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1060274

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Postat januari 16, 2019januari 18, 2019 Full storlek 4896 × 2752

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As glaciologists we are generally conducting our field activities at the glacier surface but many of the observations we perform are related to what is happening at the glacier bed. Therefore, it is very exciting when we can visit the interior of a glacier - in a safe way. Here is such an example; an old meltwater channel on Austre Brøggerbreen in Svalbard, not active any longer and easily accessible from the side of the glacier front. This part of the glacier is moving at a very low speed, so this feature remains open, partly snow filled but accessible until it melts away. Our glaciologist Jack Kohler was able to visit this beautiful spot as part of his glacier mass balance field work in Ny Ålesund. Photo: Stein Tronstad #npolar #norwegianpolarinstitute #norskpolarinstitutt #research #polar #glaciology #glacier #ice #snow #science #polarscience #Svalbard #Arctic #fieldphotofriday #fieldwork #scicomm #forskkomm

This coming Sunday we celebrate Antarctica day. This commemorates the 60th anniversary of the signing of the Antarctic Treaty on 1st December 1959. The treaty was originally signed by 12 countries – Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, the Soviet Union, the United Kingdom and the United States – who were active in Antarctic during the 1957-1958 International Geophysical Year. Since then a further 42 countries have become signatories. The treaty ensures that “Antarctica shall be used for peaceful purposes only”, promotes freedom of scientific investigation and cooperation, and bans military activity. At present around 30 countries operate 60 seasonal and 40 year-round facilities in Antarctica. Norway operates the year-round station Troll and seasonal station Tor in Dronning Maud Land. Troll is base for summertime glaciological, biological, and geological fieldwork, and year-round atmospheric and environmental monitoring. The US operates the year-round Amundsen-Scott South Pole Station. The nearby ceremonial South Pole is surrounded by the flags of the original 12 signatories of the Antarctic Treaty. Photos: Geir Tore Voktor, Stein Tronstad, Sven Lidstrom, NPI #AntarcticaDay #AntarcticTreaty #southpole #sydpolen #npolar #norwegianpolarinstitute #norskpolarinstitutt #research #science #polarscience #glacier #glaciology #ice #snow #cryosphere #fieldphotofriday #fieldwork #scicomm #forskkomm

Yesterday the sun set in Tromsø for another year. We who are privileged to live here are hoping for another winter with lots of nice snow, and good skiing; this picture was taken last weekend, when we had just such a happy combination. But several days later, temperatures went well above freezing and there was a fair amount of rain. The snowpack turned first to slush, and then after it got cold again, to ice. These “rain-on-snow” events are, unhappily, a feature of life here in the far north, not only here in Tromsø, but also in Svalbard, where we do much of our work. While there have always been winter rain events, their frequency is increasing. And once the ground has been covered by a hard ice layer, the only way it disappears again is either through a prolonged spell of warm days with rain, or once the sun has come back up again, the radiation can melt the ice. This ice not only impacts pedestrians walking the steep streets of Tromsø (emergency rooms here fill up with broken bone cases after such winter warm events), but also wildlife, such as the Svalbard reindeer, who have a more difficult time grazing through the ice layers that form on the ground. Photo: Jack Kohler #npolar #norskpolarinstitutt #norwegianpolarinstitute #glacier #glaciology #snow #ice #winter #melt #Tromsø #Svalbard #reindeer #science #polarscience #forskkomm #scicomm

In Tromsø days are growing shorter, the air is getting cold, the lakes are freezing over, and snow is falling. Its time to put the hiking boots away and reach for our skis and skates. This got us thinking “why does ice slip so well?” A recent scientific discovery may change the way we think about skating on lakes like Prestvannet. The “slippery” nature of ice is generally attributed to a thin liquid water layer generated by friction. A skate is able to “surf” on this liquid film, allowing us to enjoy winter activities such as skiing, ice-skating and curling. The properties of this thin water layer could never be measured: its thickness remained largely unknown and its properties, even its existence, remained subject to debate. Moreover, liquid water is a bad lubricant, how could it reduce friction and make the ice slippery? To resolve this paradox, ENS Physics laboratory and Hydrodynamic laboratory researchers developed a device, using a tuning fork, like those used in music. Thanks to their unique device, scientists have unambiguously demonstrated for the first time that friction does generate a film of liquid water. However, this film held several surprises: with a measured thickness of a few hundred nanometres to one micron – a hundredth the thickness of a hair – it is much thinner than suggested by theoretical estimates. More unexpectedly, it is far from being “simple water”, it consists of water as viscous as oil, with complex viscoelastic properties. This unexpected behaviour suggests that ice at the interface does not turn completely into liquid water, but into a mixed state close to “sorbet granita”, a mixture of viscous water and crushed ice. The mystery of sliding on ice resides in the sticky nature of this film of water. These results show that the theoretical descriptions suggested so far to describe friction on ice, and potentially how glaciers flow, need improving. See the article for more “granita” details: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041025 Photo: Ashley Morris #npolar #norskpolarinstitutt #glacier #glaciology #ice #physics #snow #science #polarscience #forskkomm #scicomm #ski #skate

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