Weddell Polynya
The Weddell Polynya, or Weddell Sea Polynya, is a polynya or irregular area of open water surrounded by sea ice in the Weddell Sea of the Southern Ocean off Antarctica and near the Maud Rise.[1][2] The formation of the polynya exposes relatively warmer ocean waters (at surface freezing temperatures of -1.9°C) to a cold atmosphere, leading to a large exchange of heat which drives deep convection in the ocean, often reaching depths of a 1,000 to 2,000 meters.[3]
Occurrences
The size of New Zealand, it re-occurred each winter between 1974 and 1976.[4] These were the first three austral winters observed by the Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR).[5] From 1976 to 2015 this polynya was rarely observed.[6] The polynya reoccurred in 2016, and has since appeared in 2017. The 2010s occurrence has been smaller than the 1970s occurrence, being about the size of Maine in 2017, or roughly 80,000 km2 (31,000 sq mi).[7]
Since the 1970s, the polar Southern Ocean south of the Antarctic Circumpolar Current has freshened and stratified, likely a result of anthropogenic climate change. Such stratification may be responsible for suppressing the return of the Weddell Sea polynya.[8][9]
More recently, it was found that intense cyclones occurring over the ice pack, far south from the ice edge, were at the origin of the reoccurrence of the Weddell or Maud Rise Polynya in austral winter 2017.[10] In certain winter months, the general atmospheric circulation around Antarctica exhibits a strong zonal wave 3 pattern which favor the development of polar cyclones closer to the coast i.e. over preconditioned oceanographic areas for polynya formation such as the Weddell Polynya in the Lazarev Sea and the Cosmonaut polynya in the Cosmonaut Sea around Antarctica.
Other Antarctic polynyas
The presence of polynyas in McMurdo Sound provides an ice-free area where penguins can feed, so is important for the survival of the Cape Royds penguin colony.[11]
See also
- Polar Cyclones
- Coriolis force
- Ekman layer
- Ekman number
- Ekman spiral
- Ekman transport
- Ekman velocity
- Fridtjof Nansen
- Nansen's Fram expedition
- Upwelling
- Vagn Walfrid Ekman
References
- ^ David Holland (5 May 2003). "Background - Weddell Polynya". New York University. Retrieved 16 December 2014.
- ^ D M Holland (1 June 2001). "Explaining the Weddell Polynya--a large ocean eddy shed at Maud Rise". Science. 292 (5522): 1697–700. Bibcode:2001Sci...292.1697H. doi:10.1126/science.1059322. PMID 11387470. S2CID 39712681.
- ^ Cheon, Woo Geun; Gordon, Arnold L. (6 May 2019). "Open-ocean polynyas and deep convection in the Southern Ocean". Scientific Reports. 9 (1): 6935. Bibcode:2019NatSR...9.6935C. doi:10.1038/s41598-019-43466-2. PMC 6502842. PMID 31061471.
- ^ "The Weddell Polynya". University of Toronto/NASA. Retrieved 16 December 2014.
- ^ Claire L. Parkinson; Joey C. Comiso & H. Jay Zwally (2014). "Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations". National Snow and Ice Data Center. Retrieved 16 December 2014.
- ^ "Arctic Sea Ice News and Analysis | Sea ice data updated daily with one-day lag".
- ^ Ryan Whitwam (11 October 2017). "Giant Hole Opens in Antarctic Ice Pack, and No One Knows Why". ExtremeTech.
- ^ Casimir de Lavergne, Jaime B. Palter, Eric D. Galbraith, Raffaele Bernardello & Irina Marinov (2 March 2014). "Cessation of deep convection in the open Southern Ocean under anthropogenic climate change" (PDF). Nature Climate Change. 4 (4): 278–282. doi:10.1038/nclimate2132.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Sarah Zielinski (3 March 2014). "Climate Change Felt in Deep Waters of Antarctica". Smithsonian.com. Retrieved 16 December 2014.
- ^ Diana Francis, Clare Eayrs, Juan Cuesta, David Holland (24 April 2019). "Polar Cyclones at the Origin of the Reoccurrence of the Maud Rise Polynya in Austral Winter 2017". Journal of Geophysical Research: Atmospheres. 124 (10). JGR: Atmospheres: 5251–5267. Bibcode:2019JGRD..124.5251F. doi:10.1029/2019JD030618. S2CID 149497432.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ B. Stonehouse (3 December 1967). "Penguins in high latitudes". Tuatara: Volume 15, Issue 3. Victoria University of Wellington. Retrieved 16 December 2014.
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