an abrupt decline in the autumn Arctic sea ice that occurred in the late 1990s is coincident with the beginning of the Eurasian winter cooling. This concurrent trend change is statistically significant and robustly found in both the break-point analysis and maximum covariance analysis. These results suggest that both the interannual variability and decadal trend change seen for the surface air temperature during Eurasian winters are likely influenced by regional sea-ice changes over the Barents–Kara seas.</p> Hye-Jin Kim Seok-Woo Son Copyright (c) 2020-03-20 2020-03-20 10.33265/polar.v39.3363 Little auks under the midnight sun: diel activity rhythm of a small diving seabird during the Arctic summer https://polarresearch.net/index.php/polar/article/view/3309 <p>Many animal species exhibit a diel, 24-hr pattern of activity, which is steered by timing cues, with the daily light–dark cycle considered the most powerful. This cue, however, is reduced in polar zones under continuous daylight conditions associated with the midnight sun. The rhythm of animal behaviour under such conditions is poorly understood. Here, we examine periodicity and patterns of daily activity (colony attendance and foraging) in a High-Arctic seabird, the little auk (<em>Alle alle</em>). We demonstrated a regular rhythm of colony attendance at the population level, with birds being the most abundant in the colony during hours of relatively low sun elevation. This pattern is likely to be associated with predation pressure that may be perceived by birds as lower during hours with low sun elevation, because of better predator detectability. Regarding rhythms at an individual level, however, we found the most common periodicity to be 23.2 hr (range from 19.9 hr to 30.8 hr) but no clear pattern of daily colony attendance of individuals. Such a flexibility in daily rhythms indicates that individuals may become arrhythmic in regard to the 24-hr environmental cycle, despite regularities observed at the population level. Finally, we compared males and females in terms of daily activity patterns but we did not find significant sex differences.</p> Katarzyna Wojczulanis-Jakubas Piotr Wąż Dariusz Jakubas Copyright (c) 2020-02-27 2020-02-27 10.33265/polar.v39.3309