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| Polar night | |
|---|---|
| Name | Polar night |
| Duration | Varies by latitude |
| Phenomenon | Astronomical/atmospheric |
Polar night is the interval during which a polar region experiences continuous or near-continuous darkness or twilight each day for more than 24 hours. It occurs within the Arctic and Antarctic regions and influences Aurora Australis, Aurora Borealis, International Date Line, Arctic Circle, and Antarctic Circle related activities. The phenomenon affects atmospheric circulation, seasonal ecology, and human societies in places such as Svalbard, Longyearbyen, Barrow, Alaska, Tromsø, Murmansk, Reykjavík, Nuuk, McMurdo Station and South Pole Station.
Polar night describes periods ranging from prolonged twilight to absolute darkness; classifications include civil, nautical, and astronomical twilight as recognized by observatories like Greenwich Observatory and instruments deployed by National Aeronautics and Space Administration and European Space Agency. Phenomenological features involve extended low solar elevation, crepuscular lighting, noctilucent clouds often monitored by AERONET, and enhanced visibility of Milky Way, Magellanic Clouds, and transient luminous events studied in campaigns such as International Polar Year. Local manifestations have been recorded in historical expeditions led by Roald Amundsen, Fridtjof Nansen, Robert Falcon Scott, and scientific programs funded by National Science Foundation.
The primary cause is the axial tilt of the Earth relative to its orbital plane about the Sun, producing polar insolation minima when a pole tilts away during the December solstice or June solstice. Orbital variations described in the Milankovitch cycles modulate long-term extremes. The curvature of Earth's atmosphere and refractive effects cause twilight extension; optical phenomena have been modeled using radiative transfer codes developed at institutions like Jet Propulsion Laboratory and laboratories at Max Planck Institute for Meteorology.
Polar night occurs poleward of the Arctic Circle and Antarctic Circle, with duration increasing toward the North Pole and South Pole. Regional modifiers include local topography found in the Scandinavian Mountains, Greenland Ice Sheet, and Antarctic Peninsula, as well as oceanic influences from the Barents Sea, Bering Sea, Norwegian Sea, and Southern Ocean. Urban centers such as Kirkenes, Hammerfest, Murmansk Oblast, Yakutsk, and research outposts like Rothera Research Station experience distinct twilight regimes due to latitude, altitude, and sea-ice cover changes documented by Intergovernmental Panel on Climate Change assessments.
Prolonged darkness alters radiative balance, contributing to surface cooling that affects Arctic amplification and regional feedbacks involving sea ice and the Greenland ice sheet. Polar night interacts with atmospheric circulation patterns including the Polar vortex, North Atlantic Oscillation, and Arctic Oscillation, influencing extreme weather in regions monitored by World Meteorological Organization networks. Changes during polar night have implications for heat transport studied in model intercomparisons coordinated by Coupled Model Intercomparison Project and observational programs like CryoSat and ICESat.
Biota in high-latitude ecosystems adapt to darkness through phenological and physiological strategies observed in taxa studied by researchers at Smithsonian Institution, Alfred Wegener Institute, University of Alaska Fairbanks, and University of Tromsø. Polar night triggers behavioral shifts in species such as Caribou, Reindeer, Arctic fox, Polar bear, Emperor penguin, krill, and seabirds like Atlantic puffin and snow petrel. Marine primary production cycles, phytoplankton dormancy, and microbial dynamics are influenced by light limitation and documented in programs like International Polar Year cruises and cruises funded by National Oceanic and Atmospheric Administration.
Human communities in regions such as Nunavut, Lapland, Sápmi, Chukotka Autonomous Okrug, Alaska, Greenland and settlements like Tromsø and Murmansk have cultural practices, festivals, and circadian adaptations tied to polar night; ethnographic work references traditions of the Sámi people and subsistence activities documented by Inuit Tapiriit Kanatami. Psychological and physiological effects including seasonal affective disorder have been studied by researchers at Harvard University, Karolinska Institutet, and University of Oslo. Infrastructure and logistics for Arctic Council member states and for polar stations such as McMurdo Station require specialized lighting, energy, and emergency planning.
Observation employs ground stations, polar orbiters like Landsat and Sentinel-1, lidar campaigns such as ICESat-2, radiosonde networks coordinated by World Meteorological Organization, and autonomous systems including Argo floats and Seaglider gliders. Modeling and remote sensing efforts by National Snow and Ice Data Center, European Centre for Medium-Range Weather Forecasts, and NOAA combine radiative transfer, atmospheric chemistry, and ecosystem models from groups at Los Alamos National Laboratory and Lawrence Berkeley National Laboratory to quantify polar night impacts. Historical records from expeditions by James Clark Ross and data archives curated by UK Met Office complement contemporary multisensor datasets used in studies submitted to journals like Nature and Science.
Category:Polar regions